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Histology Exam 1 > Epithelial Tissue > Flashcards

Epithelial Tissue Flashcards

1
Q

Epithelia

A
  • Covers body surfaces, lines body cavities, & forms glands
  • Contains surface epithelium of ectoderm (or endoderm), basement membrane, supporting connective tissue (lamina propria), & sometimes layers of smooth Mm (muscularis mucosae)
  • Epithithelial cells are characterized by production of keratin intermediate filaments
  • Produce different keratin (~54 types in humans); can be useful in tumor ID
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2
Q

Where is epithelia derived from?

A

ecto-, endo-, or mesoderm

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3
Q

Histogenesis of Mesoderm

A
  • Epithelium of kidneys & gonads
  • Mesothelium (lining pleura, peritoneal, & pericardial cavities)
  • Endothelium (blood & lymph vessels)
  • Adrenal cortex
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4
Q

Histogenesis of Endoderm

A
  • Respiratory epithelium
  • Alimentary epithelium (exceptoral & anal cavity)
  • Liver, pancreas, gallbladder, thyroid, parathyroid, & thymus
  • Epithelial lining of tympanic cavity & Eustaciantubes
  • Transitional epithelium of bladder
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5
Q

Epithelia functions

A
  • Barrier (e.g., skin)
  • Absorption (e.g., intestines)
  • SPM
  • Transport (e.g., cilia in trachea)
  • Secretion (e.g., stomach)
  • Sensation (e.g., taste buds)
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6
Q

Epithelia avascular

A

neverpenetrated by blood vessels

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7
Q

Epithelium cells rely on what?

A

on diffusion of O2 & nutrients from underlying tissue

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8
Q

how is epithelia supported?

A

Supported by basement membrane, separates epithelium from underlying connective tissue & blood vessels

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9
Q

mucous membrane(= mucosa)

A

Epithelium that lines cavities that connect with outside world, (e.g., alimentary, respiratory, or urogenital tracts)

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10
Q

lamina propria

A

supporting connect tissue

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11
Q

muscularis mucosae

A

layers of smooth muscle

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12
Q

serous membrane(= serosa)

A

Epithelium that lines closed body cavities (e.g., peritoneal, pleural, or pericardial cavities)

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13
Q

what does serous membrane consists of?

A
  • epithelial lining, the mesothelium, (mesodermally derived)
  • basement membrane, & supporting connective tissue
  • Lacks muscularis mucosae
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14
Q

endothelium (mesodermally derived)

A
  • Epithelium that lines blood & lymph vessels
  • Associated with variable #’s of Mm & connective tissue layers, or tunics
  • Most epithelial cells have finite lifespan
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15
Q

basement membrane

A
  • Basal surface of epithelial cells attached
  • Provides structural support, scaffolding for growth, differentiation, & migration of cells during embryonic growth & regeneration
  • Non-cellular, protein & polysaccharide-rich layer; acts as filter between epithelium & underlying connective tissue
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16
Q

external lamina

A

extracellular matrix proteins

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17
Q

how is the negative charge maintained in the basement membrane?

A

SPM for nutrients & metabolites to & from epithelium

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18
Q

how does the glomerular BM act in kidneys?

A

acts as highly selective filter for urine formation

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19
Q

Whare the the major components of BM?

A
  • GAG’s(heparan sulfate)
  • Type IV collagen
  • structural glycoproteins (laminin, fibronectin, & entactin)
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20
Q

On EM, basement membrane has….

A

electron dense layer (lamina densa) sandwiched between electron-lucent layers, (lamina lucida& lamina reticularis)

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21
Q

Lamina lucida

A

contact with basal cell membrane

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22
Q

Lamina reticularis

A

merges with surrounding tissue

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23
Q

lamina densa

A

anchored to underlying connective tissue by microfibrils of Type IV collagen

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24
Q

Anchoring filaments

A

Type IV collagen anchored to microfibrils of connective tissue

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25
Q

cell junctions

A
  • Epithelial cells adhere to one another
  • intercellular epithelial attachment sites
  • communication between cells
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26
Q

types of cell junctions (3)

A
  1. occluding
  2. adhering
  3. communicating
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27
Q

Occluding (=tight junctions)

A
  • Located beneath luminal surface of simple columnar epithelia
  • Act as gaskets
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28
Q

zonula occludens

A

Portions of opposing cell membranes fuse together, forming continuous, circumferential band around cell (seen in occluding junctions)

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29
Q

Fascia occludens

A

present between endothelial cells in wall of blood vessels

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30
Q

Adhering junctions (=anchoring junctions)

A
  • Bind cells together, act as anchoring points for cell cytoskeleton
  • Two basic morphological types & two specialized types
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31
Q

Zonula adherens

A

a continuous band characterized by transmembrane glycoproteins called cadherins

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32
Q

cadherins

A

class of cell adhesion molecules, or integrins

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33
Q

Are adjacent cell membranes fused?

A

NO

34
Q

Macula adherens (= desmosomes)

A
  • Small, circular patches; most common type of cell junction

- Located on lateral surface of cell

35
Q

Desmosomes associated with what attachments?

A

with attachment plaques containing attachment proteins:

  • desmoplakins
  • desmogleins
  • tonofilaments
36
Q

Hemidesmosomes

A

(“half desmosomes”, adhering junctions)
•Found on basal surface only, anchoring it to basement membrane via integrins (transmembrane receptor proteins)
•Associated with high mechanical abrasion/ shearing forces (e.g., skin)

37
Q

Junctional complex(= terminal bar)

A

(adhering junctions)
•Specialized, circumferential, intercellular connection
•Hybrid between adhering & occluding junctions—forms diffusion barrier between cells

38
Q

how is the junctional complex arranged by (3 zonula)?

A
  • zonula occludens (tight junction)
  • zonula adherens (adherent junction)
  • macula adherens (desmosomes)
39
Q

Communicating junctions (= gap junctions or nexus junctions)

A
  • Focal, or regional adherent zones located on lateral border of cell
  • connexons-> connexins
  • Permit passage of small molecules between adjacent cells
  • allow transport of information & metabolites between cells
40
Q

connexons

A

Roughly circular, intercellular contact areas containing hundreds of individual channels

41
Q

connexins

A

connexons, formed by ring of 6 integral proteins called connexins surrounding 2 nm diameter pores

42
Q

Types of cell surface modifications (3)

A
  1. Microvilli
  2. Stereocillia
  3. Cilla
43
Q

Microvilli

A
  • finger-like cytoplasmic projections, extend from cell surface
  • Contain actin filaments
  • ↑surface area for absorption or secretion
  • supported by terminal web
44
Q

location of striated border & brush border

A

striated border- intestine

brush border- renal tubules

45
Q

terminal web

A

network of actin microfilaments at base of microvilli; provide support

46
Q

Stereocilia

A
  • long microvilli, not cilia;
  • found only in epididymis of males & sensory cells of inner ear
  • Non-motile, also contain actin filaments
47
Q

Cilia

A
  • long, motile, cytoplasmic extensions
  • Possess axoneme
  • Each cilium arises from individual basal body
  • Cilia beat in synchronous, metachronal rhythm
  • Cilia normally contain microtubule doublets with dynein arms
48
Q

axoneme

A

9 + 2” arrangement of microtubules, seen in cilia

49
Q

basal body

A

develop from centrioles

50
Q

metachronal rhythm

A

cilia has rapid, rigid, effective stroke& slower, flexible recovery stroke

51
Q

If microtubules lack dynein arms, ciliary mobility is impaired or absent… what can it cause (3)?

A
  1. Kartagener’s syndrome
  2. Dextrocardia or situs inverses
  3. Hydrocephalus
52
Q

Kartagener’s syndrome

A

causes sterility in males due to non-functional flagella on sperm

53
Q

Dextrocardia, or situs inversus

A

(LR)—due to absence of ciliary activity during embryonic development, heart is in opposite position from normal placement

54
Q

Hydrocephalus

A

due to non-functional cilia on ependymal cells unable to circulate CSF

55
Q

Epithelia classification (3)

A
  1. # of cell layers
  2. shape of cells (at epithelial surface)
  3. surface specializations (eg. cilia, keratin)
56
Q

of layers (3)

A
  1. Simple—1 cell layer thick
  2. Stratified—2 or more cell layers
  3. Pseudostratified—looks stratified, but isn’t; all cells rest on basement membrane, but notall cells extend to epithelial surface
57
Q

shape of cells (3)

A
  1. Squamous—flattened, width > height
  2. Cuboidal—width ~= depth ~= height
  3. Columnar—height > width
58
Q

surface specializations can have what attached to it?

A

e.g. ciliated

59
Q

types of specialized epithelia (3)

A
  1. transitional
  2. endothelium
  3. mesothelium
60
Q

Transitional

A
  • lines most of urinary tract (except for parts of urethra)
  • Stratified epithelium, modified for distensibility
  • Varies from squamous to cuboidal
  • umbrella like
61
Q

Endothelium

A
  • epithelium lining blood vessels & lymphatics

- simple squamous

62
Q

Mesothelium

A
  • epithelium lining closed body cavities (i.e., thoracic, pericardial, & abdominal cavities)
  • Simple squamous
63
Q

Glands

A

composed of epithelial cells, specialized for synthesis & secretion

64
Q

Gland classification (3)

A
  1. morphology
  2. type of secretory prod
  3. mode of discharge of secretory prod
65
Q

Duct morphology (2)

A
  1. Simple gland—unbranched ducts (straight or coiled)

2. Compound gland—branched ducts

66
Q

Shape of gland (3)

A
  1. Tubular—tube-like (straight or coiled)
  2. Acinar(= alveolar)—sac-like or flask-shaped; individual sac called acinus
  3. Tubuloacinar(~= alveolar)—intermediate; tube with dilated end
67
Q

Type of secretory products (5)

A
  1. Serous
  2. Mucous
  3. Mixed (=seromucous)
  4. Sebaceous
  5. Ceruminous
68
Q

Serous

A

watery; basophilic acini (e.g., parotid)

69
Q

Mucous

A

thick, viscid secretion (mucus); clear on H&E (e.g., palatal)

70
Q

Mixed (=seromucous)

A
  • contain both mucous & serous acini

- include serous demilunes (e.g., sublingual, submandibular)

71
Q

Sebaceous

A

glands of skin, secrete lipids in form of sebum

72
Q

ceruminous

A

glands of external ear canal, secrete cerumen(ear wax)

73
Q

What are the 2 major function groups of glands?

A
  1. endocrine gland

2. exocrine gland

74
Q

endocrine gland

A

lack ducts; secrete products (hormones) directly into bloodstream

75
Q

exocrine gland

A
  • secrete product onto epithelial surface via ducts

- Contain myoepithelial cells

76
Q

myoepithelial cells

A

specialized contractile cells in exocrine gland

77
Q

myoepithelial cell location

A
  • Lie between secretory cells & basement membrane, assist in secretion
  • near Goblet cells
78
Q

goblet cells

A
  • specialized, unicellular exocrine glands, located in epithelium
  • secrete mucus
79
Q

Mode of discharge for glands(3)

A
  1. merocrine
  2. apocrine
  3. holocrine
80
Q

merocrine (= eccrine)

A
  • only secretory products released (generally proteins)
  • Most common
  • involves simple exocytosis
81
Q

apocrine

A
  • secrete membrane-bound vesicles
  • product accompanied by some cytoplasm
  • lipid products (e.g., sweat & mammary glands)
82
Q

Holocrine

A
  • entire cell-secreted (ruptures, releases contents)

- ex. sebaceous glands

Histology Exam 1 (10 decks)

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