Structure And Function Of Skin Flashcards
1
Q
Name 5 functions of Skin
A
- Camoflauge
- Barrier - bacteria cannot get through it
- Homeostasis - regulates temperature (can reduce temp through vasodilation)
- insulation
- Sensation - fingers are very sensitive
- Vitamin D
2
Q
What are the three layers of skin?
A
- Epidermis (top - varies in thickness depending on location)
- Dermis (middle - contains blood vessels and nerves etc)
- Subcutis (bottom - mainly fat cells)
3
Q
What are the 5 layers of the epidermis?
in order from deepest to most superficial
A
- Stratum Basale
- Stratum Spinosum
- Stratum Granulosum
- Stratum Lucidum
- Stratum Corneum
4
Q
Stratum Basale
A
- The layer at the base
- Stem cells - grow and divide to produce cells above
- process takes about a month
5
Q
Stratum Spinosum
A
- The spiny layer
- Contains lots of desmosomes - little plates in the membrane that connect to the cytoskeleton
- Gives the skin its strength
6
Q
Friction Blisters
A
- occur in the stratum spinosum
- Fluid from burst cells and transudate causes the cells to blow up
- the solution osmolarity is very high causing fluid to move in from blood vessels
7
Q
Stratum Granulosum
A
- The granular layer
- Keratohyalin granules (Keratin precursor)
- Lamellar bodies (lipids)
- Starts to make the protective barrier
8
Q
Stratum Corneum
A
- The horny layer
- Outermost layer
- Keratin-packed, anucleated cells
- Soft-keratin as it has a high lipid content
9
Q
Why do your fingers go wrinkly after being in the water?
A
- The granular layer is very oily meaning that water cannot pass through it
- The skin wrinkles on the top layer as it has to expand to accommodate the excess water
10
Q
Stratum Lucidum
A
- The clear layer
- only found in thick skin
- immature keratin
11
Q
What cells are found in the Stratum Spinosum?
A
- Desmosomes
- Langerhans cells
12
Q
Melanocytes
A
- Darker than other cells. We all have the same number, however they are more active in darker skinned people
- Two different types of melanin gives the pigmentation - Eumelanin (brownish black) and Pheomelanin (red/yellow)
- Melanin is diffuses from them to the top of the skin
- Stratum basale
13
Q
Langerhans cells
A
- Immune cells
- Mobile
- Antigen-presenting cells
- look for foreign bodies - report back to lymph nodes
14
Q
Merkel cells
A
Mechanoreceptors for light touch
- found in basale next to dermis
15
Q
What are the appendages of the skin?
A
- Hair follicles - hard keratin (no granular layer secreting lipids)
- Sweat glands
- Sebaceous glands - produce sebum
- Nails - hard keratin
16
Q
Different types of sweat glands
A
- Apocrine (packed in vesicles and pinched off) - smelly because bacteria metabolises the secretions - adrenergic control
- Eccrine - just sweaty. Found everywhere but especially on the palms and soles of feet - Choliergic (sympathetic control)
17
Q
Nails
A
- basically a broad thick hair, composed of hard keratin
- the nail matrix produces keratinised cells like a hair follicle
- grow at 3mm/month so takes several months to replace
18
Q
Vasculature
A
- epidermis is avascular and fed by the capillary network in the dermal papillae
- arteriovenous anastamoses are important in redistributing blood flow
having two plexuses allows different degrees of “shutting off blood to the skin” - Controlled by sympathetic vasomotor neurons innervating the AVA
19
Q
Sensory Innervation
A
- Free nerve endings in the epidermis
- Hair follicle receptors
- Ruffini endings (slowly-adapting mechanoreceptors)
- Meissner corpuscles (sense stretching of incorporated collagen fibres)
- Pacinian corpuscles (rapidly adapting mechanoreceptors)
- Merkel cell disks
All respond to slightly different modalities (pressure, vibration, temp) and differ in speed of adapting