cell biology of cardiovascular system

Question 1

what are the 3 layers of blood vessels? does the thickness of these three layers vary depending on the blood vessel? if yes what does it depend on?

Answer 1

the intimate, the media, the adventia

yes, it depends on the vessel type and its position in the vascular tree

Question 2

what is the intima’s role? and what is it composed of?

Answer 2

ensures effective exchange of gases and nutrients between blood and the rest of the body
it is composed of endothelial cells

Question 3

what is the morphology of endothelial cells of the intima?

Answer 3

these endothelial cells have a cobblestone morphology

Question 4

what are the main functions of the endothelium?

Answer 4

regulation of vascular tone, barrier function, inflammatory responses, thrombosis, angiogenesis

Question 5

what is the media’s role? and what is it composed of?

Answer 5

it is composed of vascular smooth muscle and it regulates vascular tone by undergoing contraction and relaxation

Question 6

is the regulation of contraction and relaxation of vascular smooth muscle endothelium dependent? or independent?

Answer 6

can be both

Question 7

what is the adventitia made of?

Answer 7

it is made of collagen, elastin and other ECM interspersed with fibroblasts

Question 8

what is the external elastic lamina?

Answer 8

layer of interwoven elastinfibrils between adventitia and the media

Question 9

what do the adventitia and the external elastic lamina do?

Answer 9

contribute to the compliance of a blood vessel by producing structural ECM proteins that regulate vascular compliance

Question 10

what are a few vasorelaxants?

Answer 10

nitric oxide (NO), prostacyclin (PGI2), natriuretic peptides

Question 11

what are a few vasocontrictors?

Answer 11

endothelin-1 (ET-1), angiotensin II, thromboxane

Question 12

what produces nitric oxide? and what enzyme is used to produce it?

Answer 12

L-arginine used nitric oxide synthase to produce nitric oxide

Question 13

how does nitric oxide induce vasorelaxation?

Answer 13

via the activation of soluble guanylyl cyclase which generate cyclic guanosine monophosphate

Question 14

where, from what and by what is produces prostacyclin?

Answer 14

produced in endothelial cells from arachidonic acid by cyclooxygenate enzymes

Question 15

how does prostacyclin induce vasorelaxation?

Answer 15

activates specific cell surface receptor that activate adenylyl cyclase and thereby elevate cyclin adenosine monophosphate levels
it also activates potassium channels and increase influx of K+ causing membrane hyperpolarisation which blocks influx of calcium ions required for contraction

Question 16

what produces natriuretic peptides?

Answer 16

synthesized by the heart, brain and other organs

Question 17

what are the three types of natriuretic peptides? and where are they produced?

Answer 17

atrial natriuretic peptide/A-type –> produced by the heart
brain natriuretic peptide/B-type –> produced by the heart
Cellular natriuretic peptide/C-type –> produced by the heart, chondrocytes and endothelial cells

Question 18

what does endothelin-1 act as?

Answer 18

acts as a vasoconstrictor, a pro-coagulant and activator of vascular smooth muscle proliferation and migration

Question 19

what are the two types of ET-1 receptors? what are they expressed by? and what do they do?

Answer 19

ETA expressed by smooth muscle cells and induces vasoconstriction
ETB expressed by smooth muscle cells and endothelial cells, induces vasorelaxation by stimulating endothelial production of nitric oxide and prostacyclin

Question 20

what does the ET-1 effect depend on?

Answer 20

ET-1 effects depend on the balance between the two receptors ETA and ETB

Question 21

what does angiotensin act as?

Answer 21

it acts as a vasoconstrictors and a pro-inflammatory factor which increases the generation of reactive oxygen species (ROS)

Question 22

how many receptors does angiotensin have? and what do they do?

Answer 22

2 receptors
AT1R promotes vasoconstriction by enhancing the release pf ET-1
AT2R promotes vasodilation by increasing the release of bradykinin which activates eNOS and increases NO levels

Question 23

what does thromboxane act as?

Answer 23

it acts as a vasoconstrictor and pro-coagulant

Question 24

what is angiogenesis? and how does it start?

Answer 24

growth of blood vessels from the existing vasculature
it s a must step process involving breaking of cell-cell adhesions
it starts when a small vessel is activated by an angiogenic stimulus

Question 25

what is vasculogenesis?

Answer 25

differentiation of precursor cells into endothelial cells and the de novo formation of a vascular network

Question 26

when a damage occurs because of wounding or inflammation, what does the activated endothelium produce?

Answer 26

they increase their production of pro-coagulants and decrease production of anti-coagulants

Question 27

what is the difference between normal endothelium and activated endothelium?

Answer 27

normal endothelium –> increased production of anti-coagulants
activated endothelium –> decreased production of anti-coagulants