Vascular Endothelium

Question 1

What are the 3 layers of blood vessels?

Answer 1

• tunica adventitia
• tunica media
• tunica intima

Question 2

What makes up the tunica adventitia?

Answer 2

• vasa vasorum

- nerves

Question 3

What makes up the tunica media?

Answer 3

• external elastic membrane

- smooth muscle

Question 4

What makes up the tunica intima?

Answer 4

• internal elastic membrane

- lamina propria

Question 5

What is the lamina propria?

Answer 5

• smooth muscle

- connective tissue

Question 6

What are capillaries and venules comprised of?

Answer 6

• endothelium
• pericytes (mural cells)
• basement membrane

Question 7

What happens at capillaries?

Answer 7

exchange of nutrients and oxygen between blood and tissues

Question 8

What does the microvascular endothelium do?

Answer 8

a source of angiocrine factors required to promote tissue homeostasis and organ regeneration

Question 9

What is the impact of a dysfunctional endothelium?

Answer 9

• contributes to disease
• ischemia
• chronic inflammatory diseases
• cancer
• diabetes
• atherosclerosis

Question 10

Do endothelium cells vary?

Answer 10

yes, they have organotypic properties and expression profiles

Question 11

What are the properties of endothelial cells in the muscle, lung, skin and blood brain barrier?

Answer 11

continuous non-fenestrated

Question 12

What are the properties of endothelial cells in the kidney glomerulus, GI tract?

Answer 12

continuous fenestrated

Question 13

What are the properties of endothelial cells in the liver and marrow?

Answer 13

discontinuous

Question 14

What are the properties of endothelial cells?

Answer 14

• very flat
• about 1-2 micrometers thick
• about 10-20 micrometers in diameter

Question 15

What is contact inhibition?

Answer 15

when the junctions of 2 cells join and establishes a junction causing the cells to stop growing

Question 16

What is the lifespan of endothelial cells?

Answer 16

• long
• low proliferation rate
  (unless angiogenesis is necessary)

Question 17

What are the functions of endotheliun?

Answer 17

• vascular tone
• permeability
• angiogenesis
• haemostasis and thrombosis
• inflammation

Question 18

What happens when the endothelium is at rest?

Answer 18

promotion of:

• anti-inflammatory
• anti-thrombotic
• anti-proliferative

Question 19

What happens when the endothelium is activated?

Answer 19

promotion of:

• pro-inflammatory
• pro-thrombotic
• pro-angiogenic

Question 20

What activates the endothelium?

Answer 20

• smoking
• viruses
• mechanical stress
• inflammation
• high BP
• OxLDL
• high glucose

Question 21

What happens when there is long term/chronic activation of the endothelium?

Answer 21

• thrombosis
• senescence
• permeability
• leukocyte recruitment
  all cause: atherosclerosis

Question 22

What are the characteristics of endothelial dysfunction in atherosclerosis?

Answer 22

• endothelial permeability
• leukocyte migration
• endothelial adhesion
• leukocyte adhesion

Question 23

What happens in the fatty-streak formation in atherosclerosis?

Answer 23

• smooth muscle migration
• foam cell formation
• t cell activation
• adherence and aggregation of platelets
• adherence and entry of leukocytes

Question 24

What happens in the formation of an advanced, complicated lesion of atherosclerosis?

Answer 24

• macrophage accumulation
• formation of a necrotic core
• angiogenesis
• fibrous cap formation

Question 25

What are the triggers of endothelial dysfunction in atherogenesis?

Answer 25

- oxidative stress - pro-inflammatory cytokines - infectious agents - environmental toxins - haemodynamic forces

Question 26

What are the risk factors of endothelial dysfunction causing atherogenesis?

Answer 26

- hypercholesterolaemia - DM/metabolic syndrome - hypertension - sex hormonal imbalance - ageing

Question 27

What are the mechanisms that contribute to the development of atherosclerosis?

Answer 27

- leukocyte recruitment - permeability - shear stress - angiogenesis

Question 28

What happens in the leukocyte adhesion cascade?

Answer 28

- capture - rolling - spreading - between the junctions

Question 29

When and where does leukocyte recruitment normally occur?

Answer 29

during inflammation, adherence to the post-capillary venules before entering the tissures

Question 30

What is the structure of a capillary?

Answer 30

- endothelial cells - basement membrane - pericapillary cells (pericytes)

Question 31

What is the difference in the structure of a capillary and a post-capillary venule?

Answer 31

venules have more pericytes (pericapillary cells)

Question 32

Where does leukocyte recruitment occur in atherosclerosis?

Answer 32

to the activated endothelium of of large arteries and are stuck in the sub-endothelial space - monocytes differentiate into macrophages and then foam cells

Question 33

What happens when there is increased permeability of the endothelium?

Answer 33

leakage of plasma proteins through the junctions into the subendothelial space

Question 34

What happens to blood flow in the straight parts of the arterial tree?

Answer 34

- laminar blood flow | - high an directional wall shear stress

Question 35

What happens to blood flow in the branches and curvatures of the arterial tree?

Answer 35

- disturbed blood flow | - non-uniform and irregular distribution of low wall shear stress

Question 36

What does laminar blood flow promote?

Answer 36

- anti-thrombotic, anti-inflammatory factors - endothelial survival - inhibitions of SMC proliferation - NO production

Question 37

What does disturbed blood flow promote?

Answer 37

- thrombosis, inflammation (leukocyte adhesion) - endothelial apoptosis - SMC proliferation - loss of NO production

Question 38

What is the role of NO?

Answer 38

key regulator of vascular function - reduces OxLDL - vasodilation - reduces platelet activation - inhibits monocyte adhesion - reduces release of superoxide radicals - reduces SMC proliferation

Question 39

What is angiogenesis?

Answer 39

formation of new blood vessels by sprouting from existing ones

Question 40

What is angiogenesis triggered by?

Answer 40

hypoxia

Question 41

What is angiogenesis essential for?

Answer 41

- embryonic development - wound healing - menstrual cycle

Question 42

What is the double role of angiogenesis?

Answer 42

- promotes plaque growth if therapeutic: - prevents damage post-ischemia

Question 43

What is pathological angiogenesis associated with?

Answer 43

advanced atherosclerotic plaques

Question 44

What is associated with a poor prognosis with a COVID infection?

Answer 44

- increased D-Dimers | - increased fibrinogen

Question 45

Where are the majority of endothelial cells?

Answer 45

capillaries

Question 46

What is thromboinflammation?

Answer 46

loss of the normal anti-thrombotic and anti-inflammatory functions of endothelial cells causes thrombosis with associated inflammation

Question 47

How does covid cause endothelial dysfunction?

Answer 47

- SARS-CoV2 infection - cytokine storm - endothelial activation - procoagulant switch

Question 48

What are the 2 possible ways that SARS-CoV2 causes endothelial damage?

Answer 48

- cytokine storm secondary to the infection causes the endothelial damage - SARS-CoV2 enters the cells and causes direct damage (no evidence)