Integumentary System (Ch. 6) Includes: Skin, hair, and nails Called the “cutaneous” membrane, it’s the largest organ.

Functions of skin: -prevent excess water loss - protective barrier from microorganisms and UV radiation

-production of vitamin D (needs sunlight) -regulation of body temperature (sweat or goose bumps)

-excretion of waste (sweat) -sensation of the environment -immune response

Structure of skin: -contains all 4 tissue types! -3 main layers: Epidermis Dermis Hypodermis

Epidermis- several layers of epithelium called “strata” corneum- uppermost layer of dead cells, 4-5 layers that produces keratin (tough, waterproof protein) lucidum- (only in “thick skin”) – Langerhans cells granulosum- Langerhans cells – produces immune response spinosum- Langerhans cells basale- where mitosis occurs, the “newest skin” melanocytes produces the pigment melanin Merkel cells – detect touch Epidermis- several layers of epithelium called “strata”

Dermis- mostly connective tissue (collagen - support and elastin fibers) and highly vascular contains the following: -sweat glands -sebaceous glands: produce oil (near hair follicles) -hair follicles : epithelial “tubes” that grow hair -hair: made of keratin (protein) & melanin (pigment) -errector pili muscle: make hair stand up -sensory receptors: (nerve endings)

Nerve ending of the skin- (cutaneous sensory receptors) There are receptors for: Cold Pain Itch Light Touch Hot Tickle Pressure

Hypodermis- sometimes called “subcutaneous” may contain: loose connective tissue connecting to muscle or bone adipose tissue for fat storage

Thick vs. Thin Skin Thick: Thin: Palms and soles of feet No hair Friction ridges (finger prints) Only epidermis is thicker Thin: Covers vast majority of the body

Human Anatomy, 3rd edition Fingerprints Human Anatomy, 3rd edition Prentice Hall, © 2001

Functions of Hair Protection Thermoregulation Sensory

Nail Structure Nail body Free edge Nail root Matrix Lunula (moon)

Nail Structure FG04_15.JPG Title: Structure of a Nail Notes: These drawings illustrate the prominent features of a typical fingernail as view from the surface and in section. Keywords: fingernail, hyponychium, nail bed, lateral nail groove, lunula, eponychium, phalanx, dermis, epidermis

Function of Nails 1. protecting the distal phalanx, the fingertip, and the surrounding soft tissues from injuries 2. enhance precise delicate movements of the distal digits 3. aids in the appreciation of fine touch

Aging – collagen is destroyed - wrinkles

Keratin waterproofs your skin

Skin Cancer Most skin cancers are caused by exposure to the sun.