integumentary system

Integumentary system

The integumentary systemThe skin and all its derivatives

E.g. Nails, hair, glandsProvides external protection

Fxns of the Integumentary systemProtection

Skin secretionsMelanin

Physical/mechanical barriersBiological barriers

E.g. DNA

Body temperature regulationCutaneous sensationMetabolic fxns

Synthesis of Vitamin DBlood reservoirExcretion

CharacteristicsCovers the entire body Accounts for about 7% of total body weight Pliable, yet durable Thickness: 1.5 to 4.0 mm Composed of the epidermis and dermis

Skin derivativesOriginates from the epidermis

Nails The nail matrix contains rapidly dividing cells that eventually

become dead and keratinized Hardened nails protect the delicate tissues of the fingers and toes

Hair follicles and hair Hair produced the hair follicles in the dermal layer of the skin

Hair is composed mainly of dead, keratinized cells A strand of hair is composed of three layers:

Medulla – the innermost layer Cortex – surrounds the medulla Cuticle – provides strength and maintains the structure of the

inner layers Hair color is determined by the pigment melanin produced by

melanocytes at the base of the hair follicle

Sweat glands Eccrine sweat glands

Found on the palms, soles, and forehead Secretes sweat

Sweat is composed of mainly water and salts Sweat is acidic and slows microbial growth on the skin

Apocrine sweat glands Found in the anogenital and axillary (armpit) regions Secretion contains the same components of true sweat plus fatty substances and

proteins Produces “body odor”

Ceruminous glands – produce wax Wax deters insects and blocks the entry of foreign material into the ear canal

Mammary gland – specialized sweat glands that secrete milk Sebaceous (oil) glands

Found all over the body except on the palms and soles Produce oil (sebum)

Sebum softens and lubricates the hair and skin; waterproofs the hair and skin