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Histology Cole > Lecture 12 Skin > Flashcards

Lecture 12 Skin Flashcards

1
Q

Largest organ of the body

A
  • skin
  • 15-20% of body mass
  • hair, nails,
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2
Q

4 functions of skin

A
  • protection
  • sensation
  • thermoregulation
  • metabolic functions
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3
Q

Protection

A
  • from UV, mechanical, chemical, and thermal insult

- prevents dehydration; provides physical barrier to microorganisms

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4
Q

Sensation

A
  • largest sense organ of body

- contains receptors for touch, pressure, pain, and temperature

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5
Q

Theromoregulation

A
  • insulation via hair and SQ fat; heat loss facilitated by sweat glands and dermal capillary network
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6
Q

Metabolic functions

A
  • energy stored in subcutaneous fat
    (primarily as triglycerides);
  • Vit D synthesized in skin via sunlight
  • Maintains homeostasis; excretory function (sweating) immune defense
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7
Q

Skin has 3 main layers

A
  • epidermis
  • dermis
  • hypodermis (subcutaneous)
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8
Q

Epidermis

A
  • consists of keratinized stratified squamous epithelium

- varies in thickness from <1 mm to >5

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9
Q

Cells of epidermis

A

keratinocytes

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10
Q

Thick skin

A
  • palms of hands and soles of feet
  • thick highly keratinized layer
  • lacks hair (glaborus)
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11
Q

Think skin

A
  • thin keratinized epidermis
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12
Q

Epidermis

A
  • lack blood vessels – do not penetrate basement membrane
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13
Q

Where is the skin thickest?

A
  • if dermis is included it is the back of the neck

- predators try to attack prey there

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14
Q

Epidermis supplied and nourished by blood vessels in the underlying (subadjacent) ______

A

dermis

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15
Q

Dermis

A
  • composed of dense irregular collagenous connective tissue (type 1 collagen)
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16
Q

What happens when the elastic fibers are damaged from sunlight?

A
  • sagging or “aging)

- loss of skin tone

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17
Q

Is the dermis vascular?

A
  • Yes, highly vascular and contains many sensory receptors
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18
Q

What are the 2 layers of the dermis?

A
  • superficial papillary layer

- deep reticular layer

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19
Q

Papillary layer

A

relaticely thin- interdigitates with epidermis

- corrugations increase surface area for attachement, prevent shear and mechanical abrasion

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20
Q

Epidermal ridges

A
  • epidermal projections into epidermis
  • large dermal ridges in thick skin called finger prints (dermatoglyphs) unique to individual
  • form basis of study of dermatoglyphics
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21
Q

What is the part of the dermis that is unique to individuals?

A
  • dermatoglyphs
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22
Q

Epidermal ridges (rete ridges)

A
  • epidermal projections into epidermis
  • large dermal ridges in thick skin called finger prints (dermatoglyphs) unique to individual
  • form basis of study of dermatoglyphics
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23
Q

What is the part of the dermis that is unique to individuals?

A
  • dermatoglyphs
  • dermal ridges
  • unique to identical twins
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24
Q

Dermal ridges

A
  • project into epidermis

- finger prints ( dermatoglyphs)

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25
Q

What is the thickest layer of the dermis?

A
  • the deep reticular layer

- also less cellular

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26
Q

What layer of the dermis contains hair follicles, sweat and sebaceous glands?

A
  • the deep reticular
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27
Q

What does the retiular layer of the dermis interdigitates with

A
  • underlying hypodermis (subcutis)

- thick collagen bundles and elastin fibers in reticular layer form lin

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28
Q

thick collagen bundles and elastin fibers in reticular layer form lines of tension called

A

Langers lines

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29
Q

When you are making skin incisions what lines should you make your incisions parallel to?

A

Langers lines

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30
Q

What does making skin incisions parallel to langers lines do?

A
  • makes them heal with less scarring

- slicing in between collagen bundles instead of across

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31
Q

What is the deepest layer of the dermis?

A
  • hypodermis
32
Q

What is the hypodermis composed of?

A
  • loose irregular connective tissue and adipose tissue

- (subcutis = superficial fascia= adiposus)

33
Q

Three vascular plexi of skin

A
  • superficial subpapillary plexus
  • deep cutaneous plexus
  • deeper subcutaneous plexus
34
Q

Where is the subpapillary plexus located?

A
  • at the junction of the paillary and reticular layers
35
Q

Where is the cutaneous plexus located?

A

at the junction of the reticular layer and hypodermis

36
Q

Where is the subcutaneous layer?

A
  • deep within the hypodermis

- largest of three plexi

37
Q

What are the vascular plexi used for?

A
  • thermoregulation
38
Q

Where are these plexi commonly found?

A
  • in fingertips and ears

- associated with AV shunts containing glomus bodies

39
Q

What are these glomus bodies made up of?

A
  • thickened regions of smooth muscle in wall of arterioles surrounded by connective tissue
40
Q

When its cold what do these glomus bodies do?

A
  • bypass capillary bed and re route blood from arterial to venous circulation
  • why you cant feel your fingers
  • help maintain internal body temp by bypassing them
  • could cause frostbite
41
Q

Does the epidermis stop growing?

A
  • No continuously grows and is replaced
42
Q

How long does it take for skin cells to travel from deep germinal layer, mature, and be sloughed from superficial epidermis?

A
  • 25-50 days
43
Q

What is the disease where keratinocyte maturation only takes 1 week?

A
  • psoriasis
44
Q

What are some features of psoriasis?

A
  • absence of a granular layer and abnormal keratohyaline and tonofibrils
45
Q

What is the deepest layer of epidermis?

A
  • stratum basale = stratum germinativum
46
Q

Stratum basale

A
  • mitotic layer consisting of cuboidal germinal cells that rest on basement membrane adjacent to the dermis
  • these cells are bound to basement membrane by hemidesmosomes
47
Q

Hemidesmosomes

A
  • attach to underlying dermis via anchoring filaments and microfibrils
48
Q

Stratum spinosum

A
  • prickle cell layer- cells look spiny
49
Q

What is the thickest layer of epidermis in think skin?

A
  • stratum spinosum
50
Q

What type of cells make up the stratum spinosum?

A
  • polyhedral cells with prominent intercellular bridges (desmosomes)
  • numerous cytoplasmic processes and lateral folding of cell membrane
51
Q

Why would overstaining be useful when looking at stratum spinosum?

A
  • can see lines between cells

- junctions called desmosomes (intercellular strructure)

52
Q

What is the predominant cell product of stratum spinosum?

A
  • cytokeratin
53
Q

What does the cytokeratin do?

A
  • forms tonofilaments, which aggregate into larger tonofibrils that anchor onto desmosomes
54
Q

How many types of keratin to humans produce?

A
  • 54 alpha keratin
55
Q

B keratin

A
  • tougher

- birds

56
Q

Stratum granulosum

A
  • granular cell layer
57
Q

What is stratum granulosum charcterised by?

A
  • cells containing basophilic kerathohyline granules
58
Q

What are keratohyaline granules?

A
  • non-membrane bound electron dense granules
59
Q

Keratinization

A

respresents interaction between keratohyaline granules and tonofibrils

60
Q

How is keratinization initiated?

A
  • release of lyposomal enzymes
61
Q

What does releasing lyposomal enzymes do?

A
  • causes rupture of keratohyaline granules and polymerization of their contents
  • this forms a matrix for tonofibrils of cytokeratin –> amorphous mass of mature keratin
62
Q

Release of lysosomes also leads to

A

cell death

63
Q

What happens when keratinocytes mature?

A

they die and lose nuclei

64
Q

Keratinosomes

A
  • membrane boud structures that contain glypolipids

- provide waterproof coat for skin cells

65
Q

Cells of granular level

A
  • mature to form waterproof layer of keratinized cells, with glycolipid coating on surface of epidermis
66
Q

Stratum lucidum

A
  • present only in thick skin

- homogenous compact layer of enucleate cells between stratum granulosum and stratum corneum

67
Q

What is the most superficial layer of the epidermis?

A
  • stratum corneum (cornified layer)
68
Q

Squames

A
  • present in stratum corneum

- flattened, enucleate, dead cell remnants

69
Q

What is the squames made up of?

A
  • primarily of soft keratin (acts as hydrophobic barrier, prevents desiccation)
  • waxy coating
70
Q

What does the soft keratin do?

A
  • acts as a hydrophobic barrier - prevents desiccation
71
Q

dead cells are continuously exfoliated

A
  • slough them off
72
Q

In females, exfoliated cervical epithelial cells routinely examined in Pap smear, why?

A
  • to detect cervical cancer

- pap smears taken from cervix

73
Q

Dogs tracking criminals

A
  • smelling odors attached to exfoliated skin cells
74
Q

Vet practices

A
  • only want to ship dog if they are receptive
75
Q

Common skin tumors

A
  • squamous cell carcinoma
  • basal cell carcinoma
  • melanoma
76
Q

Where are squamous cell carcinomas and basal cell carcinomas derives from?

A

epithelial cells

77
Q

Where are melanomas derived from?

A
  • melanocytes

Histology Cole (7 decks)

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