Second half of Chapter 6

Question 1

Structure of the Hair and Follicle:Dermal papilla

Answer 1

Dermal papilla: bud of vascular connective tissue encased by bulb. Only source of nutrition for hair.

Question 2

Structure of the Hair and Follicle: Hair matrix

Answer 2

Hair matrix—region of mitotically active cells immediately above papilla. Hair’s growth center.

Question 3

Structure of the Hair and Follicle:Follicle

Answer 3

Follicle—diagonal tube that extends into dermis and possibly hypodermis

Question 4

Structure of the Hair and Follicle: Epithelial root sheath

Answer 4

Epithelial root sheath. Extension of the epidermis lying adjacent to hair root. Widens at deep end into bulge—source of stem cells for follicle growth.

Question 5

Structure of the Hair and Follicle: Connective tissue root sheath

Answer 5

Connective tissue root sheath,Derived from dermis but a bit denser, Surrounds epithelial root sheath.

Question 6

Structure of the Hair and Follicle: Hair receptors

Answer 6

Hair receptors—sensory nerve fibers entwining follicles.

Question 7

Structure of the Hair and Follicle:Piloerector muscle (arrector pili)

Answer 7

Piloerector muscle (arrector pili)—smooth muscle attaching follicle to dermis. Contracts to make hair stand on end (goose bumps)

Question 8

Hair Texture and Color: Texture

Answer 8

Texture—related to cross-sectional shape of hair.Straight hair is round, Wavy hair is oval, Curly hair is relatively flat.

Question 9

Hair Texture and Color:Color

Answer 9

Color—due to pigment granules in the cells of the cortex.Brown and black hair is rich in eumelanin.Red hair has high concentration of pheomelanin.Blond hair has an intermediate amount of pheomelanin and very little eumelanin.Gray and white hair have little or no melanin. Air present in medulla.

Question 10

Three stages of hair cycle:Anagen

Answer 10

Anagen: growth stage.90% of scalp follicles at a given time.Stem cells multiply.Root sheath cells above papilla form hair cells of hair matrix.Hair cells make keratin and die as they are pushed upward.

Question 11

Three stages of hair cycle:Catagen

Answer 11

degeneration stage.Mitosis in hair matrix ceases and sheath cells below bulge die.Base of hair keratinizes into a hard club—club hair.Easily pulled out by brushing

Question 12

Three stages of hair cycle: Telogen

Answer 12

resting stage.When papilla reaches the bulge

Question 13

Hair Growth and Loss:We lose about 50-100 hairs daily

Answer 13

A club hair may fall out during catagen or telogen or be pushed out in the next anagen phase.In young adults, scalp follicles spend 6–8 years in anagen, 2–3 weeks in catagen, 1–2 months in telogen.

Question 14

Hair growth

Answer 14

scalp hairs grow 1 mm per 3 days.Alopecia—thinning of the hair or baldness.

Question 15

Pattern baldness

Answer 15

hair lost from select regions. Baldness allele is dominant in males and expressed when testosterone levels are high. Testosterone causes terminal hair on top of scalp to be replaced by vellus hair

Question 16

Hirsutism

Answer 16

excessive or undesirable hairiness in areas that are not usually hairy.

Question 17

Functions of Hair

Answer 17

Most hair on trunk and limbs is vestigial.Has little present function but kept ancestors warm.Hair receptors alert us of parasites crawling on skin.Scalp retains heat and protects against sunburn.Pubic and axillary hair signify sexual maturity and aid in transmission of sexual scents

Question 18

Functions of Hair: Guard hairs (vibrissae)

Answer 18

Guard nostrils and ear canals,Eyelashes and eyebrows, Nonverbal communication

Question 19

Nails: Fingernails and toenails

Answer 19

clear, hard derivatives of stratum corneum

Composed of thin, dead cells packed with hard keratin

Question 20

Nails:Functions

Answer 20

Improve grooming, picking apart food, other manipulations.Provide a counterforce to enhance sensitivity of fleshy fingertips to tiny objects.

Question 21

Nails: Nail plate

Answer 21

hard part of the nail:Free edge: overhangs the fingertip.

Nail body: visible attached part of nail. Nail root: extends proximally under overlying skin

Question 22

Nail fold

Answer 22

surrounding skin rising above nail

Question 23

Nail groove

Answer 23

separates nail fold from nail plate

Question 24

Nail bed

Answer 24

skin underlying the nail plate. Hyponychium—epidermis of the nail bed

Question 25

Nail matrix

Answer 25

growth zone (mitotic) of thickened stratum basale at proximal end of nail. 1 mm per week in fingernails, slightly slower in toenails. Lunule—opaque white crescent at proximal end of nail due to thickness of matrix

Question 26

Eponychium (cuticle)

Answer 26

narrow zone of dead skin overhanging proximal end of nail

Question 27

Two kinds of sweat (sudoriferous) glands: apocrine and merocrine Apocrine sweat glands

Answer 27

Apocrine sweat glands .Locations: groin, anal region, axilla, areola, beard area in men. Inactive until puberty Ducts lead to nearby hair follicles. Produce sweat that is milky and contains fatty acids.Respond to stress and sexual stimulation. Believed to secrete pheromones—chemicals that can influence behavior of others

Question 28

Two kinds of sweat (sudoriferous) glands: apocrine and merocrine: Bromhidrosis

Answer 28

Bromhidrosis—disagreeable body odor produced by bacterial action on sweat from apocrine glands.

Question 29

Two kinds of sweat (sudoriferous) glands: Merocrine (eccrine) sweat glands

Answer 29

Merocrine (eccrine) sweat glands. Most numerous skin glands—3 to 4 million in adult skin. Especially dense on palms, soles, and forehead. Simple tubular glands Watery perspiration that helps cool the body

Question 30

Two kinds of sweat (sudoriferous) glands: Myoepithelial cells

Answer 30

Myoepithelial cells—contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct. Found in both apocrine and merocrine glands

Question 31

Sweat

Answer 31

Sweat—begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland. Some sodium chloride and other small solutes remain in the sweat. Some sodium chloride reabsorbed by duct. Some drugs are excreted in sweat. On average, 99% water, with pH range of 4 to 6 Acid mantle—inhibits bacterial growth

Question 32

Sweat glands:Insensible perspiration

Answer 32

Insensible perspiration—500 mL/day. Does not produce visible wetness of skin

Question 33

Sweat glands:Diaphoresis

Answer 33

Diaphoresis—sweating with wetness of the skin. Exercise—may lose 1 L sweat per hour

Question 34

Sebaceous Glands and Sebum

Answer 34

Sebaceous glands are flask-shaped and have short ducts opening into hair follicles. Holocrine secretion style . Sebum—oily secretion of sebaceous glands Keeps skin and hair from becoming dry, brittle, and cracked. Lanolin—sheep sebum

Question 35

Ceruminous Glands

Answer 35

Ceruminous glands are simple, coiled, tubular glands in external ear canal. Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen). Keeps eardrum pliable. Waterproofs the canal. Kills bacteria. Makes guard hairs of ear sticky to help block foreign particles from entering auditory canal

Question 36

Mammary glands

Answer 36

Mammary glands—milk-producing glands that develop only during pregnancy and lactation. Modified apocrine sweat glands. Rich secretion released through ducts opening at nipple

Question 37

Mammary ridges or milk lines

Answer 37

Mammary ridges or milk lines-Two rows of mammary glands in most mammals Primates kept only two glands, but a few people have additional nipples along the milk line (polythelia)

Question 38

Skin cancer

Answer 38

Skin cancer—most cases caused by UV rays of the sun damaging skin cell DNA. Most often on the head, neck, and hands. Most common in fair-skinned people and the elderly. One of the most common, easily treated cancers. Has one of the highest survival rates if detected and treated early

Question 39

Three types of skin cancer

Answer 39

Three types of skin cancer named for the epidermal cells in which they originate. Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma

Question 40

Skin cancer: Malignant melanoma

Answer 40

Skin cancer that arises from melanocytes Less than 5% of skin cancers, but most deadly form. Can be successfully removed if caught early, but if it metastasizes it is usually fatal.Greatest risk factor: familial history of malignant melanoma.Highest incidence in men, redheads, and people who had severe sunburn as a child