Physiology of skin

Question 1

Which type of skin cells are formed from the neural crest?

Answer 1

Melanocytes

Question 2

How is the epidermis formed embyologically?

Answer 2

Ectoderm cells form single layer periderm

Gradual increase in layers of cells

Periderm cells cast off

Question 3

Which embryological layer is the dermis formed from?

Answer 3

Mesoderm

Question 4

At which stage of development are the four epidermis layers and dermis formed?

Answer 4

16 weeks

Question 5

At which stage of embyrological development is the skin formed to look like this?

Answer 5

26 weeks

Question 6

What are Blaschko’s lines?

Answer 6

Lines of skin development

Question 7

What is the epidermis?

Answer 7

The outermost layer of skin, stratified squamous epithelium

Question 8

What does most of the epidermis consist of?

Answer 8

Keratinocytes (95%)

Question 9

What are the four epidermal layers?

Answer 9

Keratin layer

Granular layer

Prickle cell layer

Basal cell layer

Question 10

How do keratinocytes allow constant regeneration of the epidermis and how long does it take to do this?

Answer 10

Keratinocytes migrate from basement membrane to the keratin layer

28 days

Question 11

How thick is the basement layer of epidermis usually and what shape are the cells?

Answer 11

1 cell thick

Small cuboidal cells

Question 12

What does the prickle layer consist of?

Answer 12

Larger polyhedral cells with lots of desmosomes, with connecting intermediate filaments

Question 13

What does the granular layer consist of?

Answer 13

2-3 layers of flatter cells
Large keratohyalin granules – contain structural filaggrin & involucrin proteins

Question 14

Which layer of epidermis contains Odland bodies?

Answer 14

Granular layer

Question 15

What does the keratin layer consist of?

Answer 15

Corneocytes - overlapping, non-nucleated cell remnants

Keratin
Fillagrin

Question 16

What are melanocytes?

Answer 16

Pigment producing dendritic cells

Question 17

Where are melanocytes found?

Answer 17

In the basal layer and above

Question 18

What do melanosomes do?

Answer 18

Convert tyrosine to melanin pigment
–Eumelanin (brown or black)
–Phaeomelanin (red, yellow)

Question 19

What does melanin do?

Answer 19

Absorbs/filters light

Forms protective cap over nucleus

Question 20

What does this diagram show?

Answer 20

Melanin caps are protecting nuclear DNA

Question 21

Which cells are of mesenchymal origin?

Answer 21

Langerhans cells

Question 22

Where are Langerhans cells found?

Answer 22

Prickle cell layer

Dermis

Lymph nodes

Question 23

What is the function of Langerhans cells?

Answer 23

Antigen presenting cell in the skin’s immune system

Pick up antigen in skin and circulate to lymph nodes via lymphatic system

Question 24

Where are Merkel cells found?

Answer 24

Basal layer

Between keratinocytes and nerve fibres

Question 25

What are Merkel cells?

Answer 25

Mechanoreceptors

Question 26

What are the phases of hair growth?

Answer 26

Anagen = growing Catagen = involuting Telogen = resting

Question 27

What is the dermo-epidermal junction?

Answer 27

Interface between epidermis and dermis

Question 28

What are the functions of the dermo-epidermal junction?

Answer 28

Support, anchorage, adhesion, growth and differentiation of epidermal cells Semi-permeable membrane acting as barrier and filter

Question 29

What is the dermis composed of?

Answer 29

Cells - mainly fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells Fibres – collagen, elastin Blood vessels, lymphatics, nerves

Question 30

What is the function of fibroblasts?

Answer 30

Secrete collagen

Question 31

What is an angioma?

Answer 31

A localised overgrowth of blood vessels in the skin

Question 32

Which special nerve sensors detect pressure and vibration in the skin?

Answer 32

Pacinian (pressure) and Meissners (vibration) corpuscles

Question 33

What are apocrine sweat glands and where are they found?

Answer 33

Scent sweat glands Found in axillae and perineum

Question 34

Where are the largest sebacous glands found?

Answer 34

Face and chest

Question 35

What are the functions of the sebaceous glands?

Answer 35

Control moisture loss Protection from bacterial and fungal infection

Question 36

What is control of apocrine sweat glands dependant on?

Answer 36

Androgen

Question 37

Where are eccrine glands found?

Answer 37

All over skin Palms, soles of feet and and axillae particularly

Question 38

How is secretion from eccrine glands controlled?

Answer 38

Parasympathetic cholingeric transmission

Question 39

How does the epidermis function as a barrier?

Answer 39

Physical: friction, mechanical trauma, ultraviolet radiation Chemical: irritants, allergens, toxins Pathogens: bacteria, viruses, fungi

Question 40

What metabolism takes place in the skin?

Answer 40

Vitamin D metabolism Thyroid hormone metabolism Defence against chemicals, drugs, pollutants & sunlight

Question 41

What role does the skin play in Vitamin D metabolism?

Answer 41

Uses UV light to synthesise vitamin D3 from cholecalciferol to be stored in the liver

Question 42

What role does the skin play in thyroid hormone metabolism?

Answer 42

Converts T4 to T3

Question 43

What role does the skin have in thermoregulation?

Answer 43

Protects against being too hot or too cold Warm/cold-sensitive thermoreceptors cause: Behavioural changes Control sweating/shivering/blood supply

Question 44

What are the functions of the skin?

Answer 44

Barrier function Thermoregulation Immune defence Metabolism & detoxification Communication Sensory functions