structure and function of the skin

Question 1

what are the 3 main layer of the skin

Answer 1

• epidermis
• dermis
• subcutis

Question 2

what are some functions of the skin

Answer 2

• physical barrier against friction and shearing forces
• protection against infection, chemicals, UV radiation
• synthesis of vitamin D
• temperature regulation
• sensation
• antigen presenting and wound healing
• hormonal synthesis

Question 3

what kind of epithelium is the epidermis

Answer 3

stratified squamous epithelium

Question 4

what are the downward projections of epidermis into the dermis called

Answer 4

rete ridges

Question 5

what is epidermis mainly composed of

Answer 5

keratinocytes

Question 6

where do keratinocytes originate

Answer 6

from basal layer

Question 7

when do keratinocytes differentiate

Answer 7

as they migrate outwards to the surface, where they are shed

Question 8

what do keratinocytes synthesis in the basal layer

Answer 8

variety of keratin filaments and desmosomal proteins (make up the cytoskeleton)

Question 9

what do keratinocytes become in the granular layer

Answer 9

lipid and lipid hydrolyses

- from a water tight intercellular lipid bilayer

Question 10

what do the lamellar bodies produce

Answer 10

abundant quantities of pro-fillagrin which is covered to fillagrin in the outer layer of cells or stratum corneum

Question 11

what are the 2 roles of filaggrin

Answer 11

• holding moisture within the cells

- component of tough protein cell envelope

Question 12

what happens to cells as they migrate outwards

Answer 12

they die, lose their nuclei and flatten into squames

Question 13

what is the outer stratum corneum like

Answer 13

tissue-paper thin but provides most fo the barrier function of the epidermis

Question 14

what does filaggrin deficiency lead to

Answer 14

leaky skin that loses water and allows entry of allergens that trigger an immunological response

Question 15

what does loss of function mutation of filaggrin cause

Answer 15

dry, scaly skin complaint, ichthyisus vulgarisms

Question 16

how long does it take for keratinocytes to migrate for the basal layer to the skin surface

Answer 16

30 days

Question 17

how long does it take for keratinocytes to migrate from basal layer to the skin surface in psoriasis

Answer 17

quicker than 30 days

Question 18

what do keratinocytes secrete

Answer 18

• cytokines (interleukins)
• interferon-gamma
• TNF

Question 19

what are the cells in the epidermis

Answer 19

• keratinocytes
• melanocytes
• Merkel cell s
• langerhans cells

Question 20

where do melanocytes originate from

Answer 20

neural crew

Question 21

where do melanocytes reside

Answer 21

in the basal layer

Question 22

what’s more abundant keratinocytes or melanocytes

Answer 22

keratinocytes

Question 23

what do melanocytes synthesise

Answer 23

pigment melanin

Question 24

where is melanin transferred into

Answer 24

surrounding keratinocytes to give protection against UV radiation

Question 25

what are racial differences in skin colour due to

Answer 25

variation in melanin production (not melanocytes number)

Question 26

where are Merkel cells found

Answer 26

in the basal layer

Question 27

where are Merkel cells numerous

Answer 27

on fingertips and in the oral cavity

Question 28

what do Merkel cells play a role in

Answer 28

sensation

Question 29

what are langerhans cells

Answer 29

dendritic cells

Question 30

where are langerhans cells derived

Answer 30

in the bone marrow

Question 31

what do langerhans cells form

Answer 31

a network across the supra-basal layer

Question 32

what do langerhans cells playa a role in

Answer 32

antigen presenting and in immunoregulation

Question 33

how is the epidermis anchored to the dermis

Answer 33

by a complex meshwork of proteins that link the keratin intermediate filaments of basal keratinocytes to collagen fibres in the superficial dermis

Question 34

what is the joining part called

Answer 34

basement membrane zone

Question 35

what can an. autoimmune deficiency of the connecting proteins cause

Answer 35

skin fragility and a variety of blistering diseases

Question 36

what is the dermis origin

Answer 36

mesodermal origin

Question 37

what is the dermis

Answer 37

matriculates of collagen and elastin fibres, surrounded by an extracellular gel-like substance

Question 38

what do the dermis fibres give skin

Answer 38

its strength and elasticity

Question 39

what cells does the dermis contain

Answer 39

- fibroblasts - mast cells - lymphocytes - dermal dendritic cells

Question 40

what does the dermis contain

Answer 40

- blood - lymphatic vessels - nerves - muscle - appendages (sweat glands, sebaceous glands and hair follicles)

Question 41

what is the lower reticular dermis like

Answer 41

thicker and denser

Question 42

where are eccrine sweat glands found

Answer 42

throughout the skin

Question 43

what are eccrine sweat glands responsible for

Answer 43

thermoregulation sweating

Question 44

where are apocrine sweat glands found

Answer 44

in the axillae and anogenital area

Question 45

when do apocrine sweat glands function

Answer 45

not until puberty

Question 46

when are sebaceous glands active

Answer 46

after puberty

Question 47

what do sebaceous glands secrete

Answer 47

oily substance called sebum

Question 48

how does sebum pass on to the skin surface

Answer 48

via the pilosebaceous duct (hair follicle)

Question 49

where are sebaceous glands found mostly

Answer 49

on the face, scalp and upper torso

Question 50

what fibres transmit touch, pain and itch

Answer 50

sensory nerve fibres

Question 51

what does the dermal autonomic innervate

Answer 51

- sweat glands - blood vessels - arrectores pilorum muscles - controls skin thermoregulatory function

Question 52

what is the skin surface covered in

Answer 52

hair

Question 53

how does hair arise

Answer 53

from modified downgrowth of epidermal keratinocytes into the dermis

Question 54

what does the hair shaft contain

Answer 54

- inner and outer root sheath - cortex - medulla

Question 55

what does the lower part of the hair follicle contain

Answer 55

expanded bulb (contains melanocytes)

Question 56

how does the hair regrow after shedding

Answer 56

from the bulb

Question 57

what are the growth cycle of hair follicles

Answer 57

- anagen (growth) - catagen (involution) - telogen (shedding)

Question 58

what stage of the cycle is most hair at

Answer 58

anagen

Question 59

what is grey hair due to

Answer 59

decreased tyrosine activity in the hair bulb melanocytes

Question 60

what is white hair due to

Answer 60

total loss of the melanocytes

Question 61

what are the 3 types of hair

Answer 61

- terminal - vellus - lanugo

Question 62

what is terminal hair

Answer 62

medullated coarse hair e.g. scalp, beard, pubic

Question 63

what is vellus hair

Answer 63

non-medullated fine, downy hairs seen on the face of women and in pre-pubertal children

Question 64

what is lanugo hair

Answer 64

non-medulalted fetal hair seen in permature babies and occasionally in malnourished people

Question 65

what are nails

Answer 65

tough plates of hardened keratin

Question 66

where do nails arise

Answer 66

in nail matrix

Question 67

how long does it take to grow a fingernail

Answer 67

6 months

Question 68

how long to grow a toenail

Answer 68

1 year

Question 69

what does the subcutaneous layer consist of

Answer 69

adipose tissue

Question 70

how is subcutaneous layer arranged into

Answer 70

lobules

Question 71

how is the subcutaneous layer separated

Answer 71

by fibrous septa

Question 72

what does the subcutaneous layer contain

Answer 72

blood vessels and nerves

Question 73

what does the subcutaneous layer provide

Answer 73

insulation and cushioning against trauma