Structure and function of skin

Question 1

Epidermis

Answer 1

Outer layer
Thin
Stratified cellular epithelium
Continuously regenerated

Question 2

Epidermis layers (from 16 weeks onwards)

Answer 2

Keratin layer (stratum corneum)
Granular layer
Prickle cell layer (spinal)
Basal layer

Question 3

Epidermis layers (4 weeks)

Answer 3

Periderm

Basal layer

Question 4

Ectoderm forms epidermis/dermis

Answer 4

Epidermis

Question 5

Mesoderm forms epidermis/dermis

Answer 5

Dermis

Question 6

Appendages

+examples

Answer 6

Everything else that’s not primary skin

nails, hair, glands, mucosae

Question 7

Blaschko’s lines

Answer 7

Developmental growth pattern of skin
If patient presents with a linear configuration on skin then it indicates that it is a congenital thing to do with development before birth

Question 8

Dermis

Answer 8

Leathery
Connective tissue
Provide strength
Beneath epidermis

Question 9

Sub-cutis

Answer 9

Predominantly fat

Question 10

Main cells in the epidermis

Answer 10

Keratinocytes (migrate from basement membrane)
Melanocytes (supra basal and basal)
Merkel Cells (basal)
Langerhans cells (supra basal)

Question 11

How many days does it take the epidermis to regenerate?

Answer 11

Around 28

Question 12

Keratin layer

stratum corneum

Answer 12

Tight waterproof barrier, physical barrier
Lots of lipids (from lammelar granules)
Corneocytes (overlapping non nucleated cell remnants)
More keratin is formed in response to mechanical pressure (i.e. guitar players)

Question 13

Granular layer

Answer 13

2-3 layers of cells
Large keratohyalin granules which contain structural filaggrin and involucrin proteins
High lipid content

Question 14

Prickle cell layer

spinal layer

Answer 14

Lots of desmosomes (connections)
- communication
- movement
large polyhedral cells

Question 15

Basal layer

Answer 15

Small, cuboidal
Usually one cell thick
Highly metabolically active
Can be used to make stem cells

Question 16

Melanocytes

Answer 16

Pigment producing dendritic cells
Produce melanin
Forms protective cap oer nucleus in basal cells

Question 17

Where do melanocytes arise from?

Answer 17

Migrate from neural crest -> epidermis (basal and supra basal layers) in the first 3 months of foetal development

Question 18

What are the function of melanosomes in melanocytes?

Answer 18

Convert tyrosine -> melanin

Question 19

2 types of melanin

Answer 19

Eumelanin (brown/black)

Phaemelanin (red/yellow)

Question 20

Melanocytes:basal cells

Answer 20

1:10
Ratio is constant irrespective of race (i.e. - dark and light skin have the same number of melanocytes but dark skin produces more melanin than light skin)

Question 21

What is melanin?

Answer 21

Gives colour to the skin and hair

Question 22

Langerhans cell

Answer 22

Type of dendritic cell involved in the skin immune system
Act as guards in the epidermis.
First line of defence

Question 23

Where do langerhans cells arise from?

And where are they located?

Answer 23

Bone marrow

Located in the prickle cell layer (supra basal)

Question 24

Melanocytes histology

Answer 24

Halo appearance around them

Question 25

Langerhans histology

Answer 25

tennis raquet appearance (brick granules)

Question 26

Merkel cells

Answer 26

Mechanoreceptors - Present the connection between the skin and the brain
Essential for light touch responses

Question 27

Merkel cells location

Answer 27

Basal layer of epidermis

At highest density at the fingertips where touch sensation is most acute

Question 28

Pacinian corpuscles

Answer 28

Detect pressure
Deep in the dermis
Look like onions

Question 29

Meissners corpuscles

Answer 29

Detect vibration

Superficial in the dermis (i.e. immediately below the DE junction)

Question 30

DE junction

Answer 30

Interface between epidermis and dermis

Semi-permeable membrane

Question 31

DE junction - functions

Answer 31

Maintain structure

Support, anchor, adhesion, growth and differentiation of basal cells, key role in messaging

Question 32

DE junction - parts

Answer 32

Lamina lucida
Lamina densa
Sub lamina densa

Question 33

Components of the dermis

Answer 33

Cells:
Fibroblasts, Macrophages, Mast cells, Lymphocytes, Langerhans cells

Fibres:
Collagen, Elastin

Blood vessels - superficial and deep plexus
lymphatics - follow the blood vessels
nerves - somatic sensory, autonomic nerves

Question 34

Fibroblasts

Answer 34

Found in dermis

Make collagen

Question 35

What happens as a result of decreased collagen

Answer 35

Increased wrinkles and therefore increased ageing

Question 36

Skin as a physical barrier

Answer 36

Trauma, Friction, UV radiation

Question 37

Skin as a chemical barrier

Answer 37

Irritants, allergens, toxins

Question 38

Skin as a pathogen barrier

Answer 38

Bacteria, viruses, fungi

Question 39

Vit D metabolism in the skin

Answer 39

Vitamin D3 is produced in the skin and is stored in the liver as hydroxycholecalciferol.
This is converted to 1,25-digydroxycholecalciferol in the kidney

Question 40

Where do we get Vit D from?

Answer 40

Sunlight

Diet

Question 41

Function of Vit D

Answer 41

Promote mineralisation of bone

Question 42

The skin and thermoregulation

Answer 42

Thermoreceptors control sweating, shivering, blood supply
As core temp increases:
- shivering decreases
- sweating increases
- blood flow to skin increases (vasodilation)