Lecture 4: Integumentary System

integumentary system

Composed of skin, hair, nails, and associated glands

epidermis

The uppermost layer of the skin, made up of stratified squamous epithelium

dermis

The second layer of the skin, made up of deeper connective tissue (collagen, elastic/reticular fibers)

hypodermis

The layer of subcutaneous tissue beneath the dermis; not part of the skin but usually studied with it

thick skin (0.5 mm)

Covers palms, soles, and corresponding surfaces of fingers and toes; has sweat glands but no hair follicles or sebaceous glands

thin skin (0.1 mm)

Covers most of the body; has sweat glands, hair follicles, and sebaceous glands

keratinocytes

Synthesize keratin (most epidermal cells)

stem cells

Undifferentiated cells that give rise to keratinocytes, in the deepest layer of the epidermis (stratum basale)

melanocytes

Synthesize the pigment melanin, which shields DNA from ultraviolet radiation

tactile cells

Touch receptor cells associated with dermal nerve fibers; located in basal layer of epidermis

tactile disc

Collective term for tactile cell and associated nerve fiber

dendritic cells

Phagocytic immune cells that guard against toxins and microbes; found in stratum spinosum and stratum granulosum

dermal papillae

Upward, fingerlike extensions of dermis

epidermal ridges

Downward waves of epidermis

papillary layer

Thin zone of areolar tissue in and near the dermal papillae; allows for mobility of leukocytes and other defense cells; rich in small blood vessels

reticular layer

Deeper, thicker layer of dermis composed of dense irregular connective tissue

stretch marks (striae)

Tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity

subcutaneous fat

Subcutaneous tissue that is comprised predominantly of adipose tissue; energy reservoir and thermal insulation

autograft

Tissue is grafted from another location on the same body

allograft

Tissue is grafted from an unrelated person (usually a deceased donor)

full thickness skin graft

A skin graft including the epidermis and dermis (sometimes hypodermis)

split thickness skin graft

Includes the epidermis and a portion of dermis

eumelanin

Brown and black pigment

pheomelanin: yellowish-reddish to pink pigment

carotene

Yellow and orange pigment

cyanosis

Blueness of the skin due to oxygen deficiency

erythema

Redness of the skin due to increased blood flow

pallor

Paleness of the skin due to decreased blood flow

albinism

White skin due to genetic lack of melanin

jaundice

Yellowing of the skin due to bilirubin in blood; can be caused by compromised liver function

hematoma

Bruising (clotted blood under skin)

pilus (plural, pili)

Slender filament of keratinized cells growing from a tube in the skin (hair follicle)

nails

Thin, dead cells packed with hard keratin; counterforce to enhance sensitivity of fingertips

nail plate

Hard part of nail including the overhanging free edge, nail body, and nail root

nail bed

Skin underlying the nail plate

hyponychium

Epidermis of nail bed

nail matrix

Growth zone at proximal end of nail; its thickness obscures underlying vessels and appears as white lunule

eponychium (cuticle)

Dead skin that overhangs proximal end of nail

eccrine (merocrine) glands

Most numerous of the sweat glands; produce watery perspiration that helps cool the body

myoepithelial cells

Found in both apocrine and eccrine glands; contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct

ceruminous glands

Modified apocrine glands found only in external ear canal

cerumen (earwax)

Waterproofs ear canal and kills bacteria

mammary glands

Milk-producing glands that develop in female during pregnancy and lactation

basal cell carcinoma

Forms from cells in stratum basale; least dangerous and seldom metastasizes

squamous cell carcinoma

Arises from keratinocytes of stratum spinosum; tends to metastasize to lymph nodes and may become lethal

melanoma

Arises from melanocytes; usually fatal