2 Skin Biology Flashcards
Functions of skin (i)
- Protection - against pressure, heat, cold, chemicals, UV, pollutants and bacteria.
- Thermoregulation - regulate body temperature.
- Cutaneous sensation - touch, pressure, vibration, tickle, temperature and pain
Functions of skin (ii)
- Excretion - metabolic waste products excreted via sweat.
- Absorption - for lipid-soluble substances.
- Vitamin D synthesis - through the presence of UV light.
Skin Layers
Epidermis
Dermis
Hypodermis
Function of epidermis
Protective barrier against moisture loss.
Penetration of particulate matter and MO.
What does epidermis contains?
- Keratinocytes - produces keratin and lamellar granules.
- Langerhans cells - responsible for skin immunology.
- Melanocytes - produces melanin.
- Merkel cells - associated with Merkel disc and they act as a slowly-adapting touch receptors.
Layers of epidermis
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
Stratum basale
New skin cells are produced here, pushing older cell towards the surface.
Stratum spinosum
Cells will be joined together by desmosomal connections.
Stratum granulosum
Keratinocytes mature here, keratin and glycolipids are produced.
Stratum corneum
Cells are dead, flattened and keratinized. In desquamation, they sloughed off and flake away.
Dermis
responsible for elasticity and strength of the skin
Dermis is made out of:
Connective tissues
Nerve endings
Hair follicles (Arrector pili muscle) and sweat glands
What does fibroblasts produce?
- Collagen fibers (70% of dermis)
Imparts toughness, strength and resistance to stretching forces. - Elastin fibers (2% of dermis)
Provides elasticity.
Sebaceous glands
Produces sebum - lubricates skin surface, provides food supply for bacteria and fungi
Types of sweat glands
Eccrine
Apocrine
Eccrine
- 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
Apocrine
- 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
Hypodermis
Serves as a protective cushion and insulator
What contributes to skin color?
- Melanin
- Haemoglobin
- Carotenes
Melanin
Melanocytes produces tyrosinase (enzyme) that converts tyrosine into melanin.
Absorbs UV radiation and protect skin from damage.