Ch. 3 Physiology and Histology of the Skin

Skin physiology and histology

The study of the structure, composition of the skin tissue, anatomy, layers and function of the skin

histology

study of the structure and composition of the tissue

Why should estheticians study and have a through under standing of the physiology and histology of the skin?

• Layers, components, and functions all work with other body systems to protect and regulate the skin and other parts of our body

• Includes learning about the aging process as well as the effects of UV damage, hormonal influences, and nutrition on skin health

• So skin therapist can confidently treat this sophisticated system

Which organ is the largest in the body?

The skin

Which amino acid maintains skin health?

Proteins

What are the appendages of the skin?

• hair

• nails

• sweat glands

• oil glands

What are the six primary functions of the skin?

• sensation

• protection

• heat regulation

• excretion

• secretion

• absoption

What is the first sense to devolp?

Touch

Where are nerve fibers most abundant?

The fingertips and are designed to be one of the most sensitive parts of the body

Which substance gives protection to the epidermis from external factors?

Sebum (oil)

Hydrolipidic

Film to protect the skin from drying out and from exposure to external factors that could damage it; provides an oil-water balance on the skins surface

What is the average acid mantle pH?

5.5

Barrier function

The skin’s mechanism that protects us from irritation and intercellular TEWL

Intercellular matrix

Fluid between epidermal cells

What is an epidermal growth factor?

Hormones that stimulate cells to reproduce and heal

What is an fibroblasts?

Proteins and peptides that stimulaters cells to rejuvenate

What happens to the arrector pili muscle when we are cold?

It contracts and we get goosebumps; it is attached the hair follicle

Sudoriferous gland (sweat gland)

Excrete perspiration; serve to prevent the body from overheating

Sebaceous gland (oil gland)

Attached to the follicles that produce sebum

What is necessary for our skin health?

Chemicals, hormones, moisture and oxygen

Where are the routes of penetration for absorption?

• follicle walls

• sebaceous glands

• intercellular

• transcellular

What 3 main components does the skin comprise?

• subcutaneous layer

• the dermis

• the epidermis

Subcutaneous layer (hypodermis)

Composed of loose connective tissue (subcutis tissue), vessels, nerves, fibers, adipose cells and fibroblasts; 80% fat; is a source of stored energy

Subcutis tissue

Creates a protective cushion that gives contour and smoothness to the the body; source of energy for the body

The dermis (true skin, derma, corium cutis)

The support layer of connective tissues that are divided into two layer; made of collagen, protein and elastin fibers above the hypodermis; supplies the skin with oxygen

Recicular layer

Denser and deeper layer of the dermis, comprised mainly of collagen and elastin but also includes glands, blood and lymph vessels, nerve endings and intercellular fluids

Papillary layer

Connects the dermis to the epidermis; touch receptors, blood vessels, capillaries and dermal papilla

Dermal papillae

membranes of ridges and grooves that attach to the epidermis; attached are either looped capillaries that nourish the epidermis or tactile corpuscles the nerve endings sensitive to touch and pressure

Collagen

Protein substance of complex fibers that gives skin its strength and is necessary for wound healing

Elastin

Fibrous protein that forms elastic tissue and gives skin its elasticity

Glycosaminoglycans (GAGs)

Large protein molecules and water-binding substance found between the fibers of the dermis

What is an example of GAG

Hyaluronic acid

Lymph vessels

Remove waste products, bacteria and excess fluid

Extracellular matrix

Comprise fluid with other components to maintain balance, provide dermal support, and assist cell metabolism, growth and migration; composed of collagen, other proteins and GAG’s

Dermal/ epidermal junction

Connects the dermis to the epidermis; layers of connective collagen tissues with many small pockets and holes

Epidermis

The outermost layer of the skin; composed of 5 layers

What are the five layers of the skin?

• Stratum corneum “The horney cells”

• Stratum lucidum “Feet and hands”

• Stratum granulosum “The grainy cells”

• Stratum spinosum “The spiny cells”

• Stratum germinativum “Growth layer”

Keratinocytes

Composed of keratin and makes up 95% of the epidermis

Keratin

Fibrous protein that provides resiliency and protection; found in all layers of the epidermis

Stem cells in the stratum germinativum do what?

The “mother” cells divide, forming new “daughter” cells”

Stratum Germinativum (basal cell layer)

Located above the dermis; composed of a single layer of basal cells laying on a membrane; stems undergo a continuous cycle mitosis to replenish the skin cells that are regularly shed from the surface

Melanocytes

Cells that produce pigment granules in the basal layer

Melanosomes

Pigment-carrying granules

Melanin

A complex protein which determines skin, eye and hair color

Stratum Spinosum “spiny layer”

Above the stratum germinativum; where cells continue to divide and change shape and enzymes are creating lipids and proteins; largest layer of the epidermis

Desmosomes

Keratin filaments; that protein bonds that create junctions between the cells; strengthen the epidermis; assist in intercellular communication

Langerhans immune cells

Protect the body from infections by identifying foreign material

Lamellar granules

Cells that contain lipid to maintain the barrier functions

Stratum granulosum “granular layer”

Layer composed of cells that resemble granules and are filled with keratin; production of keratin and intercellular lipids take place here; cells become keratinized and move to the surface and replace the cells shed from the top layer

Stratum lucidum

Thin, clear layer of dead skin cells under the top layer; made of small cells that let light pass through; this layer forms unique finger and foot prints

Corneocytes

Waterproof protective cells

Desquamation

Also known as cell turnover, the process in which keratinocytes are continually shed

Why will understanding the process of cell turnover help you with aging skin?

Help you make better decisions on how to properly treat the skin

Stratum corneum “horny layer”

Top, outermost layer of the epidermis; esthetician works extensively with this layer; thing, waterproof and premeable layer that regenerate itself, detoxifies the body and responds to stimuli; cells and oil combine to form a protective barrier layer

What is an external factor that influences melanin production?

UV exposure

Bilayer

Thin polar membrane made of two layers of lipid molecules

Tryosinase

The enzyme that stimulates melanocytes and thus produce melanin

What are the two kinds of melanin?

• Pheomelanin

• Eumelanin

What color is pheomelanin?

red to yellow in color

What color is eumelanin?

dark brown to black

Hair

An appendage of the skin; slender, threadlike outgrowth of the skin

How does genetics influence each persons hair?

• Thickness

• Quality

• Color

• Rate of growth

• Whether it is curly or straight

What are the 2 types of keratin?

• Alpha (A-keratin

• Beta (B-keratin)

Alpha (A-keratin)

Softer

Beta (B-keratin)

Harder; makes up 90% of hair

What kind of keratin is the nail composed of?

Hard keratin (B-keratin)

Nerves

Cordlike bundles of fibers made up of neurons through which sensory stimuli and motor impulses pass between the brain or other parts of the central nervous system and eyes, glands, muscles and other parts of the body

Efferent nerve (motor nerve)

Convey impulses from the brain or spinal cord to the muscles or glands

Afferent nerve (sensory nerve)

Send messages to the central nervous system and our brain to react to heat, cold, pain, pressure and touch

What two types of duct glands are in the dermis?

• Sebaceous gland

• Sudoriferous gland

Sebaceous gland

Glands connected to the hair follicles and produce oil, which protects the surface of the skin

Sudoriferous gland

Glands that help regulate the body temperature and eliminate minute amounts of waste products by excreting sweat

How many pints of sweat does the body produce a day

1 - 2 pints of trace amounts of sodium, potassium and magnesium

Apocrine gland

Coiled structures attached to the hair follicles found under the arms and genital areas; their secretions are released through oil glands

Eccrine gland

Sweat glands found all over the body but primarily on the forehead, palms of the hands and soles of the feet; not connected to the hair follicle

Leukocytes

White blood cells that have enzymes to digest and kill bacteria and parasites

T-cells

type of lymphocyte; attacks virus-infected cells, foreign cells and cancer cells

What are the fluids that nourish the skin?

• Blood

• Lymph

Ceramides

A group of waxy lipid molecules that are important to barrier function and water-holding capacity

What is regular cell turn-over necessary for?

Healthy skin

What is not easily replaced in the body once it is stretched of damaged?

Collagen and Elastin

What are the 3 different forms of UV?

• UVA

• UVB

• UVC

UVA radiation

also known as aging rays, they penetrate deeper into the skin and cause genetic damage; weakens the skin’s collagen and elastin

UVB radiation

also known as burning rays, causes burning to the skin as well as tanning, aging and cancer; wavelengths are stronger and more damaging to the skin; contributes to the body’s synthesis of vitamin D

UVC

Reacts with the ozone layer; sanitizes and kills bacteria and other germs

High-energy visible light

Blue light said to penetrate the skin more deeply than UV rays and damage, collagen, elastin and hyaluronic acid

What does sun protection do?

Defends cells from radiation, cell death, tissue breakdown and premature aging; does NOT protect the skin

What do free radicals do to the aging process?

Speed it up and creates an unhealthy state

Glycation

The binding of a protein molecule to a glucose molecule, resulting in the formation of damaged, nonfunctioning structure known as advanced glycation end products

What is a crucial hormone for good health and the appearance of the skin?

Estrogen

Couperose skin (telangiectasia)

The dilation of capillary walls

Rosacea

Chronic vascular disorder characterized by varying degrees of skin redness and congestion of the skin

Phytoestrogens

Estrogen-like compounds derived from plants