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BIOSCI 107 > (01) Epithelial Tissue > Flashcards

(01) Epithelial Tissue Flashcards

1
Q

name the main locations of epithelial tissue

A

covers body surfaces
lines hollow organs / cavities / ducts

forms the GLANDS

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2
Q

name three key functions of epithelial tissue

A

protective
selective barrier
secretory (glands)

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3
Q

name the three different surfaces of epithelial cells

A

apical (or free surface)
lateral
basal (attached to basement membrane)

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4
Q

Name the four lateral junctions

A

Tight
Adherens
Gap
Desmosome

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5
Q

what is a cytoskeleton

A

a structure that helps cells maintain their shape and internal organisation
(a network of protein filaments)

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6
Q

Important components of the cytoskeleton and the main protein each is made of

A

Microfilaments - ACTIN
Intermediate filaments - KERATIN

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7
Q

Describe microfilaments and their role

A

ACTIN
the thinnest elements of the cytoskeleton, bundles beneath cell membrane and cytoplasm

generate movement (eg. muscle contraction)
provide mechanical support (basic strength / structure of cells)
links cytoplasm to membrane + ties cells together

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8
Q

describe intermediate filaments and their role

A

KERATIN
thicker than microfilaments
Much stronger and less flexible

Adds strength
Moves materials through cytoplasm - pathways

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9
Q

describe the cellular and general locations of tight junctions

A

on lateral surfaces, near the apical end

lots in stomach / intestines / bladder

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10
Q

describe the structure of tight junctions

A

strands of pearl-like trans-membrane proteins, CLAUDINS and OCCLUDINS, seal adjacent plasma membranes together, leaving pockets of paracellular space

more strands = tighter junction

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11
Q

describe the function of tight junctions

A

joins the cytoskeletons of adjacent cells (eg. via ZO-1 to actin)

ELECTRICALLY tight - separates environments, keeps cell polarity
prevents the migration of proteins between apical and basal surfaces

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12
Q

describe the physical form and location (on cell) of adherents junctions

A

“belt desmosome” - often forms extensive zones = adhesion belt
forms a PLAQUE, with transmembrane glycoprotein

found just below tight junctions

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13
Q

define plaque

A

a dense layer of proteins on the inside of plasma membrane that attaches to membrane proteins and microfilaments of the cytoskeleton

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14
Q

explain how proteins form adherens junctions

A

CADHERIN crosses intercellular gap, joins to cadherins from adjacent cell
CATENINS link cadherins to ACTIN (microfilament)

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15
Q

function of adherens juncstions

A

prevent cell separation from tension forces (eg. in contractions)

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16
Q

describe the structure of desmosomes (incl proteins)

A

lateral wall
plaque, button-like
CADHERIN spans the gap, links to KERATIN in intermediate filament via desmoplakin

the intermediate filaments extend from desmosomes on one wall to the other

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17
Q

function of desmosomes

A

structural arrangement of connected intermediate filaments provides stability + structural integrity to the cell
resist shearing forces
prevents cells from pulling apart under tension

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18
Q

common locations of desmosomes

A

skin epithelium
cardiac cells of the heart (prevents pulling apart of muscle cells during contraction)

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19
Q

how do desmosomes appear in images (vs adherens)?

A

appears darker because of connection to thicker filaments

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20
Q

describe hemidesmosomes + function

A

looks like half a desmosome, links cellular basal intermediate filament (keratin) to basement membrane rather than adjacent walls

connects epithelia to basement membrane

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21
Q

proteins involves in hemidesmosomes

A

not cadherin but INTEGRIN
binds to LAMININ in the basement membrane and keratin in the cytoplasm

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22
Q

what is the purpose of gap junctions

A

communication
allows small molecules to pass

useful in coordinated movement (eg. in the heart - electrical impulses)

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23
Q

describe the structure of gap junctions

A

6 connexin proteins (monomer, like pizza slices) form a connexion / hemichannel
move around in membrane
2 hemichannels make up a gap junction (hydrophilic channel)

aggregation of gap junctions = plaque

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24
Q

define anchoring protein

A

actin / keratin filaments
in microfilament / intermediate filament of cytoskeleton

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25
Q

give an example of a linking protein

A

cadherin - transmembrane

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26
Q

what is a junctional complex?

A

a combination of a tight junction, adherens junction and desmosome

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27
Q

name the two layers of the basement membrane

A

Basal lamina
Reticular lamina

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28
Q

what is the basal lamina made up of

A

secreted by epithelial cells
COLLAGEN
LAMININ
other proteoglycans / glycoproteins

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29
Q

what is the reticular laminar made up of

A

produced by fibroblasts (cells of underlying connective tissue)
contains fibrous proteins: fibronectin, collagen etc

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30
Q

the basement membrane is found between the __ and ___

A

found between the EPITHELIUM and CONNECTIVE TISSUE

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31
Q

how does the exchange of nutrients / waste take place in the epithelia and why?

A

by diffusion from vessels in the connective tissue
because epithelia is AVASCULAR (but it contains nerves)

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32
Q

name four functions of the basement membrane

A

SUPPORTS overlying epithelium
Physical barrier
Growth and wound healing - provides a surface along which epithelia cells migrate to
participates in the filtration of substances in the kidneys

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33
Q

basement membrane and melanoma

A

BM can act as a barrier to invasion by malignant melanoma
once BM penetrated, chance of METASTASIS (spread) increases
tumor depth >4mm, 5year survival rate 50%

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34
Q

name the two types of epithelial tissue

A
  1. Covering / Lining epithelia
  2. Glandular epithelia
35
Q

where is covering / lining epithelia found

A

Outer covering of the skin / internal organs

inner lining of blood vessels, ducts, cavities
interior of the respiratory, digestive, urinary and reproductive systems

36
Q

where are glandular epithelia generally found + what are the two types

A

the secretory portion of glands

Exocrine: secretes onto external surfaces and into passages (ducts)

Endocrine: hormones / precursors into interstitial fluid

37
Q

covering and lining epithelia is classified by __ and __

A

arrangement (of cells)
shapes

38
Q

name and describe the three types of epithelia covering cell arrangement

A

simple = single layer
stratified = multiple layers
PSEUDOSTRATIFIED = looks like it’s layered but just a single layer (technically single) - all cells are in contact with basement membrane

39
Q

name and describe the four shapes of covering epithelia

A

squamous = flat (generally for diffusion)
cuboidal
columnar
TRANSITIONAL - can be cuboidal / flat, changes

40
Q

name one organ where transitional covering eplitheium cells are located

A

the urinary bladder
allows stretch

41
Q

where is simple squamous epithelium located

A

where there is filtration (kidney), diffusion (lung), secretion for slippery surfaces (outer layer of serous membranes)

42
Q

name the two specialised subtypes of simple squamous epithelium

A

MESOTHELIUM

ENDOTHELIUM

43
Q

name some locations of simple squamous epithelium

A

lines cardiovascular / lymphatic systems
inside blood vessels, inside heart
alveoli of lungs
Bowman’s capsule of kidney

44
Q

where is mesothelium found?

A

covers SEROUS membranes, lines big cavities

pericardial (around heart), pleural (lungs), peritoneal

(reminder: this is a type of simple squamous epithelium)

45
Q

where is endothelium found?

A

lines inside of heart / blood+lymphatic vessels

(reminder: a type of simple squamous epithelium)

46
Q

name the two functions of simple cuboidal epithelium

A

for SECRETION and ABSORPTION

47
Q

locations of simple cuboidal

A

pancreas ducts and smaller ducts of many glands
secretory chambers of thyroid + other glands
parts of kidney tubules

48
Q

describe microvilli

A

a membrane modification that increases surface area of membrane on the apical surface with fingerlike projections
NONMOTILE

(abundant in places of absorption)

49
Q

describe cilia

A

MOTILE - controlled sweeps
moves fluids along a cell’s surface

50
Q

feature of simple columnar epithelium

A

more cytoplasm, so more organelles
so more metabolically active

51
Q

name the two major subtypes of simple columnar epithelium

A

Non-ciliated (can have microvilli)
ciliated

(may have cilia and / or microvilli)

52
Q

appearance of simple columnar epithelium

A

rectangular when cut from the side
generally the nuclei (often elongated) is near the base of the cell
may contain goblet cells (for both ciliated and non-ciliated subtypes)

53
Q

what is a goblet cell and what is its purpose?

A

a modified columnar cell
contains and secretes mucus at the apical surface, lubricates

54
Q

locations of non-ciliated simple columnar epithelium

A

lines gastrointestinal tract (has microvilli for absorption)
ducts of glands
gallbladder

55
Q

locations of ciliated simple columnar epithelium

A

uterine fallopian tubes
some bronchioles
sinuses
central canal of spinal cord, ventricles of brain (cerebral spinal fluid)

think: moving fluid / mucous etc

56
Q

function of ciliated simple columnar epithelium

A

synchronous movement assists motility of mucus / objects / oocytes

57
Q

describe the appearance of stratified squamous epithelium

A

cells for layers in upper layers (which it is named after)
lower layers may be cuboidal or columnar

cells furthest from nutrition are thinner + less active

58
Q

What can stratified squamous epithelium generally withstand?

A

Severe mechanical / chemical stresses

59
Q

function of stratified squamous epithelium

A

protect against microbes
makes surfaces tough / waterproof

60
Q

name the two specialised subtypes of stratified squamous epithelium

A

keratinised
non-keratinised

61
Q

describe the function and locations of non-keratinised stratified squamous epithelium

A

protects from abrasion
defence from microbes

mouth / throat / tongue / oesophagus
anus / vagina

62
Q

describe the appearance and location of keratinised epithelium

A

has keratinised (dead) surface cells
skin

63
Q

describe the appearance of pseudo-stratified columnar epithelium

A

nuclei at different levels
appears to have several layers but actually all cells contact BM (not al reach the apical surface)

64
Q

name the two subtypes of pseudostratified columnar epithelium

A

ciliated
non-ciliated

everything columnar is either ciliated or non-ciliated!

65
Q

describe pseudo stratified ciliated columnar epithelium (+location)

A

cilia on some cells
secrete mucus (from goblet cells) - this is a main function

most upper airways

66
Q

describe pseudostratified non-ciliated columnar epithelium (+location)

A

HAS NO GOBLET CELLS!!!
and no cilia (obv)

functions to absorb + protect

larger ducts of glands
epididymus + male urethra

67
Q

where is stratified transitional epithelium located?

A

the BLADDER
as well as some parts of ureter and urethra

68
Q

what is a gland?

A

consists of a single cell / group of cells that SECRETE SUBSTANCES into ducts, onto surface or into blood

69
Q

how are glandular epithelia classified?

A

according to where they secrete their substances

70
Q

name the two classifications of glands

A

endocrine
exocrine

71
Q

define endocrine gland

A

secretes directly into blood
usually via interstitial fluid
hormones diffuse to adjacent blood supply, no duct

generally distant strong effects

72
Q

examples of endocrine glands

A

pituitary, pineal, thyroid, parathyroid

73
Q

define exocrine glands

A

secretes into DUCTS that empty onto the surface of a covering / lining epithelium

generally LOCAL effects

74
Q

examples of exocrine glands

A

sweat + salivary
oil / wax glands
pancreas (NOTE - this is mixed, does both)

75
Q

describe the endo and exocrine functions of the pancreas

A

Endo - yellow cells hormones –> blood
exo - “pizza” cells, different roots via pancreatic ducts –> digestive juices

76
Q

name the two broad types of exocrine glandular epithelia

A

single cell gland
multicellular

77
Q

what are mucous cells

A

individual secretory cells in epithelia with independent, scattered gland cells

78
Q

main parts of a mucous cell / single cell gland

A

apical cytoplasm is filled with large secretory vesicles - mucin? looks clear / foamy in light micrograph

79
Q

what three characteristics are used to categorise multicellular exocrine glands?

A

structure of the duct
structure of the secretory area
relationship between the two

80
Q

define “simple gland”

A

it has a single duct that does not divide on its way to the gland cells

81
Q

define “compound duct”

A

the duct divides one or more times on its way to the gland cells

82
Q

two main shapes of the secretory area

A

tubular - glandular cells form tubes
alveolar / acinar - glandular cells form sac-like pockets

83
Q

name the five types of simple glands + examples

A

simple tubular (intestinal glands)
simple coiled tubular (merocrine sweat glands)
simple branched tubular (gastric, mucous glands)

simple alveolar
simple branched alveolar (sebaceous glands)

84
Q

name the three types of compound glands and examples

A

compound tubular (mucous glands in mouth, in male urethra / testes)

Compound alveolar (mammary glands)

Compound tubuloalveolar (salivary glands, respiratory passages, pancreas)

BIOSCI 107 (22 decks)

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