First half of Chapter 6

Question 1

What is the integumentary system

Answer 1

(Fancy name for skin) consists of skin and accesory organs; hair, nails and cutaneous glands.

Question 2

Inspection

Answer 2

Inspection of the skin, hair and nails is significant part of a physical exam. Skin is the most vulnerable organ. Relieves more medical treatment than any other organ. Largest organ in our body.

Question 3

Skin Thickness : Thick and Thin

Answer 3

Thick skin covers front of hands, bottoms of feet, has sweat glands but no hair follicles or sebaceous (oil) glands. Thin skin covers the rest possesses hair follicles, sebaceous glands and sweat glands.

Question 4

Functions of the skin: resistance to trauma and infection

Answer 4

Keratin(predominant in skin), Dermacidin and defensins. Acid mantle.

Question 5

Functions of the skin: Other barrier functions(keep out)

Answer 5

Water, UV radiation and harmful chemicals.

Question 6

Functions of the skin: Vitamin D synthesis

Answer 6

Skin carries out of first step, liver and kidneys complete process.

Question 7

Functions of the skin: sensation

Answer 7

Sensation: skin is an extensive sense organ. Receptors for temperature, touch, pain and more.

Question 8

Functions of the skin: Thermoregulation

Answer 8

Thermoregulation:

Thermoreceptors(cool and conserve heat), Vasoconstriction/vasodilation. Perspiration.

Question 9

Functions of the skin: Nonverbal communication

Answer 9

Nonverbal communication:
Facial expression
Importance in social acceptance and self image.

Question 10

The Epidermis

Answer 10

Epidermis—keratinized stratified squamous epithelium
(inside cells but dead cells)
Includes dead cells at skin surface packed with tough keratin protein
Lacks blood vessels
Depends on the diffusion of nutrients from underlying connective tissue
Contains sparse nerve endings for touch and pain

Question 11

Cells of the Epidermis: Stem cells

Answer 11

Undifferentiated cells that give rise to keratinocytes

In deepest layer of epidermis (stratum basale)

Question 12

Cells of the Epidermis: Keratinocytes

Answer 12

Great majority of epidermal cells

Synthesize keratin

Question 13

Cells of the Epidermis: Melanocytes

Answer 13

Melanocytes
Synthesize pigment melanin that shields DNA from ultraviolet radiation
Occur only in stratum basale but have branched processes that spread among keratinocytes and distribute melanin

Question 14

Cells of the Epidermis: Tactile cells

Answer 14

Tactile cells: Touch receptor cells associated with dermal nerve fibers
In basal layer of epidermis

Question 15

Cells of the Epidermis: Dendritic cells

Answer 15

Dendritic cells
Macrophages originating in bone marrow that guard against pathogens
Found in stratum spinosum and granulosum. Special type of immune cells.

Question 16

Stratum basale (deepest epidermal layer)Layers of the Epidermis

Answer 16

Thin skin contains four strata; thick skin contains five strata
Stratum basale (deepest epidermal layer):A single layer of stem cells and keratinocytes resting on the basement membrane
Stem cells divide and give rise to keratinocytes that migrate toward skin surface to replace lost cells
Also contains a few melanocytes and tactile cells

Question 17

Stratum spinosum (Layers of the Epidermis)

Answer 17

Several layers of keratinocytes joined together by desmosomes and tight junctions
Named for appearance of cells after histological preparation (spiny)
Also contains some dendritic cells.(resist pulling apart)

Question 18

Layers of the Epidermis,Stratum granulosum

Answer 18

Stratum granulosum
Three to five layers of flat keratinocytes
Cells contain dark-staining keratohyalin granules(related to keratin)

Question 19

Layers of Epidermis, Stratum lucidum

Answer 19

Thin, pale layer found only in thick skin

Keratinocytes packed with clear protein eleidin(only in thick skin)

Question 20

Layers of epidermis:Stratum corneum

Answer 20

Stratum corneum (surface layer)
Several layers (up to 30) of dead, scaly, keratinized cells
Resists abrasion, penetration, water loss

Question 21

The Life History of a Keratinocyte:Keratinocytes

Answer 21

are produced by mitosis of stem cells in stratum basale or mitosis of keratinocytes in deepest part of stratum spinosum
Mitosis requires abundant oxygen and nutrients, so once cells migrate away from blood vessels of the dermis, mitosis cannot occur

Question 22

The Life History of a Keratinocyte:New keratinocytes

Answer 22

push older ones toward the surface
Over time, keratinocytes flatten, produce more keratin and membrane-coating vesicles
In 30 to 40 days a keratinocyte makes its way to the skin surface and flakes off (exfoliates) as dander
Slower in old age
Faster in injured or stressed skin
Calluses or corns—thick accumulations of dead keratinocytes on hands or feet.

Question 23

The Life History of a Keratinocyte:Four important events occur in stratum granulosum:

Answer 23

Keratohyalin granules release filaggrin—a protein that binds keratin into tough bundles
Cells produce tough envelope proteins beneath their membranes
Membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it
Keratinocytes’ organelles degenerate and the cells die

Question 24

The Life History of a Keratinocyte: Epidermal water barrier

Answer 24

Epidermal water barrier:
Water retention is fostered by tight junctions between skin cells and the waterproofing that occurs in the stratum granulosum
Helps prevent dehydration
Does not prevent the absorption of water by the stratum corneum when we soak in a bath (“prune fingers”)

Question 25

Dermis

Answer 25

Dermis—connective tissue layer beneath epidermis. Composed mainly of collagen Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings Houses hair follicles and nail roots Is the tissue of the facial skin to which skeletal muscles attach and cause facial expressions of emotion Has a wavy, conspicuous boundary with the superficial epidermis

Question 26

Dermal papillae

Answer 26

are upward, finger-like extensions of dermis

Question 27

Epidermal ridges

Answer 27

are downward waves of epidermis | Prominent waves on fingers produce friction ridges of fingerprints.

Question 28

Hypodermis

Answer 28

Subcutaneous tissue Has more areolar and adipose than dermis has Pads body and binds skin to underlying tissues Common site of drug injection since it has many blood vessels.

Question 29

Subcutaneous fat

Answer 29

Energy reservoir Thermal insulation Thicker in women Thinner in infants, elderly

Question 30

Skin Color:Melanin

Answer 30

Melanin—most significant factor in skin color Produced by melanocytes, accumulates in keratinocytes Two forms of the pigment: Eumelanin—brownish black Pheomelanin—reddish yellow (sulfur-containing)

Question 31

People of different skin colors have the same number of melanocytes

Answer 31

Darker skinned people Produce greater quantities of melanin Melanin breaks down more slowly Melanin granules more spread out in keratinocytes Melanized cells seen throughout the epidermis Lighter skinned people Melanin clumped near keratinocyte nucleus Little melanin seen beyond stratum basale

Question 32

Skin Color

Answer 32

This color fades as melanin is degraded and old cells are exfoliated. Exposure to UV light stimulates melanin secretion and darkens skin.

Question 33

Other pigments can influence skin color

Answer 33

Hemoglobin—pigment in red blood cells Adds reddish to pinkish hue to skin Carotene—yellow pigment acquired from egg yolks and yellow/orange vegetables Concentrates in stratum corneum and subcutaneous fat.

Question 34

The Evolution of Skin Color

Answer 34

Variations in skin color result from multiple evolutionary selection pressures, especially differences in exposure to UV light (UV accounts for up to 77% of skin tone variation) UV light has both harmful and beneficial effects Adversely: it causes skin cancer, breaks down folic acid Beneficially: it stimulates vitamin D synthesis Populations that evolved in the tropics have well-melanized skin to protect against excessive UV

Question 35

The Evolution of Skin Color, continued

Answer 35

Populations that evolved in far northern and southern latitudes (weak sun) have light skin to allow adequate UV Populations that evolved at high altitudes or dry climates (less UV filtering) also are darker skinned Importance of vitamin D for calcium (crucial for pregnancy, lactation) might explain why women are lighter skinned than men

Question 36

Hair and Nails

Answer 36

Hair, nails, and cutaneous glands are accessory organs (appendages) of the skin. Hair and nails are composed of mostly dead, keratinized cells Pliable soft keratin makes up stratum corneum of skin Compact hard keratin makes up hair and nails Tougher and more compact due to numerous cross-linkages between keratin molecules

Question 37

Pilus

Answer 37

Pilus—another name for a hair; pili—plural of pilus

Question 38

Hair

Answer 38

Hair—a slender filament of keratinized cells growing from a tube in the skin called a hair follicle

Question 39

Hair covers most of the body

Answer 39

Hair does not cover: palms, soles; palmar, plantar, and lateral surfaces and distal segments of fingers and toes; lips, nipples, and parts of genitals Limbs and trunk have 55 to 70 hairs per cm2 Face has about 10 times as many 100,000 hairs on an average person’s scalp Differences in hairiness across individuals is mainly due to differences in texture and pigment of hair

Question 40

Three types of hair-Lanugo

Answer 40

Lanugo: fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development

Question 41

Three types of hair-Vellus

Answer 41

Vellus: fine, pale hair that replaces lanugo by time of birth Two-thirds of the hair of women One-tenth of the hair of men All of hair of children except eyebrows, eyelashes, and hair of the scalp

Question 42

Three types of hair-Terminal

Answer 42

Terminal: longer, coarser, and more heavily pigmented Forms eyebrows, eyelashes, and the hair of the scalp After puberty, forms the axillary and pubic hair Male facial hair and some of the hair on the trunk and limbs

Question 43

Structure of the Hair and Follicle: Hair is divisible into three zones along its length Bulb:

Answer 43

Bulb: a swelling at the base where hair originates in dermis or hypodermis Only living hair cells are in or near bulb

Question 44

Structure of the Hair and Follicle: | Hair is divisible into three zones along its length:Root

Answer 44

Root-the remainder of the hair in the follicle

Question 45

Structure of the Hair and Follicle: | Hair is divisible into three zones along its length:Shaft

Answer 45

the portion above the skin surface