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Histology > Integument > Flashcards

Integument Flashcards

1
Q

What is the epidermis?

A

Location: Epithelial covering of the skin
Highly cellular tissue with essentially no intercellular space
Function: protective barrier (physical, biological, and chemical insults)
Avascular (dependent on diffusion from dermal vasculature)
Minimally innervated

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2
Q

What is the dermis?

A

Contains supportive connective tissue layer with a strong extracellular matrix component with comparatively few cells
Highly vascularized and innervated
Most skin appendages are found here

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3
Q

What is the hypodermis

A

Similar to superficial fascia
Primarily adipose compartmentalized by other connective tissues (highly vascular)
Function:
1) insulation
2) allows skin to move independent of muscles

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4
Q

What are the skin appendages?

A

Hair follicles
Nails
Sweat glands
Sebaceous glands

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5
Q

What epithelium makes up the epidermis?

A

Stratified squamous orthokeratinized epithelium

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6
Q

What is stratified squamous orthokeratinized epithelium?

A

Multilayered tissue where the most superficial cells are flattened
Covered superficially by sheets of keratin (remnants of dead cells)
separated from underllying dermis by a basement membrane

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7
Q

What is the Basement membrane?

A

Non-cellular sheet of protein basal to most epithelia
difficult to see directly with light microsopy
provides adhesion interface for epithelial tissues
Function: serves as filtration barrier between compartments

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8
Q

What does stratum mean?

A

Single Layer

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9
Q

What is the principle cell type found in Epidermis?

A

Keratinocyte

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10
Q

What is the function of keratinocytes?

A

differentiates to produce keratin and keratohylin granules

° also produces and secretes large amounts of glycolipid which creates a water barrier

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11
Q

Where are keratinocytes found?

A

originates deep in the epidermis and takes about 4 weeks to move to the surface

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12
Q

Where is the stratum basale located?

A

first layer of cuboidal to low columnar cells sitting on the basement membrane

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13
Q

What does the stratum basale contain?

A 
Contains mitotic cells that continually give rise to new keratinocytes
Many desmosomes (cell-cell) and hemidesmosomes (cell-BM) present
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14
Q

Where do the hemidesmosomes in the stratum basale connect to?

A

From the cells to the basement membrane

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15
Q

What is the primary cytoskeletal protein in epithelial cells?

A

Keratin

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16
Q

What is the stratum spinosum?

A

Layer superficial to Stratum basale
Variable in thickness from a few to several cell layers thick
Polyhedral shaped cells linked by spine-like processes that contains desmosomes made apparent by shrinkage artifact

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17
Q

What is the Stratum granulosum?

A

Only a few cells thick; squamous shaped cells
Contain distinct basophilic keratohylin granules
Also contain large amount of keratin filaments at this time
Last layer of living cells

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18
Q

What is the stratum lucidum?

A

Clear layer only seen in skin from palms and soles (glabrous skin)
Thin transparent layer only a few cell layers thick
Cells here have died and lost their organelles (including the nucleus)

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19
Q

What is the Stratum Corneum?

A

Keratinized or cornified layer of dead keratinocytes
Compact sheets of keratin fibers; variable thickness (eg., calluses)
Glycolipid released into the intercellular space forms the water barrier

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20
Q

What is glabrous (thick) skin and hairy (thin) skin based relative to?

A

Epidermis only

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21
Q

Where is glabrous skin found?

A

found on palms of hands and soles of feet

Hairless skin with a thick epidermis (substantial keratinized layer)

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22
Q

Where is Hairy (thin) skin found?

A

Hairy or thin skin - found on remainder of body

Has hair follicles and a thin epidermis (thinner layer of keratin)

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23
Q

What is the total thickness of skin measured by?

A 
Total thickness (epidermis+dermis+hypodermis)
So, Thin skin is thicker than thick skin
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24
Q

What is Psoriasis?

A

chronic skin disorder characterized by dark red circumscribed lesions with
obvious superficial silvery white scales

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25
Q

What is Psoriasis caused by?

A

Due to accelerated keratinocyte turnover

  • mitosis occurs in the three deepest layers of epidermis
  • overproduced keratinocytes reach surface in less than 1 week
  • not enough time to allow adequate maturation of keratinocytes
  • stratum corneum fails to become strongly cohesive layer
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26
Q

What are melanocytes and where are they found?

A

pale staining dendritic cell found interspersed in the stratum basale

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27
Q

What is the function of melanocytes?

A

Produce a brown pigment called melanin

  • Constitutively secreted by melanocytes and phagocytosed by keratinocytes
  • Colors the skin and protects from ultraviolet ray penetration
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28
Q

Do people of all races have melanocytes?

A

Yes

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29
Q

What is the concentration of melatocytes to keratinocytes?

A

10 - 25%

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30
Q

What is the effect of melanocytes on skin color?

A
  • Light skinned people store melanin in basal keratinocytes and have a faster rate of lysosomal degradation
  • Dark skinned people store melanin in all layers of the epidermis and have a much slower rate of lysosomal degradation
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31
Q

What occurs in albino people?

A

albino people have genetic defect making melanin production impossible

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32
Q

What are langerhans cells an what are their function?

A

Pale staining dendritic cell located in the three deepest layers of epidermis
Antigen presentation cell involved in cell mediated immune responses in the skin

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33
Q

What are Merkel cells?

A

clear cell located in stratum basal where it synapses with an afferent neuron

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34
Q

What is the function and location of merkel cells?

A

Prevalent where sensory perception is acute (e.g., fingertips)
Functions as a mechanoreceptor for light touch

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35
Q

What is the dermis primarily made up of?

A

primarily dense irregular connective tissue containing the skin appendages

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36
Q

What does the “dense irregular” of dense irregular connective tissue refer to?

A

How thick the actual collagen strands are and not how densely packed they are. Also, the irregular = no pattern

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37
Q

What is Dense Irregular Connective Tissue made up of?

A

thick bundles of Type I collagen running in multiple planes

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38
Q

What is the most abundant extracellular fibrillar protein?

A

Type I Collagen

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39
Q

What is the function of Dense Irregular Connective Tissue?

A

functions to limit range and direction of movement in multiple directions

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40
Q

Is the dense irregular Connective tissue able to repair itself after injury?

A

Yes because it is usually well vascularized and well innervated

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41
Q

What are elastic fibers?

A

Composed of fibrillin and elastin proteins and intermixed among the type I collagen

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42
Q

What is the elastic fibers’ function?

A

unctions to allow tissue to recoil after having been stretched

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43
Q

What fills the spaces between the CT fibers and the cells?

A

Ground substance

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44
Q

What is ground substance primarily made of?

A

Glycosaminoglycans (GAGs)

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45
Q

What are GAGs?

A 
Large unbranched polysaccharide chains of repeating disacchraides
Usually attached to a protein core (creating a proteoglycan monomer) 
High negative charge
Strongly hydrophilic (can't fold; permanently open configuration)
46
Q

What is the function of ground substance

A

functions to facilitate diffusion between cells and capillaries

47
Q

What is the most-commonly seen cell in dense irregular CT?

A

Fibroblasts

48
Q

What are fibroblasts?

A

Spindle shaped cell with long cytoplasmic processes

Round to elongated oval shaped nucleus with nucleolus

49
Q

What is the function of fibroblasts?

A

functions to produce all the matrix components in general connective tissue also maintains and repairs CT matrix

50
Q

What is the second most common cell in dense irregular CT?

A

Macrophages

51
Q

What are the function of the macrophages?

A

major functions are phagocytosis and antigen presentation

52
Q

What is the Papillary Dermis?

A

fairly narrow region immediately deep to epidermis

53
Q

Function of the papillary dermis?

A

very undulating interface exists here; contributes to adhesion

54
Q

What are dermal paillae

A

dense irregular CT projections up underneath epidermis

55
Q

What are rete pegs?

A

epithelial extensions down into CT

56
Q

What is the reticular dermis?

A

Thicker area deep to the papillary layer

57
Q

What does the reticular dermis consist of?

A

Coarser dense irregular CT (as compared to papillary dermis) with elastic fibers
Contains blood vessels, lymphatics and nerves of skin

58
Q

What is the main area of the dermis?

A

The reticular dermis because the integrity is based on this layer

59
Q

What are dermatoglyphics

A

fingerprints
Epidermal ridges corresponding to underlying dermal ridges
Dermal ridges result from rows of dermal papillae

60
Q

What are blisters

A

usually formed by excessive sheering at the dermal/epidermal interface

61
Q

What are langer’s lines?

A

parallel lines of tension in skin resulting from organized bundles of collage and elastic fibers
Surgical incision heal with least scarring when made parallel to these lines

62
Q

How does blood reach the skin?

A 
Subcutaneous arteries (deep in the hypodermis) send branches to the junction 
between the reticular layer of dermis and the hypodermis (superficial fascia)
63
Q

Where is the deep plexus?

A

between the hypodermis and the reticular dermis

64
Q

Where is the superficial plexus?

A

between the reticular dermis and the papillary dermis

65
Q

What is the epidermis nourished by?

A

epidermis is nourished by diffusion from dermal papillary capillaries

66
Q

What extends into each dermal papilla?

A

Capillary loops that extend from the superficial plexus

67
Q

What is the Arterioenous anastomoses?

A

Direct connection between arterial and venous vessels bypassing capillary beds
• Required for thermoregulation
• May be gated as necessary by the ANS

68
Q

Where are Arterioenous anastomoses found?

A

located between the two plexuses

69
Q

What are mechanoreceptors?

A

stimulated by compression or tension

70
Q

What are thermoreceptors?

A

stimulated by temperature

71
Q

What are nociceptors?

A

stimulated by chemical irritants (pain)

72
Q

What is the rank of touch from light to heavy?

A 
Merkel Cells (stratum basale)
Meissner's corpuscle (dermal papillae)
Pacinian Corpuscle (dermis/hypodermis)
73
Q

What are free nerve endings?

A

Not associated to Schwann Cells

Most numerous and function in mechanoreceptors, thermoreceptors and nociceptors

74
Q

What are encapsulated nerve endings?

A

Surrounded by modified Schwann cells

75
Q

What is a Meissner’s corpuscle?

A

mechanoreceptor sensitive to light touch

flat Schwann cells with a helical neuron

76
Q

Where are Meissner’s Corpuscles located?

A

located in dermal papillae (especially on palms and fingertips

77
Q

What are Pacinian corpuscles?

A

Mechanoreceptor sensitive to deep pressure

Quite large with concentric rings of Schwann cells and central neuron

78
Q

Where are the Pacinian corpuscles located?

A

located at dermis/hypodermis interface

79
Q

What are Ruffini corpuscles?

A

Mechanoreceptor sensitive to tension

Small spindle shaped receptor found interspersed among the collagen bundles

80
Q

What are nails?

A

protective covering on dorsal surface of terminal ends of fingers/toes

81
Q

Does hair grow continuously?

A

No

82
Q

What makes up the hair shaft?

A

multiple layers of highly organized keratin

83
Q

What makes up the hair follicle?

A

tubular downgrowth of epidermis into dermis and hypodermis

84
Q

What is the arrector pili muscle?

A

narrow band of smooth muscle associated with each hair

* runs obliquely to the foYicle and causes the shaft to become erect (ie goose bumps)

85
Q

What does exocrine mean?

A

Must have a duct, where secretions will flow and release secretions to

86
Q

What does endocrine mean?

A

No duct

87
Q

What is a simple gland?

A

No branching, only goes to one destination

88
Q

What does acinar mean?

A

Cluster shape

89
Q

What are sebaceous glands?

A

Simple Acinar Exocrine Glandular outgrowths from the hair follicle
Fairly inactive prior to puberty; large and secretory following puberty
Large polyhedral pale staining cells; mitotically active peripherally in gland

90
Q

What is sebum?

A

oily secretory product released by holocrine secretion

91
Q

What type of gland are eccrine sweat glands?

A

simple tubular exocrine glands

92
Q

Where are eccrine sweat glands found?

A

Secretory region is coiled and located in the reticular dermis
Excretory region passes through papillary dermis and epidermis to surface
Located everywhere in skin but especially concentrated in: forehead, scalp, axillae, palms and soles

93
Q

What is the function of the eccrine sweat glands?

A

secrete sweat which is important for temperature regulation

94
Q

What are appocrine sweat glands associated with?

A

associated with hair follicles

95
Q

Where are appocrine sweat glands located?

A

located in the axilla, areola and nipple, circumanal region, external genitalia

96
Q

What is the function of appocrine sweat glands?

A

Secretion is initially odorless but bacterial action on the skin creates an odor
Secretion may function as pheromone

97
Q

What is Loose (Areolar) connective Tissue?

A

Mostly thin, lacy Type I collagen fibers
Fairly fluid-like ground substance
Variety of immune cells may be present but here it’s mostly fibroblasts

98
Q

Where is Loose (areolar) connect tissue found?

A

located among loops of sweat glands, within adipose, deep to the epithelial linings
of the Gl and respiratory tracts, and in dissectable tissue planes in Gross lab

99
Q

What are the functions of loose connective tissue?

A

functions in packing, binding and anchoring in relatively small areas
~ often has a role in immune function

100
Q

What is the hypodermis?

A

Equivalent to superficial fascia
Varies greatly in thickness from glabrous to abdominal skin
Major component is adipose

101
Q

What are adipocytes?

A

mature adipocytes are non mitotic (terminal cell)

o stem cells exist to provide additional adipocytes throughout life

102
Q

What do adipocytes look like?

A

Signet ring ejppearance (diameter 100 J.lm or more)
Large lipid droplet pushes the nucleus and cytoplasm peripherally
Adipocytes are held together by thin strands of Type I collagen (difficult to discern)
Clumps of adipocytes are compartmentalized by seams of dense irregular CT

103
Q

What is the function of adipocytes?

A

Long term energy reserve source

Insulates against heat loss, fills crevices and cushions

104
Q

What is uniocular adipose?

A 
White fat (yellow); ubiquitous in the body
Adult form of fat most commonly present
105
Q

What is the structure of uniocular adipose?

A

Spherical/polygonal cells usually clustered in groups
Appears yellow Grossly and usually white Histologically
Each cell contains a single large lipid droplet which pushes organelles peripherally

106
Q

What is the function of uniocular adipose?

A

Lipid storage as the body’s long term energy reserve

Insulation, shock absorption and “body contouring”

107
Q

What is Multiocular adipose?

A

Brown fat
Most common in newborns (disappears in adult)
Typical kind of fat seen in hibernating animals

108
Q

What is the structure of multiocular adipose?

A

Smaller cells than those in unilocular fat

each cell contains, multiple small lipid droplets and many mitochondria

109
Q

What is the function of multiocular adipose?

A

metabolize fat to produce heat

110
Q

Where is the stratum basale located?

A

Sits on the basement membrane

111
Q

What does the stratum basale contain?

A 
Mitotic cells that give rise to new karatinocytes
Contain desmosomes (cell - cell)and hemidesmosomes (cell-BM)

Histology (9 decks)

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