Physiology of Skin

Question 1

In foetal skin development what are the first three layers formed?

Answer 1

Periderm
Basal layer
Dermis

Question 2

What are the final five layers of skin?

Answer 2

Keratin Layer 
Granular Layer 
Prickle Cell Layer 
Basal Cell Layer 
Dermis

Question 3

What are blaschko’s lines?

Answer 3

Developmental growth patterns of skin not following vessels, nerves or lymphatics

Question 4

What type of cell makes up the epidermis?

Answer 4

Stratified squamous epithelium

Question 5

Describe the basal layer

Answer 5

Usually one cell thick contains lots of stem cells & free nerve endings

Question 6

Describe the prickle cell layer

Answer 6

Cells move upwards to fit into each other - contains lots of desmosomes to connect intermediate filaments. Keratin is produced.

Question 7

What substance does the granular layer contain that contributes to skin hydration?

Answer 7

Filaggrin - repeat amino acid gets broken down by enzymes. The free amino acid binds to water resulting in a natural moisturiser

Question 8

What happens to the cell structure in the granular layer?

Answer 8

Cell nuclei are lost and lamellar bodies present

Question 9

Name the lamellar bodies

Answer 9

Odland bodies (secretory organelle)

Question 10

What is the other name for the keratin layer?

Answer 10

Stratum corneum

Question 11

Describe the keratin layer

Answer 11

Insoluble cornfield envelope, 80% keratin and filaggrin. Granules release lipids to produce a waterproof barrier

Question 12

What are corneocytes?

Answer 12

Overlapping non-nucleated cell remnants

Question 13

Define a scar

Answer 13

Loss of skin appendages

Question 14

Where can mucosal membranes be found?

Answer 14

Eyes, genitourinary tract, GI tract & mouth

Question 15

Name three specialised epidermal cells

Answer 15

• melanocytes
• langerhans cells
• merkel cells

Question 16

Where are melanocytes found?

Answer 16

Basal layers & above

Question 17

What is the function of melanocytes?

Answer 17

Contains melanosomes where tyrosine is converted to melanin in response to UV. Once full of melanin granules the melanosomes are transferred to adjacent keratinocytes by dendrites and the melanin cap protects the nuclei in basal cells from further UV exposure.

Question 18

Where are langerhans cells found?

Answer 18

Originate in the bone marrow - found in the prickle cel layer, dermis & within lymph nodes

Question 19

What is the function of langerhans cells?

Answer 19

Part of the immune system - present antigens & circulate to lymph nodes

Question 20

Describe Merkel cells

Answer 20

In basal layer between keratinocytes & nerve fibres act as mechanoreceptors

Question 21

What is the name of the unit which contains a hair?

Answer 21

Pilosebaceous unit

Question 22

What does the pilosebaceous unit consist of?

Answer 22

Epidermal component plus dermal papilla - adjacent sebaceous gland with arrestor pili muscle

Question 23

What are the three phases of hair growth?

Answer 23

anagen - growing
catagen - shrinking
telogen - resting

Question 24

Describe the impact of hormonal secretion on the pilosebaceous unit

Answer 24

Cells at the centre of the gland fall apart to produce sebum - holocrine secretion

Question 25

Give an example of a hormone that acts on the pilosebaceous unit

Answer 25

Androgens

Question 26

What does the nail matrix consist of?

Answer 26

Rapidly dividing epidermal cells situated at the proximal end of each nail - protected by the cuticle & nail fold

Question 27

What is the nail bed made of?

Answer 27

Tough collagen

Question 28

State the name of the white bit at the bottom of a nail

Answer 28

Lunula

Question 29

What is the epithelium underlying the free edge known as?

Answer 29

Hyponychium

Question 30

State the role of the dermo-epidermal junction

Answer 30

support, anchor & adhese basal cells

Question 31

How is the dermo-epidermal junction maintained?

Answer 31

Hemi-desmosomes (whereas the prickle cell contains desmosomes)

Question 32

How is the DE junction strengthened & increased in surface area?

Answer 32

Papilla from both layers - rete pegs from the epidermis

Question 33

Name the general components of the dermis

Answer 33

- ground substance - cells - fibres - muscles/blood vessels/lymphatics/nerves

Question 34

What cells can be found in the dermis?

Answer 34

fibroblasts, macrophages, mast cells, lymphocytes, langerhans

Question 35

What fibres can be found in the dermis?

Answer 35

Collagen & elastin

Question 36

Describe the ground substance

Answer 36

Semisolid matrix of glycosaminoglycans which allow some dermal structures to move

Question 37

What is the role of fibroblasts?

Answer 37

Synthesise - collagen, elastin & glycosaminoglycans

Question 38

Describe the relationship between supply and metabolic need in the dermis

Answer 38

Supply > need (vessel walls are well supported for blood flow)

Question 39

Describe the role of lymphatic vessels in the dermis

Answer 39

Provide continual drainage of plasma proteins, extravasated cells & excess interstitial fluid

Question 40

What is the somatic sensory supply to the dermis?

Answer 40

Free nerve endings - dermatones Pacinian - pressure Meissners - vibration

Question 41

What is the autonomic supply to the dermis?

Answer 41

Through blood vessels, nerves and glands

Question 42

Name the three types of skin gland

Answer 42

Sebaceous Apocrine Eccrine

Question 43

Describe the sebaceous gland

Answer 43

Hormone sensitive they grow & activate in puberty. Produce sebum by holocrine secretion which cells disintegrate & then release their lipid cytoplasm

Question 44

What is the function of the sebaceous gland?

Answer 44

- controls moisture loss | - protects from fungal infections

Question 45

Describe the apocrine gland?

Answer 45

Part of the pilosebaceous unit in the axilla and perineum - androgen dependent it produces an odour after bacterial decomposition

Question 46

Describe the eccrine gland

Answer 46

Found everywhere on skin surface, cholinergic nerve supply (mental, thermal, gustatory). Role is to cool & moisten.

Question 47

State six functions of skin

Answer 47

- barrier - metabolism & detoxification - thermoregulation - immune defence - communication - sensory function

Question 48

In what ways does the epidermis act as a barrier

Answer 48

- physical barrier trauma/UV - immune system stops pathogens entering body - chemical barrier

Question 49

What happens if the skin loses its barrier function?

Answer 49

Fluid & protein loss, potential infection

Question 50

How does the skin help with metabolism?

Answer 50

Vitamin D metabolism - UVB converts 7- dehydrocholesterol to vitamin D Thyroid metabolism - thyroxine (T4) is converted to triiodothyronine (T3)

Question 51

What happens if the skin can no longer help with metabolism?

Answer 51

- Rickets | - Disordered thyroxine metabolism (hypothyroidism)

Question 52

How does the skill control temperature and what will failure result in?

Answer 52

Regulates heat to prevent extremes by thermoreceptors failure will result in heat loss

Question 53

Describe the skins role in immune defence

Answer 53

Prevents infection by acting as a barrier, produces a response to sunlight & allergic reactions - both specific and non-specific

Question 54

What will happen if the skin does not adequately defend against infection?

Answer 54

Spread of infection into the body

Question 55

Name three ways the skin contributes to communication

Answer 55

- visual - odour - sociosexual Massively contributes to skin stigma and social exclusion

Question 56

What will failure in sensory function of skin result in?

Answer 56

Pain/Injury