The Skin COS810- FA

The Skin The most extensive organ system. The skin and accessory structures, include hair, nails, glands (sweat and sebaceous), and specialize nerve receptors for stimuli (changes in internal or external environment) such as touch, cold, heat, pain and pressure. Its functions include protection or internal structures, prevention of entry of disease-causing microorganisms, temperature regulation, excretion through perspiration, pigmentary protection against ultraviolet sunrays, and production of vitamin D. The body stores about half its fat in the underlying hypodermis.

About the SKIN Thickest on the palms and soles Thinnest on the eyelids Cell making factory with miles of blood vessels, millions of sweat glands, and an array of nerves within a network of fibers The skin of an average adult is 8 to 10 lbs

It averages 22 square feet Contains 1/2 to 2/3 of the blood in the body and 1/2 of the primary immune cells Each skin contains – each inch of skin: Millions of cells 15 feet of blood vessels 12 feet of nerves 650 sweat glands 100 oil glands 65 hair 1300 nerve endings 155 pressure receptors 12 cold and heat receptors

Skin Function Protection Sensation Heat regulation Excretion Secretion Absorption

Protection Protects from microorganism, injury and invasion and traps water in the body Sebum protects the outer skin from external factors Acid mantle is made up of sebum, lipids, sweat, and water to form a hyrolipidic film. Acid mantle has an average pH 5.5. Acid mantle is part of the skin’s natural barrier function

Transepidermal water loss (TEWL) Barrier function Protect from irritation and intercellular transepidermal water loss Transepidermal water loss (TEWL) Water loss caused by the evaporation on the skin’s surface Lipid Are protective oils that make up the intercellular cement Intercellular cement Found between epidermal cells Melanin Pigment that protects us from the sun

Skin Functions Sensation Heat Regulation Sensory nerve ending in the dermis respond to touch, pain, cold heat and pressure Heat Regulation Through vaso constriction and vaso dilation. Arrector pili muscle contracts and causes “goose bumps”.

Skin Functions Excreation Secretion Absorption Sudoriferous or sweat glands excrete persiration and detoxify the body. Folicles and pores Secretion Sebacaus gland secret sebum to keep the skin soft and protected for outside elements. The skin is 50 to 70% water Absorption Absorption occurs through the cells, folicles, and pores of the skin

Epidermis, Dermis, Hypodermis

Epidermis Protective covering of the body. It contains no blood vessels, but has many small nerve endings Has 5 layers called strata Desquamation occurs every 28, 35, 45 days

Dermis Is the underlying or inner layer of the skin Is it know as the true skin Composed of collagen protein that adds strength), reticular fiber (thin protein fibers that add support) and elastic fiber (a protein that adds flexibility Has two layers Papillary layer – loose connective tissue Reticular layer – dense connective tissue

Hypodermis Also know as the subcutaneous layer lies beneath the dermis Loose connective tissue such as adipose tissue insulates the body Contains blood vessels, lymph vessels, and bases of the hair follicles and sweat glands.

The Skin

Stratum Germinativum Also know as the basal layer Deepest layer of the epidermis live layer Cells continuously divide - mitosis As new cells form older cell migrate to the surface Melanocytes are present in this layer

Stratum Spinosum Also know as the prickly layer Cells continue to divide and change shape here Enzymes are creating lipids and proteins and becomes desmosomes Immune cells are also found here

Stratum Granulosum Also called the granular layer 1 to 4 layers of cells that are flat and granular shaped Production of keratin and intercelluar lipids takes place here These cells move upward to replace the cells shed at the stratum corneum

Stratum Lucidum Also know as the clear layer This is one layer of small cells which are transparent and loosely packed to allow light to pass through Found on the palms and soles

Stratum Corneum Also know as the horny layer – scale like cells made of soft keratin It is between 15 and 20 layers of tightly packed cells Cells constantly turn over every 28 days Protective layer

Dermis 25 times thicker then the epidermis Two layers Papillary layer Reticular layer Contains blood and lymph vessels nourish the skin Capillaries, sebaceous glands, sudoriferous glands, nerves, addition receptors and the arrector pili muscle are located here

Papillary Layer Connects the dermis to the epidermis forming the epidermal-dermal conjunction Contains elastic tissue called papillae Dermal papillae are membranes of ridges and groves attached to the epidermis Dermal papillae are either looped capillaries that nourish the epidermis

Reticular Layer Deepest layer of the dermis Contains criss-crossing collagen fibers the form a strong elastic network Collage, produced by fibroblasts makes up 70 percent of the dermis Base of hair follicles, glands, blood and lymph vessels, nerve ending, collagen and elastin are found here

Subcutaneous Tissue Also know as the hypodermis Loose connective tissue such as adipose tissue protects and contours the body Acts as a protective cushion Also contain blood vessels, lymph vessels, hair follicle base and sweat glands