Structure and Function

Question 1

Name the three layers in skin.

Answer 1

Epidermis (100-150microm), dermis and sub-cutis.

Question 2

From what does the epidermis develop?

Answer 2

Ectoderm

Question 3

From what does the dermis develop?

Answer 3

Mesoderm

Question 4

What cells are found in the epidermis?

Answer 4

Stratified squamous epithelium:
Keratinocytes
Melanocytes
Langerhans cells
Nerves

Question 5

What are the four layers in the epidermis.

Answer 5

Basal layer
Prickle cell layer
Granular layer
Keratin layer

Question 6

How long does it take a cell to migrate from top to bottom?

Answer 6

~28 days

Question 7

Describe the basal layer

Answer 7

Once cell thick, skin stem cells, small and cuboidal, lots of intermediate filaments and highly metabolically active.

Question 8

Describe the prickle cell layer

Answer 8

Large polyhedral cells that don’t touch each other but with lots of desmosomes to move them. Differing thickness throughout layer.

Question 9

Describe the granular layer

Answer 9

2-3 layers of flattened cells that produce proteins such as filaggrin and involucrin. They shrink in size and lose their nucli. Have a high lipid content.

Question 10

Describe the keratin layer

Answer 10

Consists of corneocytes (overlapping cell remnants full of keratin and filaggrin) to form an insoluble cornified envelope. Intracellular space filled with lipids for waterproofing.

Question 11

What role does the filaggrin protein play?

Answer 11

Chopped up to AA which bind H2O to hydrate skin.

Question 12

Where does skin end?

Answer 12

Where mucosal membranes begin.

Question 13

What are skin appendages?

Answer 13

Additional non-keratinocyte things that are added into skin.

Question 14

Give examples of skin appendages.

Answer 14

Hair, nails, melanocytes, Langerhans cells, neuronal cells.

Question 15

Where do melanocytes originate from and where are they found?

Answer 15

Neural crest and found in basal and prickle cell layers.

Question 16

What do melanocytes do?

Answer 16

Convert tyrosine to melanin pigment to protect from UV radiation.

Question 17

What are the two kinds of melanin produced?

Answer 17

Eumelanin- Brown or black

Phaeomelanin- Red or yellow

Question 18

Once produced what happens to melanin?

Answer 18

Transferred to keratinocytes in melanosomes to form a protective cap over nucli.

Question 19

Where do Langerhans cells originate from and where are they found?

Answer 19

Mesenchymal cells (bone) and found in prickle cell layer, dermis and lymph nodes.

Question 20

What do Langerhans cells do?

Answer 20

Detect infection upon which they migrate to the lymph system and present the antigens to immune system. Antigen Presenting Cells.

Question 21

What is found in Langerhans cells?

Answer 21

Birbeck granules (look like tennis rackets).

Question 22

What is a pilosebaceous unit?

Answer 22

Hair and sebaceous gland.

Question 23

What are the three phases of hair growth and how long do they last for?

Answer 23

Anagen- growth. 3-7 years
Catagen- involuting. 3-4 weeks
Telogen- resting/falling out. 50-100 fall out a day.

Question 24

What can affect hair growth rates?

Answer 24

Hormones such as androgen increase it.

Autoimmune attack can cause alopecia.

Question 25

How do nails differ from normal skin?

Answer 25

Instead of forming a prickle cell layer cells form a huge layer of keratin.

Question 26

Where does nail grow from?

Answer 26

Nail matrix and bed.

Question 27

What is the role of the cuticle?

Answer 27

To prevent infection.

Question 28

What is the lunula?

Answer 28

The part of the nail matrix visible under the nail.

Question 29

What is the dermo-epidermal junction?

Answer 29

The interface between dermis and epidermis.

Question 30

What are the three layers of the dermo-epidermal junction?

Answer 30

Lamina lucida Lamina densa Sub-lamina densa zone

Question 31

What is the dermis made up of?

Answer 31

Ground substance Fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells. Collagen and elastin Muscles, blood vessels, lymphatics and nerves.

Question 32

List three factors that can decrease elastic fibres?

Answer 32

Age, smoking and UV light.

Question 33

Why is the blood supply far greater than its metabolic needs?

Answer 33

For thermal regulation.

Question 34

List three ways in which the skin can regulate heat.

Answer 34

Radiation Evaporation Behavioural changes

Question 35

What kind of structures do small lymphatic vessels form?

Answer 35

Mesh

Question 36

Describe the flow of lymphatic vessels.

Answer 36

Along the same route as blood vessels.

Question 37

What are the two nerve types found in the skin?

Answer 37

``` Somatic sensory (give rise to dermatomes) Autonomic (supply blood vessels etc) ```

Question 38

What do Pacinian corpuscles sense?

Answer 38

Pressure

Question 39

What do Meissners corpuscles sense?

Answer 39

Vibration

Question 40

What are the three kinds of gland found in the skin?

Answer 40

Apocrine Eccrine Sebaceous

Question 41

Describe sebaceous glands

Answer 41

Found in face and chest. Very hormone sensitive therefore active in puberty. Produce sebum to protect from fungal infection and control water loss. Acne occurs here.

Question 42

Describe apocrine glands

Answer 42

Part of the pilosebaceous unit and produce an oily fluid. Function unclear. Found in axillae and perineum. Regulated by androgen.

Question 43

Describe eccrine sweat glands

Answer 43

Found all over skin. Supplied by sympathetic nerves. Cool down the body by evaporation.

Question 44

List the functions of the skin (6 points)

Answer 44

``` Barrier Met and detox Thermoreg Immune defence Comms Sensory ```

Question 45

What happens if the physical barrier is breached?

Answer 45

Infection Water loss Protein loss

Question 46

List two things the skin is involved in metabolising.

Answer 46

VD and thyroid hormone

Question 47

What can the skin detoxify?

Answer 47

Chemicals, drugs and pollutants.

Question 48

What are the major cells involved in the skins immune response?

Answer 48

Langerhans, T cells, mast cells and macrophages.

Question 49

Is the skin an innate or adaptive immune response?

Answer 49

Innate

Question 50

List a number of ways that the skin can be used in communication.

Answer 50

Visual such as flushing, pigmentation etc Odour Pheromones.

Question 51

What can the skin sense?

Answer 51

Touch, vibration and pressure. Pain and itch Temperature