Structure/ Function Skin (M1)

Question 1

Describe Melanocytes

Answer 1

• Found in the stratum basale of the epidermis.
• Melanin protects DNA from UV-B

Question 2

LO’s

Answer 2

1. Describe how the structure of skin varies depending on its functional role
2. Describe the structure and function of sweat glands
3. Describe the composition and function of sweat and the regulation of sweating
4. Describe the structure and function of hair and sebaceous glands

Question 3

What is the purpose of glaborous (non-hairy) and hairy skin?

Answer 3

• Glaborous skin is thick skin.
• It is used for protection against abrasion and grip.
• It has fine tactile sensation.
• Hairy skin: is used for protection and sensation.

Question 4

Why does glaborous/thick skin have more fine tactile sensation than glaborous skin?

Answer 4

Glaborous/thick skin possesses more of these receptors:

• Meissners Corpuscles
• Pacinian Corpuscles
• Merkel Cells
• Ruffini Corpuscles

Question 5

Describe Eccrine glands

Answer 5

• Eccrine sweat glands are also known as merocrine sweat glands. Merocrine means that the cells release their substance from the cell by exocytosis into the lumen of the gland. No cell bits/membrane goes with the substance.
• They empty directly onto the skin surface- through a pore.
• They have myoepithelial cells that contract and expel the secretions of exocrine glands.
• They are involved in thermoregulation. Allows us to sweat and get temperature down when we go running for example.
• Found on the head, palms and hands.

Question 6

Describe Apocrine glands

Answer 6

1. Apocrine sweat glands empty on to a hair follicle, not a pore.
2. Aprocrine sweat glands are larger than eccrine sweat glands.
3. Portions of the cells pinch off in the gland and contain the substance.
4. Found in armpits and pubic area.

Question 7

How is sweating regulated?

Answer 7

• Sweat glands are innervated by sympathetic nerve fibres. When tempreture goes up, signal sent to the sympathetic nerve fibre.
• The sympathetic nerve fibre releases Ach (be aware that sympathetic nerve fibres usually secrete norepinephrine/ epinephrine).
• This stimulates the sweat gland to secrete ‘colourless solution v’ from coil cells secretory component.
• The substance is similar in composition to protein free plasma (NaCl / Lactate / Water).

Question 8

How does reabsorption of sweat happen?

Answer 8

• In the secretory component, the cells release sodium, chloride and water into the lumen.
• This secreted solution flows along the sweat duct. But in the absorptive component, the sodium and chloride is reabsorbed into the cells, but water is not.
• Remember the coiled up bit is the secretory component, but the tube going to the pore is the absoptive component).
• Final secretory fluid is therefore always hypotonic to plasma.

Question 9

What happens to sweat reabsorption in CF?

Answer 9

The CFTR gene is faulty, so sodium can’t be reabsorbed, so they have salty skin.

Question 10

What benefit do energy drinks provide when replacing lost water?

Answer 10

• Isotonic (same osmotic pressure) as plasma, so keep taken up as quickly as water, but also have salt in them to replace some that is still lost in sweat.

Question 11

What is the pilo-sebaceous unit?

Answer 11

This is the stuff each unit of hair has:

1. Sebaceous Glands: these are holocrine glands (the glands have cells that undergo apoptosis, and release their substance into the sabaceous gland). They release sebum which waterproofs the skin.
2. Apocrine sweat glands
3. Arrector Pili Muscles: may aid movement of sebum and apocrine secretions out of the hair. Raise the hair to give goosebumps.
4. A hair, and its root/ follicle.

Question 12

What is a hair follicle and what are the parts of it called?

Answer 12

• An invagination into the epidermis. It is the root of the hair.
• It has a number of components:
  
  • Hair bulb: the bottom of the root/follicle. Where the cells produce hair.
  • Dermal papilla: loose connective tissue at the bottom of the hair bulb.
  • Matrix cells: produce keratinocytes that differentiate into hair producing cells and the internal root sheath.

Question 13

What causes fingertips to wrinkle in water?

Answer 13

• A sympathetic response, not osmotic gain of water.
• Because people with nervous problems don’t wrinkle.

Question 14

How do apocrine and eccrine sweat gland differ in histology?

Answer 14

• Apocrine sweat glands are larger and have a bigger lumen.

Question 15

What are the layers in each hair?

Answer 15

• Hair is made of dead keratinocytes.
• Each strand of hair has three layers.
• The middle of each hair is called the medulla, it is an air space.
• Surrounding the middle of each hair is the cortex. This is where the pigment is.
• The outer layer is the cuticle.