Skin structure & function

Question 1

What are the 4 layers of the epidermis?

Answer 1

Keratin Layer
Granular layer
Prickle cell layer
Basal layer

Question 2

What are Blaschko’s lines?

Answer 2

Developmental growth pattern of skin (not following nerves, vessels, lymphatics)

Question 3

What is the sub-cutis predominantly made up of?

Answer 3

Fat

Question 4

What cels make up 95% of the epidermis?

Answer 4

Keratinocytes

Question 5

What cells are in the epidermis?

Answer 5

Kertinocytes
Melanocytes
Langerhans cells
Merkel cells

Question 6

What factors control epidermal turnover?

Answer 6

Growth factor
Cell death
Hormones

Question 7

In what conditions is there a loss of control of epidermal turnover?

Answer 7

Skin cacer

Psoriasis

Question 8

Where do keratinocytes migrate from?.

Answer 8

Basement membrane

Question 9

How long does it take keratinocytes to migrate from the basement membrane to top of skin?

Answer 9

2 days

Question 10

How many cells thick is the basal layer?

Answer 10

One

Question 11

What are the properties of the basal layer?

Answer 11

Highly metabolically active

Question 12

What is the prickle cell layer made up of?

Answer 12

Larger polyhedral cells with lots of desmosomes

Question 13

What does the granular layer contain?

Answer 13

2-3 layers of flatter cells
Large keratohyalin granules
Odland bodies
High lipid content

Question 14

What does a HPV infection of keratinocytes cause?

Answer 14

Warts

Question 15

What are the main 2 compenents of the keratin layer?

Answer 15

Keratin

Filaggrin

Question 16

What is the function of the keratin layer?

Answer 16

Tight waterproof barrier

Question 17

What is the embryological origin of melanocytes?

Answer 17

Migrrate from neural crest to epidermis in the first 3 months of foetal development

Question 18

In which layers are melanocytes found?

Answer 18

Basal layer and above

Question 19

What are the organelles inside melanocytes called?

Answer 19

Melanosomes

Question 20

What is the function of melanocytes?

Answer 20

Convert tyrosine to melanin pigment

Question 21

What are the 2 types of melanin pigment?

Answer 21

Eumelanin (brown or black)

Phaemelanin (red, yellow)

Question 22

How are melanosomes transferred to adjacent keratinocytes?

Answer 22

Via dendrities

Question 23

What is vitiligo?

Answer 23

Autoimmune disease with loss of melanocytes

Question 24

What is the embryonic origin of langerhans cells?

Answer 24

Mesenchymal origin - bone marrow

Question 25

Where are Langerhan cells found?

Answer 25

PCL in epidermis also found in deris & lymph nodes

Question 26

What is the function of Langerhans cells?

Answer 26

Immune system - antigen presenting & pick up antigen in skin and circulat eot lymph nodes via lymphatic system

Question 27

Where are merkel cells found?

Answer 27

Basal layer betwee keratinocytes & nerve fibres

Question 28

What is the function of merkel cells?

Answer 28

Mechanoreceptors

Question 29

Which gland is adjacent to hair follicles?

Answer 29

Sebaceous gland

Question 30

What are the 3 phases of hair growth?

Answer 30

Anagen (growing) Catagen (involuting) Telogen (resting)

Question 31

What is the role of the DEJ?

Answer 31

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

Question 32

Which inherited skin fragilities arise from a mutation in one of the proteins in the DEJ?

Answer 32

Epidermolysis bullosa - simplex (EBS) or dystrophic (EBD)

Question 33

Wha acquired conditions arise from auto-antibodies to the proteins in the DEJ?

Answer 33

Bullous pemphigoid Bullous pemphigus Dermatitis herpeteformis

Question 34

What are the main components of the dermis?

Answer 34

Cells Fibres (collagen, elastin) Ground substance Blood vessels/lymphatics/nerves

Question 35

What do fibroblasts do in the dermis?

Answer 35

Secrete collagen

Question 36

What do macrophages do in the dermis?

Answer 36

Scavengers | Antigen presentation

Question 37

What is the function of lymphocytes in the dermis?

Answer 37

Immune reactions

Question 38

What is the function of Langerhan cells in the dermis?

Answer 38

Antigen presentation

Question 39

Why is the blood suply to the skin greater than metabolic needs?

Answer 39

Temperature control

Question 40

Examples of a localised overgrowth of blood vessels?

Answer 40

Port wine stain

Question 41

What do lymphatic vessels continually drain from the skin?

Answer 41

Plasma proteins | excess interstitial fluid

Question 42

What are the important immune function of lymphatic vessels in the skin?

Answer 42

Immune surveillance by circulating lymphocytes and Langerhans cells Channelling of micro-organisms/toxins

Question 43

What do pacinian corpuscles sense?

Answer 43

Pressure

Question 44

What do meissners corpuscles sense?

Answer 44

Vibration

Question 45

Where on the body are sebaceous glands normally found?

Answer 45

Face & chest

Question 46

What stimulates sebaceous glands?

Answer 46

Hormones (quiescent pre-puberty)

Question 47

What do sebaceous glands produce?

Answer 47

Sebum

Question 48

Functions of sebaceous glands?

Answer 48

Control moisture loss | Protection from bacterial & fungal infection

Question 49

Where on the body are apocrine sweat glands normally found?

Answer 49

Axillae & perineum

Question 50

What stimulates apocrine glands?

Answer 50

Androgen

Question 51

What do apocrine glands produce?

Answer 51

Oliy fluid (odour after bacterial decomposition)

Question 52

Where in particular are eccrine glands found?

Answer 52

Palms, soles and axillae

Question 53

What stimulates eccrine glands?

Answer 53

sympathetic cholinergic nerve supply

Question 54

What are the functions of eccrine glands?

Answer 54

Cooling by evaporation | Moisten palms/soles to aid grip

Question 55

What are the functions of the skin?

Answer 55

``` Barrier function Metabolism & detoxification Thermoregulation Immune defence Communication Sensory functions ```

Question 56

What are the consequences of the failure of the skin as a barrier?

Answer 56

Dehydration Hypoalbuminaemia Infection

Question 57

______ is converted to Vitamin D3 by UV light?

Answer 57

Cholecalciferol

Question 58

What is Vitamin D3 stored as and where?

Answer 58

Stored as dihydroxycholecalciferol in the kidney

Question 59

Where is T4 converted to T3?

Answer 59

``` 20% = thyroid gland 80% = peripheral tissues including skin ```