Physiology

Question 1

what is the largest organ in the body?

Answer 1

the skin

Question 2

layers of the skin

Answer 2

1. epidermis
2. appendages
3. dermo-epidermal junction
4. dermis
5. sub-cutis (fat)

Question 3

what is the epidermis epithelium?

Answer 3

stratified squamous epithelium

Question 4

four distinct layers of the epidermis

Answer 4

• keratin layer
• granular layer
• prickle cell layer
• basal layer

Question 5

another name for the keratin layer

Answer 5

stratum corneum

Question 6

what does the keratin layer consist of?

Answer 6

corneocytes (overlapping, non-nucleated fragments) with lamellar granules

Question 7

function of the stratum corneum

Answer 7

waterproof barrier

Question 8

what does the granular layer consist of?

Answer 8

2-3 layers of flattened cells with keratohyalin granules containing filaggrin and involucrin

Question 9

what does the prickle cell layer consist of?

Answer 9

polyhedral cells with lots of desmosomes connected to intermediate filaments

Question 10

what does the basal layer consist of

Answer 10

cuboidal cells with intermediate filaments

Question 11

function of the basal layer

Answer 11

high metabolic/mitotic rate

melanocytes are found here and transfer melanin via dendritic processes

Question 12

describe epidermal turnover

Answer 12

keratinocytes migrate from the BM to the stratum corner over 28 days

Question 13

what is epidermal turnover regulated by?

Answer 13

growth factors
cell death
hormones

Question 14

when is epidermal turnover regulation lost?

Answer 14

cancer

psoriasis (immature epidermis)

Question 15

other cells in the epidermis

Answer 15

• melanocytes
• Langerhans cells
• Merkel cells

Question 16

describe melanocytes

Answer 16

pigment producing dendritic cells that contain melanosomes that transfer to keratinocytes
convert tyrosine to melanin (absorbs sunlight forming a protective cap over nucleus)

Question 17

what are Langerhans cells associated with?

Answer 17

birbeck granules

Question 18

merkel cells

Answer 18

mechnoreceptor

viral cancer

Question 19

three types of appendages in the skin

Answer 19

1. nails
2. hair
3. glands

Question 20

what are nails

Answer 20

specialised keratins

Question 21

what is hair made of?

Answer 21

keratin

Question 22

what is hair attached to?

Answer 22

sebaceous gland

Question 23

how is hair pigmented?

Answer 23

melanocytes above the dermal papilla

Question 24

phases of growth in hair

Answer 24

anagen
catagen
telogen

Question 25

hormone influences on hair?

Answer 25

thyroxine

androgens

Question 26

three types of glands

Answer 26

sebaceous
apocrine
eccrine

Question 27

describe sebaceous glands

Answer 27

attached to hairs
hormone sensitive and produce sebum (protective from infection)
control moisture loss

Question 28

describe apocrine glands

Answer 28

present in axilla and perineum

androgen dependent

Question 29

describe eccrine glands

Answer 29

whole skin surface
under sympathetic cholinergic nerves
ultrafiltration and thermoregulation

Question 30

describe the derma-epidermal junction

Answer 30

epithelial-mesenchymal interaction

Question 31

what is the BM made of

Answer 31

laminin and collagen

Question 32

what does the dermis consist of?

Answer 32

connective tissue
fibroblasts, macrophages, mast cells
fibres: collagen and elastin
ground substances: HA and chondroitin sulphate

Question 33

accessories in the dermis

Answer 33

blood vessels arranged in horizontal plexuses
muscles- arrector pili attached to hair follicles
lymphatics

Question 34

two types of nerves in the dermis

Answer 34

1. somatic sensory (dermatomes): free nerve endings with Pacinian and Meissner’s corpuscles
2. autonomic supplying blood vessels, nerves and glands

Question 35

functions of the skin

Answer 35

barrier
thermoregulation
immune defence
metabolism (vit D and thyroxine)
communications (visual, odour, stigma)
sensation