8 Skin

Question 1

*Q: Describe the basic structure of the skin. (5) Also includes? (2)

Answer 1

A: TOP: stratum corneum
epidermis
papillary dermis
reticular dermis
(hypodermis) subcutaneous /subcutis

pilo-sebaceous unit and sweat glands

Question 2

*Q: What mainly forms the epidermis? variation? Growth?

Answer 2

A: keratinocytes (4 layers= keratinocytes differ in each: basal cell->prickle cell->granular cell-> corneocytes: lose nucleus)

layer names: stratum basale, spinosum, granulosum, corneum

-start at basement membrane and proliferate and move up skin -> differentiate -> whole purpose is to make keratin (protein)

Question 3

*Q: What are langerhans cells in the epidermis? (2)

Answer 3

A: are dendritic cells (APC)

part of immune recognition

Question 4

*Q: What are merkel cells in the epidermis to do with? What can happen to them?

Answer 4

A: sensation

can get MC carcinomas (can result in death)

Question 5

*Q: What are melanocytes in the epidermis? (2)

Answer 5

A: mature melanin-forming cell

are dendritic and sit on basement membrane

Question 6

*Q: What’s the function of the stratum corneum? Defects in it lead to?

Answer 6

A: barrier function of skin (stops irritants and allergies and prevents inflammation)

eczma (filagrin mutation is common for eczma patients)

Question 7

*Q: What are corneocytes? where? make majority of?

Answer 7

A: differentiated, anucleated cells of keratinocyte lineage

constitute the majority of stratum corneum, the outermost layer of the epidermis

Question 8

Q: Histology. How can you spot a melanocyte? Langerhans cell?

Answer 8

A: look like they’ve got a vacuole

wouldn’t be able to see

Question 9

Q: Describe the stratum corneum structure. How can it be damaged?

Answer 9

A: between cells get a glue of sorts -> combo makes effective barrier

either the lipids or proteins are damaged -> lose function

Question 10

*Q: What is the function of melanin? How is it produced? How is it transmitted to cells?

Answer 10

A: chemical that helps you block some UV damage to nuclei (surface is at risk as is exposed. damage to DNA can cause mutation -> if accumulates = cancer)

keratinocytes have messaging system that when exposed to UV -> produce melanocyte stimulating hormone -> melanocytes then produce lots of melanin -> hence get a tan)

packaged into melanosomes-> go down dendritic pathway -> interact with keratinocytes and transmit melanin to cells

Question 11

*Q: What causes naturally darker skin?

Answer 11

A: don’t have more melanocytes but their baseline production of melanin is higher

by having more and larger melanosomes

Question 12

Q: What happens if adults get vitamin D deficiency? (4)

Answer 12

A: have more chance of getting bone fractures

weaker immune system

lowered mood

less healthy hair growth

Question 13

Q: What causes rickets? Important clinical features? (2)

Answer 13

A: vitamin D deficiency

• swelling in wrists and ankle joints
• bowling of legs

Question 14

Q: What is a malignant melanoma?

Answer 14

A: cancer from melanocytes (uncontrolled growth)

Question 15

*Q: Where is the epidermis derived from embryologically? Dermis? Result?

Answer 15

A: exoderm

mesoderm

• since they’re derived from different origins -> there’s a number of proteins involved in sticking them together
• proteins stick epidermis to basement membrane and proteins within BM stick it to itself and proteins stick BM to dermis

Question 16

*Q: Lack of what component causes blisters? where? (2)

Answer 16

A: proteins (holds epidermis and dermis and BM together) in dermo-epidermal junction = basement membrane zone

Question 17

Q: What is epidermolysis bullosa?

Answer 17

A: inherited skin disorders that cause the skin to become very fragile. Any trauma or friction to the skin can cause painful blisters

will heal with scarring but gets damaged constantly

Question 18

*Q: What is the dermis? consists of? (3) 2 main cells? Thickness? (2)

Answer 18

A: supportive connective tissue matrix

70% collagen, elastin, glycosaminoglycan GAG

fibroblasts (make components above) and immune cells=dermal dendritic cells

varies in thickness (0.1mm eyelids and 3mm back)

Question 19

Q: Histology. Describe collagen.

Answer 19

A: pink strings = collagen fibres

Question 20

Q: Histology. Describe fibroblasts.

Answer 20

A: black nuclei

Question 21

Q: How does the skin help regulate core body temperature? What should it be?

Answer 21

A: 36.8

-variations in skin blood flow (can restrict or dilate)

Question 22

Q: What’s the structure of blood vessels to the skin? (3)

Answer 22

A: dermal papilla (right at surface)

superficial plexus (thicker than prev)

middle plexus

Question 23

Q: How does sweating help regulate core body temperature? Production?

Answer 23

A: sweat (salty) cools the skin through evaporation

produced by eecrine (direct to skin surface) and apocrine (with hair shaft- more viscous sweat) sweat glands (coiled)

Question 24

Q: Where are appocrine sweat glands mainly located? Subject to?

Answer 24

A: armpits and groin

subject to bacteria infection

Question 25

Q: Where do melanocytes embryologically originate from?

Answer 25

A: neural crest

Question 26

*Q: What are the functions of skin? (8)

Answer 26

A: -protect against injury

• protect against pathogenic organisms
• waterproofing and fluid conservation
• thermoregulation
• protection against radiation, absorption of UV and vitamin D production
• surface for grip
• sensory organ
• cosmetic

Question 27

*Q: What makes the pilo-subaceous unit? (4)

Answer 27

A: follicle
hair shaft
sebaceous gland
pili erector muscle

Question 28

*Q: Through which mechanisms does the skin have relationships with other organ systems? (4)

Answer 28

A: endocrine
immune
vascular
neural

Question 29

*Q: Apart from keratinocytes, which cells are tin the epidermis? (3)

Answer 29

A: melanocytes (melanin production)
langerhans cells (antigen presenting cell)
merkel cell (involved in sensation)

Question 30

*Q: What is the basement membrane zone? 3 key features. Why it is clinically important?

Answer 30

A: dermo-epidermal junction

-attached via hemi-desmosomes, anchoring plaques and proteins

genetic abnormalities in it can lead to abnormality of protein in this region and cause blistering eg epidermolysis bullosa

Question 31

*Q: What does the subcutaneous layer consist of? (2)

Answer 31

A: connective tissue and fat