Skin

Question 1

Skin functions

Answer 1

1. Thermoregulation
2. Environmental sensory input
3. Osmoregulation
4. Immunity
5. Blood reservoir
6. Vitamin D synthesis

Question 2

Thermoregulation

Answer 2

1. Vasoconstriction –> reduced blood flow to surface of skin –> heat retention
2. Vasodilation –> increased blood flow to surface capillaries –> heat loss
3. Sweating

• -Skin has warmth and cold receptors
• -Thermoregulation is under the influence of hormonal control

Question 3

Osmoregulation

Answer 3

• -Skin is relatively impermeable to water

- -SOME water and salts are excreted through skin via diffusion

Question 4

Blood reservoir

Answer 4

–Vessels in the dermis hold up to 10% of the blood of a resting adult

Question 5

Vitamin D synthesis

Answer 5

• -UV radiation activates a molecule in the skin that is a precursor to Vitamin D
• -Precursor travels back to liver and kidneys and is turned to Vitamin D by enzymes there

Question 6

Skin parts

Answer 6

1. Epidermis - superficial layer
2. Dermis
3. subcutaneous tissue - superficial fascia or hypodermis

Question 7

Epidermis

Answer 7

• -avascular
• -epithelial tissue
• -Consists of 4 major cell types:
  1. keratinocytes - 90%
  2. melanocytes
  3. langerhans cells
  4. Merkel cells

Question 8

keratinocytes

Answer 8

• -produce the protein keratin, which helps waterproof the skin
• -produced by stem cells and then are pushed to the top layer of the epidermis
• -As they rise, they accumulate keratin and die, losing their cytoplasm, nucleus, and other organelles
• -Slough off when they reach top layer
• -Outermost layer of epidermis consists of 25-30 layers of flat, dead cells

Question 9

melanocytes

Answer 9

transfer melanin (skin pigment) to keratinocytes

Question 10

Langerhans cells

Answer 10

interact with helper T-cells of immune system

Question 11

Merkel cells

Answer 11

attach to sensory neurons and function in the sensation of touch

Question 12

Dermis

Answer 12

• -the layer under the epidermis
• -Derived from mesoderm
• -embedded with blood vessels, nerves, glands, and hair follicles
• -Functions to provide skin with strength, extensibility, and elasticity from collagen and elastic fibers
• -Receptors that transmit sensations for pressure, paint, and temperature are located in the dermis
• -Hair follicles embedded in dermis

Question 13

Hair

Answer 13

• -column of keratinized cells held tightly together

- -purpose of tactile sensation and thermoregulation

Question 14

nails

Answer 14

–keratinized cells

Question 15

glands of the dermis

Answer 15

• -hairs associated with a sebaceous (oil) gland that empties oil directly into the follicle and onto the skin
• -sweat glands:
  1. eccrine sweat glands - found all over surface of skin and produce sweat in response to heat
  2. apocrine sweat glands - found only in certain regions of the dermis and produce sweat in response to stress