Structure & Function of Skin Flashcards
How much of the body weight does skin take up?
15%
Name 5 functions of the skin?
- Barrier
- Homeostasis
- Insulation
- Sensation
- Vitamin D - metabolism
What are the 3 layers of skin?
Epidermis, dermis & subcutis
Describe the main four layers of the avascular epidermis?
- Stratum basale - Stem cells, a month for turnover, migrate superficially - in psoriasis, growth gets disordered
- Stratum Spinosum - Lots of desmosomes, strong little plates anchoring cells together (look spiny), gives skin strength
- Stratum granulosum - make protective barrier element of skin, keratohyalin granules, precursor for keratin (essential), lamellar bodies make lipids
- Stratum corneum - keratin-packed, anucleated cells (flat), easily shed
What is a friction blister and where do they form?
Often form in the stratum spinosum, constant friction blows up the cells, clear fluid builds up - no blood present as no vessels - slowly becomes a raised bump.
The clear fluid has high osmolarity, so fluid moves from vessels under epidermis into the spinosal layer causing further buildup.
What is the difference in terms of keratin with your hair and nails in comparison to skin?
Skin is soft keratin, whereas hair and nails are hard keratin minus the lipid content
Which layer of the epidermis stains the darkest?
Stratum granulosum
What is a tattoo?
Lasts for life, so must be below that basal layer, has to be in dermis.
Why does our skin go wrinkly when in water?
Granular layer is where we make keratin and lipids, know that as skin proceeds upwards, it gets dryer (so less oily) - left with just keratin, so granular layer soaks up water, and has to wrinkle in order to expand.
If there was no oil, body would soak up all the water by osmosis and you’d die.
The thicker corneum, more wrinkly/expansion.
What is the stratum lucidum?
Stratum lucidum - the clear layer, in thick skin only, consists of immature keratin (eleidin)
What does darker skin depend on in terms of melanocytes?
Darker skin = melanocytes are more ACTIVE, most people have same number of melanocytes, but just at different levels of activity.
More active = more melanin
What happens in the skin in eczema/allergic reactions?
Langerhans cells produce antigens, and sometimes they can malfunction and find everyday proteins and mount an immune response when it’s not required
What are some appendages of the skin?
- Hair follicles - arrector pili m.
- sweat glands - eccrine, apocrine
- sebaceous glands - holocrine
What type of secretion smells the most and what makes it smell?
Apocrine, bacteria feed off of their secretions
What is the difference between merocrine, apocrine and holocrine?
Merocrine/eccrine is granules of substance leaving via fusion with the membrane.
Apocrine secretion is when they make the substance ready to secrete and pinch it off the cell membrane
Holocrine is when they keep making substance (eg. sebum) until they explode
