Integumentary system

Question 1

what are the functions of the skin

Answer 1

• thermoregulation
• secretion
• cutaneous sensation
• prevent moisture loss
• absorption
• reduces effects of harmful UV radiation
• physical protection
• vitamin D synthesis
• social perception

Question 2

what are the 2 main layers of the skin

Answer 2

• epidermis (above dermis)
• dermis

Question 3

what is under the dermis

Answer 3

a subcutaneous layer of areolar and adipose connective tissue

Question 4

epidermis

Answer 4

• most superficial layer of the skin
• composed of stratified keratinised
  squamous epithelium
• has no blood vessels or nerve endings
  but deeper layers of epidermis are
  bathed in interstitial fluid - provides O2
  and nutrients and drains away as lymph

Question 5

dermis

Answer 5

• formed from connective tissue,
  containing collagen and elastic fibres
• cells in the dermis are fibroblasts,
  macrophages and mast cells
• dermis contains blood and lymph
  vessels, sensory nerve endings, sweat
  glands, hairs, arrector pili muscles and
  sebaceous glands

sensory nerves end in receptors - sensitive to touch, temperature, pressure and pain:
- light pressure - meissner’s corpuscle
- deep pressure - pacinian corpuscle and
ruffni’s corpuscle

Question 6

skin colour

Answer 6

• melanin - pigment derived from tyrosine
  and secreted by melanocytes in stratum
  basale
• protects from harmful UV exposure
• colour is determined by
  number of size of melanosome
  haemoglobin and circulating blood
  genetics
  UV radiation
  hormonal instances

Question 7

cells of dermis

Answer 7

• fibroblasts
• mast cells

Question 8

fibroblasts

Answer 8

• synthesise collagen, elastin, and viscous
  gel surrounding these structures
• provide strength and elasticity

Question 9

mast cells

Answer 9

• contains chemical which act on small
  blood vessels
• part of the inflammatory and immune
  response

Question 10

skin appendages - nails

Answer 10

• hardened, dense keratin
• growth carries between individuals
• provide protection, tactile sensitivity and
  help to grasp items
• nail grows from a nail root/matrix under
  the cuticle and from the nail bed

Question 11

skin appendages - hair

Answer 11

• hair develops from matrix cells within
  the hair bulb
• process of keratinisation
• hair colour genetically determined -
  amount of melanin
• provides protection, sensory reception,
  thermoregulation, sweat gland products,
  psychosocial
• 3 types - terminal, vellus, lanugo

Question 12

sebaceous gland

Answer 12

• lobed gland producing sebum
• antimicrobial, waterproofing, softens
  hair, prevents drying and cracking
• absent from palms and soles
• can be associated with hair follicles
• can be independent of hair follicles
• activity increases at puberty

Question 13

sweat glands

Answer 13

• formed by epithelial cells, their bodies of
  the glands lie in subcutaneous tissue
• 2 types: endocrine and apocrine

Question 14

function of the skin - thermoregulation

Answer 14

• core temperature approx 36.8 degrees
• hypothalamus is sensitive to circulating
  blood temperature (neg feedback)
• heat production via metabolic activity

Question 15

function of the skin - mechanisms of heat loss

Answer 15

• mainly through skin
• affected by environmental temp,
  amount of skin exposed + type of
  clothes
• heat is lost via
  radiation
  convection
  conduction
  evaporation

Question 16

functions of the skin - vitamin D synthesis

Answer 16

• sunlight converts 7 - dehydrocholesterol in to vitamin D
• made from cholesterol in the skin
• used in formation and maintenance of bone tissue and absorption of calcium and phosphorous

Question 17

3 stages of wound healing

Answer 17

• inflammation
• proliferation
• maturation

Question 18

healing can take place by 2 methods

Answer 18

• primary healing
• secondary healing

Question 19

inflammatory process

Answer 19

1. damage tissue attracts mast cells releases histamine - diffuses into blood vessels
2. histamine causes vessels to dilate and become leaky - complement proteins leave the vessels attracting phagocytes
3. blood plasma and phagocytes move into infected tissue from vessels
4. phagocytes engulf bacteria and dead cells
5. histamine and complement signalling cease phagocytes are no longer attracted
6. growth factors from white blood cells and platelets stimulate cell division in skin cells, healing the wound

Question 20

healing by first intention

Answer 20

Typical initial injury - disruption of tissue
Day 1 - inflammation - clot and exudate, neutrophils, hemorrhage
Day 3-7 - granulation tissue stage - mitoses, fibroblasts, new capillaries, macrophages
Day 30 - scar tissue - narrow scar, collagen

Question 21

healing by second intention

Answer 21

Typical initial injury - necrosis of epidermis and dermis, capillaries
Day 1 - inflammation - clot and exudate, neutrophils, hemorrhage
Day 3-7 - granulation tissue stage - mitoses, fibroblasts, new capillaries, macrophages
Day 30 - scar tissue - wide scar, wound contraction, collagen