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Our first step we walked to get our organism. Our group consist of  Alex,Ava,Landry, and Parker. 

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Our first step we walked to get our organism. Our group consist of  Alex,Ava,Landry, and Parker. 

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Ava gathered a bug. A big black beetle in a cut down tree. 

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Ava gathered a bug. A big black beetle in a cut down tree. 

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Alex donated her hair for our beetle who eats hair.

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Alex donated her hair for our beetle who eats hair.

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Parker took photos and notes for our project . 

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Parker took photos and notes for our project . 

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Landry gathered bark for our beetle because our beetle was in the wood of a termite infested tree. 

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Landry gathered bark for our beetle because our beetle was in the wood of a termite infested tree. 

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Kami Export - Ava Tidwell - Evolution packet (1)

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(not the same as our ground beetle but it was all we can find)

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Skin with hair

The skin, with hair. Illustration by Dr. Gheorghe Constantinescu.

The epidermis is composed of multiple layers of cells consisting of keratinocytes, melanocytes, Langerhans cells, and Merkel cells.

Keratinocytes function to produce a protective barrier. They are produced from columnar basal cells attached to a basement membrane. The rate of cell mitosis and subsequent keratinization are controlled by a variety of factors, including nutrition, hormones, tissue factors, immune cells in the skin, and genetics. Keratinocytes play a key role in the skin immune system and in regulating the growth and renewal of cells. The dermis may also exert significant control over the growth of the epidermis. It has been hypothesized that photoperiod and reproduction cycles may affect the epidermis in animals. Glucocorticoids decrease mitotic activity; disease and inflammation also alter normal epidermal growth and keratinization.

As keratinocytes migrate upward, they undergo a complex process of programmed cell death or keratinization. The goal of this process is to produce a compact layer of dead cells called the stratum corneum, which functions as an impermeable barrier to the loss of fluids, electrolytes, minerals, nutrients, and water, while preventing the penetration of infectious or noxious agents into the skin. The structural arrangement of keratin and the lipid content of the skin are critical to this function. The vitamin D precursor, 7-dehydrocholesterol, is formed in the epidermis. The epidermis is thickest in large animals. The stratum corneum is continuously shed or desquamated.

Melanocytes are located in the basal cell layer, outer root sheath, and ducts of sebaceous and sweat glands. They are responsible for the production of skin and hair pigment (melanin). Production of pigment is under hormonal and genetic control. Melanocytes provide constitutive pigmentation, the genetically programmed pigment and facultative pigmentation, that occurs as a result of stimulation from hormones, UV light, inflammation, etc.

Langerhans cells are mononuclear dendritic cells that are intimately involved in regulating the immune system of the skin. They are damaged by excessive UV light exposure and glucocorticoids. Antigenic and allergenic material is processed by these cells and transported to local and nodal T cells to induce hypersensitivity reactions. Epidermal proteins may also conjugate with exogenous haptens, rendering them antigenic.

Merkel cells are specialized sensory cells associated with skin sensory organs, eg, whiskers and tylotrich pads. These are slow-adapting mechanoreceptors. These cells may also influence cutaneous blood flow and sweat production, coordinate keratinocyte proliferation, and stimulate stem cell growth of hair follicles.

The basement membrane zone serves as a site for attachment of basal epidermal cells and as a protective barrier between the epidermis and dermis. A variety of skin diseases, including several autoimmune conditions, can cause damage to this zone. Vesicles are an example of a damaged basement membrane zone. The basement membrane zone has important functions:

The dermis is a mesenchymal structure that supports, nourishes, and to some degree, regulates the epidermis and appendages. The dermis consists of ground substance, dermal collagen fibers, and cells (fibroblasts, melanocytes, mast cells, and occasionally eosinophils, neutrophils, lymphocytes, histiocytes, and plasma cells). Blood vessels responsible for thermoregulation, nerve plexuses associated with cutaneous sensation, and both myelinated and unmyelinated nerves are present in the dermis. Motor nerves are primarily adrenergic and innervate blood vessels and arrector pili muscles. Except in horses, apocrine glands do not appear to be innervated. Sensory nerves are distributed in the dermis, hair follicles, and specialized tactile structures. The skin responds to the sensations of touch, pain, itch, heat, and cold.

These structures grow out of (and are continuous with) the epidermis and consist of hair follicles, sebaceous and sweat glands, and specialized structures (eg, claw, hoof). The hair follicles of horses and cattle are simple, ie, the follicles have one hair emerging from each pore. The hair follicles of dogs, cats, sheep, and goats are compound, ie, the follicles have a central hair surrounded by 3-15 smaller hairs all exiting from a common pore. Animals with compound hair follicles are born with simple hair follicles that develop into compound hair follicles.

The growth of hair is controlled by a number of factors, including nutrition, hormones, and photoperiod. The growing stage of the hair is referred to as anagen, and the resting stage (mature hair) is referred to as telogen. The transitional stage between anagen and telogen is catagen. Animals normally shed their hair coat in response to changes in temperature and photoperiod; most animals undergo a shed in the early spring and early fall.

The size, shape, and length of hair is controlled by genetic factors but may be influenced by disease, exogenous drugs, nutritional deficiencies, and environment. Hormones have a significant effect on hair growth. Thyroxine initiates hair growth, and glucocorticoids inhibit hair growth.

The primary functions of the hair coat are to provide a mechanical barrier, to protect the host from actinic damage, and to provide thermoregulation. In most species, trapping dead air space between secondary hairs conserves heat. This requires that the hairs be dry and waterproof; the cold-weather coat of many animals is often longer and finer to facilitate heat conservation. The hair coat can also help cool the skin. The warm-weather coat of animals, particularly large animals, consists of shorter thicker hairs and fewer secondary hairs. This anatomic change allows air to move easily through the coat, which facilitates cooling. The hair coat also helps conceal or camouflage the animal.

Sebaceous glands are simple or branched alveolar, holocrine glands that secrete sebum into the hair follicles and onto the epidermal surface. They are present in large numbers near the mucocutaneous junction, interdigital spaces, dorsal neck area, rump, chin, and tail area; in some species, they are part of the scent-marking system. For example, in cats, sebaceous glands are present on the face, dorsum, and tail in high concentration; cats mark territories by rubbing their face on objects and depositing a layer of sebum laced with feline facial pheromones. Sebum is a complex lipid material containing cholesterol, cholesterol esters, triglycerides, diester waxes, and fatty acids. Sebum is important to keep the skin soft and pliable and to maintain proper hydration; it gives the hair coat sheen and has antimicrobial properties.

Sweat glands (epitrichial [formerly apocrine] and atrichial [formerly eccrine]) are part of the thermoregulatory system. Atrichial glands are only present in the foot pads. Epitrichial glands are not present on footpads or on the planum nasale. The evaporation of sweat from the skin is the primary body cooling mechanism for horses and primates and, to a lesser degree, pigs, sheep, and goats. There is some clinical evidence to suggest that limited sweating occurs in dogs and cats, and that it may have a minor role in cooling the body. Dogs and cats thermoregulate primarily by panting, drooling, and spreading saliva on their coats (cats). Cats also sweat through their paws, especially when excited; this is most commonly seen as wet paw prints on surfaces, eg, examination tables.

The "twitch muscle" (panniculus carnosus) is the major subcutaneous muscle. The subcutaneous fat (panniculus adiposus) serves many functions, including insulation; reservoir for fluids, electrolytes, and energy; and shock absorber.

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The Integumentary System in Animals - Integumentary System - Merck Veterinary Manual

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Learn about the veterinary topic of The Integumentary System in Animals. Find specific details on this topic and related topics from the Merck Vet Manual.

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Plant integumentary system Invertebrate integuments Vertebrate integumentary systems Human integumentary system Skin disorders
The integumentary system includes the skin and the related structures that cover and protect the bodies of plants and animals. The integumentary system of plants includes the epidermis, cuticle, plant hairs, and glands. The integumentary system of invertebrates includes shells and exoskeletons as body covering. The integumentary system of vertebrates comprises skin, scales, feathers, hair and glands. The human integumentary system is made up of the skin that includes glands, hair, and nails. In humans, the skin protects the body, prevents water loss, regulates body temperature, and senses the external environment.

The epidermis is the main surface tissue of young plants and the covering material of all leaves. Usually the epidermis is one cell deep; its cells have thick outer and side walls. On the parts of the plant that are above ground, the epidermal cells secrete an outer waxy cuticle that is water resistant. The thickened cell walls, together with the cuticle, prevent drying out, injury, and fungus infection. The epidermis in aerial parts of the plant gives rise to plant hairs, spines, and glands. In leaves, the epidermis develops guard cells that regulate the size of pores or stomata, which allows the exchange of gases with the atmosphere. Root epidermis lacks the waxy cuticle found in aboveground parts of the plant, allowing it to absorb water from the soil. Root hairs that increase absorbing surface arise from epidermal tissue. When a plant diameter grows, stem and root epidermis is replaced by periderm, which contains cork cells whose walls after cell death provide a protective waterproof outer covering.

Snails, slugs, oysters, and clams are protected by a hard shell made of calcium carbonate secreted by the mantle, a heavy fold of tissue that surrounds the molluscs internal organs. Spiders, insects, lobsters, and shrimp, have bodies covered by an external skeleton, the exoskeleton, which is strong, impermeable, and allows some arthropods to live on land. The exoskeleton is composed of layers of protein and a tough polysaccharide called chitin, and can be a thick hard armor or a flexible paper-thin covering. Arthropods grow by shedding their exoskeletons and secreting a larger one in a process called molting.

Keratin, an insoluble protein in the outer layer of the vertebrate skin, helps prevent water loss and dehydration and has contributed to the successful adaptation to life on land. Keratin is also the major protein found in nails, hooves, horns, hair, and wool. Feathers, scales, claws and beaks of birds and reptiles are also composed of keratin.

The human integumentary system is made up of the skin, hair, nails, and glands, and serves many protective functions. It prevents excessive water loss, keeps out microorganisms that could cause illness, and protects underlying tissue from mechanical damage. Pigments

called melanin absorb and reflect the suns harmful ultraviolet radiation.

The skin also helps regulate body temperature. If heat builds up, sweat glands produce more sweat, which evaporates and cools the skin. In addition, when the body overheats, blood vessels expand and bring more blood to the skin surface, allowing body heat to be lost. If the body is too cold, on the other hand, blood vessels in the skin contract, putting less blood at the body surface and conserving heat. In addition, the skin serves as a minor excretory organ, since sweat removes small amounts of nitrogenous wastes produced by the body, and functions as a sense organ since it contains millions of nerve endings that detect touch, heat, cold, pain, and pressure. Finally, the skin produces vitamin D in the presence of sunlight, and renews and repairs damage to itself.

In an adult, the skin covers about 21.5 square feet (2 sq m), and weighs about 11 pounds (5 kg). Depending on location, the skin ranges from 0.02-0.16 inch (0.5-4.0 mm) thick. Its two principal parts are the outer layer, or epidermis, and a thicker inner layer, the dermis. A subcutaneous layer of fatty or adipose tissue is found below the dermis. Fibers from the dermis attach the skin to the subcutaneous layer, and the underlying tissues and organs also connect to the subcutaneous layer.

The epidermis

Ninety percent of the epidermis, including the outer layers, contains keratinocytes cells that produce keratin, a protein that helps waterproof and protect the skin. Melanocytes are pigment cells that produce melanin, a brown-black pigment that adds to skin color and absorbs ultraviolet light, thereby shielding the genetic material in skin cells from damage. Touch-sensitive Merkels cells are found in the deepest layer of the epidermis of hairless skin.

In most areas of the body, the epidermis consists of four layers. On the soles of the feet and palms of the hands, where there is a lot of friction, the epidermis has five layers. In addition, calluses (abnormal thickenings of the epidermis), occur on skin subject to constant friction. At the surface, the uppermost layer consists of about 25 rows of flat dead cells that contain keratin.

The dermis

The dermis is made up of connective tissue that contains protein, collagen, and elastic fibers. It also contains blood and lymph vessels, sensory receptors, related nerves, and glands. The outer part of the dermis has fingerlike projections, called dermal papillae, that indent the lower layer of the epidermis. Dermal papillae cause ridges in the epidermis above it, which in the digits give rise to fingerprints. The ridge pattern of fingerprints is inherited, and is unique to each individual.

The dermis is thick in the palms and soles, but very thin in other places, such as the eyelids. The blood vessels in the dermis contain a volume of blood. If a part of the body, such as a working muscle, needs more blood, vessels in the dermis constrict, causing blood to leave the skin and enter the circulation that leads to muscles and other body parts. Sweat gland ducts pass through the epidermis to the outside and open on the skin surface through pores embedded in the deep layers of the dermis.

Hair follicles and roots also originate in the dermis; hair shafts extend from the root through the skin layers to the surface. Also in the dermis are sebaceous glands associated with hair follicles which produce an oily substance called sebum. Sebum softens the hair and prevents it from drying, but if sebum blocks a sebaceous gland, a whitehead appears on the skin. A blackhead results if the material oxidizes and dries. Acne is caused by infections of the sebaceous glands. When this occurs, the skin breaks out in pimples and can become scarred.

The skin is an important sense organ and as such includes a number of nerves that are mainly in the dermis, with a few reaching the epidermis. Nerves carry impulses to and from hair muscles, sweat glands, and blood vessels, and receive messages from touch, temperature, and pain receptors. Some nerve endings are specialized, such as sensory receptors that detect external stimuli. The nerve endings in the dermal papillae are known as Meissners corpuscles, these detect light touch, such as a pat, or the feel of clothing on the skin. Pacinian corpuscles, located in the deeper dermis, are stimulated by stronger pressure on the skin. Receptors near hair roots detect displacement of the skin hairs by stimuli such as touch or wind. Bare nerve endings throughout the skin report information to the brain about temperature change (both heat and cold), texture, pressure, and trauma.

Some skin disorders result from overexposure to the ultraviolet (UV) rays in sunlight. At first, over-exposure to sunlight results in injury known as sunburn. UV rays damage skin cells, blood vessels, and other dermal structures. Continual overexposure leads to leathery skin, wrinkles, and discoloration and can also lead to skin cancer. Anyone excessively exposed to UV rays runs a risk of skin cancer, regardless of the

KEY TERMS

amount of pigmentation normally in the skin. Seventy-five percent of all skin cancers are basal cell carcinomas that arise in the epidermis and rarely spread (metastasize) to other parts of the body. Physicians can surgically remove basal cell cancers. Squamous cell carcinomas also occur in the epidermis, but these tend to metastasize. Malignant melanomas are life-threatening skin cancers that metastasize rapidly. There can be a 10-20 year delay between exposure to sunlight and the development of skin cancers.

PERIODICALS

Czarnecki, D. 10-Year Prospective Study Of Patients With Skin Cancer. Journal of Cutaneous Medicine and Surgery 6 no. 5 (2002): 427-429.

Fackelmann, Kathy A. Skin Cancers Return: How Big a Threat? Science News (27 June 1992).

Willis, Judith Levine. Acne Agony. FDA Consumer (July-August 1992).

OTHER

Estrella Mountain Community College. The Integumentary System <http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookINTEGUSYS.html> (accessed November 29, 2006).

Skin Deep. video and videodisc. Princeton, NJ: Films for the Humanities and Sciences, 1995.

University of Western Australia, School of Anatomy and Human Biology. Blue HistologyIntegumentary System < http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm> (accessed November 29, 2006).

Bernice Essenfeld

Definition

The integumentary system includes the skin and the related structures that cover and protect the body. The human integumentary system is composed of the skin, and includes glands, hair, and nails. The largest organ in the body, the skin protects the body, prevents water loss, regulates body temperature, and senses the external environment.

Description

The integumentary system serves many protective functions for the body. It acts as a mechanical barrier, simultaneously preventing water from entering the body and excessive water loss. It also limits access of microorganisms that could cause illness, and protects underlying tissues from mechanical damage. Pigments in the skin called melanin, give skin its color, and absorb and reflect the sun's harmful ultraviolet radiation.

Function

In addition to serving as a protective barrier, the skin helps to regulate the body temperature by several mechanisms. If heat builds up in the body, sweat glands in the skin produce more sweat that evaporates and cools the skin. When the body overheats, blood vessels in the skin dilate (expand), bringing more blood to the surface, and allowing body heat to dissipate. When the body is too cold, the blood vessels in the skin constrict, shunting blood away from the body surface, thus conserving heat. Along with temperature regulation, the skin serves as a minor excretory organ, since sweat removes small, clinically insignificant amounts of nitrogenous wastes produced by the body. The skin also functions as a sense organ since it contains millions of nerve endings that detect touch, heat, cold, pain and pressure. Finally, the skin produces vitamin D in the presence of sunlight, and renews and repairs damage to itself.

In an adult, the skin covers about 21.5 sq. ft (2 sq. m), and weighs about 11 lb. (5 kg). Depending on location, the skin thickness ranges from 0.02-0.16 in (0.5-4.0 mm). Skin is composed of an outer layer, or epidermis, and a thicker inner layer, the dermis. A subcutaneous layer of fatty or adipose tissue is immediately below the dermis. Fibers from the dermis attach the skin to the subcutaneous layer, and the underlying tissues and organs also connect to the subcutaneous layer.

The epidermis

Ninety percent of the epidermis, including the outer layers, contains keratinocytes, cells that produce keratin, a protein that helps waterproof and protect the skin. Melanocytes are pigment cells that produce melanin, a brown-black pigment that adds to skin color and absorbs ultraviolet light, thereby shielding the genetic material in skin cells from damage. Merkel's cells disks are touch-sensitive cells found in the deepest layer of the epidermis of hairless skin.

In most areas of the body, the epidermis consists of four layers. On the soles of the feet and palms of the hands where there is considerable friction, the epidermis has five layers. Calluses, abnormal thickenings of the epidermis, occur on skin subject to constant friction. At the skin surface, the outer layer of the epidermis constantly sheds the dead cells containing keratin. The uppermost layer consists of about 25 rows of flat dead cells that contain keratin.

The dermis

The dermis is made up of connective tissue that contains protein, collagen, and elastic fibers. It also contains blood and lymph vessels, sensory receptors, related nerves, and glands. The outer part of the dermis has fingerlike projections, called dermal papillae, that indent the lower layer of the epidermis. Dermal papillae cause ridges in the epidermis above it, which in the digits give rise to fingerprints. The ridge pattern of fingerprints is inherited, and is unique to each individual. The dermis is thick in the palms and soles, but very thin in other places, such as the eyelids.

The blood vessels in the dermis contain a volume of blood. When a part of the body, such as a working muscle, needs more blood, blood vessels in the dermis constrict, shifting blood from the skin to supply muscles and other body parts. Sweat glands with ducts that pass through the epidermis and open on the skin surface through pores are embedded in the deep layers of the dermis. Hair follicles and hair roots also originate in the dermis, and the hair shafts extend from the hair root through the skin layers to the surface. The dermis also contains sebaceous glands associated with hair follicles. Sebaceous glands produce an oily substance called sebum. Sebum softens the hair and prevents it from drying, but if sebum blocks a sebaceous gland, a whitehead appears on the skin. A blackhead results if the material oxidizes and dries. Acne pimples are caused by infections of the sebaceous glands.

The skin is an important sense organ and as such includes a number of types of nerves, which are mainly in the dermis, with a few reaching the epidermis. Nerves carry impulses to and from hair muscles, sweat glands, and blood vessels, and receive messages from touch, temperature, and pain receptors. Some nerve endings are specialized such as sensory receptors that detect external stimuli. The nerve endings in the dermal papillae, known as Meissner's corpuscles, detect light touch, or the feel of clothing on the skin. Pacinian corpuscles, located in the deeper dermis, are stimulated by stronger pressure on the skin. Receptors near hair roots detect displacement of the skin hairs by stimuli such as touch or wind. Bare nerve endings throughout the skin supply information to the brain about temperature change (both heat and cold), texture, pressure, and trauma.

Role in human health

Along with its vital roles as shield against micro-organisms and regulating body temperature, skin often provides information about overall health and a variety of medical conditions. The color, texture, temperature, and elasticity of skin can aid in diagnosing a variety of disorders. For example, patients with hepatitis may have a characteristic yellow tinge to their skin. Similarly, cold sores and fever blisters are indications of infection with herpes simplex virus, and warts (intraepidermal skin tumors) result from infection with human papilloma virus (HPV).

Skin testing is an important diagnostic tool in the evaluation of allergies. Skin testing involves a series of superficial injections of one or more suspected allergens. A positive response, such as redness, or inflammation, at the site of the skin test, helps to pinpoint the culprit.

Common diseases and disorders

Acne, caused by clogged pores and bacterial infection, is commonly diagnosed in teenagers and young adults. Acne may be mild, moderate, or severe and is characterized by blackheads, whiteheads, papules, pustules, and cysts on the face, shoulders, chest, and back. Mild acne may be treated with topical antimicrobial agents to kill the bacteria on the skin and topical retinoids to open the pores. Moderate and severe acne often respond to treatment with systemic antibiotics such as tetracycline or doxycycline.

Common bacterial skin infections are impetigo, folliculitis, and cellulitis. Impetigo is a contagious skin infection caused by streptococci or staphylococcus. It produces crusty patches on the skin. Local outbreaks may be treated with antibacterial ointment, and patients with widespread infections are given oral antibiotics. Infectious folliculitis produces erythema (redness) and pustules. It is caused by staphylococcus and treated with oral antibiotics. Cellulitis is swelling, erythema, warmth, and pain caused by infection of the dermis and subcutaneous tissue often near a wound site. Cellulitis is usually caused by Group A streptococci or staph aureus and is treated with a course of anti-strep or anti-staph antibiotics.

Common viral skin disorders include infection with herpes simplex or herpes zoster. Herpes simplex is responsible for cold sores, fever blisters, and lesions on the genitals and buttocks. Herpes zoster produces a painful rash characterized by vesicles. Both conditions are treated with acyclovir, or other orally administered anti-viral agent.

Skin reactions include eczema, allergic contact dermatitis (rashes), such as those resulting from contact with poison ivy, sumac, or oak, and hives. Contact dermatitis, an eruption of itchy skin vesicles, is an allergic skin reaction. Patients are advised to avoid contact with the suspected allergen, and mild cases may be treated with warm soaks and topical ointments to reduce inflammation and soothe inflamed skin.

Cosmetic damage as well as potentially fatal skin disorders may result from overexposure to the ultraviolet (UV) rays in sunlight. At first, overexposure to sunlight results in injury known as sunburn. UV rays damage skin cells, blood vessels, and other dermal structures. Continual overexposure produces leathery skin, wrinkles, and discoloration and may also lead to skin cancer. Anyone excessively exposed to UV rays runs a risk of skin cancer, regardless of the amount of pigmentation normally in the skin. Seventy-five percent of all skin cancers are basal cell carcinomas that arise in the epidermis and rarely metastasize (spread) to other parts of the body. Physicians can surgically remove basal cell cancers. Squamous cell carcinomas also occur in the epidermis, and these may metastasize. Malignant melanomas are life-threatening skin cancers that metastasize rapidly. There can be a 10 to 20 year delay between exposure to sunlight and the development of skin cancers.

Dermatology is the medical specialty devoted to the diagnosis and treatment of skin disorders. In addition to the disorders previously described, primary care physicians and dermatologists are frequently called upon to diagnose and treat the following conditions:

alopecia (hair loss)

athlete's foot (fungus infection)

moles

psoriasis (scaly skin on the scalp, trunk, arms and legs)

rosacea (symmetrically distributed papules and pustules on the nose and cheeks)

scabies (skin infestation with mites that produces inflammatory papules in the wrists, web spaces, and sides of feet)

seborrheic dermatitis (facial redness and scaling)

spider veins, varicose veins

vitiligo (loss of skin color on patches of skin, usually affects the face and extremities)

Today, many dermatologists also provide a range of cosmetic services to reduce the signs of aging, such as wrinkles, sagging skin and discoloration, and reverse some of the effects of sun damage to skin. Microdermabrasion, laser skin resurfacing, and injections of collagen are among the techniques used to improve the appearance of skin.

KEY TERMS

Chitin- Polysaccharide that forms the exoskeleton of insects, crustaceans, and other invertebrates.

Dermis- Thicker layer of skin lying below the epidermis.

Epidermis- Thinner outermost layer of the skin.

Keratin- Insoluble protein found in hair, nails, and skin.

Melanin- Brown-black pigment found in skin and hair.

Resources

BOOKS

Freedberg, Irwin, et al. Fitzpatrick's Dermatology In General Medicine, Fifth Edition. Vols. I, II, and III. New York, NY: McGraw-Hill, 1999.

Odom, Richard B., et al. Andrew's Diseases of the Skin. Philadelphia, PA: W.B. Saunders Company, 2000.

OTHER

Skin Deep. Video and videodisc. Princeton, NJ: Films for the Humanities and Sciences, 1995.

The integumentary system includes the skin and the related structures that cover and protect the bodies of plants and animals. The integumentary system of plants includes the epidermis, cuticle, plant hairs, and glands . The integumentary system of invertebrates includes shells and exoskeletons as body covering. The integumentary system of vertebrates comprises skin, scales, feathers, hair and glands. The human integumentary system is made up of the skin which includes glands, hair, and nails. In humans, the skin protects the body, prevents water loss, regulates body temperature , and senses the external environment.

Plant integumentary system

The epidermis is the main surface tissue of young plants and the covering material of all leaves. Usually the epidermis is one cell deep; its cells have thick outer and side walls. On the parts of the plant that are above
ground, the epidermal cells secrete an outer waxy cuticle that is water resistant. The thickened cell walls, together with the cuticle, prevent drying out, injury, and fungus infection . The epidermis in aerial parts of the plant gives rise to plant hairs, spines, and glands. In leaves, the epidermis develops guard cells that regulate the size of pores or stomata, which allows the exchange of gases with the atmosphere. The epidermis of roots lacks the waxy cuticle found in the parts of the plant above ground, allowing the root epidermis to absorb water from the soil . Root hairs that increase the absorbing surface of the root arise from epidermal tissue. When a plant grows in diameter, the epidermis is replaced by the periderm, in the stem and the roots. The periderm contains cork cells whose walls after cell death provide a protective waterproof outer covering for plants making up the bark of older trees.

Invertebrate integuments

Snails , slugs , oysters, and clams are protected by a hard shell made of calcium carbonate secreted by the mantle, a heavy fold of tissue that surrounds the mollusc's internal organs. Spiders, insects , lobsters , and shrimp , have bodies covered by an external skeleton, the exoskeleton, which is strong, impermeable, and allows some arthropods to live on land. The exoskeleton is composed of layers of protein and a tough polysaccharide called chitin, and can be a thick hard armor or a flexible paper-thin covering. Arthropods grow by shedding their exoskeletons and secreting a larger one in a process called molting.

Vertebrate integumentary systems

Keratin, an insoluble protein in the outer layer of the skin of vertebrates, helps prevent water loss and dehydration and has contributed to the successful adaptation to life on land. Keratin is also the major protein found in nails, hooves, horns, hair, and wool. Feathers, scales, claws and beaks of birds and reptiles are also composed of keratin.

Human integumentary system

The human integumentary system is made up of the skin, hair, nails, and glands, and serves many protective functions for the body. It prevents excessive water loss, keeps out microorganisms that could cause illness, and protects the underlying tissues from mechanical damage. Pigments in the skin called melanin absorb and reflect the sun's harmful ultraviolet radiation . The skin helps to regulate the body temperature. If heat builds up in the body, sweat glands in the skin produce more sweat which evaporates and cools the skin. In addition, when the body overheats, blood vessels in the skin expand and bring more blood to the surface, which allows body heat to be lost. If the body is too cold, on the other hand, the blood vessels in the skin contract, resulting in less blood is at the body surface, and heat is conserved. In addition to temperature regulation , the skin serves as a minor excretory organ , since sweat removes small amounts of nitrogenous wastes produced by the body. The skin also functions as a sense organ since it contains millions of nerve endings that detect touch , heat, cold, pain, and pressure . Finally, the skin produces vitamin D in the presence of sunlight, and renews and repairs damage to itself.

In an adult, the skin covers about 21.5 sq ft (2 sq m), and weighs about 11 lb (5 kg). Depending on location, the skin ranges from 0.02-0.16 in (0.5-4.0 mm) thick. Its two principal parts are the outer layer, or epidermis, and a thicker inner layer, the dermis. A subcutaneous layer of fatty or adipose tissue is found below the dermis. Fibers from the dermis attach the skin to the subcutaneous layer, and the underlying tissues and organs also connect to the subcutaneous layer.

The epidermis

Ninety percent of the epidermis, including the outer layers, contains keratinocytes cells that produce keratin, a protein that helps waterproof and protect the skin. Melanocytes are pigment cells that produce melanin, a brown-black pigment that adds to skin color and absorbs ultraviolet light thereby shielding the genetic material in skin cells from damage. Merkel's cells disks are touch-sensitive cells found in the deepest layer of the epidermis of hairless skin.

In most areas of the body, the epidermis consists of four layers. On the soles of the feet and palms of the hands where there is a lot of friction , the epidermis has five layers. In addition, calluses, abnormal thickenings of the epidermis, occur on skin subject to constant friction. At the skin surface, the outer layer of the epidermis constantly sheds the dead cells containing keratin. The uppermost layer consists of about 25 rows of flat dead cells that contain keratin.

The dermis

The dermis is made up of connective tissue that contains protein, collagen , and elastic fibers. It also contains blood and lymph vessels, sensory receptors, related nerves, and glands. The outer part of the dermis has fingerlike projections, called dermal papillae, that indent the lower layer of the epidermis. Dermal papillae cause ridges in the epidermis above it, which in the digits give rise to fingerprints. The ridge pattern of fingerprints is inherited, and is unique to each individual . The dermis is thick in the palms and soles, but very thin in other places, such as the eyelids. The blood vessels in the dermis contain a volume of blood. If a part of the body, such as a working muscle, needs more blood, blood vessels in the dermis constrict, causing blood to leave the skin and enter the circulation that leads to muscles and other body parts. Sweat glands whose ducts pass through the epidermis to the outside and open on the skin surface through pores are embedded in the deep layers of the dermis. Hair follicles and hair roots also originate in the dermis and the hair shafts extend from the hair root through the skin layers to the surface. Also in the dermis are sebaceous glands associated with hair follicles which produce an oily substance called sebum. Sebum softens the hair and prevents it from drying, but if sebum blocks up a sebaceous gland, a whitehead appears on the skin. A blackhead results if the material oxidizes and dries. Acne is caused by infections of the sebaceous glands. When this occurs, the skin breaks out in pimples and can become scarred.

The skin is an important sense organ and as such includes a number of nerves which are mainly in the dermis, with a few reaching the epidermis. Nerves carry impulses to and from hair muscles, sweat glands, and blood vessels, and receive messages from touch, temperature, and pain receptors. Some nerve endings are specialized such as sensory receptors that detect external stimuli. The nerve endings in the dermal papillae are known as Meissner's corpuscles, which detect light touch, such as a pat, or the feel of clothing on the skin. Pacinian corpuscles, located in the deeper dermis, are stimulated by stronger pressure on the skin. Receptors near hair roots detect displacement of the skin hairs by stimuli such as touch or wind . Bare nerve endings throughout the skin report information to the brain about temperature change (both heat and cold), texture, pressure, and trauma.

Skin disorders

Some skin disorders result from overexposure to the ultraviolet (UV) rays in sunlight. At first, overexposure to sunlight results in injury known as sunburn. UV rays damage skin cells, blood vessels, and other dermal structures. Continual overexposure leads to leathery skin, wrinkles, and discoloration and can also lead to skin cancer . Anyone excessively exposed to UV rays runs a risk of skin cancer, regardless of the amount of pigmentation normally in the skin. Seventy-five percent of all skin cancers are basal cell carcinomas that arise in the epidermis and rarely spread (metastasize) to other parts of the body. Physicians can surgically remove basal cell cancers. Squamous cell carcinomas also occur in the epidermis, but these tend to metastasize. Malignant melanomas are life-threatening skin cancers that metastasize rapidly. There can be a 10-20 year delay between exposure to sunlight and the development of skin cancers.

Resources

periodicals

Czarnecki, D. "10-Year Prospective Study Of Patients With Skin Cancer." Journal of Cutaneous Medicine and Surgery 6, no. 5 (2002): 427-429.

Fackelmann, Kathy A. "Skin Cancer's Return: How Big a Threat?" Science News (June 27, 1992).

Willis, Judith Levine. "Acne Agony." FDA Consumer (July-August 1992).

other

Skin Deep. Video and videodisc. Princeton, NJ: Films for the Humanities and Sciences, 1995.

Bernice Essenfeld

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chitin

-Polysaccharide that forms the exoskeleton of insects, crustaceans, and other invertebrates.

Dermis

-The internal layer of skin lying below the epidermis. It contains the sweat and oil glands, hair follicles, and provides replacement cells for those that are shed from the outer layer.

Epidermis

-The thinner, outermost layer of the skin. Also the thin outermost covering in plants.

Keratin

-Insoluble protein found in hair, nails, and skin.

Melanin

-Brown-black pigment found in skin and hair.

The integumentary system of an organism is its protective outer covering. All organisms have an integument or covering that separates the organism from its environment and serves several other important functions. The integument of vertebrates (animals with a backbone) is called skin. Skin can vary widely, from the impenetrable shell of an armadillo to the amazingly smooth skin of a porpoise.

Every organism has some sort of covering that holds together its body organs and fluids and makes it separate from its environment. This outer covering protects it from foreign bodies and matter and sometimes allows it to communicate with the world outside itself. In both one-celled organisms and plants, the integument is the same as its cell membrane and any secretion or coating that it produces. More complex invertebrates (animals without a backbone) have an integument that consists of a single layer of cells called an ectoderm. Only in vertebrates is the integument a many-layered, complex organ system that serves many functions.

THE INTEGUMENTARY SYSTEM OF PLANTS

The integument, or outer covering, of plants does the same thing that skin does for animals-it protects plants from injury and prevents underlying tissue from drying out. Higher plants, or those that have seeds and a vascular system (an internal system of tubing that carries fluid), have a living epidermis usually one cell thick. It may be thin, like the covering on lettuce leaves, or thick and tough like that on pine needles. The epidermis has openings called stomates that regulate temperature and water loss. It can have coatings like the wax on an apple or sensitive hairs like those on a Venus's flytrap. Overall, most plant integuments are fairly fragile compared to animal coverings.

THE INTEGUMENTARY SYSTEM OF INVERTEBRATES

The integument of more complex invertebrates is usually a single layer of cells that secrete some type of cuticle. The cuticle oozes out of the epidermis and hardens, affording it some type of protection. In crustaceans like crabs and lobsters, this functions as an external skeleton and is very hard and tough. Insects have an outer covering made up of chitin fibers that is secreted by the epidermis. Chitin forms a type of flexible, natural plastic and acts as an outer skeleton to which muscles are attached. In insects, the cuticle is a living structure and can produce sensitive hairs as well as bristles, scales, claws, or wings, depending on the species. Insects grow by shedding the cuticle and growing a new, larger one. Mollusks, like clams and snails, also form a hard, external shell.

INTEGUMENTARY SYSTEMS IN VERTEBRATES

Only in vertebrates, however, is the integumentary system considered to be a vital organ. That is, it not only provides protection for the delicate tissue underneath, but it gathers and conveys information to the organism itself about the outside environment. The skin of all vertebrates consists of two layers: the relatively thin (outer) epidermis, and the tough, inner dermis. The epidermis is several cells thick, and its outermost layer of cells is made up of dead cells composed of keratin, the protein found in hair, nails, claws, beaks, feathers, scales, and quills, among other things. Vertebrates replace this outer layer of dead cells every twenty-eight days, with the new layer identical to the old. In mammals, the inner dermis is highly developed, and is richly supplied with blood vessels, glands, and nerve endings. Besides acting as a barrier against infection and retaining the body's fluids, the dermis also has a regulatory function of letting the organism know whether to raise or lower body temperature or to move to where it is cooler or warmer. In endothermic (warm-blooded) animals, the skin plays an important role in regulating the body's temperature. In humans, the epidermis also contains a dark pigment called melanin that protects the skin from the Sun's ultraviolet radiation. It is the amount of melanin an individual's body produces that accounts for what we describe as the many different colorings of human "races."

Mammals. In mammals, the presence of hair is a distinguishing characteristic. As an outgrowth from a mammal's skin, hair grows from a pit in the dermis called a hair follicle. This pit also has a small gland that secretes an oily substance that keeps the hair oiled. For most mammals, the hair's main function is to act as insulation against the cold. Hair also serves as a sensory organ (like long whiskers) for certain night-prowling animals. Eyelashes in humans serve to make the eyes reflexively shut if they are hit by a speck of dust. There are also other glands in the dermis that keep the skin oiled and waterproof. Humans also have sweat glands in the dermis that act as a temperature control by means of evaporation, and most mammals also have dermal glands that produce odors that are thought to be a form of sexual communication.

In humans, the skin is considered the largest organ of the body. It changes considerably over time, and as it ages it becomes less elastic and more wrinkled. As with all vertebrates, human skin provides both protection from and communication with its environment. The dermis is rich with nerve fibers that can respond rapidly to changing environmental conditions, reporting its findings to the brain, which makes the necessary adjustments.

Besides its practical functions as barrier and regulator, the human skin also possesses the exquisite and indescribable sense of touch. Its surface is usually home to many bacteria, mostly harmless, and the skin can be subject to many diseases or injuries.

The human integumentary system is made up of the skin, hair, nails, and associated glands. Its main function is to protect the body. It prevents excessive water loss, keeps out microorganisms that could cause illness, and shields the underlying tissues from external damage.

The skin helps to regulate body temperature. If heat builds up in the body, sweat glands in the skin produce sweat, which evaporates and cools the skin. When the body overheats, blood vessels in the skin expand and bring more warm blood to the surface, where it cools. When the body gets too cold, the blood vessels in the skin contract, leaving less blood at the body surface, and its heat is conserved.

In addition to temperature regulation, the skin serves as a minor excretory organ. Sweat removes small amounts of wastes produced by the body. These wastes include salts and urea (a chemical compound of carbon, hydrogen, nitrogen, and oxygen). The skin also functions as a sense organ since it contains millions of nerve endings that detect heat, cold, pain, and pressure. Finally, the skin produces vitamin D in the presence of sunlight and renews and repairs damage to itself.

In an adult, the skin covers about 21.5 square feet (2 square meters), and weighs about 11 pounds (5 kilograms). Depending on location, the skin ranges from 0.02 to 0.16 inch (0.5 to 4.0 millimeters) thick. Its two principal parts are the epidermis (the outer layer) and dermis (thicker inner layer). A subcutaneous (under the skin) layer of adipose or fatty tissue is found below the dermis. Fibers from the dermis attach the skin to the subcutaneous layer, and the underlying tissues and organs also connect to the subcutaneous layer.

The epidermis

Ninety percent of the epidermis, including the outer layers, contain cells that produce keratin, a protein that helps waterproof and protect the skin. Keratin is also the major protein found in nails and hair. Pigment cells called melanocytes produce melanin, a brown-black pigment that gives color to the skin and absorbs and reflects the Sun's harmful ultraviolet rays.

Words to Know

Calluses: Abnormal thickenings of the epidermis.

Dermis: Thicker layer of skin lying below the epidermis.

Epidermis: Thinner outermost layer of the skin.

Keratin: Insoluble protein found in hair, nails, and skin.

Melanin: Brown-black pigment found in skin and hair.

Subcutaneous layer: Layer of fatty tissue found beneath the skin.

In most areas of the body, the epidermis consists of four layers. The epidermis on the soles of the feet and palms of the hands has five layers, since these areas receive a lot of friction. Calluses, abnormal thickenings of the epidermis, can occur on any area of the skin where there is irritation or constant pressure. The uppermost layer of the epidermis consists of about 25 rows of flat dead cells that contain keratin. At the skin surface, dead cells are constantly shed.

The dermis

The dermis is thick in the palms and soles, but very thin in other places, such as the eyelids. The dermis is composed of connective tissue that contains protein fibers (called collagen) and elastic fibers. It also contains blood and lymph vessels, sensory nerves, and glands. Sweat glands are embedded in the deep layers of the dermis. Their ducts pass through the epidermis to the outside and open on the skin surface through pores.

Hair and hair roots also originate in the dermis. Hair shafts (containing the bulb of hair) extend from the hair root through the skin layers to the surface. Attached to the hair shaft is a sebaceous gland, which produces an oily substance called sebum. Sebum softens the hair and prevents it from drying. If sebum blocks up a sebaceous gland, a whitehead appears on the skin. A blackhead results if the material oxidizes and dries. Acne is caused by infections of the sebaceous glands. When this occurs, the skin breaks out in pimples and can become scarred.

Nerves in the dermis carry impulses to and from hair muscles, sweat glands, and blood vessels. Bare nerve endings throughout the skin report information to the brain about temperature change (both heat and cold), pressure, and pain.

The Sun and skin

Some skin disorders result from overexposure to the ultraviolet (UV) rays in sunlight. UV rays damage skin cells, blood vessels, and other dermal structures. At first, overexposure to sunlight results in injury known as sunburn. Continual overexposure leads to leathery skin, wrinkles, and discoloration. It can eventually lead to skin cancer, regardless of the amount of melanin in the epidermis. There can be a 10- to 20-year delay between exposure to sunlight and the development of skin cancer.

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Insects, like all other arthropods, have an open circulatory system which differs in both structure and function from the closed circulatory system found in humans and other vertebrates. In a closed system, blood is always contained within vessels (arteries, veins, capillaries, or the heart itself).

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Annual Review of Entomology, том 65, издание 1, страницы 121-143

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Although the insect circulatory system is involved in a multitude of vital physiological processes, it has gone grossly understudied. This review highlights this critical physiological system by detailing the structure and function of the circulatory organs, including the dorsal heart and the accessory pulsatile organs that supply hemolymph to the appendages. It also emphasizes how the circulatory system develops and ages and how, by means of reflex bleeding and functional integration with the immune system, it supports mechanisms for defense against predators and microbial invaders, respectively. Beyond that, this review details evolutionary trends and novelties associated with this system, as well as the ways in which this system also plays critical roles in thermoregulation and tracheal ventilation in high-performance fliers. Finally, this review highlights how novel discoveries could be harnessed for the control of vector-borne diseases and for translational medicine, and it details principal knowledge gaps that necessitate further investigation.

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X-rays that effectively peel away the opaque outer-cover off beetles have revealed the bugs have a more complex breathing apparatus at work than previously suspected.

Despite their relatively small body size, insects need more than a simple, mini-respiratory system to suck in enough oxygen to carry out basic processes such as scuttling around.

Results from a recent study reveal that rather than air just passively flowing in and out, a graceful inflation and deflation of tracheal tubes helps shuttle oxygen through the bodies of ground beetles.

"These tubes are being compressed in rhythmic fashion, and in this species it happens in the course of a second," said researcher Jake Socha of Argonne National Laboratory in Illinois. Socha presented the research at a meeting of the American Physiological Society (APS) in Washington, D.C. last month.

"Tracheal compression," analogous to breathing in humans and other vertebrates, might be choreographed by a muscle pump of sorts, the research suggests.

Air shuttle
Beetles breathe in a way that is already fairly sophisticated, using up to 18 tiny openings, called spiracles, that dot the middle and hind part of their bodies. When the pores open, oxygen-rich air can diffuse into tracheal tubes hooked up to the holes. The oxygen then gets shuttled through thousands of interconnected and branching tubes and dumped into cells. The waste product, carbon dioxide, then travels through the tubes and out the holes.

"There's a fundamental problem with the gas-exchange system design, and this is an issue of scale," Socha said.

What he means is that as an animal gets bigger, its volume increases more than its surface area, and the same holds for its cells. Gas molecules get into the cells through the surface, so the size of this "entrance" directly affects how much oxygen can move in and out.

"If you look at a single cell, as the cell gets larger diffusion isn't going to work to get oxygen into the cell because diffusion only goes a certain distance," said Scott Kirkton of Union College in New York. Kirkton studies insect respiration but was not involved in this beetle study.

This random movement of oxygen molecules, called diffusion, can only carry the incoming air so far and then it's up to mechanical processes to pick up the slack. "As the surface area to volume ratio gets smaller, you're not going to be able to get [oxygen] in. You need to have some other way to transport it," Kirkton told LiveScience.

Recent studies have shown that insects, including beetles, dragonflies and cockroaches, employ active body movements to ensure tip-top respiration. Some pump their wings to eschew air in and out of their bodies while others squeeze their bellies to pull in the needed oxygen. The mechanisms all fall under the umbrella of convection, or bulk movement of air.

"[Insect] breathing is much more similar to us than what people originally thought. They have a convective component like we do, and they have a diffusive component like we do," Kirkton said.

X-ray vision
Until now, the inner workings of insects, from dragonflies to tiny beetles, have been off limits to human eyes. "Mainly because insects are opaque, you can't see what's going on with these tubes," Socha said.

A technique that relies on high-powered X-ray beams has allowed scientists like Socha an under-the-hood view of living, breathing beetles.

In the recent study, Socha and his colleagues collected ground beetles from a local forest and taped each to a tiny mount. Then, they placed the beetles on a spot in a circular particle accelerator called the Advanced Photon Source at Argonne National Laboratory. The accelerator revs up electrons to near the speed of light, a process that generates X-rays that are a billion times more powerful than the kind used in hospitals.

The result was a video showing "pencil outlines" of the hair-thin breathing tubes. The tiny tubes squeezed and released in a pattern of undulations that started in a perfectly timed cycle. "So in a second you have deflation and then rapid re-inflation. It appears to be happening everywhere at once," Socha said.

They noticed a bizarre pattern of tiny indentations along each tube as the animal inhaled and exhaled. "These compressions appear to be these football-shaped dimples that are being pushed into the tracheal tubes," Socha said.

The scientists are not certain how exactly these compressions are helping the beetle. "The squeeze out may speed up the flow of fresh air in, aiding oxygen exchange," Socha explained. Another idea is that by moving carbon dioxide out quicker, the spiracles would open for only a short time, which would decrease water loss from the pores. "Or it may simply move air within the body," Socha said.

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Beetle breathing highly complex, study finds

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X-rays that effectively peel away the opaque outer-cover off beetles have revealed the bugs have a more complex breathing apparatus at work than previously suspected.

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Development of the tracheal system in Drosophila melanogaster.

An insect's respiratory system is the system with which it introduces respiratory gases to its interior and performs gas exchange.

Air enters the respiratory systems of insects through a series of external openings called spiracles. These external openings, which act as muscular valves in some insects, lead to the internal respiratory system, a densely networked array of tubes called tracheae. This network of transverse and longitudinal tracheae equalizes pressure throughout the system.

It is responsible for delivering sufficient oxygen (O ₂) to all cells of the body and for removing carbon dioxide (CO ₂) that is produced as a waste product of cellular respiration. The respiratory system of insects (and many other arthropods) is separate from the circulatory system.

Indian moon moth (Actias selene) with some of the spiracles identified

Scanning electron micrograph of a cricket spiracle valve

Insects have spiracles on their exoskeletons to allow air to enter the trachea. In insects, the tracheal tubes primarily deliver oxygen directly into the insects' tissues. The spiracles can be opened and closed in an efficient manner to reduce water loss. This is done by contracting closer muscles surrounding the spiracle. In order to open, the muscle relaxes. The closer muscle is controlled by the central nervous system but can also react to localized chemical stimuli. Several aquatic insects have similar or alternative closing methods to prevent water from entering the trachea. Spiracles can sometimes also be surrounded by hairs to minimize bulk air movement around the opening, and thus minimize water loss.

The spiracles are located laterally along the thorax and abdomen of most insects-usually one pair of spiracles per body segment. Air flow is regulated by small muscles that operate one or two flap-like valves within each spiracle-contracting to close the spiracle, or relaxing to open it.

After passing through a spiracle, air enters a longitudinal tracheal trunk, eventually diffusing throughout a complex, branching network of tracheal tubes that subdivides into smaller and smaller diameters and reaches every part of the body. At the end of each tracheal branch, a special cell provides a thin, moist interface for the exchange of gases between atmospheric air and a living cell. Oxygen in the tracheal tube first dissolves in the liquid of the tracheole and then diffuses across the cell membrane into the cytoplasm of an adjacent cell. At the same time, carbon dioxide, produced as a waste product of cellular respiration, diffuses out of the cell and, eventually, out of the body through the tracheal system.

Each tracheal tube develops as an invagination of the ectoderm during embryonic development. To prevent its collapse under pressure, a thin, reinforcing "wire" of cuticle ( the taenidia) winds spirally through the membranous wall. This design (similar in structure to a heater hose on an automobile or an exhaust duct on a clothes dryer) gives tracheal tubes the ability to flex and stretch without developing kinks that might restrict air flow.

The absence of taenidia in certain parts of the tracheal system allows the formation of collapsible air sacs, balloon-like structures that may store a reserve of air. In dry terrestrial environments, this temporary air supply allows an insect to conserve water by closing its spiracles during periods of high evaporative stress. Aquatic insects consume the stored air while under water or use it to regulate buoyancy. During a molt, air sacs fill and enlarge as the insect breaks free of the old exoskeleton and expands a new one. Between molts, the air sacs provide room for new growth-shrinking in volume as they are compressed by expansion of internal organs.

Small insects rely almost exclusively on passive diffusion and physical activity for the movement of gases within the tracheal system. However, larger insects may require active ventilation of the tracheal system (especially when active or under heat stress). They accomplish this by opening some spiracles and closing others while using abdominal muscles to alternately expand and contract body volume. Although these pulsating movements flush air from one end of the body to the other through the longitudinal tracheal trunks, diffusion is still important for distributing oxygen to individual cells through the network of smaller tracheal tubes. In fact, the rate of gas diffusion is regarded as one of the main limiting factors (along with weight of the exoskeleton) that limits the size of insects. Periods in Earth's ancient history, however, such as the Carboniferous, featured much higher oxygen levels (up to 35%) that allowed larger insects, such as meganeura, along with arachnids, to evolve.

Insects were once believed to exchange gases with the environment continuously by the simple diffusion of gases into the tracheal system. More recently, large variation in insect ventilatory patterns have been documented, suggesting that insect respiration is highly variable. Some small insects do demonstrate continuous respiration and may lack muscular control of the spiracles. Others, however, utilize muscular contraction of the abdomen along with coordinated spiracle contraction and relaxation to generate cyclical gas exchange patterns and to reduce water loss into the atmosphere. The most extreme form of these patterns is termed discontinuous gas exchange cycles (DGC). Recent modeling has described the mechanism of air transport in cyclic gas exchange computationally and analytically.

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Respiratory system of insects - Wikipedia

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An insect's respiratory system is the system with which it introduces respiratory gases to its interior and performs gas exchange. Air enters the respiratory systems of insects through a series of external openings called spiracles. These external openings, which act as muscular valves in some insects, lead to the internal respiratory system, a densely networked array of tubes called tracheae.

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Abstract

In the vast majority of insects respiration takes place by means of internal air-tubes known as tracheae These ramify through the organs of the body and its appendages, the finest branches being termed tracheoles. The air generally enters the tracheae through paired, usually lateral, openings termed spiracles, which are segmentally arranged along the thorax and abdomen. More rarely the spiracles are closed or wanting, respiration in such cases being cutaneous. In the immature stages of many aquatic insects special respiratory organs known as gills or branchiae are present, and these may or may not co-exist with open spiracles. The respiratory organs of insects are always derived from ectoderm: the tracheae are developed from solid ingrowths or tubular invaginations of that layer and the gills arise as hollow outgrowths. Histologically, both are composed of a layer of cuticle, the epidermis and usually a basement membrane, all directly continuous with similar layers forming the general body-wall. All or most of the cuticular lining of the tracheo-spiracular system is usually shed at ecdysis. A tracheal system is absent in most Collembola, some Protura and some endoparasitic Hymenopteran and Dipteran larvae.

Keywords
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Authors and Affiliations

Imperial College, University of London, UK

O. W. Richards M.A., D.Sc., F.R.S. (Emeritus Professor of Zoology and Applied Entomology) & R. G. Davies M.Sc. (Reader in Entomology)

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© 1977 O. W. Richards and R. G. Davies

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Richards, O.W., Davies, R.G. (1977). The Respiratory System. In: IMMS' General Textbook of Entomology. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-6514-3_13

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In the vast majority of insects respiration takes place by means of internal air-tubes known as tracheae These ramify through the organs of the body and its appendages, the finest branches being termed tracheoles. The air generally enters the tracheae through paired,...

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Landry Smith- Reproductive system of a human.

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Landry Smith- Reproductive system of a human.

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This is the reproductive system of a human.

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This is the reproductive system of a Tennessee ground bettle 

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Landry Smith- Reproductive system of a Tennessee ground beetle. 

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Landry Smith- Reproductive system of a Tennessee ground beetle. 

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Through compound eyes: A closer look at mountain pine beetle

The relationship between mountain pine beetle and their host pine trees has been evolving for hundreds of years. The anatomy of the beetle reflects this relationship with adaptations designed specifically for penetrating the bark and phloem of the host tree.

In general, bark beetles have a hard exoskeleton, a three-region body (head, thorax, and abdomen), two compound eyes, three pairs of jointed legs, and two antennae. The legs and wings are attached to the thorax. The front pair of hardened wings forms the "elytra" which protect the hind wings. Mountain pine beetle are small, dull (not shiny), cylindrical, and have elbowed, club-like antennae. The following is a detailed description of mountain pine beetle anatomy.

What's in a name?

They are over 300 000 known beetle species on the planet. They make up over 40% of all known species of insects! To keep track of all the organisms on earth, scientists have developed a classification system where each is given a Latin name that tells us something about the species. The Latin name for mountain pine beetle is Dendroctonus ponderosae Hopkins. "Dendroctonus" means "tree-killer, and "ponderosae" refers to "pine tree." When a non-italicized name appears after the Latin name (like Hopkins) it usually refers to the person who discovered and named the species.

Many Latin names in the classification system describe anatomical features that separate one group of animals from another. Mountain pine beetle is a part of these larger groups in the classification system, and their names provide information about their bodies:

Kingdom: Animalia, meaning all living or extinct animals
Phylum: Arthropoda, meaning "jointed limbs"
Class: Insecta - meaning "incised." This refers to the fact that insects generally have a sharp division between the head and thorax and between the thorax and abdomen.
Order: Coleoptera - includes all beetles - and means "sheath wings" - referring to the hardened forewings or "elytra" that cover the membranous - see through - hind wings

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The exoskeleton

Beetles don't have bones and an internal skeleton like we do. They have an exoskeleton that is like a large shell. It protects them and gives them shape. Tiny hairs called "setae" on the outside of the exoskeleton help improve the beetle's perception of touch and sound.

Antennae
Each mountain pine beetle has a set of antennae on its head. Antennae are very important to beetles, as they provide constant information about touch, smell and taste. Beetles use taste and smell receptors on their antennae to locate food and also to identify pheromones.

When beetles walk, a foreleg and hind leg on one side and a middle leg on the other are always touching the ground. This creates a "tripod" on which the beetle balances, and on the next step the beetle alternates to the other three legs to form a new tripod. Walking from tripod to tripod is called "hexapody."

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The relationship between mountain pine beetles and their host pine trees has been evolving for hundreds of years. The anatomy of the beetle reflects this relationship with adaptations designed specifically for penetrating the bark and phloem of the host tree.

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Do you know when you're looking at an insect? All insects have six legs, three body segments, antennae, and an exoskeleton. Insects don't have bones. Instead, they have hard shells called exoskeletons. Like a little suit of armor, an exoskeleton protects the insect's body and also keeps it from drying out. Although people call any crawling critter with an exoskeleton a "bug", the "true bugs" are insects that have special mouth parts for piercing and sucking. And, spiders are not bugs or even insects. They're built differently with only two main body parts and eight legs instead of six.

If you think you have a wild time growing up, take a look at an insect's life. Most insects go through at least four stages of growth - egg (little round thing), larva (a bit like a worm), pupa (insect in a cocoon), and adult. It's a long road to maturity for an insect.

Everyone's buzzing about the "Insects" episode. Don't miss it.

The Big Ideas

Insects have their skeletons on the outside of their body.

Many insects grow in stages.

Did You Know That?

The world's insects weigh more than all the people and land animals combined?

Insects consume about 10% of the world's human food supply every year?

African Goliath beetles can grow up to 15 centimeters (6 inches) long?

Books of Science!

"Insects" by John Bonnett Wexo. Published by Creative Education, 1989.

"Eyewitness: Juniors Amazing Insects" by Laurence Mound. Published by Alfred A. Knopf, 1993.

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Bill Nye's not here to bug you - he just wants to tell you about insects.

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Johnson Pest Control - Pest Control & Extermination Services

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Actual Size: 1.5 to 25 mm

Characteristics: Dark black or brown, slightly flat and elongated

Legs: 6

Antennae: Yes

Wings: 2 pairs, but unable to fly

Habitat: Live and breed in the soil, often under rocks, logs, leaves, and more.
Habits:

Sometimes confused with cockroaches as they are both dark and shiny.

When exposed, ground beetles move quickly to find shelter but rarely fly.

Ground beetles are short-lived indoors and do not reproduce inside structures.

Ground Beetles in Eastern Tennessee

Ground beetles make up one of the largest groups of beetles in North America, with more than 2600 species. Most ground beetles are shiny, black or brown and iridescent, and are sometimes confused with cockroaches. Both are dark in color and move quickly, however, ground beetles are harmless, while cockroaches may create larger issues. They are very common outdoor insects that occasionally become pests by wandering into houses and buildings by mistake.

Ground Beetle Habitat

Ground beetles are commonly found outdoors under objects such as wood, logs, rock, and other debris on the ground. During the summer, in many parts of the country, ground beetles appear in tremendous numbers. They feed mostly at night and are attracted to porch lights and other exterior lights. Ground beetles can become an annoyance by crawling into homes and buildings through small cracks or openings, or through open doorways and windows. Once inside, they can be found in hidden, damp areas in the basement or under boxes or other objects on the floor.

Ground Beetle Behaviors, Threats, or Dangers

Ground beetles do not damage household structures or furniture and are harmless to people and pets. When exposed, ground beetles move quickly to find shelter but rarely fly. Outdoors, they are actually considered beneficial because they feed on insect larvae. However, during summer, ground beetle infestations inside a home or commercial building can be overwhelming for any property owner. Although certain species have been known to release odorous secretions when threatened, none will bite or attack humans.

If you are dealing with a ground beetle infestation, always contact your local beetle exterminators.

Related pests

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Ground Beetle Identification, Habits & Behavior | Johnson Pest Control

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Get more information about the Ground Beetle in our pest library including Johnson Pest Control's beetle control methods. Learn more here!

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doi: 10.1016/j.asd.2022.101217.

Affiliations

¹ Center for Reproductive Evolution, Department of Biology, Syracuse University, Syracuse, NY, USA. Electronic address: rgomez02@syr.edu.

² Department of Life Sciences, University of Siena, Italy. Electronic address: david.mercati@unisi.it.

³ Department of Life Sciences, University of Siena, Italy. Electronic address: pietro.lupetti@unisi.it.

⁴ Department of Life Sciences, University of Siena, Italy. Electronic address: paolo.fanciulli@unisi.it.

⁵ Department of Life Sciences, University of Siena, Italy. Electronic address: romano.dallai@unisi.it.

doi: 10.1016/j.asd.2022.101217.

Affiliations

¹ Center for Reproductive Evolution, Department of Biology, Syracuse University, Syracuse, NY, USA. Electronic address: rgomez02@syr.edu.

² Department of Life Sciences, University of Siena, Italy. Electronic address: david.mercati@unisi.it.

³ Department of Life Sciences, University of Siena, Italy. Electronic address: pietro.lupetti@unisi.it.

⁴ Department of Life Sciences, University of Siena, Italy. Electronic address: paolo.fanciulli@unisi.it.

⁵ Department of Life Sciences, University of Siena, Italy. Electronic address: romano.dallai@unisi.it.

Abstract

Relatively few studies have focused on evolutionary losses of sexually selected male traits. We use light and electron microscopy to study the male and female reproductive anatomy of Apotomus ground beetles (Coleoptera, Carabidae), a lineage that we reconstruct as likely having lost sperm conjugation, a putative sexually selected trait. We pay particular attention to the structure of the testes and spermatheca. Both of these organs share a strikingly similar shape-consisting of long blind canals arranged into several concentric overlapping rings measuring approximately 18 mm and 19.5 mm in total length, respectively. The similarity of these structures suggests a positive evolutionary correlation between female and male genital organs. Males are characterized by unifollicular testes with numerous germ cysts, which contain 64 sperm cells each, and we record a novel occurrence of sperm cyst "looping", a spermatogenic innovation previously only known from some fruit fly and Tenebrionid beetle sperm. The sperm are very long (about 2.7 mm) and include an extraordinarily long helicoidal acrosome, a short nucleus, and a long flagellum. These findings confirm the structural peculiarity of sperm, testis, and female reproductive tract (FRT) of Apotomus species relative to other ground beetles, which could possibly be the result of shifts in sexual selection.

Keywords: Carabidae; Ejaculate-female interactions; Evolution; Postcopulatory sexual selection; Sperm morphology.

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Morphology of male and female reproductive systems in the ground beetle Apotomus and the peculiar sperm ultrastructure of A. rufus (P. Rossi, 1790) (Coleoptera, Carabidae) - PubMed

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Relatively few studies have focused on evolutionary losses of sexually selected male traits. We use light and electron microscopy to study the male and female reproductive anatomy of Apotomus ground beetles (Coleoptera, Carabidae), a lineage that we reconstruct as likely having lost sperm conjugatio ...

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Ground beetle genitals could get strange, but don’t | Science News

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A new look at the genetics of sex organs finds underpinnings of conflicts over genital size.

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Feeding Mechanisms of Certain Ground Beetles (Coleoptera: Carabidae) on JSTOR

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Trevor G. Forsythe, Feeding Mechanisms of Certain Ground Beetles (Coleoptera: Carabidae), The Coleopterists Bulletin, Vol. 36, No. 1 (Mar., 1982), pp. 26-73