CH 5

Question 1

What are the two distinct regions of skin?

Answer 1

1. epidermis– epithelium; avascular
2. dermis–underlies the epidermis. Connective tissue; vascular.

Question 2

What is the hypodermis? is it considered apart of the skin?

Answer 2

it is superficial fascia. subcutaneous layer. not apart of the skin. adipose tissue; anchors skin

Question 3

What is the epidermis composed of?

Answer 3

keratinized stratified squamous epithelium

Question 4

List and describe each cell found in the epidermis

Answer 4

1. keratinocytes: keratin, most epidermal cells are keratinocytes, tied together by desmosomes
2. melanocytes: deep epidermis, pigment clusters packaged in melanosomes
3. dendritic (Langerhans) cells: macrophages, immune system.
4. Tactile (merkel) cells: sensory receptors; touch

Question 5

Identify and describe the layers of the epidermis

Answer 5

1. stratum basale (deepest epidermal layer): attached to the dermis. crazy amount of mitosis. also known as stratum germinativum. 10-25% are melanocytes.
2. Stratum spinosum (prickly layer): several layers thick. keratinocytes appear spick (prickle cells)
3. Stratum granulosum (granular layer): four to six cells thick. thin layer: flat cells. Cell appearance starts to change. Nuclei and organelles disintegrate. keratinization begins.
4. Stratum lucidum (only in thick skin) (clear layer): two-three rows of clear, flat, dead keratinocytes. superficial to stratum granulosum.
5. Stratum Corneum (horny layer): 20-30 rows of flat, anucleated, keratinized dead cells. 3/4 of epidermal thickness.

Question 6

What are the characteristics of the dermis?

Answer 6

strong flexible connective tissue; contains fibroblasts, macrophages, mast cells, and white blood cells. also contains nerves, blood vessels, lymphatic vessels, epidermal hair follicles, oil glands, and sweat glands.

Question 7

Name and describe the two dermal layers

Answer 7

1. papillary: the superficial layer of areolar connective tissue. Dermal papillae: fingerlike projection into the epidermis (in thick skin, dermal papillae give rise to epidermal ridge resulting in friction ridges, gripping, sense of touch resulting in fingerprint patterns)
2. reticular: about 80% of the dermal thickness. coarse, dense fibrous connective tissue.
   -cutaneous plexus: network of blood vessels between reticular layer and hypodermis.
   -extracellular matrix: pockets of adipocytes
   -Cleavage (tension) line in reticular layer caused by many collagen fibers running parallel to skin surface. Externally invisible. incision.
   -flexure line of the reticular layer is a dermal fold at our near joints.

Question 8

Name the three pigments that contribute to skin color

Answer 8

1. melanin: made in skin by melanocytes. amino acid tyrosine. melanosomes. Skin color differences are because of varying amounts and forms of melanin. Freckles and moles are local accumulations of melanin.
2. Carotene: yellow-orange pigment; diet. most obvious in palms and soles. accumulates in stratum corneum and hypodermis. Can be converted to vitamin A and epidermal health.
3. hemoglobin: pinkish hue of fair skin. the skin of Caucasians is most transparent, so the color of hemoglobin shows through.

Question 9

Define cyanosis

Answer 9

blue skin color; low oxygenated of hemoglobin

Question 10

define erythema

Answer 10

redness. fever, hypertension, infammatory, allergy.

Question 11

Define jaundice

Answer 11

yellow cast. liver disorders.

Question 12

define bruises

Answer 12

black and blue marks. also called ecchymoses or hematomas. clotted blood beneath the skin. color of bruise changes as clot breaks down

Question 13

What is hair made of? what are the functions of hair?

Answer 13

Flexible strands of the dead, keratinized cells. produced by hair follicles. Contains hard keratin, not like soft keratin found in skin.

Functions include:
-warn of insects on skin
-hair on head-physical trauma
-protect from heat loss
-shield skin from sunlight.

Question 14

What is the shaft and root of hair?

Answer 14

Shaft: the area above scalp; keratinization is complete.
root: area within scalp; keratinization still occuring.

Question 15

What are the three parts of hair shaft?

Answer 15

1. medulla: central core of large cells and air spaces
2. cortex: several layers of flattened cells surrounding medulla
3. cuticle: outer layer consisting of overlapping layer of single cells

Question 16

What results in hair color?

Answer 16

hair pigments are made by melanocytes in hair follicles
-combinations of different melanines (yellow, rust, brown, black) create all the hair colors. Red hair has additional pheomelanin pigment. Grey/white hair-melanin production decreases; air bubbles replace melanin in shaft.

Question 17

what are the structure of a hair follicle?

Answer 17

1. Hair bulb: expanded area at deep end of follicle
2. hair follicle receptor (root hair plexus): sensory nerve endings wrapped around bulb. hair is a sensory touch receptor.
3. Follicle wall: composed of:
   -peripheral connective tissue sheath (fibrous sheath) (derived from dermis)
   
   • glassy membrane: thickened basal lamina.
4. epithelial root sheath: derived from epidermis.
5. hair matrix: area at the bottom of bulb. active area of bulb; produces hair cells. as new cells are made, older ones pushed upward.
6. arrector pili: small band of smooth muscle attached to follicle. “goosebumbs”
7. hair papilla: dermal tissue containing a ton of capillaries that supplies nutrients to growing hair.

Question 18

What is the difference from vellus and terminal hair?

Answer 18

Vellus hair: pale fine body hair of children and adult females

Terminal hair: coarse long hair
-scalp, eyebrows.
-at puberty: axillary and pubic regions

Question 19

What are nails and what are their purose?

Answer 19

scale-like modification of epidermis; contains hard keratin. to protect.

Question 20

identify and describe structure of the nail

Answer 20

1. protective cover: distal, dorsal surface of fingers and toes
   -free edge, nail plate and root
2. nail bed– under the keratinized nail plate
3. nail matrix- thickened portion of nail bed responsible for nail growth.
4. nail fold: lateral skin folds overlapping nail border
5. epinychium- bottom nail folds also called cuticle
6. hyponychium- are under free edge of nail plate that accumulates dirt
7. lunule (lunula): half moon shaped area at bottom, most active growing region of the nail.

Question 21

What are the two main types of sweat glands

Answer 21

1. eccrine (merocrine) sweat glands: most numerous type. abundant on plams, soles and forehead. ducts connect to pores. functions in thermoregulation. (sympathetic nervous system). Their secretion is swat (99% of water, salt, vitamin C, antibodies, dermcidin and metabolic waste)
2. apocrine sweat glands: axillary and anogenital area. secretions are a fatty substance and proteins. (bacteria break down sweat–> body odor). Larger than eccrine sweat glands; ducts empty into hair follicles. Begins functioning at puberty.

Question 22

What are ceruminous and mammary glands?

Answer 22

Ceruminous glands: lining od external ear canal; secret cerumen (earwax)

mammary glands: secrete milk

Question 23

Describe the characteristics of sebaceous (oil) glands

Answer 23

widely distributed, except for palms and soles. most develop from hair follicles; secrete into hair follicles. relatively inactive until puberty.
-secrete sebum: oily holocrine secretion, bactericidal properties. softens and waterproof hair and skin.

Question 24

What are the functions of skin?

Answer 24

1. protection
2. body temperature
3. cutaneous sensations
4. metabolic functions
5. blood reservoir
6. excretion of wastes

Question 25

explain the Chemical, physical and biological barriers of skin

Answer 25

Chemical
-secretes: sweats (antimicrobial proteins), sebum and defensins (kill bacteria)
-acid mantle: skins low pH slows bacterial multiplication
-melanin: barrier against UV radiation damage

Physical
-blocks most water and water soluble substances.
-some chemical have limited penetration of skin
-lipid-soluble substances
-plant oleoresins
-salts of heavy metals
-some drugs

Biological
-dendritic cells of epidermis engulf forein antigens (invaders) and helps activate that immune response
-dermis contains macrophages
-DNA can absorb harmful UV radiation, covering it to harmless heat.

Question 26

How does skin help regulate body temperature

Answer 26

-normal , resting body temperature, sweat glands produce about 500 ml/day insensible perspiration

-Body temperature increases, dermal vessels dilate;
increase sweat gland activity sensible perspiration

-Cools body by evaporation

-When body temperature cools, dermal blood vessels constrict

Question 27

What are the most common skin disorders?

Answer 27

Infections (most common) , skin cancer and burns.

Question 28

What are the three types of skin cancer?

Answer 28

Basal cell carcinoma
-Least malignant; most common
-Stratum basale cells proliferate; slowly invade dermis and hypodermis
-Cured by surgical excision in 99% of cases

Squamous cell carcinoma
-Second most common type; can metastasize
-involves keratinocytes of stratum spinosum
-Scaly reddened papule on scalp, ear, lower lip, or hands
-Good prognosis if treated by radiation therapy or removed surgically

Melanoma
-Cancer of melanocytes; most dangerous type, highly metastatic; resistant to chemotherapy
-Treated by wide surgical excision accompanied by immunotherapy

Question 29

Why are burns so dangerous?

Answer 29

-Tissue damage caused by heat, electricity, radiation or certain chemicals
-Denatures proteins, destroys cell

-Immediate threat-dehydration and electrolyte imbalance

Question 30

What is the rule of Nines?

Answer 30

-body - 11 sections; each section representing 9% of body surface (except genitals, which account for 1%)
-Used to estimate volume of fluid loss

Question 31

How are burns classified? describe each?

Answer 31

First degree
-Epidermal damage only

Second degree
-Epidermal and upper dermal damage

Third degree
-Entire thickness of skin involved (referred to as full-thickness burns)
-Skin color turns gray-white, cherry red or blackened; skin grafting usually necessary
-Area is not painful because nerve endings are destroyed