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histology > unit 1 > Flashcards

unit 1 Flashcards

1
Q

epithelium

A

avascular tissue that covers the exterior body surface, lines internal closed cavities and body tubes that communicate with the exterior

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2
Q

epithelium forms what portion of glands?

A

the secretory portion and their ducts

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3
Q

epithelium provides

A

a selective permeable barrier between the external environment and underlying connective tissue

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4
Q

three principal characteristics of epithelium

A

closely apposed to each other by cell-to-cell adhesions via cell junctions
exhibit functional and morphological polarity
basal surfaces attach to an underlying basement membrane

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5
Q

what are the two extracellular structures separating epithelium from CT

A

basal lamina and basement membrane

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6
Q

basal lamina

A

structural attachment site for over-lying epithelial cells and underlying CT

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7
Q

what is the basement membrane

A

basal lamina and the underlying contributions of the connective tissue

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8
Q

all epithelia rest upon what

A

a basement membrane

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9
Q

are basal lamina and basement membrane synonymous?

A

no

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10
Q

what are the three layers of the basement membrane

A

lamina lucida, lamina densa, lamina fibroreticular

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11
Q

what are components of the basement membrane

A

type IV collagen, laminin

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12
Q

what is classification of epithelium based on?

A

number of cell layers and shape of the surface cells

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13
Q

simple squamous cells are usually joined together by what

A

intercellular junctions

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14
Q

where can simple squamous cells be found

A

lining Bowman’s capsule, blood and lymphatic vessels, pleural and abdominal cavities

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15
Q

what do simple squamous epithelium permit

A

diffusion and bidirectional movement of gases, fluids, and nutrients from the free surface to underlying tissue

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16
Q

simple cuboidal epithelium

A

provides protection, forms conduits for gland ducts, may be specialized for active secretion and absorption

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17
Q

where are simple cuboidal epithelium found

A

in glands, salivary ducts, pancreas and kidney

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18
Q

simple cuboidal epithelium may have

A

microvilli or cilia

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19
Q

where are simple columnar epithelium mainly found

A

in areas engaged in protection of wet surfaces, nutrient absorption, and secretion

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20
Q

simple columnar epithelium often have what on free surfaces

A

microvilli

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21
Q

where are stratified squamous epithelium found

A

in areas that need protection from abrasion, i.e. skin

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22
Q

where are stratified cuboidal epithelium usually found

A

lining ducts of sweat glands and exocrine glands

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23
Q

where are stratified columnar epithelium usually found

A

pharynx, larynx, conjunctiva of eyelids, major ducts of exocrine glands, anorectal junction, parts of the male urethra

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24
Q

two special classifications of epithelium

A

psuedostratified and transitional

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25
Q

pseudostratified epithelium

A

some cells do not reach the free surface, but all rest on the basement membrane

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26
Q

transitional epithelium

A

lines lower urinary tract, extends from major calyces to proximal part of urethra

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27
Q

microvilli

A

cytoplasmic projections on the apical surface of most epithelial cells
anchored to villin at the tip of the microvillus

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28
Q

terminal web

A

composed of actin filaments stabilized by spectrin, which anchors it to the apical cell membrane

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29
Q

stereocilia, in the repro track

A

immotile microvilli of an unusual length, function to facilitate absorption

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30
Q

stereocilia, in the ear

A

sensory epithelium that are sensitive to mechanical vibration, serve as mechanoreceptors
high density of actin cross-linked by espin

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31
Q

stereocilia organization

A

internal bundles of actin filaments that are cross-linked by fibrin
organization is similar to microvilli, longer, anchored by ezrin to the plasma membrane

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32
Q

cilia

A

hair-like extensions of the apical plasma membrane

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33
Q

primary cilia

A

function as signal receptors that sense the flow of fluid in organs - mechanoreceptors
mutations in PKD affect the development of primary cilia, leads to disease

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34
Q

nodal cilia

A

present only embryologically, establishes the left-right asymmetry of internal organs

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35
Q

glands are either

A

exocrine or endocrine

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36
Q

exocrine glands

A

release their secretory product into a duct or lumen of a hollow organ

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37
Q

endocrine gland

A

release their secretion into the circulation which distributes it to the target organs

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38
Q

three types of junctional complexes

A

occluding junctions, anchoring junctions, communicating junctions (gap junctions)

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39
Q

other names for occluding junctions

A

zonula occludens, tight junctions

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40
Q

anchoring junction types

A

zonula adherens, macula adherens, focal adhesions, hemidesmosomes

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41
Q

structural integrity of epithelium is maintained by

A

adhesion of the constituent cells both to each other and to structural extracellular matrix

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42
Q

adhesions are maintained by what two systems

A

cell membrane proteins that act as adhesion molecules
specialized areas of cell membranes are incorporated in cell junctions

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43
Q

occluding junctions function

A

establish a barrier between different compartments of the body and allow epithelial cells to function as selective barrier

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44
Q

occluding junction proteins

A

4 groups of transmembrane proteins:
Claudins
occludin
junctional adhesion molecule
tricellulin

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45
Q

anchoring junctions function

A

mechanical stability, through anchoring the cytoskeleton of one cell to the cytoskeleton of an adjacent cell
play a role in cell-to-cell recognition, morphogenesis and differentiation

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46
Q

types of cell-to-cell adhesion

A

zonula adherens, macula adherens

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47
Q

zonula adherens

A

interacts with network of actin filaments
requires Ca++
cadherins and nectins

48
Q

macula adherens

A

interacts with intermediate filaments
desmogleins and desmocollins provide linkage between cell-to-cell membrane

49
Q

types of anchoring cells to CT

A

focal adhesions, hemidesmosomes (found where cells anchor to extracellular materials like basal lamina)

50
Q

gap junctions

A

allow for movement of larger molecules between cells
formed by connexin proteins, six connexin make a connexon

51
Q

integument

A

includes the skin, nails, hair, sweat glands, and sebaceous glands

52
Q

layers of the skin

A

epidermis, dermis, hypodermis

53
Q

skin categorization

A

thick or thin

54
Q

rete ridges

A

form evagination of epidermis into the underlying dermis

55
Q

cell types of the epidermis

A

keratinocytes, melanocytes, Merkel cells, Langerhans cells

56
Q

layers of epidermis

A

stratum corneum
stratum lucidum (only in thick skin)
stratum granulosum
startum spinosum
stratum basale

57
Q

stratum basale

A

single layer of cells that rests on the basal lamina and continuously divides to replace cells
has extensive cell junction (desmosomes & hemidesmosomes)
also contain melanin, is transferred to melanocytes

58
Q

keratinocytes in stratum spinosum

A

keratinocytes with intercellular bridges and centrally located nucleus
larger, several layers thick with apparent cytoplasmic processes or spines

59
Q

stratum spinosum function

A

resist abrasion and shearing forces
many desmosomes connect cytoplasmic processes

60
Q

where is an increase of keratin produced?

A

stratum spinosum, assembled into keratin filaments that make the cytoplasm eosinophilic

61
Q

what projects into the spines of the keratinocytes? what do they do?

A

tonofibrils (large bundles of keratin), connect to desmosomes at tip and link to spine of neighboring cells

62
Q

keratinocytes of stratum granulosum

A

stratified layer 2-5 cells thick, most superficial nonkeratinized epidermis
cytoplasm contain non-membrane bound granules that are strongly basophilic

63
Q

keratohyalin granules

A

cystine and histidine rich proteins
precursors of flaggrin

64
Q

flaggrin

A

promotes tonofibril formation and keratinization

65
Q

what are lamellar bodies? what do their contents form?

A

cytoplasmic secretary granules
lipid-rich contents form extracellular sheets to create a barrier impermeable to water

66
Q

when do cells undergo apoptosis in the epidermis?

A

as they exit stratum granulosum

67
Q

stratum lucidum

A

only a few cell layers thick and only found in thick skin
highly refractive, contains eosinophilic cells where keratinization is well advanced

68
Q

stratum corneum

A

15-30 layers thick
dead, flattened, desiccated cells filled almost entirely with keratin filaments

69
Q

what is desquamation

A

when the most superficial cells of stratum corneum are shed

70
Q

what is the major contributor to the protection/barrier function of epidermis?

A

stratum corneum

71
Q

what is the predominant cell in the epidermis?

A

keratinocyte

72
Q

how are melanocytes distributed??

A

to keratinocytes by phagocytosis

73
Q

Merkel cell

A

ovoid cells with dense cytoplasmic granules

74
Q

how do you get a Merkel disc?

A

Merkel cell + associated sensory nerve ending
mechanoreceptor, LIGHT TOUCH!

75
Q

where are Langerhans cells found?

A

in all layers of the epidermis, but primarily stratum spinosum

76
Q

Langerhans cells

A

star shaped, dendritic type cell
process and present cutaneous antigens to lymphoid cells

77
Q

what are Langerhans cell essential for?

A

immune surveillance in skin

78
Q

what are the two layers of the dermis?

A

papillary and reticular

79
Q

what are the two parts of the epidermal-dermal junction?

A

dermal papillae and epidermal ridges (rete ridges)

80
Q

what does the papillary layer of the dermis consist of?

A

loose CT, less abundant collagen fibers, fibroblasts, abundant mast cells and macrophages, some lymphocytes

81
Q

what layer of the skin are blood vessels not found in?

A

epidermis

82
Q

reticular layer of dermis

A

thicker, less cellular than papillary
dense irregular CT with abundant blood vessels and nerve fibers, thick bundles of type I collagen, and course elastic fibers

83
Q

hypodermis

A

loose CT often with abundant adipose, large blood vessels and nerve fibers are observed in this layer

84
Q

what does the hypodermis do?

A

loosely binds skin to underlying organ and structures

85
Q

what is the most common nerve supply to the skin?

A

free nerve endings (lack CT or Schwann cell)

86
Q

where do free nerve endings terminate?

A

in stratum granulosum, often reach stratum corneum

87
Q

what sensations do free nerve endings convey?

A

fine touch, heat, cold, pain

88
Q

what are the encapsulated sensory receptors?

A

pacinian corpuscles, meissner’s corpuscles, Ruffini’s corpuscles

89
Q

what are pacinian corpuscles?

A

deep pressure sensors found in deep dermis/hypodermis
nerve endings surrounded by concentric layers of support cells

90
Q

what are meissner’s corpuscles?

A

fine touch, vibration, and pressure sensors found in dermal papillae layer
nerve endings spiral thru corpuscle surrounded by few support cells

91
Q

what are Ruffini’s corpuscles?

A

encapsulated mechanoreceptor that detects pressure, temp, and stretching
found in reticular layer of dermis

92
Q

matrix cells

A

cells that give rise to keratinizing cells of hair shaft

93
Q

dermal papilla (hair bulb)

A

tuft of loose CT at base of the hair bulb - vascular supply to hair follicle

94
Q

where are sebaceous glands located?

A

between a hair follicle and its arrestor pili muscle in dermis

95
Q

sebum

A

secretary product of lipid rich decomposed cells

96
Q

what are sebaceous gland ducts composed of?

A

stratified squamous epithelium

97
Q

what are eccrine sweat glands?

A

coiled secretory unit located deep in the dermis and straight duct that opens into the skin

98
Q

what are the lumens of the secretory portion of the eccrine sweat gland lined by?

A

pseudostratified epithelium

99
Q

what are the lumens of the ductus portion of the eccrine sweat gland lined by?

A

stratified cuboidal epithelium
stain darker!!

100
Q

what system controls eccrine sweat glands and what are they used for?

A

autonomic control, thermoregulation (heat and stress)

101
Q

what do apocrine sweat glands do?

A

secrete a thick, odorous fluid into hair follicles for an unknown function

102
Q

apocrine sweat glands

A

large lumen tubular glands associated with hair follicles

103
Q

what epithelium lines the secretory portion of apocrine glands?

A

simple cuboidal

104
Q
A

goblet cell

105
Q
A

terminal bar

106
Q
A

cilia

107
Q
A

keratinized cell

108
Q
A

urothelium
dome shaped cell on top, tear drop shaped cell lower

109
Q
A

mucous cell
elongated nuclei, clear cytoplasm

110
Q
A

serous cell

111
Q
A

acinus

112
Q
A

meissner’s corpuscle

113
Q
A

paccini corpuscle

114
Q
A

sebaceous gland

115
Q
A

apocrine gland

116
Q
A

sebaceous gland

histology (15 decks)

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