Milady chapter 10 skin physiology and histology

follicle wall, intracellular, transcellular, sebaceous gland

FITS; routes of product absorption into the skin

epidermis

Outermost layer of the skin composed of five layers that covers the body. Cell types include keratinocytes, melanocytes, immune cells, and Merkel cells (nerve receptors). Thin and protective with many cells, mechanisms, and nerve endings.

Sensation, heat regulation, absorption, protection, excretion, secretion

SHAPES - the primary functions of the skin

Molecular size and lipid-solubility

What determines a products ease of absorption (among other things)

undifferentiated stem cell

a stem cell that keeps dividing for constant self-renewal over a lifetime. Divided daughter cells also stay undifferentiated and therefore continue to divide OR become programmed to develop into a specialized cell, such as a keratinocyte, gland, nerve, etc.

Integumentary system

aka Skin, the largest organ in the body. Comprised of skin layers, nerves, cellular functions, hair follicles, and glands.

subcutis tissue

aka adipose tissue; tissue creates protective cushion giving contour and smoothness, and provides energy to the body

sensory nerves

aka afferent; send messages to the CNS and brain to react to heat, cold, pain, pressure, and touch

dermis

aka derma, corium, cutis, or true skin. Below the epidermis. 25 times thicker than the epidermis. Primarily connective tissues made of collagen protein and elastin fibers. Supplies the skin with oxygen and nutrients. Two layers are papillary and reticular.

motor nerves

aka efferent; impulses between the brain/spinal cord to the muscles or glands. These stimulate muscles (i.e. arrector pilli) and include secretory nerve fibers attached to sweat and oil glands. They regulate excretion from sudoriferous glands and control sebum output.

extracellular matrix

aka ground substance; composed of collagen, other proteins, and GAGs (glycosaminoglycans).

Sebaceous glands

aka oil glands; appendages attached to follicles that produce sebum. Can be over stimulated by emotional stress and hormone imbalances which can lead to excess sebum and skin problems.

stratum spinosum

aka spiny layer; largest layer of the epidermis above the germinativum. Cells continue to divide and change shape here, and enzymes are creating lipids and proteins. Cell appendages resembling prickly spines become desmosomes. Home to Langerhans immune cells. Keratinocytes and melanocytes work to form the even placement of pigment granules.

sudoriferous glands

aka sweat glands; excrete perspiration and detoxify the body by excreting excess water, salt, and unwanted chemicals through the pores.

stratum granulosum

aka the granular layer; composed of cells that resemble granules and are filled with keratin. Production of keratin and intercellular lipids takes place here. Enzymes dissolve the desmosomes that hold cells together.

Stratum Corneum

aka the horny layer; the top, outermost layer of the epidermis. The layer the esthetician is primarily concerned with. Very thin, yet waterproof, permeable, regenerates itself, detoxifies the body, and responds to stimuli. Generally has 15-20 layers of cells and a thickness of .01-.04 mm

1/2-2/3

amount of blood in the body skin contains

stratum germinativum

basal cell layer, located above the dermis, comprised of a single layer of basal cells laying on a "basement membrane". Stem cell keratinocytes undergo continuous division/mitosis to replenish desquamation in above layers. Lipids that form cell membranes are formed here, as well as Merkel (sensory) cells.

Proteins

basic material and building blocks for our body's tissues. Made up of amino acids.

subcutaneous layer

below the reticular layer, aka the hypodermis, composed of loose connective tissue or subcutis; this layer is 80% fat

melanocytes

cells that produce pigment granules in the basal layer (about 5-10% of cells in the germinativum)

fibroblasts

cells that stimulate cells, collagen, and amino acids that form proteins and trigger healing

Polypeptides

chains of amino acids

apocrine glands

coiled sweat glands attached to hair follicles found under the arms and in the genital area. Their secretions are released through the oil glands. These are more active during emotional changes. Bacterially odorous.

keratinocytes

composed of keratin, comprise 95% of the epidermis. Contain both proteins and lipids. These cells are surrounded by lipids to protect them from water loss and dehydration.

nerves

cordlike bundles of fibers made up of neurons through which sensory stimuli and motor impulses pass between the brain or CNS and other parts of the body (eyes, glands, muscles, etc.)

reticular layer

deeper, denser layer of the dermis. Damage to elastin here is the primary cause of sagging, wrinkles, and aging as well as stretch marks.

tyrosinase

enzyme that stimulates melanocytes and thus produces melanin

Elastin

fibrous protein that forms elastic tissue and gives skin its elasticity. 1/15th as much as collagen in the dermis.

keratin

fibrous protein that provides resiliency and protection to the skin. Found in ALL layers of the epidermis. Hard versions of these cells make up hair and nails.

hydrolipidic

film that is an oil-water balance that protects the skin's surface

Amino acids

form peptides (part of a protein) and proteins. Held together by peptide bonds.

hyaluronic acid

glycosaminoglycan found in the dermis

ceramides

group of waxy lipid molecules important to barrier function and water-holding capacity such as glycolipids; make up 50% of the lipids in the stratum corneum!

epidermal growth factor

hormone that stimulates skin cells to reproduce and heal. One of several.

Desmosomes

keratin filaments - the protein bonds that create the junctions between the cells. Formed in the stratum spinosum by the spiny appendages of morphing keratinocytes. THese strengthen the epidermis and assist in intercellular communication

glycosaminoglycans

large protein molecules and water-binding substances found between the fibers of the dermis. These are polysaccharides - protein and sugar complexes. GAGs include hyaluronic acid

Corneum, lucidum, granulosum, spinosum, germinativum

layers of the epidermis (top to bottom); horny, clear, grainy, spiny, basal

intercellular matrix

lipid substances between corneum cells that protect the cells from water loss and irritation

Lymph vessels

located in dermis; remove waste products, bacteria, and excess water

thermoregulation

maintained through evaporation, perspiration, radiation, and insulation (RIPE)

eumelanin

melanin that is dark brown to black. Dark-colored people mostly produce this type

pheomelanin

melanin that is red to yellow in color. Light-skinned people mostly produce this type

dermal papillae

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

Stem cell keratinocytes

mother cells that divide in the basal layer (germinativum) forming new daughter cells. These daughter cells move up through the layers before become hardened corneocytes of the stratum corneum.

sebum

oil that provides protection for the epidermis from external factors and lubricates both the skin and hair; keeps skin soft and protected. Slows down TEWL and helps maintain water levels in cells

melanosomes

pigment carrying granules (produced by melanocytes) that themselves produce melanin

1/2

primary immune cells in the body that skin contains

desquamation

process in which keratinocytes are continually shed from the skin and replaced by new cells coming to the surface from the lower stratums; aka cell turnover. Occurs every ~28 days in healthy addults and slows with age.

Langerhans immune cells

protect the body from infections by identifying foreign material (antigens). They then help destroy these foreign invaders

acid mantle

protective barrier made up of sebum, lipids, sweat, and water. pH of average 5.5. Maintaining this pH protects from pathogens and regulates enzymatic functions

collagen

protein substance of complex fibers that gives skin its strength and is necessary for wound healing. Produced by fibroblasts; 70% of the dermis

healthy skin

skin that is slightly moist, soft, smooth, and somewhat acidic.

barrier function

skin's mechanism that protects us from irritation and intercellular transepidermal water loss. Lipids are an important part of this function. Damage to this layer is the cause of many skin problems including sensitivities, aging, and dehydration

hair papillae

small, cone-shaped structures at the bottome of the hair follicles.

arrector pilli

small, involuntary muscles in the base of the hair follicle that cause goose flesh when the appendage contracts

physiology

study of the functions of living organisms

skin histology

study of the structure and composition of the skin tissue

eccrine glands

sweat glands found all over the body, primarily on forehead, palms, and foot soles. They have a duct and pore through which secretions are release directly on the skin's surface and NOT through hair follicles. More active during physical activity and high heat. Generally little to no odor

Vitamin D

synthesized and produced in the skin upon exposure to the sun.

squamous

term to describe flat and scaly keratinized cells on the surface of the stratum corneum

Pores

the openings for sweat glands. Used as a lay term for "follicle" because both are openings on top of the epidermis

transepidermal water loss

the water loss caused by evaporation on the skin's surface

stratum lucidum

thin, clear layer of dead skin cells under the stratum corneum. Small cells that let light pass through. This layer is thickest on palms of hands and soles of feet. Keratinocytes contain CLAR keratin. Cells in this layer release lipids forming bilayers of oil and water; also forms finger and foot prints

estheticians

those who specialize in the health and beauty of the skin. AKA technicians, skin therapists, or skin specialists. Primarily focused on preserving, protecting, and nourishing the skin.

melanin

tiny grains of pigment that are produced by melanocytes and deposited into cells in the stratum germinativum layer of the epidermis and in the papillary layers of the dermis. It is a protein that determines hair, eye, and skin color; a defense mechanism to protect skin from the sun. There are two types: pheomelanin and eumelanin.

papillary layer

top layer of the dermis; 10-20% of the dermis. callagen and elastin more widely spaced here than in the reticular layer

Merkel cells

touch receptors located in the basal germinativum

Natural moisturizing factors

triglycerides, ceramides, waxes, fatty acids and other intercellular lipids made in the stratum granulosum and released as part of the skin's waterproofing barrier function and sent upward to the top layers. They are water-soluble and hydrate the lipid layer surrounding cells, absorb water, and prevent water loss.

tyrosinase inhibitor

type of skin brightening agent that suppresses melanin production

corneocytes

waterproof, hardened, protective keratinocyte in the stratum corneum. These "dead" protein cells are dried out and lack nuclei.

terminal differentiation

when a daughter cell has been programmed as a specific type and cannot divide any longer

fingertips

where sensory nerve fibers are most abundant

palms of hands and soles of feet

where skin is the thickest

leukocytes

white blood cells that have enzymes to digest and kill bacteria and parasites. These while blood cells also respond to allergies.