Structure and function of skin 1-4

Question 1

What germ layers are the epidermis and dermis formed from?

Answer 1

Epi- ecto

Dermis- meso

Question 2

What are the four layers of the epidermis?

Answer 2

Keratin layer
Granular cells
Prickle cells
Basal cells

Question 3

Where do melanocytes develop from?

Answer 3

Neural crest

Question 4

What does disease which abides Blatschko’s iines indicate?

Answer 4

That it is congenital

Question 5

What are the possible consequences if control is lost over skin turnover?

Answer 5

Skin cancer

Psoriasis

Question 6

What is the rate of migration of keratinocytes in psoriasis compared to normally?

Answer 6

around 3-5 days compared to 28 days normally

Question 7

What is the basal cell layer characterised by?

Answer 7

Single layer of cells, many intermediate filaments

Question 8

What is the distinguishing feature of the prickle cell layer?

Answer 8

Desmosomes between cells- cells are motile but retain a cohesive structure

Question 9

Which layer of the epidermis is the origin of the cornified envelope?

Answer 9

Granular layer

Question 10

Which proteins are contained within keratohyalin granules in the granular layer, and what is their purpose?

Answer 10

Fillagrin and involucrin

Structural

Question 11

What are corneocytes and where are they found?

Answer 11

Non-nucleated remnants of keratinocytes, within the keratin layer

Question 12

Truncation mutations in fillagrin and involucrin are associated with which disease?

Answer 12

Eczema

Question 13

What is the distinguishing feature of the keratin layer?

Answer 13

Waterproof, but can also transpire- helps maintain fluid homeostasis

Question 14

Which layer of the epidermis is infected by HPV, and how does it cause the characteristic symptoms?

Answer 14

Prickle cell layer- reactive hyperkeratinisation

Question 15

Which reaction takes place in melanosomes?

Answer 15

Tyrosine is converted to melanin

Question 16

How does the melanin produced in melanocytes protect adjacent cells from UV damage?

Answer 16

“full” melanosomes are transferred to adjacent keratinocytes via dendrites, where they form a protective shield around the nucleus and absorb UV light

Question 17

Describe the underlying cause in these diseases associated with melanin production:

a) Vitiligo
b) albinism
c) Nelson’s syndrome

Answer 17

a) autoimmune destruction of melanocytes
b) disruption in biochemical pathway of melanin production
c) excess melanin stimulating hormone from the pituitary

Question 18

What is the function of Langerhans cells?

Answer 18

Antigen presenting cells of the skin

Question 19

Which structural element are Langerhans cells distinguished by?

Answer 19

Racket organelles (Birbeck granules)

Question 20

Where are Merkel cells found and what is their function?

Answer 20

In the basal layer between keratinocytes and nerve fibres- mechanoreceptors for the sensation of light touch

Question 21

Where does hair pigmentation derive from?

Answer 21

Melanocytes above the dermal papilla

Question 22

What is the hair shaft lubricated by?

Answer 22

Adjacent sebaceous glands

Question 23

What are the three phases of hair growth?

Answer 23

Anagen -growing (90% of hairs)
Catagan- involuting (10%)
Telogen- shedding

Question 24

What is telogen effluvium and when does it typically occur?

Answer 24

Thinning/shedding of hair

Post-partum and in ageing males (male-pattern baldness)

Question 25

What is alopecia areata?

Answer 25

Autoimmune hair loss

Question 26

Where does nail growth occur from?

Answer 26

The nail matrix

Question 27

What are the three layers of the basement membrane?

Answer 27

Lamina lucida Lamina densa Sub-lamina dense

Question 28

How are the basal cells of the epidermis linked to basement membrane?

Answer 28

Hemidesmosomes

Question 29

How are the cells of the papillary dermis linked to the basement membrane?

Answer 29

Anchoring fibrils

Question 30

What causes a) epidermolysis bullosa b) bullous pemphigoid

Answer 30

a) lack of adhesion at the DEJ causing blistering | b) auto-antibodies to DEJ proteins

Question 31

What are the main fibres found in the dermis, and which cells produce them?

Answer 31

Collagen and elastin, secreted by fibroblasts

Question 32

What kinds of cells are found in the dermis?

Answer 32

``` Fibroblasts Macrophages Langerhans cells Lymphocytes Mast cells ```

Question 33

What is ground substance?

Answer 33

Polysaccharides and glycosaminoglycans- an intercellular amorphous gelatinous material that resists compression

Question 34

What is photoaging?

Answer 34

Characteristic changes to skin caused by chronic UV exposure

Question 35

What is solar elastosis?

Answer 35

Accumulation of abnormal elastin in the skin of patients with history of chronic UV overexposure

Question 36

Describe the blood supply to the dermis.

Answer 36

Greater than the metabolic needs of the tissue | Superficial (supplies the dermis) and deep vascular plexuses

Question 37

What is an angioma?

Answer 37

Localised overgrowth of blood vessels in fixed dilatation. Often seen from birth

Question 38

Describe the lymphatic drainage of the dermis.

Answer 38

Sub-epidermal networks of small vessels leading to larger contractile lymphatic trunks. Jobs- drainage of plasma proteins, extravasated cells, excess tissue fluid

Question 39

What can be the consequence of blockage in the lymphatic vessels of the skin?

Answer 39

Chronic lymphoedema

Question 40

Which sensory corpuscles are responsible for the sensation of a) pressure b) vibration

Answer 40

a) Pacinian | b) ) Meissners

Question 41

Other than sensory, describe the nerve supply to the skin

Answer 41

Autonomic- parasympathetic and sympathetic motor fibres

Question 42

What causes neurofibromatosis?

Answer 42

Overgrowth of neural tissue in the skin

Question 43

Which substance is produced by sebaceous glands?

Answer 43

Sebum- antibacterial

Question 44

What causes acne? Why is it more prominent in puberty?

Answer 44

Overproduction of sebum, blockage of sebaceous glands, bacterial activity Sebaceous glands are hormone sensitive

Question 45

What is the role of apocrine glands and where are the found?

Answer 45

Produce sweat- in the axilla and perineum

Question 46

Where are eccrine sweat glands found and what is their purpose?

Answer 46

The whole skin- ultrafiltration and cooling by evaporation

Question 47

What is the innervation of the eccrine sweat glands?

Answer 47

Sympathetic supply- inputs from mental, thermal and gustatory systems

Question 48

How is the skin involved in: a) Vitamin D metabolism b) Thyroid hormone metabolism c) Drug metabolism

Answer 48

a) 290-320nm UV light converts cholecalciferol to Vit D3 b) conversion of T4-T3 c) Cytochrome enzymes are present in skin

Question 49

What actions are initated by skin thermoreceptors to regulate temperature?

Answer 49

Sweating Shivering Hair erection Changes in blood flow

Question 50

For each function of the skin, describe what the consequences of skin failure might be: a) barrier b) metabolism c) thermoregulation d) communication/social e) immune defebce

Answer 50

``` a) Fluid loss and dehydration Protein loss Infection b) disordered thyroxine metabolism c) hypothermia d) stigma/social isolation e) spread of infection ```