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CSIM > Endothelium > Flashcards

Endothelium Flashcards

1
Q

Where are Endothelilal cells found?

A

They make up the single cell layer lining the inner surface of blood vessels. Found in lymph vessels too

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2
Q

Processes controlled by endothelial cells

A

Vaso reactivity (tissue perfusion), initiating, stopping and reversing clotting, directing immune cells, gas, waste & nutrient exchange, tissue repair & angiogenesis

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3
Q

4 layers of arteries

A

Adventitia, elastic lamina, media, intima (endothelial cells)

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4
Q

What happens to the volume and pressure in capillaries compared to arteries?

A

Volume increases, pressure drops

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5
Q

Embryological origin of endothelium

A

Mesoderm - primitive vasculoblast forms arteries and veins

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6
Q

Direction of endothelial cells in relation to smooth muscle cells

A

Perpendicular to increase contact

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7
Q

Function of pericytes

A

Support and maintain structure of endothelium - can become muscle or endothelium

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8
Q

Function of tight junctions

A

Stops anything passing between cells and maintains polarity of cell by keep transporters and receptors in the right place

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9
Q

Function of gap junctions

A

Allow communication between endothelium cells - rapid

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10
Q

Function of adherens junctions

A

Hold cells together for structure in endothelium and epithelium - connected to actin so involved in movement of the cell and important in angiogenesis

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11
Q

Transport across endothelium - filtration

A

Moves down a pressure gradient (hydrostatic and oncotic)

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12
Q

Where is active transport found in the endothelium?

A

The brain

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13
Q

Locations of continuous capillary endothelium

A

Skin, muscle, lung and cns-allows smooth passage of blood

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14
Q

Locations of fenestrated endothelium

A

Exocrine glands, renal glomeruli, intestinal mucosa - leaky so parts of blood pass out

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15
Q

Locations of discontinuous endothelium

A

Liver, spleen, bone marrow -whole cells can pass out eg immune cells

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16
Q

Function of blood brain barrier

A

Protect brain from circulating toxins and infection etc

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17
Q

Structure of BBB

A

Endothelial cells with extremely tight tight junctions, high density of pericytes on basal lamina, surrounded by astrocytes (structural cells in brain)

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18
Q

What molecules can cross bbb?

A

Very small ones and lipid soluble ones(esp if small)

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19
Q

Effect on filtration if efferent renal arteriole constricts

A

Filtration increases as pressure increases

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20
Q

What are podocytes? Function?

A

Epithelial cells lining capillaries of Bowman’s capsule - prevent passage of large molecules such as proteins, support membrane and allow small water soluble molecules to pass through such as urea

21
Q

Function of renal endothelium

A

Ready passage of small water soluble molecules, prevent passage of proteins and cells, sense change in flow rate and secrete renin accordingly

22
Q

Structure of liver endothelium

A

Sinusoidal, no basement membrane - sinusoids contain mix from hepatic artery and portal vein

23
Q

Function of endothelial cells in angiogenesis

A

Can divide in situ (clonal expansion) or migrate locally - also have circulating endothelial progenitor cells from BM.

24
Q

Growth factors that cause migration of endothelial cells in angiogenesis

A

VEGF and PDGF

25
Q

Benefits of angiogenesis for malignancy

A

Promotes primary tumour growth and facilitates malignancy - tumour secrets growth factors to cause angiogenesis - target angiogenesis to treat

26
Q

Why do CNS primaries rarely metastasise?

A

Hard for tumour cells to break through BBB tight barriers

27
Q

How do endothelial cells rapidly auto regulate blood flow?

A

Direct contact with smooth muscle cells - detect change in pressure and signals accordingly

28
Q

Does the endothelium secrete mainly vaso constrictive or dilatory factors?

A

Dilatory

29
Q

What factors control vascular tone?

A

Neuronal, hormonal and local factors

30
Q

How does calcium influx cause dilation?

A

Activates nitric oxide synthase

31
Q

Vasodilatory molecules

A

NO, prostanoids, hyperpolorizing factors

32
Q

Vasoconstrictive molecules

A

Endothelin

33
Q

How does the endothelium regulate platelet aggregation and coagulation?

A

Releases pro and antithrombotic factors

34
Q

Under normal conditions, what does the endothelium promote with regards to clotting?

A

Anti platelet aggregation factors, fibrinolytic proteins, anticoagulant factors

35
Q

What does chronic endothelial damage do to its control of clotting?

A

Reduces its anti-clotting effects

36
Q

What does VWF do in clotting and when is it released? Role in atherosclerosis?

A

Its released when collagen exposed, binds to platelets and activates fibrinogen cascade forming platelet clump - happens pathological in atherosclerosis

37
Q

What does VWF protease do?

A

Cleaves platelet aggregation and turns off clotting

38
Q

How does the endothelium interact with the immune system?

A

Expresses selectins and adherins at site of infection to bind immune cells (adhesion) and allow extravasation (follow chemokine gradient after this)
Release pro inflam cytokines to recruit immune cells
Cause local tissue damage by releasing proteases and inducing necrosis

39
Q

Why do steroids cause a rise in neutrophil level?

A

Stops immune cell adhesion so less neutrophils stuck to lining and more free in plasma

40
Q

5 features of inflammation

A

Pain, erythema, fever, oedema, loss of function

41
Q

Effects of sepsis on endothelium and smooth muscle

A

Triggers localised apoptosis and necrosis (cytokines), weakens junctions between endothelial cells, increases expression of adhesion molecules, increase NO & prostacyclin synthesis (vasodilation), Increase VWF and prothrombotic factors (clotting then bleeding when all used up)

42
Q

Effect of excess NO production (may be from bacterial endotoxin)

A

Hypotension, oedema with protein loss reducing hydrostatic and oncotic pressure (can breakdown BBB)

43
Q

What is vasculitis? Severity?

A

Inflammation of the blood vessels-can occlude or can leak (primarily arteries but can be others). Severity ranges from benign to rapid life threatening

44
Q

Causes of vasculitis

A 
Infections
Autoimmune (immune complex deposition or immune mediated tissue destruction)
45
Q

Causes of chronic activation of the endothelium

A

Hyperlipidaemia, hyperglycaemia, smoking, hypertension

46
Q

How does chronic endothelial activation cause atherosclerosis/diabetic vasculopathy?

A

Reduces NO production causing unopposed sympathetic constriction
Cells more permeable to lipoprotein which accumulates
Increased production of extra-cellular matrix helping form plaque
Inflam response alters expression of cell surface receptors regulating anticoag and neutrophil/monocyte diapedesis

47
Q

How does impaired NO production in endothelial dysfunction contribute to angina and PVD?

A

Can’t increase NO when required e.g. in exercise

48
Q

How does atherosclerotic plaque rupture lead to thrombus formation?

A

Exposes collagen causing clotting

CSIM (5 decks)

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