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The dermis is where all the action happens! This layer contains blood vessels, nerve endings, hair follicles, and various glands. It's divided into two regions: the papillary region (upper) and reticular region (lower). 🌟

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The papillary region (or papillary layer) is the outermost layer of the dermis, located directly beneath the epidermis:

The papillary layer connects the dermis to the epidermis.

It contains dermal papillae, which are membranes of ridges and grooves that attach to the epidermis.

These dermal papillae may contain looped capillaries that nourish the epidermis or tactile corpuscles, which are nerve endings sensitive to touch and pressure.

The papillary layer comprises about 10–20% of the dermis and has loosely arranged collagen and elastin fibers, making it less dense than the deeper reticular layer.

The top of the papillary layer, where it meets the epidermis, is called the dermal-epidermal junction

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The reticular region (or reticular layer) is the deeper and denser layer of the dermis, located beneath the papillary layer.

The reticular layer supplies the skin with all of its oxygen and nutrients through a rich network of blood vessels and lymphatic channels.

It is composed mainly of dense connective tissue, including collagen and elastin fibers, which provide the skin with strength, structure, and elasticity.

This layer contains fat cells, blood vessels, sweat (sudoriferous) glands, sebaceous (oil) glands, hair follicles, and arrector pili muscles.

Damage to the collagen and elastin fibers in the reticular layer is a primary cause of sagging, wrinkles, and loss of skin elasticity as part of intrinsic aging.

The reticular layer is thicker than the papillary layer and forms the bulk of the dermis, supporting the skin’s overall structure and resilience

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Also called the subcutaneous layer, the hypodermis is our deepest skin layer. It's primarily made of adipose (fat) tissue and helps regulate body temperature and provide cushioning. Think of it as your body's built-in insulation! 🏠

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The epidermis is our skin's outermost layer and first line of defense! It contains 4-5 layers: stratum corneum, stratum lucidum (only in thick skin), stratum granulosum, stratum spinosum, and stratum germinativum (basale). Let's explore each one! 🔍

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The stratum corneum is the outermost layer of the epidermis, serving as the skin’s primary barrier to the external environment. It consists of 15–30 layers of dead, flattened cells called corneocytes, which are filled with keratin and embedded in a lipid matrix made of ceramides, cholesterol, and fatty acids. This structure provides protection against infection, dehydration, chemicals, and mechanical stress. It contains the acid mantel, a protective barrier made up of sebum, lipids, sweat, and water. It also contains the hydrolipidic film which is essential for protecting the skin from infections, dehydration, pollution, and premature aging by acting as a physical, chemical, and biological barrier on the skin’s surface.

Its “bricks and mortar” organization-corneocytes as bricks, lipids as mortar-ensures both strength and selective permeability, helping to keep moisture in and harmful substances out!

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This is the clear, translucent layer under the stratum corneum. It consists of small cells through which light can pass and is found only on the palms of the hands, soles of the feet, and digits. This layer forms our unique fingerprints and footprints.

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These proteins are the stars of the dermis! Collagen provides strength and support, while elastin gives our skin its amazing ability to stretch and bounce back. As we age, we produce less of both - that's why wrinkles form!

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The hypodermis serves many important functions:
- Energy storage
- Temperature regulation
- Cushioning for organs
- Attachment point for muscles and bones

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Anatomy and Physiology of the Skin, Animation

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Recent research has discovered that skin cells actually have the same types of receptors that taste bitter flavors in your mouth. These receptors, called TAS2Rs, are found in keratinocytes (the main cells in the outer layer of skin). When these skin cells "sense" bitter compounds, they can trigger defense mechanisms-like ramping up the skin’s immune response or helping wounds heal faster. 🦠

https://phys.org/news/2025-02-bitter-receptors-skin-cells-function.html

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The stratum granulosum, also known as the granular layer, and is composed of cells that look like granules and are filled with keratin. In this layer, the production of keratin and intercellular lipids takes place. As the cells become keratinized, they move to the surface to replace cells shed from the stratum corneum. Natural moisturizing substances such as triglycerides, ceramides, waxes, fatty acids, and other intracellular lipids are produced here and are excreted from the cells to form the skin’s waterproof barrier function, helping to hydrate the lipid layer and prevent water loss.

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These amazing cells make up about 90% of the epidermis! They start at the bottom layer and gradually move up, becoming flatter and eventually flaking off. This process takes about 28 days!✨

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The stratum spinosum, also known as the spiny layer, is a sub-layer of the epidermis located just above the basal layer (stratum germinativum) and beneath the stratum granulosum. This layer is where the process that causes skin cells to shed begins. It is often classified as part of the stratum germinativum and is recognized for its "spiny" appearance due to the presence of desmosomes-structures that hold the cells together and provide strength to the skin

This layer also contains Langerhans cells, a type of immune cell. These cells are part of the dendritic cell/macrophage family and play a crucial role in antigen presentation and immune surveillance in the skin.

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These amazing structures are actually modified epidermis! Each hair follicle has its own tiny muscle (arrector pili) that makes your hair stand up when you're cold or scared. 👻

Scar tissue lacks hair as well as sweat glands!

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Located in the stratum basale, melanocytes produce melanin, which gives our skin its color and protects us from harmful UV rays. Did you know that all humans have roughly the same number of melanocytes? The difference in skin color comes from how active these cells are!

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pheomelanin - It is yellow to red and is formed by a combination of DOPA and cysteine

eumelanin - typically brown to black and is built from DOPA (dihydroxyphenylalanine)

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Oil Glands (Sebaceous Glands):

Also known as sebaceous glands, these are connected to hair follicles.

They consist of small sacs with ducts that open into the follicles.

Sebaceous glands secrete sebum, an oily substance that lubricates the skin and hair, helping to keep them soft and preventing water loss from the skin’s surface.

Sebaceous glands that keep skin moisturized! 💦

Sweat Glands (Sudoriferous Glands):

Sweat glands are responsible for excreting perspiration (sweat) from the body.

They help regulate body temperature and eliminate waste products through the skin.

There are two main types: eccrine glands (found all over the body and important for temperature regulation) and apocrine glands (found mainly in areas like the underarms and groin, associated with scent).

Your skin has two main types of sweat glands:
- Eccrine: All over your body, helping control temperature
- Apocrine: Found in armpits and groin, activated during puberty

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This is also known as the basal cell layer or stratum germinativum, is the deepest, live layer of the epidermis. It is responsible for producing new epidermal skin cells and is the layer where skin growth begins. This layer contains special pigment-producing cells called melanocytes.

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It acts as a cushion to protect underlying structures, provides insulation to help regulate body temperature, and serves as a major site for energy storage in the form of fat. Adipose tissue is a type of loose connective tissue primarily composed of fat cells (adipocytes).

This tissue is sometimes referred to as the "fatty tissue" and is critical for both protection and energy storage.

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Large protein molecules and water binding substances found between fibers

Plays a crucial role in skin health and hydration

They are also thought to contribute to skin's elasticity, firmness, and may play a role in preventing wrinkleS

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The average body temperature should be at 98.6 degrees Fahrenheit

Skin renews itself every 28 days

Sweat only detoxifies the body by less than 1%

Hair and nails are 90% hard keratin

The skin is 50-70% water

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Transcellular: going in and out of cells

Intercellular: between the cells

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Fibroblasts are the main cells responsible for producing the extracellular matrix, a network of proteins and other molecules that supports the epidermis and provides structure to the skin. They also play a vital role in wound healing by migrating to the injury site and releasing ECM components to facilitate tissue repair.

Fibroblasts are found in both the papillary dermis (upper layer) and the reticular dermis (lower, thicker layer).

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Desmosomes are intercellular junctions that provide strong adhesion between cells, particularly in epithelial tissues like the skin.

They consist of transmembrane proteins that connect to intracellular structures, specifically the intermediate filament network.

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Purpose for learning about the skin:

To understand the complexity of the skin

To understand the aging process and factors that affect the skin’s health and appearance

To know how to maintain and treat the skin

Primary focus with skin treatments: preserve, protect, and nourish the skin

Only working on the Epidermis!

Other names for estheticians: technician, skin therapist/specialist

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amino acids: make up proteins >>>Proteins are basic building blocks for bodies tissues