The Skin in Health and Disease Chapter 6 The Skin in Health and Disease

The Integumentary System Skin and associated structures form integumentary system

A. Epidermis i. It is the surface layer of the skin; consists of 2 layers ii. Constantly lost through wear and tear iii. Is avascular: (meaning it has no blood vessels within it)

Stratum basale (germinativum) 1. Deepest layer of the epidermis 2. Nourishment provided by capillaries in the dermis 3. Only living cells exist here 4. Cells are constantly dividing , pushing upward to the surface; (a new layer every month)

5. produce melanin a pigment that colors the skin (melanocytes produce melanin)

Epidermis is made up of 2 layers: iv. Stratum Corneum 1. uppermost layer of the epidermis 2. cells die from loss of nourishment 3. develops large amount of keratin (type of protein) 4. keratin thickens and protects the skin

Cross section of the skin.

B. Dermis – the middle layer i. Also called the corium ii. Made up of elastic connective tissue iii. Is Vascular: it has blood vessels and nerves iv. All appendages start here v. Thickness varies in different parts of the body

vi. Some portions extend into the epidermis to form papillae (ridges, fingerprints) vii. Ridges (papillae) are determined by heredity.

C. Subcutaneous layer – deepest layer 1. Under the dermis 2. sometimes called superficial fascia or hypodermis 3. connects the skin to the muscles 4. Consists of loose connective tissue and lots of fat 5. fat is for insulation and energy reserves 6. blood vessels supply cells with nutrients and regulate body temperature 7. lot of nerves and nerve endings

1. Sebaceous glands i. secrete oil called sebum ii. Lubricates the skin and hair iii. Ducts open into the hair follicles iv. Blackheads are mixtures of dried sebum and keratin v. Pimples result if infections set in

2. Sudoriferous (sweat) glands i. Coiled, tube-like structures in dermis and subcutaneous layers ii. Each one opens at a pore (eccrine glands) Iii. Regulate body temperature through evaporation of sweat. iv. Sweat consists of small amounts of dissolved salts and wastes v. Secretions from underarms (apocrine glands) mix with bacteria and cause body odor

Other glands vii. Ceruminous glands in ear canals produce ear wax (cerumen). viii. Ciliary glands at the edges of the eyelids secrete tears ix. Mammary glands in the breast secrete milk.

Portion of skin showing associated glands and hair. ZOOMING IN • How do the sebaceous glands and apocrine sweat glands secrete to the outside? What kind of epithelium makes up the sweat glands?

c. Hair a. covers almost all of the body, except palms and soles, lips b. composed of keratin and not living cells c. starts from cells at the bottom of hair follicles d. Arrector pili muscle is attached to hair follicle, causing goosebumps when contracted

c. Hair E. Shaft is the part that projects above the skin F. Root the portion below the skin G. Purpose in animals is a warning sign, and a means of conserving heat

D. Nails a. protect fingers and helps in grasping objects b. Made of hardened keratin from cells in the epidermis c. new cells form at the nail root d. Remainder of the nail plate rests on the nail bed. e. Lunula – pale end is lighter because it is thicker f. Sicknesses cause changes in nail color, thickness, shape and texture; such as Heart disease Malnutrition Anemia

White spots fungus ridges