Structure And Function Of Skin

Question 1

Name 5 functions of Skin

Answer 1

• Camoflauge
• Barrier - bacteria cannot get through it
• Homeostasis - regulates temperature (can reduce temp through vasodilation)
• insulation
• Sensation - fingers are very sensitive
• Vitamin D

Question 2

What are the three layers of skin?

Answer 2

• Epidermis (top - varies in thickness depending on location)
• Dermis (middle - contains blood vessels and nerves etc)
• Subcutis (bottom - mainly fat cells)

Question 3

What are the 5 layers of the epidermis?

in order from deepest to most superficial

Answer 3

• Stratum Basale
• Stratum Spinosum
• Stratum Granulosum
• Stratum Lucidum
• Stratum Corneum

Question 4

Stratum Basale

Answer 4

• The layer at the base
• Stem cells - grow and divide to produce cells above
• process takes about a month

Question 5

Stratum Spinosum

Answer 5

• The spiny layer
• Contains lots of desmosomes - little plates in the membrane that connect to the cytoskeleton
• Gives the skin its strength

Question 6

Friction Blisters

Answer 6

• 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

Question 7

Stratum Granulosum

Answer 7

• The granular layer
• Keratohyalin granules (Keratin precursor)
• Lamellar bodies (lipids)
• Starts to make the protective barrier

Question 8

Stratum Corneum

Answer 8

• The horny layer
• Outermost layer
• Keratin-packed, anucleated cells
• Soft-keratin as it has a high lipid content

Question 9

Why do your fingers go wrinkly after being in the water?

Answer 9

• 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

Question 10

Stratum Lucidum

Answer 10

• The clear layer
• only found in thick skin
• immature keratin

Question 11

What cells are found in the Stratum Spinosum?

Answer 11

• Desmosomes

- Langerhans cells

Question 12

Melanocytes

Answer 12

• 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

Question 13

Langerhans cells

Answer 13

• Immune cells
• Mobile
• Antigen-presenting cells
• look for foreign bodies - report back to lymph nodes

Question 14

Merkel cells

Answer 14

Mechanoreceptors for light touch

- found in basale next to dermis

Question 15

What are the appendages of the skin?

Answer 15

• Hair follicles - hard keratin (no granular layer secreting lipids)
• Sweat glands
• Sebaceous glands - produce sebum
• Nails - hard keratin

Question 16

Different types of sweat glands

Answer 16

• 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)

Question 17

Nails

Answer 17

• 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

Question 18

Vasculature

Answer 18

• 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

Question 19

Sensory Innervation

Answer 19

• 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