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Cardiovascular Unit > The Cardiovascular System > Flashcards

The Cardiovascular System Flashcards

1
Q

vascular system mission

A

maintain quality & volume of ECF

 - this occurs in the microvascular (i.e. capillary) bed
 - all cells must be <200 micrometers of a capillary (or else the cells will die)!
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2
Q

at what level of the vascular system does metabolism, gas and nutrient exchange take place?

A

at the microscopic capillary level

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3
Q

BVs have 3 “tunics”. what are the 3 tunics and what comprises each layer?

A 
from the outside in:
Tunica Adventitia: outer
– CT (connective tissue) 
Tunica Media: most variable
– SMCs (especially on the arterial side, less on the venous side) & CT
Tunica Intima: inner
– endothelium, of endothelial cells (ECs)
• simple squamous with basal lamina
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4
Q

what is the turnover rate of endothelial cells?

A

1%/day

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5
Q

what are the layers of the heart?

A

from inside out:

Tunica Intima = endocardium
– simple squamous endothelium/basal lamina
Tunica Media = myocardium
– myocytes &fibroblasts
– attaches to dense CT ‘skeleton’
Tunica Adventitia = epicardium
– simple squamous
– niche of adult resident cardiac stem cells? (NEW idea!)
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6
Q

how do epicardial cells grow during development?

A

during development, epicardial cells grow over the surface of the heart as a mono-cellular layer.

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7
Q

what do epicardial cells give rise to?

A 
• “cardiac” fibroblasts (we are not sure if these are the same or different from fibroblasts we find elsewhere)
• coronary arteries 
     – endothelial cells
     – SMCs
* cardiac myocytes?
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8
Q

composition and characteristics of large arteries

A

Large “Elastic” Arteries: thick wall
1. Adventitia: external elastic membrane
2. Media: thickest
• circular SMCs with 40-70 elastic lamellae
3. Intima: endothelial cells
• tight junctions (so things cannot get into the extracellular space) & pinocytotic vesicles (nutrients exchange occurs through this mechanism)

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9
Q

function and clinical applications related to large arteries

A

Function: elastic recoil to maintain BP during diastole
Clinical: aneurysm

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10
Q

composition and characteristics of large veins

A

Large Veins: thin wall

The adventitia is the thickest tunic in large veins.

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11
Q

composition and characteristics of medium arteries

A 
Medium Vessels
Muscular Arteries:
1. Adventitia:
2. Media: prominent ~ 40 layers SMC, less elastin 
3. Intima: internal elastic lamina
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12
Q

function of medium arteries

A

Function: SMCs regulate BP.

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13
Q

clinical relevance related to medium arteries/vessels

A

Atherosclerosis = intimal plaques from ‘foam cells’
1.macrophagesingestLDL(badcholesterol)
2. SMCs –> intima, ingest LDL
=macrophages and SMCs form foam cells
Plaques calcify, platelets attach–>thrombus–> MI/stroke

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14
Q

composition and characteristics of small arteries and arterioles

A

Small Arteries & Arterioles:

t. media: ~8 layers SMC in small artery, down to ~2 layers SMC in arteriole

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15
Q

functional and clinical relevance related to small arteries and arterioles

A

Function: SMC (in the tunica media) regulates bloodflow to capillary bed (where metabolic action occurs).
Clinical: lipid uptake by SMCs narrows lumen –> hypertension

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16
Q

composition and characteristics of capillaries

A

• diameter of lumen accepts ~1 RBC ~ 7.5 micrometers
• 1 endothelial cell can make up a tube
• simple squamous endothelium with basal lamina
- no media, no adventitia

17
Q

3 types of capillaries

A
  • Type I: continuous
  • Type II: fenestrated
  • Type III: sinusoidal
18
Q

characteristics of Type I capillaries

A

– tight junctions: admit proteins only smaller than 10 kDa
– pinocytotic vesicles: permit passage of proteins >10 kDa
– Pinocytotic vesicles are not present in the CNS.

19
Q

characteristics of Type II capillaries

A

– 100 nm windows = permanent pinocytotic vesicles (holes in the cells…things can get through easily)

20
Q

characteristics of Type III capillaries

A
  • discontinuities (spaces between cells)
  • larger than capillaries type I & II; ~30 μm diam. (about 4 RBCs can pass through a Type III capillary at the same time)
21
Q

Locations of Type I capillaries and the items transported

A 
locations:
CNS
heart
skeletal muscle lung
item transported:
oxygen/gases
22
Q

Locations of Type II capillaries and the items transported

A 
locations:
endocrine glands GI tract
kidneys
items transported:
hormones, nutrients, ions
23
Q

Locations of Type III capillaries and the items transported

A 
locations:
bone marrow spleen
liver
item transported:
whole cells
24
Q

function of endothelial cells

A
  1. exchange gases & nutrients
    – gases: thru cell membrane
    – nutrients: thru pinocytotic vesicles, fenestrations, discontinuities
    2. secrete regulatory molecules – vasoactive factors
    • endothelin:vasoconstrictor
    • NO (nitric oxide): vasorelaxant
    – growth factors
    • FGF: fibroblast growth factor
    • PDGF: platelet-derived growth factor
    • VEGF: vascular endothelial growth factor
    =>PDGF, VEGF (and maybe FGF too) are growth factors for active angiogenesis!!
25
Q

angiogenesis

A 
new blood vessels growing out perpendicular from existing BVs
-7 steps
first and last step:
1. Activation...
• of endothelial cell receptors
7. Inhibition...
• of angiogenic growth
26
Q

angiogenesis; targets, receptors, inhibitors

A

Angiogenesis: new vessels from existing BVs (adult)
• Vasculogenesis is embryonic BV development.
• target –> endothelial cells
– receptors: VEGFR, FGFR, TIE-2
– ligands:VEGF, FGFs, angiopoietin-1
– inhibitors: angiostatin, endostatin

27
Q

clinical therapies that target angiogenesis

A

Clinical Therapies
• Pro-Angiogenic: for ischemia in heart & extremities
– VEGF & FGF-induced BV growth
• Anti-Angiogenic: combat tumors
– 1 endothelial cell can support 50 tumor cells!
– angiostatin & endostatin inhibit new BV growth

28
Q

examples in which angiogenesis has been used for treatments

A
  • Pro-Angiogenic gene therapy for lower limb ischemia, using VEGF cDNA (at this point, this is not clinically useful, however. Dr. Lough things FGF injection may be more promising!)
  • Anti-Angiogenic Therapy in Mice using Endostatin (translating this into a human context has been much more difficult!)
29
Q

Bevacizumab (Avastin)

A

anti-VEGF monoclonal antibody

  • ->this attacks and neutralizes VEGF
  • ->shrinks the vascular supply of tumors

Cardiovascular Unit (16 decks)

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