Skin and Body Membranes

Skin and Body Membranes

Skin and Body Membranes Chapter 4 Skin Functions Protection

Mechanical damage physical bumps Chemical damage relatively impermeable Bacterial damage unbroken surface w/ acid mantle Ultraviolet radiation Melanin

Thermal Contains hot/cold/pain receptors Desiccation resists drying out. Skin Functions Aids in heat loss or heat retention Sweat glands

Closes capillaries Aids in excretion of urea and uric acid Contained in sweat Synthesizes Vitamin D

Sunlight converts cholesterol into vit. D Skin Structure Two True skin layers: epidermis and dermis

Epidermis is stratified squamous cells. Can become keratinized hard and tough Dermis is dense connective tissue

Epidermis and Dermis are firmly connected Become separated due to friction or a burn This allows fluid to accumulate between

layers causing a blister Skin Structure Skin Structure Unofficial third layer subcutaneous tissue (aka hypodermis)

Mostly adipose (fat) tissue Connects skin to underlying tissues and organs Shock absorber.

insulator Epidermis Strata (layers) From the bottom up Stratum Basale nourished by blood in the connective tissue, constantly going through mitosis. Daughter cells are constantly pushed upward to become

new layers of superficial skin. Stratum spinosum and granulosum living cells that are being pushed up by new cells from the Basale Epidermis Strata Stratum Lucidum: found in extremely thick, hairless, skin (palms and soles)

Stratum Corneum: 20-30 cells thick. Fully keratinized (extremely durable). Slowly flakes off naturally but is replenished from beneath by the basale layer. Epidermis Strata Melanin Yellow/brown pigment

Made by melanocytes directly above basale layer Melanin acts like an umbrella, protecting basale cell nuclei from harmful UV light. Melanocytes are activated by sunlight to create more melanin (tanning) Melanin

Melanin Melanin does have protective effects, however excessive sun exposure will damage the skin. Elastic fibers like collagen to clump and produce leathery skin Depresses the immune system

Alter DNA of Basale cells causing cancer People with naturally high melanin levels have a low rate of skin cancer. Dermis Strata Papillary layer the top layer, directly below the

epidermis. Dermal papillae are the projections that loop up and down. Filled with capillaries to supply blood to the basale epidermis. Also contains nerves for touch. Tips of the fingers and palms have a genetically determined pattern that forms your fingerprints (increases friction for grip).

Dermis Strata Dermis Strata Reticular Layer the deepest skin layer, contains blood vessels, sweat and oil glands, and deep pressure receptors Dermis Characteristics

Has phagocytes to kill bacteria Full of nerves for environmental interpretation. Both collagen and elastic fibers present With age, the number decreases and skin sags and wrinkles Supplied with blood

Capillaries can rise and fall in the dermis to stabilize body temp. Too hot capillaries rise to release heat (blushing). Too cold capillaries sink to hold heat (blue fingertips) Tattoos When a tattoo is applied, ink pigment is

directly injected into the dermis of the skin. Overtime, pigments can fade or migrate in the dermis, changing the appearance of the tattoo. Skin Color The amount and type of melanin produced

Amount of Carotene (orange) pigment Amount of dermal blood vessels Others

Redness due to embarrassment, hypertension, inflammation or allergy Pallor due to LBP or fear Jaundice yellowing due to liver problem Bruises blood released into tissue space causing hematomas. Skin Appendages Cutaneous Glands

Sebaceous (oil) glands Usually empty into hair follicle (oily hair) Produce Sebum keeps skin soft and has

chemical that kills bacteria Become very active in adolescence causing oily skin When sebaceous glands become blocked they can become infected and cause acne. Skin Appendages Sweat Glands sweat is clear secretion that is

mostly water. Contains salts, vitamin C and metabolic waste (ammonia, urea, uric acid) Sweat is acidic (4-6pH) which inhibits bacterial growth Nerves near sweat glands cause them to sweat when body temp goes up. Evaporative cooling. Hair Relatively useless, used to be for

insulation Minor protective properties Help insulate head from heat loss Shield eyes from debris

keep debris out of respiratory tract (nose hair) Hair Flexible epithelial structure that is created in a follicle. Part of hair in the follicle is called to root. Part above the skin surface is shaft.

In the follicle, cell division occurs, pushing cells upward as this continues. The new cells become keratinized and die Hair Each hair has a central core called Medulla

surrounded by cortex. Both of these are covered by the cuticle Cuticle prevents hair sticking together, when broken, split ends Melanocytes in the follicle give hair its color.

Hair Shaft shape determines hair types Oval shaft would produce smooth, wavy hair

Flat shaft would produce curly hair Round shaft would produce coarse, straight hair. Hair Arrector Pili small muscle that connects each hair to the dermis. When contracted, hair stands on end, and

goose bumps are produced. Reaction is due to fear or cold: This reaction is evolutionary for us, it is used in animals to fluff up the fur to create an insulating layer. Nails

Scale like modifications like a hoof or claw in other animals Has a free edge and a root Three borders of nails are covered by skin folds, the most prominent is the cuticle. Nails are almost completely clear, but appear pink due to the blood supply

directly underneath. Skin Ailments Athletes foot caused by fungus growing in the epidermis Boils inflammation of hair follicles Cold sores Small fluid blisters caused by the herpes simplex virus. Outbreaks caused by stress, fever, or UV

Contact Dermatitis Chemical exposure (poison ivy) Skin Ailments Impetigo Water filled lesions caused by infection Psoriasis overproduction of skin cells that leads to scaling.

Burns Tissue damage caused by heat, electricity, UV light or chemicals Can cause severe dehydration and chemical imbalance. Rule of nines deals with percent of body burned. Head, right arm, left arm, anterior

superior trunk, anterior inferior trunk, posterior superior trunk, posterior inferior trunk, anterior right leg, posterior right leg, anterior left leg, posterior left leg. 11 sections 9% each = 99% Final 1% would be the genital region. Burn Degrees First Degree only the epidermis is

damaged, redness and irritation. Will resolve on its own. Sunburn Second Degree the epidermis and upper dermis are damaged. Blisters will form between the two layers. Usually will heal without scaring since sufficient epithelial cells remain. Burn Degrees

Third Degree The entire epidermis and dermis are destroyed. Regeneration is not possible. Skin grafts are needed to cover the area.

Skin Cancers Most common form of cancer effecting 1 in 5 people during their life. Multiple causes, mostly UV Light exposure, or chemical exposure. Basal Cell Carcinoma

ABCD Rule Four signs of potential skin cancer: refers to moles

Asymmetry not symmetrical Border Irregularity not a clean edge Color pigmented spots, black and brown Diameter larger then 6mm

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