chapter 16: skin

Question 1

epidermis

Answer 1

a thin, cellular membrane layer; containing keratin
-layer 1

• > composed of squamous epithelial cells (flat and scale-like)
• arranged in several layers (strata) to form stratified squamous epithelium

->lacks blood vessels, lymphatic vessels, and connective tissue. relies on dermis for nutrients

layers of the epidermis:

• > deepest layer: basal layer
• the cells in this layer are always growing and multiplying and are the source of all the other cells in the epidermis
• these cells are pushed upward and away from the blood supply of the dermal layer
• > most superficial layer: stratum corneum.
• in the cells movement towards this layer they shrink, flatten, lose their nuclei, and die becoming filled with keratin (hard protein). the cells are then called keratinocytes.

Question 2

dermis

Answer 2

dense, fibrous, connective tissue layer; containing collagen
-layer 2

• The dermis is composed of interwoven elastin (protein that is elastic and helps skin to return to its original position when pinched or poked) and collagen fibers.
• Collagen fibers support and protect the blood and nerve networks that pass through the dermis.

Question 3

subcutaneous layer

Answer 3

thick, fat-containing tissue

-layer 3

Question 4

basal layer of the epidermis

Answer 4

-contain special cells called melanocytes, which contain the pigment melanin

Question 5

type of melanin

Answer 5

• > Eumelanin:
• more common is a brown-black pigment
• people with darker skin have more of this
• > Pheomelanin:
• is a red-yellow pigment
• people with lighter skin have more pheomelanin

Question 6

hair

Answer 6

• > filled with hard protein-keratin
• > Deep-lying cells in the hair root produce keratinized cells that move upward through hair follicles
• > melanocytes are located at the root of the hair follicle, and they donate the melanin pigment to the cells of the hair fiber

Question 7

what causes hair color?

Answer 7

Concentration of eumelanin and pheomelanin cause the variations in hair color.

Question 8

nails

Answer 8

• > Composed of keratinocytes that are cemented together tightly and can extend indefinitely unless cut or broken
• > lunula: is a semilunar (half-moon–shaped) whitish region at the base of the nail plate
• > The paronychium is the soft tissue surrounding the nail border.
• > nail growth and appearance alter during disease
• grooves in nails may occur with high fevers and serious illness, and spoon nails (flattening of the nail plate) develop in iron deficiency anemia

-> Onycholysis (onych/o= nail) is the loosening of the nail plate with separation from the nail bed. may occur with infection of the nail and is often seen in psoriasis

Question 9

sebaceous glands

Answer 9

• located all over the body except the palms, soles, and lips
• secrete sebum which contains lipids. it lubricates the skin and minimizes water loss
• sebum also released into hair follicle
• sebaceous glands are influenced by sex hormones , which cause them to hypertrophy at puberty and atrophy at old age

Question 10

sweat glands

Answer 10

• most common type is eccrine sweat glands: all over body but most numerous in palms and soles
• originates deep in dermis
• Perspiration is controlled by the sympathetic nervous system, whose nerve fibers are activated by the heart regulatory center in the hypothalamic region of the brain, which stimulates sweating.

-> apocrine sweat gland: active only from puberty onward. concentrated in a few areas near the reproductive organs and in the armpits.
^The milk-producing mammary gland is another type of apocrine gland; it secretes milk after the birth of a child.