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MSK Week 4 > ICL 1.1: Histology of the Skin > Flashcards

ICL 1.1: Histology of the Skin Flashcards

1
Q

what are the functions of the skin?

A
  1. protection
  2. sensation
  3. thermoregulation (sweat)
  4. metabolism
  5. maintain body fluid
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2
Q

how does skin help with metabolism?

A
  1. storage of fat
  2. vitamin D metabolism

vitamin D can be ingested or through UV radiation (activates a precursor)

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3
Q

what are the 3 layers of skin?

A
  1. epidermis
  2. dermis
  3. hypodermis
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4
Q

what is the epidermis made of?

A

it’s stratified squamous keratinized epithelium that is NON-vascularized

there are 5 layers to the epidermis

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5
Q

how does the epidermis get nutrients and blood?

A

the dermal papilla has loops that feed blood to the tips of the dermis which then seep into the epidermis

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6
Q

what are the layers of the dermis?

A
  1. papillary layer (superficial)

less eosinophilic, less pink because the collagen bundles aren’t as thick as in the reticular layer

  1. reticular layer (deep)
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7
Q

what is the difference between the papillary and reticular layers of the dermis?

A

papillary = irregular loose CT

reticular = irregular dense CT

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8
Q

what is the hypodermis mainly composed of?

A

fat

so it will appear very white in the micrographs

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9
Q

describe the border between the epidermis and dermis

A

they are connected by hemidesmosomes

the border is made of epidermal ridges that increase surface area – this helps the epidermis not shear off the dermis

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10
Q

what are langer lines?

A

they are a depiction of the main overall direction of collagen fibers in the reticular layer of the dermis

these langer lines guide surgical incisions

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11
Q

what is the cutaneous plexus?

A

a collection of vasculature located in the deep part of the dermis (reticular layer)

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12
Q

what is the arrector pili?

A

attaches to a hair follicle and pulls the dermal/epidermal interface which causes goose bumps!

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13
Q

what are the 5 layers of the epidermis?

A
  1. Stratum corneum (superficial)
  2. Stratum lucidum
  3. Stratum granulosum
  4. Stratum spinosum
  5. Stratum basale (deep)
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14
Q

why is the stratum corneum different colors?

A

as the keratinocytes progress more superficially, they begin to die and the the keratin becomes more prominent and that’s why the stratum corneum is different colors

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15
Q

what are the characteristics of the stratum basale?

A
  1. constant active proliferation
  2. attaches tot he underlying basement membrane by hemidesmosomes
  3. single cuboidal layer
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16
Q

what is bullous pemphigoid?

A

there are antibodies attacking the hemidesmosomes in the stratum basale which would cause the epidermis to unattach from the underlying dermis

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17
Q

what are the characteristics of the stratum spinosum?

A
  1. the keratinocytes in this layer are attached by desmosomes and they protect the layers underneath
  2. cytokeratin aggregates to form tonofibrils
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18
Q

what is pemphigus vulgaris?

A

auto-antibodies against the desmosomes in the stratum spinosum of the epithelium

this will result in blisters on the skin

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19
Q

what are the two granules found in the stratum granulosum? what is their function

A
  1. keratinosomes

contain hydrophobic glycolipid that binds keratin together

  1. keratohyaline granules

combine with cytokeratin to produce keratin

when these granules get to the stratum lucidum they combine to form keratin

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20
Q

what are the 4 types of cells in the epidermis?

A
  1. keratinocytes

produce keratin (most populous)

found in all layers of the epithelium

  1. melanocytes

produce melanin; protect the keratinocytes from UV rays

found in stratum basale

  1. langerhans cells

macrophages of skin

mostly found in stratum spinosum

  1. Merkel cells:

touch receptors

found in stratum basale

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21
Q

what are keratinocytes?

A

the most common type of skin cells

they make keratin, a protein that provides strength to skin, hair, and nails.

keratinocytes form in the deep, basal cell layer of the skin and gradually migrate upward, becoming squamous cells before reaching the surface of the skin over the course of a month

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22
Q

where do keratinocytes proliferate?

A

they constantly proliferate in the stratum basale

they have a 1-2 month life span as they progress more superficially

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23
Q

what is the pH throughout the epidermis?

A

the pH decreases and becomes more acidic as you progress from the stratum lucidum to the stratum corneum

this change in pH causes the desmosomes to disintegrate and the keratinocytes to be released

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24
Q

what is psoriasis?

A

due to an improper progress of keratinocytes through the epidermis

if the keratinocytes don’t properly progress through the layers of the epidermis, you get psoriasis

patients present with whiteish plaque on elbows and knees

25
Q

what is basal cell carcinoma?

A

the keratinocytes in the stratum basale are also called basal cells

so unregulated differentiation of the keratinocytes in that layer is basal cell carcinoma

26
Q

what is a squamous cell carcinoma?

A

any of the keratinocytes i any of the layers of the epidermis outside the stratum basale differentiating in an unregulated manner

27
Q

where are melanocytes found?

A

stratum basale

28
Q

what is the function of melanocytes?

A

they deposit melanin on the apical side of the keratinocytes to protect them from UV rays

29
Q

what is vitiligo?

A

patches of deep pigmented skin as a result of auto-immune destruction of melanocytes

30
Q

what is a melanoma?

A

unregulated proliferation of melanocytes

31
Q

what are langerhans cells? where are they mainly located?

A

macrophages of the skin

they clean up the debris in and around the keratinocytes of the skin

they are largely located within the stratum spinosum

32
Q

what are the ways that the skin achieves thermoregulation?

A
  1. insulation
  2. sweating
  3. arteriovenous shunts
  4. constriction and dilation of papillary loops
33
Q

what is an AV shunt?

A

arteriovenous shunt

a channel for blood to bypass the more superficial layer of the dermis

on a cold day, the shunt opens to allow blood to bypass the more superficial layer of the epidermis to keep us warm – the blood vessels constrict so that heat isn’t being lost out the epidermis

they’re mainly located at fingertips and external ear

34
Q

where are papillary loops located?

A

thin skin only

35
Q

what are the 3 types of secretion?

A
  1. merocrine
  2. apocrine
  3. holocrine
36
Q

what is merocrine secretion?

A

eccrine and apocrine sweat glands

37
Q

what is apocrine secretion?

A

pinch/release of vesicle

mammary glands

38
Q

what is holocrine secretion?

A

the entire cell forms a secretory product – the entire cytoplasm is filled with secretory product and it all gets secreted

sebaceous glands

39
Q

what are eccrine sweat glands?

A

smaller than apocrine sweat glands

they empty their contents on the skin surface

they are distributed throughout the body

40
Q

what are apocrine sweat glands?

A

they are larger than eccrine sweat glands

they empty their contents into a hair shaft

they are influences by hormones! so during puberty they develop due to hormones

they are localized in the armpits, groin and perianal area

41
Q

what do sebaceous glands do?

A

sebum moisturizes skin, lubricates hair and reduces water loss

the cell starts to die and lose its nucleus and the entire contents of the cell are secreted as sebum = holocrine secretion

blockage of duct of sebaceous gland causes acne

42
Q

what are the 3 types of hair?

A
  1. lanugo
  2. velus
  3. terminal hair

hair is ONLY found in thin skin

43
Q

what is lanugo?

A

very fine hair present on newborn

44
Q

what is vellus hair?

A

fine, short pale hair

majority of human hair is of the vellus type

45
Q

what is terminal hair?

A

large, coarse, dark hair

ex. scalp, eyebrows

46
Q

what are the 3 phases of hair growth?

A
  1. anagen
  2. catagen
  3. telogen

then back to anagen

47
Q

what’s the difference between a hair shaft and follicle?

A

hair follicle is the dilated part of a hair at the bottom

48
Q

what is a hair root?

A

where you find matrix cells that are stem cells that are going to form the epithelial cells of the hair

when these epithelial cells first arise from the stem cells they’re called matrix cells

the dermal papilla deep to the hair root is what has arteries and nerves that provide nutrients to the matrix cells

49
Q

what are the parts of a nail?

A
  1. nail plate
  2. nail bed
  3. nail matrix
  4. nail root
50
Q

what is the nail plate?

A

the main part of the nail that we can see

the cells that make up the nail plate are epithelial cells with hard keratin

51
Q

what are free nerve endings?

A

they travel between the keratinocytes of the epidermis and are responsible for pain, itch, temperature = termoreceptors and nociceptors

A-delta fibers = myelinated & fast

C fibers = unmyelinated & slow

52
Q

what are merkel cells?

A

they are mechanoreceptor for deep touch, pressure and proprioception

slowly adapting

they are interspersed among keratinocytes of the stratum basale

53
Q

what is a meissner’s corpuscle?

A

mechanoreceptors for light touch

quickly adapting

exclusively located in dermal papilla of thick skin

54
Q

what is a pacinian corpuscle?

A

mechanoreceptor for pressure, vibration and light touch

quickly adapting

onion-like appearance

located deep in dermis and in hypodermis, as well as in joints

55
Q

what are ruffini corpuscles?

A

mechanoreceptor for tension and stretch in finger tips

also they’re mechanoreceptors for joint angle changes in joints

slowly adapting

56
Q

the epidermis is comprised of what type of epithelium?

A

stratified squamous keratinized

57
Q

what are the 4 types of burns?

A

1st degree = only epidermis

2nd degree = Epidermis and dermis

3rd degree = Epidermis, dermis and hypodermis

4th degree = epidermis, dermis, hypodermis, and even underlying muscle, bone or tendon

58
Q

During the visit, the patient tells you that he has been having difficulty distinguishing hot and cold sensations in the areas of injury to his skin. Damage to which receptor best explains this symptom?

A

free nerve ending

59
Q

autoimmune destruction of which cells is responsible for the depigmented patches of skin?

A

melanocytes

MSK Week 4 (11 decks)

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