Lecture 20 - Skin

Question 1

skin is a part of the _____________ system

Answer 1

integumentary

Question 2

what does the integumentary system consist of?

Answer 2

Skin and its associated derivatives (hair, skin, nails, sweat and mammary glands)

Question 3

true or false, skin is the largest organ of the body

Answer 3

true

Question 4

how much body weight and surface area does the skin take up?

Answer 4

15-20% of body weight
1.5 - 2m^2 surface area

Question 5

what are the function of skin?

Answer 5

• barrier
• excretory organ
• synthesis of vitamin D
• Sense organ

Question 6

what does the skin barrier protect us from?

Answer 6

• water loss and entry
• microorganisms (physical and antibacterial)
• Barrier against UV radiation by melanin production

Question 7

how are burn patients effected through damage to the skin barrier?

Answer 7

water loss and dehydration happens

Question 8

how does the skin protect us from microorganisms?

Answer 8

physical barrier
sebum/oil is antibacterial
sweat is slightly acidic and inhibits bacterial growth

Question 9

how is the skin an excretory organ?

Answer 9

sweat excretes salts, toxins and drugs

Question 10

how does the skin synthesise vitamin D?

Answer 10

UV light acts on a precursor to vitamin D

Question 11

how does vitamin D deficiency occur?

Answer 11

lack of UV light means less vitamin D available for bone growth, and this impairs Ca2+ metabolism and causes rickets

Question 12

true or false, the skin is also the largest sense organ in our bodies

Answer 12

true

Question 13

what can our skin sense?

Answer 13

touch, pain, pressure, heat and cold

Question 14

true or false, the skin plays an important role in thermoregulation through dilation and constriction of blood vessels and sweating

Answer 14

true

Question 15

what are the three layers of the skin and their major components?

Answer 15

• epidermis - keratinocytes (epithelial cells)
• dermis - layers of connective tissue
• Hypodermis - subcutaneous layer

Question 16

what type of epithelia is the epidermis?

Answer 16

stratified squamous

Question 17

what are the 5 zones of the epidermis?

Answer 17

1: stratum corneum (dead cell layer)
2: stratum lucidum (only found in thick skin)
3: stratum granulosum (waterproofing with oils and proteins)
4: stratum spinosum (provide structure to skin via spot desmosomes)
5: stratum basale (basal layer contains stem cells)

Question 18

which epidermis layer is replaced?

Answer 18

stratum corneum

Question 19

what shape are the stratum spinosum cells

Answer 19

cuboidal

Question 20

how long does it take for stem cells to migrate from, the base, stratum basale to be lost from the surface, stratum corneum?

Answer 20

40 days

Question 21

describe the thick skin

Answer 21

• epidermis is 1/2mm thick
• palms of hands and soles of feet and toes
• protection in places of mechanical stress

Question 22

describe thin skin

Answer 22

• epidermis is ~100uM thick
• contains stratum lucidum

Question 23

where is the thickest skin of the body?

Answer 23

the back - but doesn’t have the thickest epidermis

Question 24

where is the thinnest skin of the body and why

Answer 24

the eyelid, only 0.2mm thick
- for flexible movement and folding

Question 25

which layer (aside from stratum lucidum) changes the most from thin to thick skin?

Answer 25

stratum corneum - much bigger in thick skin than thin skin

Question 26

what are the major cells types of the epidermis?

Answer 26

keratinocytes melanocytes langerhans cells merkel cells

Question 27

what is the function of keratinocytes?

Answer 27

gives the epithelia its strength, and produce cytokines that can activate other cells

Question 28

what is the function of melanocytes?

Answer 28

produce melanin and deposit them in keratinocytes

Question 29

true or false, people with darker skin have more melanocytes

Answer 29

false, they just have more active melanocytes

Question 30

which layer of the epidermis are melanocytes in?

Answer 30

the stratum basale along with the basal cells

Question 31

what is the function of langerhans cells?

Answer 31

Dendritic antigen presenting cells - detect foreign bodies and initiate an immune response

Question 32

what is the function of merkel cells

Answer 32

- detects fine touch (small receptor fields) - attached to tactile discs which connect merkel cells to the spinal cord

Question 33

what are the main epidermal proteins?

Answer 33

keratin melanin

Question 34

what is the function of keratin

Answer 34

- protection, waterproofing, insoluble - provides strength to the skin

Question 35

keratin is the key structural material that makes up?

Answer 35

the epidermis Hair nails

Question 36

which has more tightly packed and more tightly bound keratin, keratin in hair and nails, or the epidermis, and why?

Answer 36

hair and nails - due to an increase in sulfur atoms which help to form covalent disulfide bonds between keratin molecules (stronger)

Question 37

melanin production occurs after what?

Answer 37

UV exposure

Question 38

why does our skin produce melanin?

Answer 38

it is an extremely effective absorber of light, which protects skin cells from UV radiation damage

Question 39

what attaches the epidermis to the dermis?

Answer 39

basement membrane of the epidermis attaches to dermis epidermal ridges causes the epidermis to be pegged onto the dermis

Question 40

epidermal ridges lead to the formation of what common skin structure?

Answer 40

fingerprints

Question 41

describe the two layers of the dermis

Answer 41

a papillary layer of areolar connective tissue a reticular layer with dense irregular connective tissue

Question 42

where does most of the cell movement occur in the skin?

Answer 42

the papillary layer of the dermis - macrophages to site of breach in skin

Question 43

describe the reticular layer of the dermis

Answer 43

bundles of collagen which are arranged in different orientations to provide strength to the skin while allowing movement in different directions.t

Question 44

true or false, there are sensory receptors call ruffini corpuscles and lamellated/pacinian corpuscles in the dermis

Answer 44

true

Question 45

what are dermal papillae/dermal pegs?

Answer 45

provide nutrients to hair follicles and the epidermis, because the epidermis is avascular

Question 46

where are the majority of the elastin fibres of the dermis?

Answer 46

the reticular layer

Question 47

what are the major cell types of the dermis?

Answer 47

fibroblasts mast cells in papillary layer Macrophages

Question 48

what do fibroblasts do?

Answer 48

secrete collagen and elastin

Question 49

what do mast cells in the papillary layer do?

Answer 49

produce cytokines and cause inflammation as a part of the local immune response

Question 50

what are the main dermal proteins?

Answer 50

collagen and elastin

Question 51

degradation of what leads to wrinkles?

Answer 51

collagen fibers. less strength and elasticity of skin

Question 52

what does elastin do in the dermis?

Answer 52

allows skin to return to original position after stretching or contracting aging leads to loss of elastin fibers

Question 53

describe the structure of the hypodermis

Answer 53

contains loose connective tissue and adipocytes with reticular fibers

Question 54

what is the function of the hypodermis?

Answer 54

binds skin to underlying tissue, provides padding and thermal insulation

Question 55

what are some skin derivatives that are EXTENSIONS of the epidermis?

Answer 55

Nails Hair Sebaceous glands Sweat glands

Question 56

how is the nail formed in the finger?

Answer 56

from the nail matrix of the epidermis - keratin is packed more tightly

Question 57

how is the hair produced in the hair follicle?

Answer 57

at the hair matrix

Question 58

what is the hair papilla?

Answer 58

contain blood vessels that nourish the hair

Question 59

true or false, hair and nails are living issue

Answer 59

false

Question 60

what is a hair bulb?

Answer 60

part of the epidermal layer

Question 61

what do sebaceous glands do?

Answer 61

secrete oily sebum to lubricate our skin via holocrine secretion

Question 62

where do we find sebaceous glands?

Answer 62

normally associated with a hair follicle

Question 63

what are the two types of sweat glands in our skin?

Answer 63

merocrine sweat secrete watery fluid we call sweat to cool body, sweat constantly and often unnoticeably Apocrine sweat glands - are found in the armpits, groin and nipples, often thick fluid and have associated odor due to metabolism by bacteria

Question 64

what are the three branches of receptors in the skin?

Answer 64

thermoreceptors (heat) nociceptors (pain) mechanoreceptors (touch and pressure)

Question 65

look at lecture slides for histology

Answer 65

yes

Question 66

what are TRP receptors?

Answer 66

thermoreceptors in which each type detects a different range of temperatures, between noxious cold , innocuous temperature and noxious hot

Question 67

why do we sense eucalyptus and menthol as cold?

Answer 67

because they are ligands that bind to noxious cold receptors

Question 68

which TRP receptor is activated by capsacian?

Answer 68

TRPV1

Question 69

where is thermoregulation controlled in the brain

Answer 69

primary sensory cortex via lateral spinothalamic tract (conscious response) hypothalamus (autonomic response)

Question 70

describe the autonomous response to temperature

Answer 70

sent to the thermoregulatory center of the hypothalamus, which can activate skeletal muscle (shivering), sweat glands, and even dilation (when its hot) and constriction (when its cold) of blood vessels