INTEGUMENTARY SYSTEM THE STRUCTURES

See figure 5-2 on page 73 and leave open to reference back to LAYERS OF THE SKIN Epidermis Dermis Subcutaneous See figure 5-2 on page 73 and leave open to reference back to

EPIDERMIS Outer layer; no blood vessels present (avascular) Stratum corneum Outermost of three epidermal layers Made of dead cells Contains keratin: protein that renders the skin dry and provides a waterproof covering Stratum germinativum Undergoes continuous cell division Deepest epidermal layer Contains keratinocytes and melanocytes

Epidermis continued… Melanocytes and melanin Papillae Melanocytes make melanin Melanin: protein which protects the skin against the UV rays of the sun Papillae Ridges in the stratum germinativum Come from the dermal layer and push into the stratum germinativum Pronounced in the fingers, soles of the feet, and palms of the hands and raise the skin into permanent ridges Prevents slipping when grabbing objects What do these papilae create?

DERMIS Thicker, inner layer Connective tissue Blood vessels: aid in regulating body temp. Dilate to bring warmed blood to surface be cooled (when warm) Constrict bring warmed blood closer to vital organs (when cold) This dilation or constriction cannot be maintained for long periods of time Nerve endings Those for touch are near the surface and those for pressure are deeper Muscles Hair follicles Oil and sweat glands Fat cells

SUBCUTANEOUS Hypodermal layer or superficial fascia Not a true part of the integumentary system Consists of loose connective tissue and about ½ of the body’s stored fat (adipose) Attaches the integumentary system to the surface muscles underneath

APPENDAGES Hair Nails Glands Sudoriferous/Sweat Sebaceous/Oil Related ducts

HAIR Distributed over most of the surface of the body and composed of a root shaft, outer cuticle layer, and inner medulla Length, thickness, type, and color of the hair vary with the different parts of the body Cortex and medulla Cortex: the outer cuticle layer and consists of elongated, keratinized, nonliving cells; hair pigment is located here Medulla: inner cuticle layer

continued Root and shaft Root: part of the hair that is implanted in the skin Shaft: projects from the skin surface Hair follicle: in-pocketing of the epidermis where the root is embedded Papilla: contains capillaries which nourish the hair follicle cells Arrector pili muscle: smooth muscle that is attached to each hair follicle on the side toward which it slopes When stimulated it contracts and causes the skin to pucker around the hair (called “goosebumps”)

LOOK AT FIGURE 5-3 ON PAGE 76

NAILS Some disease conditions may be revealed by the color of a person’s nails. (Look on the bottom of page 76, the table and figure) Matrix Nail bed where the nail forms Epidermal cells first appear as elongated cells Keratin Elongated cells then fuse together to form hard, keratinized plates

GLANDS Sudoriferous/Sweat Sebaceous/Oil Perspiration is 99% water with only small quantities of salt and organic materials (waste products) Distributed over the entire skin surface Sebaceous/Oil Sebum: thick, oily substance that protects the skin; lubricates the skin, keeping it soft and pliable Discussed more in the next section: Function