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Anatomy Semester 1 > SKIN > Flashcards

SKIN Flashcards

1
Q

what 3 layers is the skin composed of?

A
  1. epidermis
  2. dermis
  3. hypodermis/subcutis
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2
Q

what is the epidermis and what is it composed of?

A

= most superficial layer

  • composed of strata, avascular stratified squamous epithelium,
  • largely formed of layers of keratinocytes undergoing terminal maturation
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3
Q

what are the 4 cell types in the epidermis and what do they do?

A
  1. keratinocytes - manufactures stratum corneum, make keratin
  2. melanocytes - produce melanin
  3. langerhans cells - on infection they take up and process microbial antigens to become fully-functional antigen-presenting cells
  4. merkel’s cells - receptor cells
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4
Q

name the 5 layers of the epidermis from the bottom to the top

A
  1. stratum germinativum/basale
  2. stratum spinosum
  3. stratum granulosum
  4. stratum lucidum
  5. stratum corneum
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5
Q

what is the difference between thin skin and thick skin?

A
  • thin skin, which covers most of the body surface, has 4 layers of keratinocytes
  • thick skin, which occurs on the palms of the hand and the soles of the feet, contains a 5th layer — the stratum lucidum
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6
Q

how long does it take a keratinocytes to mature from the stratum basale to the stratum corneum?

A

28-30 days

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7
Q

where are keratinocytes shed and what as?

A

keratinocytes develop at the bottom and then rise to the top, where they are shed from the surface as dead cells

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8
Q

what is the stratum basale/germinativum and what happens here?

A

= deepest layer of the skin, composed of a single row of keratinocytes
= mitosis of keratinocytes occurs here

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9
Q

what is the stratum spinosum and what happens here?

A

= 4th deepest layer of skin, 8-10 layers of keratinocytes

= keratinocytes are joined by tightintercellular junctions called desmosomes

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10
Q

what is the stratum granulosum and what happens here?

A

= 3-5 layers of keratinocytes derived from the stratum spinosum, here cells secrete lipids and other waterproofing molecules
= keratinocytes stop dividing here

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11
Q

what is the stratum lucidum and what happens here?

A

= it is only present in thick skin
= here cells lose nuclei and drastically increase their keratin production
= fattened, densely packed cells filled with keratin
= a clear glassy layer

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12
Q

what is the stratum corneum and what happens here?

A

= most superficial layer
= 15-30 layers of keratinised cells
= dead cells remain tightly interconnected by desmosomes
= cells lose all organelles, continue to produce keratin
= this layer is water resistant (not waterproof)
= maintenance of this layer is involves coating the layer with lipid secretions from subaceous glands

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13
Q

what attaches cells of the stratum basale to the basal lamina (basement membrane)?

A

hemidesmosomes

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14
Q

what happens if damage breaks connections between superficial and deep layers of the epidermis (or between epidermis and dermis?

A

fluid will accumulate in the pockets — blisters

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15
Q

what is the dermis?

A

= lies between the epidermis and the subcutaneous layer

= has 2 layers — the superficial papillary layer and the deeper reticular layer

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16
Q

what is the papillary layer formed of?

A

formed of loose irregular connective tissue, blood vessels (papillary plexus)

17
Q

what is the reticular layer composed of?

A
  • formed of dense irregular connective tissue
  • considerably thicker and features thicker bundles of collagen fibres that provide more durability
  • has elastic fibres permitting stretching and recoiling
18
Q

what are the 4 cell types in the dermis?

A
  1. fibroblasts
  2. mast cells
  3. blood vessels and cutaneous sensory nerves
  4. skin appendages
19
Q

what do fibroblasts do?

A

synthesis the extracellular matrix, which is mainly composed of collagen and elastin

20
Q

what are mast cells?

A

histamine granule-containing cells of the innate immune system

21
Q

what are skin appendages?

A

= eg. hair follicles, nails, sebaceous and sweat glands

= derived from epidermis which descend into dermis during development

22
Q

what are sebaceous glands? how is sebum secreted?

A

= “oil glands” — secrete an oily lipid secretion (sebum) into hair follicles
- the arrector pili muscles contract, squeezing the sebaceous gland and secreting sebum

23
Q

what are 2 functions of sebum?

A
  1. inhibits the growth of bacteria

2. lubricates the skin

24
Q

what are the 2 different sweat gland types and what are the differences?

A
  1. APOCRINE SWEAT GLANDS = larger sweat glands, located in the axillary and genital regions. products can be broken down by cutaneous microbes, producing body odour. secrete products into hair follicles. start secreting at puberty.
  2. ECCRINE GLANDS = the major sweat glands of the body. release a clear odourless substance, compromised mostly of NaCl and H20. secrete products directly onto skin surface (via exocytosis)
25
Q

what are the functions of sweat?

A
  1. cooling the surface of the skin to reduce body temperature
  2. excreting water and electrolytes
  3. providing protection from environmental hazards
26
Q

what are sweat glands innervated by?

A

sympathetic autonomic nervous system

27
Q

what is dermatitis and what layer of the skin does it involve?

A

= inflammation of the skin that primarily involves the papillary layer of the dermis

28
Q

what is the hypodermis (subcutaneous layer) and what does it consist of?

A

= immediately deep to the dermis

  • it is a major body store of adipose tissue
  • consists of adipose tissue, fibrous connective tissue (making it quite elastic), and blood vessels (cutaneous plexus)
29
Q

what are the functions of subcutaneous fat?

A
  1. insulation
  2. substantial energy reserve
  3. shock absorber
30
Q

what are tight junctions?

A

the area where 2 cells membranes join together to form a virtually impermeable barrier to fluid

31
Q

what are gap junctions?

A

specialised intercellular connection between cells. it directly connects the cytoplasm of 2 cells, which allows various molecules and ions to pass freely between the cells

32
Q

differences between thick and thin skin

A
  1. epidermis of thin skin is much thinner and less well developed
  2. no clear layer (stratum lucidum) in thin skin
  3. thick skin does not have hair, smooth muscles, or sebaceous glands
33
Q

what are some general functions of the skin?

A
  1. protection
  2. excretion
  3. production (keratin, melanin)
  4. storage
  5. detection
  6. immunological barrier

Anatomy Semester 1 (15 decks)

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