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Z BIOSCI 107 > (01) Epithelial Tissue > Flashcards

(01) Epithelial Tissue Flashcards

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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
give an example of a linking protein
cadherin - transmembrane
26
what is a junctional complex?
a combination of a tight junction, adherens junction and desmosome
27
name the two layers of the basement membrane
Basal lamina Reticular lamina
28
what is the basal lamina made up of
secreted by epithelial cells COLLAGEN LAMININ other proteoglycans / glycoproteins
29
what is the reticular laminar made up of
produced by fibroblasts (cells of underlying connective tissue) contains fibrous proteins: fibronectin, collagen etc
30
the basement membrane is found between the __ and ___
found between the EPITHELIUM and CONNECTIVE TISSUE
31
how does the exchange of nutrients / waste take place in the epithelia and why?
by diffusion from vessels in the connective tissue because epithelia is AVASCULAR (but it contains nerves)
32
name four functions of the basement membrane
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
33
basement membrane and melanoma
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%
34
name the two types of epithelial tissue
1. Covering / Lining epithelia 2. Glandular epithelia
35
where is covering / lining epithelia found
Outer covering of the skin / internal organs inner lining of blood vessels, ducts, cavities interior of the respiratory, digestive, urinary and reproductive systems
36
where are glandular epithelia generally found + what are the two types
the secretory portion of glands Exocrine: secretes onto external surfaces and into passages (ducts) Endocrine: hormones / precursors into interstitial fluid
37
covering and lining epithelia is classified by __ and __
arrangement (of cells) shapes
38
name and describe the three types of epithelia covering cell arrangement
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
name and describe the four shapes of covering epithelia
squamous = flat (generally for diffusion) cuboidal columnar TRANSITIONAL - can be cuboidal / flat, changes
40
name one organ where transitional covering eplitheium cells are located
the urinary bladder allows stretch
41
where is simple squamous epithelium located
where there is filtration (kidney), diffusion (lung), secretion for slippery surfaces (outer layer of serous membranes)
42
name the two specialised subtypes of simple squamous epithelium
MESOTHELIUM ENDOTHELIUM
43
name some locations of simple squamous epithelium
lines cardiovascular / lymphatic systems inside blood vessels, inside heart alveoli of lungs Bowman's capsule of kidney
44
where is mesothelium found?
covers SEROUS membranes, lines big cavities pericardial (around heart), pleural (lungs), peritoneal (reminder: this is a type of simple squamous epithelium)
45
where is endothelium found?
lines inside of heart / blood+lymphatic vessels (reminder: a type of simple squamous epithelium)
46
name the two functions of simple cuboidal epithelium
for SECRETION and ABSORPTION
47
locations of simple cuboidal
pancreas ducts and smaller ducts of many glands secretory chambers of thyroid + other glands parts of kidney tubules
48
describe microvilli
a membrane modification that increases surface area of membrane on the apical surface with fingerlike projections NONMOTILE (abundant in places of absorption)
49
describe cilia
MOTILE - controlled sweeps moves fluids along a cell's surface
50
feature of simple columnar epithelium
more cytoplasm, so more organelles so more metabolically active
51
name the two major subtypes of simple columnar epithelium
Non-ciliated (can have microvilli) ciliated (may have cilia and / or microvilli)
52
appearance of simple columnar epithelium
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
what is a goblet cell and what is its purpose?
a modified columnar cell contains and secretes mucus at the apical surface, lubricates
54
locations of non-ciliated simple columnar epithelium
lines gastrointestinal tract (has microvilli for absorption) ducts of glands gallbladder
55
locations of ciliated simple columnar epithelium
uterine fallopian tubes some bronchioles sinuses central canal of spinal cord, ventricles of brain (cerebral spinal fluid) think: moving fluid / mucous etc
56
function of ciliated simple columnar epithelium
synchronous movement assists motility of mucus / objects / oocytes
57
describe the appearance of stratified squamous epithelium
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
What can stratified squamous epithelium generally withstand?
Severe mechanical / chemical stresses
59
function of stratified squamous epithelium
protect against microbes makes surfaces tough / waterproof
60
name the two specialised subtypes of stratified squamous epithelium
keratinised non-keratinised
61
describe the function and locations of non-keratinised stratified squamous epithelium
protects from abrasion defence from microbes mouth / throat / tongue / oesophagus anus / vagina
62
describe the appearance and location of keratinised epithelium
has keratinised (dead) surface cells skin
63
describe the appearance of pseudo-stratified columnar epithelium
nuclei at different levels appears to have several layers but actually all cells contact BM (not al reach the apical surface)
64
name the two subtypes of pseudostratified columnar epithelium
ciliated non-ciliated everything columnar is either ciliated or non-ciliated!
65
describe pseudo stratified ciliated columnar epithelium (+location)
cilia on some cells secrete mucus (from goblet cells) - this is a main function most upper airways
66
describe pseudostratified non-ciliated columnar epithelium (+location)
HAS NO GOBLET CELLS!!! and no cilia (obv) functions to absorb + protect larger ducts of glands epididymus + male urethra
67
where is stratified transitional epithelium located?
the BLADDER as well as some parts of ureter and urethra
68
what is a gland?
consists of a single cell / group of cells that SECRETE SUBSTANCES into ducts, onto surface or into blood
69
how are glandular epithelia classified?
according to where they secrete their substances
70
name the two classifications of glands
endocrine exocrine
71
define endocrine gland
secretes directly into blood usually via interstitial fluid hormones diffuse to adjacent blood supply, no duct generally distant strong effects
72
examples of endocrine glands
pituitary, pineal, thyroid, parathyroid
73
define exocrine glands
secretes into DUCTS that empty onto the surface of a covering / lining epithelium generally LOCAL effects
74
examples of exocrine glands
sweat + salivary oil / wax glands pancreas (NOTE - this is mixed, does both)
75
describe the endo and exocrine functions of the pancreas
Endo - yellow cells hormones --> blood exo - "pizza" cells, different roots via pancreatic ducts --> digestive juices
76
name the two broad types of exocrine glandular epithelia
single cell gland multicellular
77
what are mucous cells
individual secretory cells in epithelia with independent, scattered gland cells
78
main parts of a mucous cell / single cell gland
apical cytoplasm is filled with large secretory vesicles - mucin? looks clear / foamy in light micrograph
79
what three characteristics are used to categorise multicellular exocrine glands?
structure of the duct structure of the secretory area relationship between the two
80
define "simple gland"
it has a single duct that does not divide on its way to the gland cells
81
define "compound duct"
the duct divides one or more times on its way to the gland cells
82
two main shapes of the secretory area
tubular - glandular cells form tubes alveolar / acinar - glandular cells form sac-like pockets
83
name the five types of simple glands + examples
simple tubular (intestinal glands) simple coiled tubular (merocrine sweat glands) simple branched tubular (gastric, mucous glands) simple alveolar simple branched alveolar (sebaceous glands)
84
name the three types of compound glands and examples
compound tubular (mucous glands in mouth, in male urethra / testes) Compound alveolar (mammary glands) Compound tubuloalveolar (salivary glands, respiratory passages, pancreas)

Z BIOSCI 107 (22 decks)

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