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Integrating Cells into Tissues and Organs BL3 Flashcards

1
Q

What are the different types of epithelial cell adherence systems?

A

Lateral -> tight junctions, adherens junctions, desmosome, gap junctions, cell adhesion molecules
Basal -> hemi-desmosomes, focal adhesions, integrins, proteoglycans, cell adhesion molecules

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2
Q

What is the name of the process where small molecules (sugars, AA, water) can cross the epithelium into the gut?

A

Paracellular transport

Controlled by tight junctions and gap junctions

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3
Q

Where are adhesion junctions found?

A

1/3 of the way down from the apical surface of epithelial cells
Found in pairs

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4
Q

What are adhesion junctions made from?

A

Intracellular actin filaments, liked to E-cadherin proteins that cross the intercellular space
Form an adhesion belt
Need Calcium ions

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5
Q

Which is the strongest cell-cell adhesion?

A

Desmosomes

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6
Q

Where are desmosomes found?

A

1/2 way down lateral surface of cell
Tissues which experience a lot of mechanical stress (eg. cardiac muscle, bladder tissue, gastrointestinal mucosa, epithelia, pregnant uterus)

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7
Q

What are desmosomes made from?

A

Cytokeratin fibres intracellularly, E-Cadherins intercellularly

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8
Q

Which is the only cell-cell adhesion found in skin cells?

A

Desmosomes

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9
Q

Where are gap junctions found?

A

Near base of lateral surface

Cardiac & smooth muscle cells

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10
Q

Which cell-cell adhesions communicate between cells eg. for a wave of electrical impulse?

A

Gap junctions

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11
Q

Which cells do not have gap junctions?

A

Spermatozoa, erythrocytes, other motile cells

Nerve cells

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12
Q

What are gap junctions made from?

A

They’re hexamers (hexagonal patterned cylinder) made of proteins (connexins)
Change in the connexin (eg. connexin 34 to 45 occurs in myometrium of pregnant uterus in preparation for birth to get coordinated contractions) can open/close the channel, as can ATP

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13
Q

What is the extracellular matrix made of?

A

Fibronectin, collagen, laminin fibres

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14
Q

What are hemi-desmosomes made of?

A

Cytokeratin internally (intermediate filaments), integrins connect across the membrane to laminin

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15
Q

What is the basal lamina connected to the connective tissue layer by?

A

Elastin, fibrillin, other collagens

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16
Q

What are focal adhesions made of?

A

Intracellular actin filaments, across the membrane by integrins

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17
Q

What do focal adhesions bind to in the basal lamina? what about hemi-desmosomes?

A

Focal - fibronectin

Hemi - laminin

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18
Q

What happens when the integrins in focal adhesions bind to fibronectin in the basal lamina?

A

There is a conformational change which results in them binding to collagen fibres

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19
Q

What do kinases do, in general?

A

Phosphorylate other proteins

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20
Q

How do integrins always work?

A

As an alpha-beta dimer
As a dimer they bind to the extracellular matrix weakly, but phosphorylation by focal adhesion kinase produces a heterotetramer which has a greater binding capacity, so a stronger bond

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21
Q

What do adhesion properties require?

A

Calcium ions

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22
Q

How are intracellular intermediate filaments (cytokeratin) connected extracellularly?

A

By E-Cadherins proteins in desmosomes

By integrins to basal lamina, hemi-desmosomes

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23
Q

How do epithelial cells adhere to each other?

A

Through cell surface proteins (E-Cahderins)

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24
Q

How do epithelial cells bind to the basal lamina?

A

Cellular adhesion molecules

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25
How do epithelial cells adhere to muscle cells?
Through connective tissue fibres | Same for different types of tissue adhering to each other
26
What is the function of adherence proteins?
To maintain the survival and structure of cells and hence of tissues To prevent pathogens from gaining entry to the internal environment
27
What is a good example of an organ which contains all 4 tissues?
Mucosal membrane
28
Where are mucosal membranes found?
They line all the 'moist' hollow internal organs of the body Continuous with the skin at various openings (eyes, ears, inside nose and mouth, anus etc.) GI tract, respiratory tract, urinary tract
29
What does mucus contain?
Mucins (proteins), electrolytes, antiseptic enzymes (lysozymes), immunoglobulins
30
What is the function of the mucosal membrane?
Lubrication, preventing entering of pathogens and dirt, preventing dehydration of bodily tissues
31
What is the mucous membrane (mucosa) always composed of?
Epithelium, basal lamina, lamina propria
32
What type of tissue is the lamina propria?
Loose connective tissue
33
What is the muscularis mucosae?
A thin, discontinuous smooth muscle layer
34
What is the submucosa?
A connective tissue layer that contains arteries and veins
35
What is the muscularis externa?
A smooth muscle layer that have muscle fibres going generally in two different directions An inner circular muscle An outer longitudinal muscle
36
What is the serosa?
A connective-tissue layer | Contains collagen and elastin fibres with some small arteries and veins and some nerve fibres
37
What does the serosa do?
Stops muscle expanding
38
What layers are present in a GI tract?
``` Mucosa lining the lumen Muscularis mucosae Submucosa Muscularis externa Serosa Sometimes an outer layer of epithelial cells ```
39
What does gastric mucosa secrete? (in stomach)
Acid, digestive enzymes and the hormone gastrin
40
What type of smooth muscles are there?
Circular, longitudinal and, in stomach, oblique
41
What are folds of gastric mucosa called? What do they do?
They are rugae They form ridges in an empty stomach When they are flat, the stomach send signals that you've eaten too much
42
What are plicae circulares?
Circular folds of mucosa and submucosa which project into the gut lumen
43
What are the crypts of Lieberkühn?
The folds between the villi; they trap various pathogens, produce mucus and supply cells to the surface
44
What are the functions of the mucosa?
To absorb substances from the lumen (microvilli, peristalsis, rugae,) Prevent ingress of pathogens (lymphatic tissue in lamina propria, microvilli) Move contents and expel waste (muscularis externa)
45
What is peristalsis?
A series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. The process of peristalsis begins in the esophagus when a bolus of food is swallowed.
46
Which muscle layer performs peristalsis?
Muscularis externa, not mucosae | Muscularis mucosae folds the mucosa
47
What is a nephron?
A nephron is the basic structural and functional unit of the kidney
48
What type of epithelial cells line the renal corpuscules? What about the collecting ducts? (in the kideys)
Corpuscules - flattened (squamous) | Duct - Square shaped (cuboidal)
49
How can you tell apart proximal and distal tubules on a histology image? Which direction does each go?
Proximal have a ciliated surface | Proximal are descending, distal are ascending
50
Where are muscle layers first found in the urinary tract?
Ureter and bladder, as it has to expand so it doesn't burst
51
What type is the epithelium of the bladder, and what is its name?
Transitional, urothelium
52
What are some features of the urothelium?
Produces mucus Protects the bladder from damage by acidic urine Tight junctions are very well packed; prevents leakage to inner cell layers
53
What type of epithelial cells are in the urethra? What do they do?
Squamous, keratinised near outlet | They produce sticky mucus to prevent ingress of pathogens
54
What are the two parts of the respiratory tract?
Conducting (nasal cavity to bronchioles) | Respiratory (bronchioles to alveoli)
55
What type of muscle is in the pharynx?
Skeletal | It doesn't have muscularis mucosae or submucosa, as it is not a mucosal membrane
56
How does the trachea ensure it stays open?
It has a hyaline cartilage ring around it
57
What is the structure of the primary bronchi and trachea?
Mucosa (pseudostratified ciliated columnar epithelium) Very thin lamina propria No longitudinal muscularis mucosa, but does have circular Submucosa (mainly collagen, elastin, fibroblasts, seromucous glands) Hyaline cartilage (perichondrium and chondrogenic layer, cells can interconvert between chondroblasts to chondrocytes so can make both hyaline and elastic cartilage) No outer layer of smooth muscle
58
What do secretions from the epithelium of trachea contain?
Mucins and water, serum proteins (lubricate), lysozyme (destroy bacteria), anti-proteases (inactivate bacterial enzymes)
59
What specifically secretes mucus?
Goblet cells
60
What is the mucociliary escalator?
Cilia wave moves 12 times a second (12Hz) | In trachea
61
How thick is the trachea's basement membrane?
Unusually thick
62
What is the difference between primary and secondary bronchi in terms of histology?
Primary have full cartilage ring | Secondary and tertiary isn't a full circle
63
What is alveolar epithelium called?
Endothelium
64
What are some histological features of alveoli?
Flattened endothelium Folded basal lamina Collagen at junctions provides some rigidity to mucosa Many layers of elastin fibres which provide elastic recoil when sac returns to empty state on exhaling
65
What are cell adhesion molecules? (examples)
Integrin, selectin, CAM

Revision (17 decks)

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