2 Skin Biology

Question 1

Functions of skin (i)

Answer 1

1. Protection - against pressure, heat, cold, chemicals, UV, pollutants and bacteria.
2. Thermoregulation - regulate body temperature.
3. Cutaneous sensation - touch, pressure, vibration, tickle, temperature and pain

Question 2

Functions of skin (ii)

Answer 2

4. Excretion - metabolic waste products excreted via sweat.
5. Absorption - for lipid-soluble substances.
6. Vitamin D synthesis - through the presence of UV light.

Question 3

Skin Layers

Answer 3

Epidermis
Dermis
Hypodermis

Question 4

Function of epidermis

Answer 4

Protective barrier against moisture loss.

Penetration of particulate matter and MO.

Question 5

What does epidermis contains?

Answer 5

1. Keratinocytes - produces keratin and lamellar granules.
2. Langerhans cells - responsible for skin immunology.
3. Melanocytes - produces melanin.
4. Merkel cells - associated with Merkel disc and they act as a slowly-adapting touch receptors.

Question 6

Layers of epidermis

Answer 6

Stratum corneum 
Stratum lucidum
Stratum granulosum 
Stratum spinosum
Stratum basale

Question 7

Stratum basale

Answer 7

New skin cells are produced here, pushing older cell towards the surface.

Question 8

Stratum spinosum

Answer 8

Cells will be joined together by desmosomal connections.

Question 9

Stratum granulosum

Answer 9

Keratinocytes mature here, keratin and glycolipids are produced.

Question 10

Stratum corneum

Answer 10

Cells are dead, flattened and keratinized. In desquamation, they sloughed off and flake away.

Question 11

Dermis

Answer 11

responsible for elasticity and strength of the skin

Question 12

Dermis is made out of:

Answer 12

Connective tissues
Nerve endings
Hair follicles (Arrector pili muscle) and sweat glands

Question 13

What does fibroblasts produce?

Answer 13

1. Collagen fibers (70% of dermis)
   Imparts toughness, strength and resistance to stretching forces.
2. Elastin fibers (2% of dermis)
   Provides elasticity.

Question 14

Sebaceous glands

Answer 14

Produces sebum - lubricates skin surface, provides food supply for bacteria and fungi

Question 15

Types of sweat glands

Answer 15

Eccrine

Apocrine

Question 16

Eccrine

Answer 16

• More abundant
• Clear, slightly salty fluid
  98-99% H2O, 1-2% inorganic and organic compounds (NaCl, lactic acid etc)
• Odorless fluid
• Cools body and prevent overheating

Question 17

Apocrine

Answer 17

• Less abundant
• Milky fluid containing fatty acids
• H2O, protein, CHO, ammonium salts
• Characteristic odor (fatty organic compounds are broken down by bacteria)
• Does not thermoregulate

Question 18

Hypodermis

Answer 18

Serves as a protective cushion and insulator

Question 19

What contributes to skin color?

Answer 19

1. Melanin
2. Haemoglobin
3. Carotenes

Question 20

Melanin

Answer 20

Melanocytes produces tyrosinase (enzyme) that converts tyrosine into melanin.

Absorbs UV radiation and protect skin from damage.