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Epithelial Tissue Flashcards

1
Q

Key Functions of Epithelial tissues

A

Selective Barriers (limit or aid transfer)
Secretory (onto a free surface)
Protective (especially from abrasion)

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1
Q

Epithelial tissue

A

covers body surface
lines hollow organs, cavities and ducts
forms the glands of the body

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2
Q

The cells of an epithelium are arranged…

A

1) in continuous sheets as single or multiple layers

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3
Q

The cells of an epithelium are held together by cell junctions such as..

A

Tight junctions
Adherens junctions
Gap junctions
Desmosomes
Hemidesmosomes

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4
Q

What are the 3 bases of epithelial cells

A

Apical (free surface), Lateral & Basal (Attached) surface

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5
Q

Lateral surface junctions?

A

Tight Junctions
Adherens junctions
Gap junctions
desmosomes

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6
Q

Basal surface junction?

A

Hemidesmosomes

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7
Q

Cytoskeleton

A

Microfilaments
Intermediate filaments

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8
Q

Microfilaments

A

(brown) – e.g. ACTIN
-bundles beneath cell membrane and
cytoplasm;
-strength, alter cell shape; link cytoplasm to membrane; tie cells together; muscle
contraction

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9
Q

Intermediate filaments

A

(purple)
e.g. KERATIN
-Strength

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10
Q

Tight junctions are found in

A

Stomach, intestines & bladder

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11
Q

Tight junctions are made up of

A

Individual sealing strands- the more strands, the tighter the junction.
- transmembrane
Join the cytoskeletons of adjacent
cells e.g. via ZO-1 to actin
* Keep cell polarity by preventing
migration of proteins between apical
and basal surfaces

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12
Q

Two key proteins involved in Tight junctions

A

Claudins & Occludins

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13
Q

Adherens junction

A

“Belt desmosome” or “adhesion belts (zonula adherens) in some epithelial cells

Others cells are less continuous and are called “adhesion plaques”
* More basal located than tight junctions
Adherens junctions prevent cell separation from tension forces like in contractions

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14
Q

Adherens junction proteins

A

Have a plaque layer of proteins on the inside of the cell to join actin to cadherins
– Cadherins (span the gap)
– Catenins link the Cadherins to Actin (microfilament in cell cytoplasm

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15
Q

Desmosomes junction

A

Lateral wall
* Have “plaque” just like adherens junctions
* Resist shearing forces
Cadherin spans the gap and binds to Desmoplakin
* Links cell surface to Keratin (a cytoskeletal intermediate filament)
* Keratin spans from one desmosome to another on other side of the cell – structural integrity
* Example: they bind muscle cells; most common in skin epithelium and cardiac cells of the
heart to prevent pulling apart.

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16
Q

Gap junctions

A

Direct connection between cells
* 6 connexIn protein molecules form
connexOn or hemichannel
* 2 hemichannels make up gap junction
* Allows up to ~1kDa small molecules
through

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17
Q

Anchoring proteins

A

Actin filaments (in adherens)
Keratin filaments (desmosomes)

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18
Q

Linking proteins

A

cadherin (adherens and desmosomes)

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19
Q

Complex protein

A

eg. occludin

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20
Q

Hemidesmosomes

A

Connect epithelia to basement
membrane
* Links cellular basal intermediate
filament (Keratin) to basement
membrane
* Hemidesmosome
– INTEGRIN linker protein (instead
of cadherin)
– binds to LAMININ in the BM and,
– to Keratin intermediate filament in
cytoplasm

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21
Q

Tight junctions are..

A

Electrically tight (Na + etc.)
e.g. of content: Occludin

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22
Q

Adeherns junctions are..

A

e.g. transmembrane Cadherin links to
microfilament Actin – cytoplasmic contractile
protein)

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23
Q

Gap junctions

A

eg. connexin

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24
Desmosome junctions
transmembrane glycoprotein cadherin links to intermediate filament called Keratin
25
Hemidesmosome
e.g. Integrin instead of cadherin binds to Laminin in the BM and Keratin intermediate filament in cytoplasm
26
The combination of: tight junction, adherens junction and desmosome is called a...
Junctional complex
27
All epithelia overlay a basement membrane composed of two parts:
BASAL LAMINA (secreted by the epithelial cells) containing collagen, laminin, other proteoglycans, glycoproteins, etc RETICULAR LAMINA (produced by cells of the underlying connective tissue known as fibroblasts) containing fibrous proteins such as fibronectin, collagen etc
28
The basement membrane is found between the..
epithelium and connective tissue.
29
Epithelia contain nerves but do not contain ...
Blood vessels (avascular)
30
The exchange of nutrients and wastes takes place by...
Diffusion from vessels in the connective tissue.
31
functions of the Basement Membrane?
-Supports the overlying epithelium -Provides a surface along which epithelial cells migrate during growth and wound healing -Acts as a physical barrier -Participates in the filtration of substances in the kidney.
32
The basement membrane can act as a barrier to invasion by..
malignant melanoma. Once the barrier has been penetrated, the chances of metastasis (spread) occurring increase.
33
The ABCD of melanoma warning signs:
A for asymmetry: one half of a mole doesn’t match the other; * B for border irregularity: edges are ragged, notched or blurred; * C for colour: mix of brown, black, red, white, or blue; * D for diameter greater than 6 mm
34
What are the TWO types of Epithelial tissue?
1) Covering and Lining Epithelia – Outer Covering e.g. skin and some internal organs. – Inner Lining e.g. example blood vessels 2) Glandular Epithelia – Constitute the secretory portion of glands.
35
Covering and Lining Epithelia Classified according to...
a. the ARRANGEMENT of cells b. the SHAPES of the cells.
36
Arrangement; simple??
single layer (secretion; absorption; filtration)
37
Arrangement; Stratified?
two or more layers (protective)
38
Arrangement; Pseudostratified??
appears to have multiple layers as judged by positions of nuclei. Not all cells reach the apical surface. * All cells are in contact with the basement membrane i.e. actually a simple epithelium (secretion).
39
Shape; Squamous?
flat and thin (helps allow passage by diffusion)
40
Shape; Cuboidal?
about as tall as they are wide (secretion; absorption)
41
Shape; Columnar?
more tall than wide (secretion; absorption)
42
Shape; Transitional?
a stratified epithelium in which the cells can change shape from cuboidal to flat shape depending on organ shape (allow stretch e.g. urinary bladder)
43
Different simple (single) layer epithelium types;
Simple squamous* Simple cuboidal* Simple columnar* (ciliated and non-ciliated) Pseudostratified (actually a single layer) Pseudostratified columnar* (ciliated and non-ciliated)
44
Different stratified layer epithelium types;
Stratified squamous* (keratinized and non-keratinized) Stratified cuboidal Stratified columnar Transitional
45
Glandular Epithelia
Glands consist of a single cell or a group of cells that secrete substances into ducts, onto a surface or into blood. They are classified according to where they secrete their substances. The function of all glandular epithelia is secretion.
46
Endocrine gland
Secrete directly into blood via traversing interstitial fluid eg. Pituitary, pineal, thyroid, parathyroid Generally distant strong effects
47
Exocrine gland
Secrete into ducts that empty onto the surface of a covering or lining epithelium. eg. Sweat and salivary glands; oil glands; wax glands; pancreas; Generally local effects
48
Some glandular organs are mixed secreting into ducts and into the blood such as..
Pancreas
49
EXOCRINE GLANDULAR EPITHELIA- single cell gland
eg. goblet cells- Goblet cells are type of mucous single cell exocrine gland (Not all mucous cells are goblet shaped)
50
3 characteristics used to describe structure of multicellular glands
i. Structure of duct ii. Structure of secretory area iii. Relationship between the two Sometimes all called “flask-like”
51
Simple Squamous Epithleium Features
Most delicate epithelium Where there is filtration (kidney); diffusion (lung); secretion where slippery surface needed (e.g. outer layer of serous membranes)
52
Simple Squamous Epithleium Appearance
Thin flat and somewhat irregular like jigsaw * Cells are “like fried eggs” or paving stones
53
Simple Squamous Epithleium Specialised Subtypes
Mesothelium lines pericardial, pleural, peritoneal cavities Endothelium lines inside of heart and the blood and lymphatic vessels
54
Simple Squamous Epithleium Specialised Subtypes info
A serous membrane (serosa) lining the body cavity and viscera (mesothelium + connective tissue Mesothelium: a layer of squamous epithelial cells covering the serous membranes (peritoneum, pericardium, pleura) of the adult
55
Locations of Simple Squamous Epithleium
In Bowman’s capsule of kidney, lines cardiovascular and lymphatic systems, inside eye, alveoli of lungs, visceral cavity linings, inside blood vessels and inside heart
56
Simple Cuboidal Epithelium features
Where there is SECRETION and ABSORPTION
57
Simple Cuboidal Epithelium appearance
Cuboidal or hexagonal boxes. * The distance between adjacent nuclei is approx. the height of epithelium
58
Simple Cuboidal Epithelium Specialised Subtypes
nil
59
Simple Cuboidal Epithelium locations
Pancreas ducts; parts of kidney tubules, smaller ducts of many glands; secretory chambers of thyroid; anterior surface of lens; pigmented epithelium at posterior of retina; secretory part of some glands like thyroid
60
Membrane modifications
Microvilli (brush boarder) Cillia (moves stuff around- like seaweed)
61
Simple Columnar Epithelium features
More cytoplasm so more organelles Often more metabolically active than squamous cells
62
Simple Columnar Epithelium appearance
Rectangular * Often hexagonal but taller and more slender than cuboidal * Nuclei often elongated and near the base of the cell * Height of cell is several times the distance between adjacent nuclei
63
Simple Columnar Epithelium - 2 subtypes
Non-ciliated simple columnar epithelium Ciliated simple columnar epithelium
64
Simple Columnar Epithelium Specialised Subtypes
Simple columnar epithelium can have: cilia or microvilli
65
Non-Ciliated Simple Columnar Epithelium features
Single layer * Microvilli on apical surface * Have goblet cells interspersed Can have Microvilli (e.g. small intestine) Non-motile cytoplasmic projections. Increase surface area for absorption. “Brush boarder”
66
Location examples of non-ciliated columnar epithelium
Examples: lines gut mucosa from stomach to anus; ducts of many glands; gall bladder. Function: secretion and lubrication (mucus goblet cells) ; absorption; Features * Single layer * Microvilli on apical surface * Have goblet cells interspersed
67
Ciliated Simple Columnar Epithelium (move materials) features
Single layer * Have goblet cells as well
68
Ciliated Simple Columnar Epithelium (move materials locations
Examples: some bronchioles, uterine fallopian tubes, sinuses; central canal of spinal cord, ventricles of brain Function: synchronous movement assists motility of mucus and foreign objects or oocytes Features * Single layer * Have goblet cells as well
69
Stratified Squamous Epithelium features
Located where mechanical or chemical stresses are severe * All forms protect against microbes * Apical cells are packed with keratin in places where mechanical stress and dehydration are a major issue– makes the surface tough and waterproof
70
Stratified Squamous Epithelium appearance
Cells form layers like plywood or pancakes in upper layers * Lower layers maybe cuboidal or columnar * Cells furthest from nutrition are thinner, and less active.
71
Stratified Squamous Epithelium Specialised Subtypes
Keratinised * Non-keratinised
72
Stratified Squamous Epithelium Location examples:
Keratinised: skin * Non-keratinised: mouth, throat, tongue, esophagus, anus, and vagina
73
stratified Squamous Epithelium (non-keratinized
Examples: mouth, throat, tongue, esophagus, anus, and vagina Function: protection from abrasion, defence from microbes, require secretions from glands This gives the name
74
Psuedo-stratified Columnar Epithelium appearance
Nuclei at all different levels * Appears to have several layers but it is not actually the case
75
Psuedo-stratified Columnar Epithelium features
All cells contact BM but not all reach the apical surface of the tissue * Actually a simple epithelium
76
Psuedo-stratified Columnar Epithelium Specialised Subtypes
Pseudostratified ciliated columnar epithelium i) Cilia on some cells ii) Secrete mucus (from goblet cells) Pseudostratified non-ciliated columnar epithelium i) No cilia ii) Lack goblet cells Appearance * Nuclei at all different levels * Appears to have several layers but it is not actually the case
77
Pseudostratified Columnar Epithelium (con’t)
Ciliated has goblet cells (Non-ciliated have no goblet cells) Examples: Ciliated: most of upper airways Non-ciliated: larger ducts of glands, epididymis, part of male urethra. Function: Ciliated: – secrete mucus, and move it Non-ciliated: absorption and protection Ciliated has goblet cells (Non-ciliated have no goblet cells)
78
simple tubular
one teardrop shaped
79
simple branched tubular
many branched teardrops
80
simple coiled tubular
one coiled
81
simple acinar (alveolar)
one angled teardrop
82
simple branched acinar (alveolar)
many branched angled teardrops
83
compound tubular
many extending long leaf tear drops
84
compound acinar (alveolar)
many extending rounder leaf shaped
85
compound tubuloalveolar
both extending types combined
86
what are plaques
collection of proteins into a larger structure on the cell membrane made up of lots of diff proteins
87
what tissue is responsible for making the basal lamina
epithelial
88
what tissue is responsible for making the reticular lamina
connective tissue- fibroblasts
89
stratified columnar epithelium features
unccomon type of epithelium protection & secretion
90
startified columnar epithelium appearance
basal layers shortned irregular cells only apical layers has columnar cells
91
sratified epithelia does it have cilia?
NO
92
locations of startfied columnar epithelia
part of urethra ; large excertory ducts of some glands eg oesophagus, pancreas, saliovary glands, areas of anas mucosa , part of conjuctiva of eye
93
stratified cuboidal epithelia features
unccom type of epithelium protection limited secretion and absoption
94
stratified cuboidal epithelia appearance
appears to have sevral layers only apical layers has cuboidal cells
95
stratified cuboidal epithelia locations
ducts of sweat glands ; oesphgal glands lubrication and protection of oeophagus from stomach acids; part of male uretha
96
endothelium found where
in vessels/cornea- internal pathways
97
mesothelium found where
in cavity- major body cavities eg. peritoneum (abdomen cavity) secreetes lubricant film called srous fluid
98

Cells & Tissues (5 decks)

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