Skin Anatomy and Physiology Advanced Course Course Author—Dr. Patti Farris Dr. Farris is a Nu Skin...
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Transcript of Skin Anatomy and Physiology Advanced Course Course Author—Dr. Patti Farris Dr. Farris is a Nu Skin...
Skin Anatomy and Physiology Advanced Course
Course Author—Dr. Patti Farris• Dr. Farris is a Nu Skin Professional Advisory Board
Member.• She is a clinical assistant professor at Tulane and in
private practice in Metairie, Louisiana. • She has authored twenty-five scientific publications
and is known for her expertise in the treatment of aging skin.
• She has appeared in over 200 health related television segments including appearances on CNN, NBC Weekend, and Regis and Kathie Lee.
• She has been quoted extensively in magazines (e.g., Newsweek, Allure, In Style, and Oprah Magazine).
Did You Know?
Beautiful, healthy skin is determined by the healthy structure and proper function of components within the skin. Find out why in this course.
Objectives
After viewing this course, you should have an understanding of the following:
• In-depth anatomy and physiology of the layers of the skin: hypodermis, dermis, and epidermis.
• How skin health and beauty are determined by the healthy structure and function of the skin.
Previous Curriculum Review
In the Skin Anatomy and Physiology Basics course, you learned the following:
• The six purposes of the skin: protection, thermoregulation, excretion, secretion, sensation, and vitamin synthesis.
• The skin’s different layers: hypodermis, dermis, and epidermis.
• Basic skin anatomy and physiology.
Introduction
Major Layers of the Skin Hypodermis: subcutaneous (just
beneath the skin) fat that functions as insulation and padding for the body.
Dermis: provides structure and support.
Epidermis: functions as a protective shield for the body.
Let’s talk about each of these in greater detail, starting with the hypodermis.
Epidermis
Dermis
Hypodermis
Muscle
Hypodermis(deepest section)
Hypodermis
The hypodermis refers to the fat tissue below the dermis that insulates the body from cold temperatures and provides shock absorption. Fat cells of the hypodermis also store nutrients and energy.
The hypodermis is thickest in the buttocks, palms of the hands, and soles of the feet. As we age, the hypodermis begins to atrophy, contributing to the thinning of aging skin.
Hypodermis
Dermis(between the hypodermis and epidermis)
DermisThe dermis is a fibrous network of tissue that provides structure and resilience to the skin. Dermal thickness varies but is on average 2 mm thick. Major components of the dermis include the following:
• Collagen.• Elastin.• Glycosaminoglycans.• Blood and lymph vessels.• Specialized cells: mast cells and
fibroblasts.
Dermis
Epidermis
Blood vessels
Mast cell
Collagen fiber
Elastin fiber
Fibroblast cell
Dermal - epidermal junction
Glycosaminoglycans
Dermis: Network of Structural Proteins
The major components of the dermis work together as a network, composed of structural proteins, blood and lymph vessels, and specialized cells. This mesh-like network is surrounded by a gel-like substance called the ground substance, composed mostly of glycosaminoglycans.
Dermis
Epidermis
Blood vessels
Mast cell
Collagen fiber
Elastin fiber
Fibroblast cell
Dermal - epidermal junction
Glycosaminoglycans
Dermis: Ground Substance
The major components of the dermis are surrounded by a gel-like material called the ground substance. This ground substance is composed of moisture-binding glycosaminoglycans and plays a critical role in the hydration and moisture levels within the skin.
Dermis
Epidermis
Glycosaminoglycans
Dermis: Collagen
The most common structural component within the dermis is the protein collagen. It forms a mesh-like framework that gives the skin strength and flexibility. The glycosaminoglycans—moisture binding molecules—enable collagen fibers to retain water and provide moisture to the epidermis.
Dermis
Epidermis
Collagen fiber
Dermis: Elastin
Another protein found throughout the dermis is the coil-like protein, elastin, which gives skin the ability to return to its original shape after stretching (elasticity). Dermis
Epidermis
Elastin fiber
Dermis: Fibroblasts
Both collagen and elastin proteins are produced in specialized cells called fibroblasts, located mostly in the upper edge of the dermis bordering the epidermis. Dermis
Epidermis
Fibroblast cell
Dermis: Mast Cells
Intertwined throughout the dermis are blood vessels, lymph vessels, nerves, and mast cells. Mast cells are specialized cells that play an important role in triggering the skin’s inflammatory response to invading microorganisms, allergens, and physical injury.
Dermis
Epidermis
Mast cell
Dermis: Blood Vessels
Blood vessels in the dermis: • Help in thermoregulation
(blood vessels constrict or dilate to conserve or release heat).
• Aid in immune function (healing).
• Provide oxygen and nutrients to the lower layers of the epidermis.
Dermis
Epidermis
Blood vessels
Dermis: Blood Vessels
Blood vessels do not extend into the epidermis. Nourishment that diffuses (seeps) into the epidermis only reaches the very bottom layers. For this reason, the cells in the upper layers of the epidermis are dead (because they do not receive oxygen and nutrients).
Dermis
Epidermis
Blood vessels
Dermis: Epidermal Junction
The junction between the dermis and epidermis is a wave-like border that provides an increased surface area for the exchange of oxygen and nutrients between the two sections.
Dermal - epidermal junction
Dermis: Dermal Papillae
Along this junction are projections called dermal papillae. As one ages, the dermal papillae tend to flatten, decreasing the flow of oxygen and nutrients to the epidermis.
Dermal - epidermal junction
Dermal papillae
Epidermis(outermost layer)
Epidermis
The epidermis consists of anywhere between 50 cell layers (in thin areas) to 100 cell layers (in thick areas) and acts as a protective shield for the body. Skin cells within the epidermis are referred to as keratinocytes. Average epidermal thickness is 0.1 mm (about the thickness of one sheet of paper).
Epidermis: Five Differentiated Layers
The epidermis is composed of five horizontal layers:
1 - Stratum basale 2 - Stratum spinosum3 - Stratum granulosum4 - Stratum lucidum5 - Stratum corneum
1
2
3
4
5
Epidermis: Stratum Basale
Stratum Basale (germinative layer)
• The deepest layer of the epidermis, sitting directly on top of the dermis, is a single layer of cube-shaped cells.
Stratum basale 1
2
3
4
5
Stratum Basale (continued)
New epidermal skin cells, called keratinocytes, are formed in this layer through cell division to replace those shed continuously from the upper layers of the epidermis. This regenerative process is called skin cell renewal. As we age, the rate of cell renewal decreases.
Basal cells divide to
replace cells lost at the
surface
1
2
3
4
5
Stratum Basale (continued)
Melanocytes, found in the stratum basale, are responsible for the production of skin pigment (melanin). They transfer the melanin to nearby keratinocytes that will eventually migrate to the surface of the skin. Melanin is photoprotective: it helps protect the skin against ultraviolet radiation (sun exposure). Stratum
basale
Melanocyte
1
Epidermis: Stratum Spinosum
Stratum Spinosum (prickle-cell layer)
• The stratum spinosum is composed of 8–10 layers of polygonal (many-sided) keratinocytes.
• In this layer, keratinocytes are beginning to become somewhat flattened.
Stratum spinosum
2
3
Epidermis: Stratum GranulosumStratum Granulosum (granular layer)
• Composed of 3–5 layers of flattened keratinocytes.
• In this layer, keratin—a tough, fibrous protein that gives skin its protective properties—begins to form inside the keratinocytes.
• Cells in this layer are too far from the dermis to receive nutrients through diffusion, so they begin to die.
Stratum granulosum
Keratin
Epidermis: Stratum Lucidum
Stratum Lucidum (clear layer)
• The stratum lucidum is present only in the fingertips, palms, and soles of the feet.
• It is 3–5 layers of extremely flattened cells.
Stratum lucidum
4
Epidermis: Stratum Corneum
Stratum Corneum (horny layer) • The top, outermost layer of
the epidermis, the stratum corneum, is 25–30 layers of flattened, dead keratinocytes.
• The stratum corneum layer is the real protective layer of the skin.
Stratum corneum
5
Stratum Corneum (continued)
Keratinocytes in the stratum corneum are continuously shed by friction and replaced by the cells formed in the deeper sections of the epidermis (stratum basale). The epidermis totally renews itself approximately every 28 days.
Stratum corneum
Stratum Corneum (continued)
In between the keratinocytes in the stratum corneum are epidermal lipids (ceramides, fatty acids, and lipids) that act as a cement (or mortar) between the skin cells (bricks).
Epidermal lipids
Stratum Corneum: Moisture Barrier
This combination of keratinocytes with interspersed epidermal lipids (brick and mortar) forms a waterproof moisture barrier that minimizes transepidermal water loss (TEWL) to keep moisture in the skin.The composition of these lipids in the moisture barrier is: ceramides (40%), fatty acids (25%), and cholesterol (25%).
Stratum corneum can be referred to as the moisture barrier
Stratum Corneum: Moisture Barrier (continued)
The moisture barrier protects against invading microorganisms, chemical irritants, and allergens.If the integrity of the moisture barrier is compromised, the skin will become vulnerable to dryness, itching, redness, stinging, and many other skin care concerns.
Keeps microbes, irritants, and allergen out.
Stratum Corneum: Acid Mantle
In the very outer layers of the stratum corneum, the moisture barrier has a slightly acidic pH (4.5 to 6.5). These slightly acidic layers of the moisture barrier are called the acid mantle.The acidity is due to a combination of secretions from the sebaceous and sweat glands.
(pH 4.5 to 6.5)
Acid mantle
Stratum Corneum: Acid Mantle (continued)
The acid mantle functions to inhibit the growth of harmful bacteria and fungi. The acidity also helps maintain the hardness of keratin proteins, keeping them tightly bound together. If the skin’s surface is alkaline, keratin fibers loosen and soften, losing their protective properties.
Acid mantle
Inhibits bacteria and other microbes
Stratum Corneum: Acid Mantle (continued)
When the pH of the acid mantle is disrupted (becomes alkaline)—a side-effect of common soaps—the skin becomes prone to infection, dehydration, roughness, irritation, and noticeable flaking.
Acid mantle
(pH 4.5 to 6.5)
Skin Components Common to Dermis and Epidermis
Skin Components Common to Dermis and Epidermis
There are a number of components common to both the dermis and the epidermis.
• Pores• Hair• Sebaceous glands• Sweat glands
Blood vessels
Sweat gland
Hair follicle
Sebaceous gland
Epidermis
Dermis
Pore
Pores Pores are formed by a folding in of the epidermis into the dermis. The skin cells that line the pore (keratinocytes) are continuously shed, just like the cells of the epidermis at the top of the skin.
The keratinocytes being shed from the lining of the pore can mix with sebum and clog the pore. This is the precursor to acne. If oil builds up inside the pore, or if tissue surrounding the pore becomes agitated, the pores may appear larger.
Epidermis
Dermis
Pore
Hair
Hair grows out of the pores and is composed of dead cells filled with keratin proteins. At the base of each hair is a bulb-like follicle that divides to produce new cells. The follicle is nourished by tiny blood vessels and glands. Hair prevents heat loss and helps protect the epidermis from minor abrasions and exposure to the sun’s rays.
Hair follicle
Epidermis
Dermis
Sebaceous Glands
Sebaceous glands are usually connected to hair follicles and secrete sebum to help lubricate the follicle as it grows. Sebum also contributes to the lipids and fatty acids within the moisture barrier.Oil production within the sebaceous gland is regulated by androgen levels (hormones such as testosterone).
Sebaceous gland
Epidermis
Dermis
Epidermis
Dermis
Sweat Glands
Sweat glands are long, coiled, hollow tubes of cells. The coiled section is where sweat is produced, and the long portion is a duct that connects the gland to the pore opening on the skin's surface. Perspiration excreted by the sweat glands helps cool the body, hydrate the skin, eliminate some toxins (i.e., salt), and maintain the acid mantle.
Sweat gland
Review
Dermis
• Major components of the dermis are surrounded by gel-like, moisture-binding glycosaminoglycans.
• Collagen is a structural protein within the dermis that gives skin strength and flexibility.
• Elastin is a coil-like structural protein that gives skin the ability to return to its original shape after being stretched.
• Both collagen and elastin are produced in the fibroblasts.
Review
Epidermis
• In the deepest layer (stratum basale), new keratinocytes are formed by cell division. Melanocytes are also present in this layer.
• In the third layer (stratum granulosum), keratinocytes begin to fill with the tough protein keratin. Also in this layer, keratinocytes begin to die.
• In the outermost layer (stratum corneum), keratinocytes are surrounded by lipids and fatty acids, making up the moisture barrier.
• The acidic area of the moisture barrier is referred to as the acid mantle.
Maintain the Beauty of Skin
Maintain the Beauty of Skin
Beautiful, healthy skin is determined by the healthy structure and proper function of components within the skin. To maintain beautiful skin, and slow the rate at which it ages, the structures and functions of the skin must be supplemented and protected.
Maintain the Beauty of Skin
Flexibility, elasticity, firmness:
Maintain the moisture barrier and acid mantle.
Protect collagen and elastin levels.
Soft, supple skin:
Radiant, youthful complexion:Promote healthy cell renewal and guard against free radical damage.
Translucent, luminous tone:Avoid UV damage and other causes of discoloration. Maintain healthy cell renewal.
Smooth, even texture:Maintain healthy cell renewal and frequently refinish and exfoliate. Keep pores clear. Promote healthy cell repair.
Test Your Knowledge
Congratulations!
You have completed the Skin Anatomy and Physiology Advanced Course.