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Squamous Cells functions as a barrier against irritation and injury

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The male urethra and the ducts of some glands.
Secretes and protects

https://courses.lumenlearning.com/boundless-ap/chapter/epithelial-tissue/

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Characteristics of Epithelial Tissue

The human body consists of four types of tissue: epithelial, connective, muscular, and nervous. Epithelial tissue covers the body, lines all cavities, and composes the glands.

Learning Objectives

Describe the primary functions and characteristics of epithelial tissue

Key Takeaways

Key Points

Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another. Epithelial layers are avascular, but innervated.

Epithelial cells have two surfaces that differ in both structure and function.

Glands, such as exocrine and endocrine, are composed of epithelial tissue and classified based on how their secretions are released.

Key Terms

epithelium: A membranous tissue composed of one or more layers of cells that form the covering of most internal and external surfaces of the body and its organs.

avascular: Lacking blood vessels.

vascular: Containing blood vessels.

Functions of the Epithelium

Epithelia tissue forms boundaries between different environments, and nearly all substances must pass through the epithelium. In its role as an interface tissue, epithelium accomplishes many functions, including:

1. Protection for the underlying tissues from radiation, desiccation, toxins, and physical trauma.

2. Absorption of substances in the digestive tract lining with distinct modifications.

3. Regulation and excretion of chemicals between the underlying tissues and the body cavity.

4. The secretion of hormones into the blood vascular system. The secretion of sweat, mucus, enzymes, and other products that are delivered by ducts come from the glandular epithelium.

5. The detection of sensation.

Characteristics of Epithelial Layers

Epithelial tissue is composed of cells laid out in sheets with strong cell-to-cell attachments. These protein connections hold the cells together to form a tightly connected layer that is avascular but innervated in nature.

The epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. One side of the epithelial cell is oriented towards the surface of the tissue, body cavity, or external environment and the other surface is joined to a basement membrane. The basement layer is non-cellular in nature and helps to cement the epithelial tissue to the underlying structures.

Types of Epithelial Tissue

Epithelial tissues are identified by both the number of layers and the shape of the cells in the upper layers. There are eight basic types of epithelium: six of them are identified based on both the number of cells and their shape; two of them are named by the type of cell (squamous) found in them. Epithelial tissue is classified based on the number of cells, the shape of those cells, and the types of those cells.

Types of Epithelial Tissue

Epithelial tissue is classified by cell shape and the number of cell layers.

Learning Objectives

Classify epithelial tissue by cell shape and layers

Key Takeaways

Key Points

There are three principal cell shapes associated with epithelial cells: squamous epithelium, cuboidal epithelium, and columnar epithelium.

There are three ways of describing the layering of epithelium: simple, stratified, and pseudostratified.

Pseudostratified epithelium possesses fine hair-like extensions called cilia and unicellular glands called goblet cells that secrete mucus. This epithelium is described as ciliated pseudostratified epithelium.

Stratified epithelium differs from simple epithelium in that it is multilayered. It is therefore found where body linings have to withstand mechanical or chemical insult.

In keratinized epithelia, the most apical layers (exterior) of cells are dead and and contain a tough, resistant protein called keratin. An example of this is found in mammalian skin that makes the epithelium waterproof.

Transitional epithelia are found in tissues such as the urinary bladder where there is a change in the shape of the cell due to stretching.

Key Terms

simple columnar: A columnar epithelium that is uni-layered.

pseudostratified epithelium: A type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia.

squamous: Flattened and scale-like.

cuboidal: Resembling a cube.

Keratinized: To produce or become like keratin.

columnar: Having the shape of a column.

Most epithelial tissue is described with two names. The first name describes the number of cell layers present and the second describes the shape of the cells. For example, simple squamous epithelial tissue describes a single layer of cells that are flat and scale-like in shape.

Simple Epithelia

Simple epithelium consists of a single layer of cells. They are typically where absorption, secretion and filtration occur. The thinness of the epithelial barrier facilitates these processes.

Simple epithelial tissues are generally classified by the shape of their cells. The four major classes of simple epithelium are: 1) simple squamous; 2) simple cuboidal; 3) simple columnar; and 4) pseudostratified.

Simple Squamous

Simple squamous epithelium cells are flat in shape and arranged in a single layer. This single layer is thin enough to form a membrane that compounds can move through via passive diffusion. This epithelial type is found in the walls of capillaries, linings of the pericardium, and the linings of the alveoli of the lungs.

Simple Cuboidal

Simple cuboidal epithelium consists of a single layer cells that are as tall as they are wide. The important functions of the simple cuboidal epithelium are secretion and absorption. This epithelial type is found in the small collecting ducts of the kidneys, pancreas, and salivary glands.

Simple Columnar

Simple columnar epithelium is a single row of tall, closely packed cells, aligned in a row. These cells are found in areas with high secretory function (such as the wall of the stomach), or absorptive areas (as in small intestine ). They possess cellular extensions (e.g., microvilli in the small intestine, or the cilia found almost exclusively in the female reproductive tract).

Pseudostratified

These are simple columnar epithelial cells whose nuclei appear at different heights, giving the misleading (hence pseudo) impression that the epithelium is stratified when the cells are viewed in cross section.

Pseudostratified epithelium can also possess fine hair-like extensions of their apical (luminal) membrane called cilia. In this case, the epithelium is described as ciliated pseudostratified epithelium. Ciliated epithelium is found in the airways (nose, bronchi), but is also found in the uterus and fallopian tubes of females, where the cilia propel the ovum to the uterus.

Stratified Epithelium

Stratified epithelium differs from simple epithelium by being multilayered. It is therefore found where body linings have to withstand mechanical or chemical insults.

Stratified epithelia are more durable and protection is one their major functions. Since stratified epithelium consists of two or more layers, the basal cells divide and push towards the apex, and in the process flatten the apical cells.

Stratified epithelia can be columnar, cuboidal, or squamous type. However, it can also have the following specializations:

Keratinized Epithelia

In keratinized epithelia, the most apical layers (exterior) of cells are dead and lose their nucleus and cytoplasm. They contain a tough, resistant protein called keratin. This specialization makes the epithelium waterproof, and it is abundant in mammalian skin. The lining of the esophagus is an example of a non-keratinized or moist stratified epithelium.

Transitional Epithelia

Transitional epithelia are found in tissues that stretch and it can appear to be stratified cuboidal when the tissue is not stretched, or stratified squamous when the organ is distended and the tissue stretches. It is sometimes called the urothelium since it is almost exclusively found in the bladder, ureters, and urethra.

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The human body consists of four types of tissue: epithelial, connective, muscular, and nervous. Epithelial tissue covers the body, lines all cavities, and composes the glands. Describe the primary functions and characteristics of epithelial tissue Key Points Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another.

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Secretion, Excretion, and Absorption

https://byjus.com/questions/what-is-the-function-of-the-simple-columnar-epithelium/#:~:text=The%20simple%20columnar%20epithelium%20is,the%20beating%20of%20their%20cilia.

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What is the function of the simple columnar epithelium? - Biology Q&A

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What is the function of the simple columnar epithelium? - Get the answer to this question and access a vast question bank that is tailored for students.

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The primary function of squamous epithelia is to facilitate the diffusion of gasses and small molecules

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These are common for skin cancer that forms in the squamous cells.

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These are common for skin cancer that forms in the squamous cells.

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https://www.mayoclinic.org/diseases-conditions/squamous-cell-carcinoma/symptoms-causes/syc-20352480

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Overview

Squamous cell carcinoma of the skin is a common form of skin cancer that develops in the squamous cells that make up the middle and outer layers of the skin.

Squamous cell carcinoma of the skin is usually not life-threatening, though it can be aggressive. Untreated, squamous cell carcinoma of the skin can grow large or spread to other parts of your body, causing serious complications.

Most squamous cell carcinomas of the skin result from prolonged exposure to ultraviolet (UV) radiation, either from sunlight or from tanning beds or lamps. Avoiding UV light helps reduce your risk of squamous cell carcinoma of the skin and other forms of skin cancer.

Squamous cells are found in many places in your body, and squamous cell carcinoma can occur anywhere squamous cells are found. Squamous cell carcinoma of the skin refers to cancer that forms in the squamous cells found in the skin.

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Symptoms

Squamous cell carcinoma of the skin most often occurs on sun-exposed skin, such as your scalp, the backs of your hands, your ears or your lips. But it can occur anywhere on your body, including inside your mouth, the bottoms of your feet and on your genitals.

Signs and symptoms of squamous cell carcinoma of the skin include:

A firm, red nodule

A flat sore with a scaly crust

A new sore or raised area on an old scar or ulcer

A rough, scaly patch on your lip that may evolve to an open sore

A red sore or rough patch inside your mouth

A red, raised patch or wartlike sore on or in the anus or on your genitals

When to see a doctor

Make an appointment with your doctor if you have a sore or scab that doesn't heal in about two months or a flat patch of scaly skin that won't go away.

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Causes

Squamous cell carcinoma of the skin occurs when the flat, thin squamous cells in the middle and outer layers of your skin develop changes (mutations) in their DNA. A cell's DNA contains the instructions that tell a cell what to do. The mutations tell the squamous cells to grow out of control and to continue living when normal cells would die.

Most of the DNA mutations in skin cells are caused by ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds.

But sun exposure doesn't explain skin cancers that develop on skin not ordinarily exposed to sunlight. This indicates that other factors may contribute to your risk of skin cancer, such as having a condition that weakens your immune system.

Risk factors

Factors that may increase your risk of squamous cell carcinoma of the skin include:

Fair skin. Anyone, regardless of skin color, can get squamous cell carcinoma of the skin. However, having less pigment (melanin) in your skin provides less protection from damaging UV radiation.

If you have blond or red hair and light-colored eyes and you freckle or sunburn easily, you're much more likely to develop skin cancer, including squamous cell carcinoma, than is a person with darker skin.

Excessive sun exposure. Being exposed to UV light from the sun increases your risk of squamous cell carcinoma of the skin. Spending lots of time in the sun - particularly if you don't cover your skin with clothing or sunblock - increases your risk of squamous cell carcinoma of the skin even more.

Use of tanning beds. People who use indoor tanning beds have an increased risk of squamous cell carcinoma of the skin.

A history of sunburns. Having had one or more blistering sunburns as a child or teenager increases your risk of developing squamous cell carcinoma of the skin as an adult. Sunburns in adulthood also are a risk factor.

A personal history of precancerous skin lesions. Having a precancerous skin lesion, such as actinic keratosis or Bowen's disease, increases your risk of squamous cell carcinoma of the skin.

A personal history of skin cancer. If you've had squamous cell carcinoma of the skin once, you're much more likely to develop it again.

Weakened immune system. People with weakened immune systems have an increased risk of skin cancer. This includes people who have leukemia or lymphoma and those who take medications that suppress the immune system, such as those who have undergone organ transplants.

Rare genetic disorder. People with xeroderma pigmentosum, which causes an extreme sensitivity to sunlight, have a greatly increased risk of developing skin cancer.

Complications

Untreated squamous cell carcinoma of the skin can destroy nearby healthy tissue, spread to the lymph nodes or other organs, and may be fatal, although this is uncommon.

The risk of aggressive squamous cell carcinoma of the skin may be increased in cases where the cancer:

Is particularly large or deep

Involves the mucous membranes, such as the lips

Occurs in a person with a weakened immune system, such as someone who takes anti-rejection medications after an organ transplant or someone who has chronic leukemia

Prevention

Most squamous cell carcinomas of the skin can be prevented. To protect yourself:

Avoid the sun during the middle of the day. For many people in North America, the sun's rays are strongest between about 10 a.m. and 3 p.m. Schedule outdoor activities for other times of the day, even during winter or when the sky is cloudy.

Wear sunscreen year-round. Use a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy days. Apply sunscreen generously, and reapply every two hours - or more often if you're swimming or perspiring.

Wear protective clothing. Cover your skin with dark, tightly woven clothing that covers your arms and legs, and a broad-brimmed hat, which provides more protection than does a baseball cap or visor.

Some companies also sell protective clothing. A dermatologist can recommend an appropriate brand. Don't forget sunglasses. Look for those that block both types of UV radiation - UVA and UVB rays.

Avoid tanning beds. Tanning beds emit UV rays and can increase your risk of skin cancer.

Check your skin regularly and report changes to your doctor. Examine your skin often for new skin growths or changes in existing moles, freckles, bumps and birthmarks. With the help of mirrors, check your face, neck, ears and scalp.

Examine your chest and trunk and the tops and undersides of your arms and hands. Examine both the front and back of your legs and your feet, including the soles and the spaces between your toes. Also check your genital area and between your buttocks.

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Squamous cell carcinoma of the skin - Symptoms and causes

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Squamous cell carcinoma of the skin is a common form of skin cancer that develops in the squamous cells that make up the middle and outer layers of the skin. Squamous cell carcinoma of the skin is usually not life-threatening, though it can be aggressive.

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Outermost surface of the skin

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Goblet cells, those lining the pharynx, sex organs, respiratory tract, fallopian tubes, etc.

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Large, polygonal cells that have small round nuclei

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These turn into squamous cell skin cancer when they grow out of control, leading to skin cancer.

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These turn into squamous cell skin cancer when they grow out of control, leading to skin cancer.

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https://www.cancer.org/cancer/basal-and-squamous-cell-skin-cancer/about/what-is-basal-and-squamous-cell.html

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Where do skin cancers start?

Most skin cancers start in the top layer of skin, called the epidermis. There are 3 main types of cells in this layer:

Squamous cells: These are flat cells in the upper (outer) part of the epidermis, which are constantly shed as new ones form. When these cells grow out of control, they can develop into squamous cell skin cancer (also called squamous cell carcinoma).

Basal cells: These cells are in the lower part of the epidermis, called the basal cell layer. These cells constantly divide to form new cells to replace the squamous cells that wear off the skin's surface. As these cells move up in the epidermis, they get flatter, eventually becoming squamous cells. Skin cancers that start in the basal cell layer are called basal cell skin cancers or basal cell carcinomas.

Melanocytes: These cells make the brown pigment called melanin, which gives the skin its tan or brown color. Melanin acts as the body's natural sunscreen, protecting the deeper layers of the skin from some of the harmful effects of the sun. Melanoma skin cancer starts in these cells.

The epidermis is separated from the deeper layers of skin by the basement membrane. When a skin cancer becomes more advanced, it generally grows through this barrier and into the deeper layers.

Basal cell carcinoma

Basal cell carcinoma (also called basal cell skin cancer) is most common type of skin cancer. About 8 out of 10 skin cancers are basal cell carcinomas (also called basal cell cancers).

These cancers start in the basal cell layer, which is the lower part of the epidermis.

These cancers usually develop on sun-exposed areas, especially the face, head, and neck. They tend to grow slowly. It's very rare for a basal cell cancer to spread to other parts of the body. But if it's left untreated, basal cell cancer can grow into nearby areas and invade the bone or other tissues beneath the skin.

If not removed completely, basal cell carcinoma can come back (recur) in the same place on the skin. People who have had basal cell skin cancers are also more likely to get new ones in other places.

Squamous cell carcinoma

About 2 out of 10 skin cancers are squamous cell carcinomas (also called squamous cell cancers). These cancers start in the flat cells in the upper (outer) part of the epidermis.

These cancers commonly appear on sun-exposed areas of the body such as the face, ears, neck, lips, and backs of the hands. They can also develop in scars or chronic skin sores elsewhere. They sometimes start in actinic keratoses (described below). Less often, they form in the skin of the genital area.

Squamous cell cancers can usually be removed completely (or treated in other ways), although they are more likely than basal cell cancers to grow into deeper layers of skin and spread to other parts of the body.

Pre-cancerous and other skin conditions related to squamous cell carcinoma

Actinic keratosis (solar keratosis)

Actinic keratosis (AK), also known as solar keratosis, is a pre-cancerous skin condition caused by too much exposure to the sun. AKs are usually small (less than 1/4 inch across), rough or scaly spots that may be pink-red or flesh-colored. Usually they start on the face, ears, backs of the hands, and arms of middle-aged or older people with fair skin, although they can occur on other sun-exposed areas. People who have them usually develop more than one.

AKs tend to grow slowly and usually do not cause any symptoms (although some might be itchy or sore). They sometimes go away on their own, but they may come back.

A small percentage of AKs may turn into squamous cell skin cancers. Most AKs do not become cancer, but it can be hard sometimes to tell them apart from true skin cancers, so doctors often recommend treating them. If they are not treated, you and your doctor should check them regularly for changes that might be signs of skin cancer.

Squamous cell carcinoma in situ (Bowen disease)

Squamous cell carcinoma in situ, also called Bowen disease, is the earliest form of squamous cell skin cancer. "In situ" means that the cells of these cancers are still only in the epidermis (the upper layer of the skin) and have not invaded into deeper layers.

Bowen disease appears as reddish patches. Compared with AKs, Bowen disease patches tend to be larger, redder, scalier, and sometimes crusted. Like AK, Bowen disease usually doesn't cause symptoms, although it might be itchy or sore.

Like most other skin cancers (and AKs), these patches most often appear in sun-exposed areas. Bowen disease can also occur in the skin of the anal and genital areas (where it is known as erythroplasia of Queyrat or Bowenoid papulosis). This is often related to sexually transmitted infection with human papillomaviruses (HPVs), the viruses that can also cause genital warts.

Bowen disease can sometimes progress to an invasive squamous cell skin cancer, so doctors usually recommend treating it. People who have these are also at higher risk for other skin cancers, so close follow-up with a doctor is important.

Keratoacanthoma

Keratoacanthomasare dome-shaped tumors that are found on sun-exposed skin. They may start out growing quickly, but their growth usually slows down. Many keratoacanthomas shrink or even go away on their own over time without any treatment. But some continue to grow, and a few may even spread to other parts of the body. They can be hard to tell apart from squamous cell skin cancer, and their growth is often hard to predict, so many skin cancer experts recommend treating them (typically with surgery).

Other types of skin cancer

Melanoma

These cancers develop from melanocytes, the pigment-making cells found in the epidermis. Melanomas are much less common than basal and squamous cell cancers, but they are more likely to grow and spread if left untreated. Melanoma are discussed in Melanoma Skin Cancer.

Less common types of skin cancer

Other types of skin cancer are much less common and are treated differently. These include:

Together, these types account for less than 1% of all skin cancers.

Benign skin tumors

Most skin tumors are benign (not cancerous) and rarely if ever turn into cancers. There are many kinds of benign skin tumors, including:

Most types of moles (see Melanoma Skin Cancer for more about moles)

Seborrheic keratoses: tan, brown, or black raised spots with a waxy texture or occasionally a slightly rough and crumbly surface when they are on the legs (also known as stucco keratosis)

Hemangiomas: benign blood vessel growths, often called strawberry spots

Lipomas: soft tumors made up of fat cells

Warts: rough-surfaced growths caused by some types of human papillomavirus (HPV)

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What Are Basal and Squamous Cell Skin Cancers? | Types of Skin Cancer

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Most skin cancers start in the top layer of skin, called the epidermis. There are 3 main types of cells in this layer: Squamous cells: These are flat cells in the upper (outer) part of the epidermis, which are constantly shed as new ones form.

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A composed of epithelial cells that are column-shaped. The cell comprising the columnar epithelium is taller than it is wide. Its height is approximately four times its width. The nucleus in each cell is elongated and is often found near the base.

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A composed of epithelial cells that are column-shaped. The cell comprising the columnar epithelium is taller than it is wide. Its height is approximately four times its width. The nucleus in each cell is elongated and is often found near the base.

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A composed of epithelial cells that are column-shaped. The
https://www.biologyonline.com/dictionary/columnar-epithelium

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Biology Articles, Tutorials & Dictionary Online

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Definition
noun, plural: columnar epithelia
An epithelial tissue comprised of columnar epithelial cells, with or without cilia, and is involved primarily in secretory, absorptive, or excretory functions
Supplement
The epithelial tissue (also called epithelium) is one of the different types of animal tissues. It is made up of one or more layers of cells closely packed together. It is primarily involved in protecting the underlying structures, secretion, regulation, and absorption. This tissue may be classified histologically according to the cell shape. The different types of epithelia based on the cell shape are: (1) squamous epithelium, (2) columnar epithelium, and (3) cuboidal epithelium.
The columnar epithelium is composed of epithelial cells that are column-shaped. The cell comprising the columnar epithelium is taller than it is wide. Its height is approximately four times its width. The nucleus in each cell is elongated and often found near the base. Some of them may have microvilli at the apical surface. When present, the microvilli increase the surface area (such as during absorption). Cilia may also be present. Ciliated columnar cells aid in the movement of mucus (as seen during mucociliary clearance).
The columnar epithelium may be classified according to the number of layers that make it up. For example, a simple columnar epithelium is one that which is made up of a single layer of columnar epithelial cells. A stratified columnar epithelium is comprised of more than one layer of columnar epithelial cells. A special type of single columnar epithelium is the so-called pseudostratified. Its name is derived from its appearance. It seems it is a stratified type of epithelium but in truth is it is comprised of only one layer of cells. The cells are oriented in a way that they appear to be in multiple layers when in fact there is only one layer of epithelial cells.
Examples of columnar epithelia are Goblet cells, those lining the pharynx, sex organs, respiratory tract, fallopian tubes, etc.
Also called:

columnar epithelial tissue

Last updated on March 1st, 2021

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Definition noun, plural: columnar epithelia An epithelial tissue comprised of columnar epithelial cells, with or without cilia, and is involved primarily in secretory, absorptive, or excretory functions Supplement The epithelial tissue (also called epithelium) is one of the different types of animal tissues. It is made up of one or more layers of cells closely packed together.

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Squamous - thin and flat cells. Usually found on top of skin cells, lining of hollow organs, and respiratory and digestive tracts. 

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Squamous - thin and flat cells. Usually found on top of skin cells, lining of hollow organs, and respiratory and digestive tracts. 

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https://www.cancer.gov/publications/dictionaries/cancer-terms/def/squamous-cell-carcinoma

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NCI's Dictionary of Cancer Terms provides easy-to-understand definitions for words and phrases related to cancer and medicine.