Anatomy of the skin

Question 1

what is the function of the skin?

Answer 1

A barrier between the external environment and internal body content
- Protect against chemical, osmotic, mechanical, thermal and UV damage
- Protects against microbial invasion
- Plays a role in vitamin D synthesis
- Regulation of body temp
- Psychosexual communication
Sensory organ- touch, temp, pain, other stimuli

Question 2

What are the three layers of the skin?

Answer 2

• Epidermis
• Dermis
• Hypodermis

Question 3

which cells are found in the epidermis?

Answer 3

most superficial
- KERATIN: Largely formed of keratinocytes- produce keratin. Keratin migrates towards the external surface ‘cornification’ (makes the skin waterproof)

- MELANOCYTES: melanin production and pigment formation. Pockets of melanin (melanosomes) are transferred from the melanocytes. Melanosomes protect the nucleus from UV harm
- LANGERHAN CELLS: antigen-presenting dendritic cells

MERKEL CELLS: sensory mechanoreceptors

Question 4

What are the layers of the epidermis?

CLGSB

Answer 4

Come Let’s Get Sun Burn

1. Stratum Corneum
2. Straturm Lucidum
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basale

Question 5

What’s the function of the layers of the epidermis?

Answer 5

1) Stratum CORNEUM
Cells loose all orgallenelles and produce keratin

2) Stratum LUCIDUM Cells lose nuclei and drastically increase keratin production

3) Stratum GRANULOSUM Cells secrete lipids and other waterproofing molecules in this layer

4) Stratum SPINOSUM Keratinocytes are joined by tight intercellular junctions (desmosomes)

5) Stratum BASALE (mitosis of keratinocytes occurs in this layer)  This is where keratinocytes are first made

Question 6

Stratum Basale (keratinocytes)

Answer 6

• single layer of cuboidal stem cells continually divides and create new keratinocytes
• Keratinocytes mature and ascend up the layers then eventually flatten out to a SQUAMOUS shape at the top
• stratum basale contains melanocytes which secrete melanin
• Keratinocytes exposed to sun sends a signal to melanocytes to create more melanin
• Melanin is moved into melanosomes

Keratinocytes metabolise the melanin= natural sunscreen (protein structures scattered UV light to prevent DNA damage)

Question 7

Glabrous skin (examples)

Answer 7

Thick skin found on palms, soles of feet, flexor surfaces of fingers (free from hair)

Question 8

2. DERMIS

Answer 8

Immediately deep to the epidermis
Tightly connected through a highly corrugated dermo-epidermal junction
CONNECTIVE TISSUE- COLLAGEN: strength and elasticity (stretch)

two layers:
papillary layer
reticular layer (thicker bundles of collagen)

Question 9

Cells in the dermis

Answer 9

• Fibroblasts- synthesise extracellular matrix (collagen and elastin)
  
  • Mast cells (histamine granule containing cells of innate immune system)
  • Blood vessels and cutaneous sensory nerve
  • lymphatics
  • Skin appendages (hair follicles, nails, sebaceous , sweat glands)

Question 10

Sebaceous sweat glands in the dermis

Answer 10

i) Eccrine glands: major sweat gland. Clear, odourless substance. NaCl and H2O
ii) Apocrine glands: sweat glands - axilla.

Question 11

hypodermis

Answer 11

Sub-cutaenous tissue deep to the dermis

Stores adipose tissue

Question 12

5 types of skin

Answer 12

I: never tans, always burns (red hair, freckles, blue eyes)

II: usually tans, always burns

III: always tans, sometimes burns (Dark hair, brown eyes)

IV: always tans, rarely burns (olive skin)

V: sunburn, tanning after extreme. UV exposure (brown skin- Indian)

VI: black skin (Afro-Caribbean) never tans, never burns