Endothelium Flashcards Preview

Vascular Biology > Endothelium > Flashcards

Flashcards in Endothelium Deck (25)
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1
Q

Squamous endothelium

A

thin cell layer that covers the blood and lymphatic vessels (very heterogenic according to organ/tissue)

2
Q

Polarity of endothelium

A

luminal = blood vessels
aluminal = tissue
polarity is guaranteed tough tight junctions
polarity is required for lumen formation

3
Q

Zona occulens

A

formed by tight junctions → “occluding junctions”

4
Q

Zona adherence

A

formed by adhesion junctions/belt, desmosomes, hemidesmosomes → “anchoring junctions”

5
Q

Structure and function of tight junctions

A
  • built by occludin and claudia (+ JAM) protein complex which connect directly to the plasma
  • impermeable occlusion → no transport between cells → keeps polarity
6
Q

Structure and function of gap junctions

A
  • build by connexins which form a connexone which forms a hemichannel → connecting channel between cells
  • allows <1,2 nm molecules to pass through (Ca2+, cAMP, Metabolites)
  • high amounts of extracellular calcium (injury) can close GJ to seal of neighbouring cells
  • functions: 1. metabolite transfer 2. intercellular communication via 2.messenger 3. modulate opening and closing
7
Q

Structure of the adhesion belt

A
  • located under tight junctions
  • cells form a band of cadherin to stabilise their interaction
  • supporting function and mechanical coherence
8
Q

Structure of the basal membrane

A
  • Network of collagen type IV cross linked via laminin, entactin and proteoglycan perlecan
  • Laminin connects to integrins through collagen IV and sulphated lipids
  • Integrins connect ECM and cell
9
Q

Types of capillary endothelia

A
  1. Continuous endothelia: muscle, heart, lung, brain
  2. Fenestrated endothelia: kidney, intestinal villus
  3. Discontinuous/ Sinusoid endothelium: liver, spleen, bone marrow
10
Q

Structure of the blood brain barrier

A

Is a system of BMVEC (brain microvascular endothelial cells) that together with astrocytes, pericytes, neutrons and basement membranes for the neuromuscular unit.

11
Q

Endothelia of the kidney

A
  • glomeruli endothelial cells
  • fenestrae
  • glomerular filtration of water and small solutes through fenestrae
12
Q

Endothelia of the liver

A
  • liver sinusoidal endothelial cells (LSEC)

- sinusoids: capillaries with pores and fenestrae lacking a diaphragm

13
Q

What causes dilation/ contraction of fenestrae?

A

Dilation: Acetylcholin, Ethanol
Contraction: Nicotine, Ethanol abuse, Adrenalin

Diameter of fenestrae is regulated by actin, myosin and calmodulin (Ca2+ dependant)

14
Q

What regulated the vascular tonus?

A
  1. contraction state of smooth muscle cells
  2. circulating factors (acetylcholine, bradykinin, angiotensin II)
  3. heamodynamic forces (stress)
15
Q

Endothelial vasodilators

A
  1. NO (Nitric oxide)
  2. PGI2 (Prostacyclin)
  3. EDHF (Endothelial hyperpolarising factor)
16
Q

Vasodilating effect of NO

A

Acetylcholin or bradykinin bind to beta-receptor on endothelial cell → Ca2+ released and signals NO-Synthetase III to release of NO from L-Arginine → NO activates guanylcyclase in smooth muscle cells to form cGMP from GTP → cGMP activates protein kinase G-type (PKG) → smooth muscle cells relax

17
Q

Prostacyclin

A
  • Synthesised by arachidonic acid
  • enhances NO release (vasodilating)
  • Thromboxan A2 antagonist
18
Q

Mechanism of Endothelial derived hyper polarising facto

A

Haemodynamic forces → EDHF release in endothelial cells → K+ storms out of smooth muscle cell → causes hyper polarisation → relaxation of smooth muscle cell

19
Q

Endothelial vasoconstrictors

A
  1. Endothelia-1

2. Angiotensin II

20
Q

Adhesion of leukocytes to the endothelium

A
  1. Rolling/Chemotaxis: Leukocytes interact with Selectins expressed by endothelial cells
  2. Adhesion: Leukocytes bind to ICAMs through interns → firm adhesion
  3. Diapedesis: leukocytes form pseudopods that dissolve cell contacts to facilitate extravasation of leukocytes
  4. Migration: extravasation of leukocytes towards the site of inflammation
21
Q

Arteriosclerosis

A

stiffening or hardening of the artery wall

22
Q

Atherosclerosis

A

narrowing of the artery due to plaque formation

23
Q

Fibroatheroma

A

Formation of fibrous plaque

24
Q

Sepsis/SIRS

A

= systemic inflammatory responce syndrome

exaggerated defence response to a noxious stressor

25
Q

Aneurysm

A

abnormal localised dilation of a blood vessel → weakens blood vessel