Blood Vessels (Vascular System)

Question 1

What is the mission of the vasculature?

Answer 1

Maintain quality & volume of ECF

Question 2

How far does the cell have to be from a capillary?

Answer 2

<200 μm

Question 3

Where do the lymphatics drain from?

Where do the lymphatics drain to?

Answer 3

Drain from small vessels (arterioles, venules, capillaries)

Drain to large veins

Question 4

What are the layers of the BV walls and what do they consist of?

Answer 4

Tunica Adventitia: Outer Layer; CT (connective tissue)
Tunica Media: Most variable; Smooth Muscle Cells (SMCs) & CT
Tunica Intima: Inner layer; Endothelial Cell layer (Simple squamous with basal lamina)

Question 5

What is PECAM?

Answer 5

Platelet Endothelial Cell Adhesion Molecule aka CD31

Marker for vascularization

Question 6

What are the heart’s tunica layers called and what is special about each of them?

Answer 6

T. intima - Endocardium
T. media - Myocardium
Contains myocytes & fibroblasts
T. adventitia - Epicardium
Also might possibly include niche of adult resident cardiac stem cells?

Question 7

What is the developmental role of epicardial cells?

What cell types do epicardial cells give rise to?

Answer 7

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

Epicardial cells give rise to:
“Cardiac” fibroblasts
Coronary arteries - Endothelial cells, SMCs
Maybe cardiac myocytes?

Question 8

Layers of Elastic Arteries

Answer 8

Thick wall
Adventitia: External Elastic Membrane
Media: Thickest layer, circular SMCs with 40-70 elastic lamellae
Intima: Tight junctions & pinocytotic vesicles

Question 9

What is the function of large vessels? What is a clinical finding for this vessel?

Answer 9

Function: Elastic recoil to maintain BP during diastole
Clinical: Aneurysm

Question 10

What is different between large veins and large arteries?

Answer 10

Thin walled compared to arteries

Adventitia is the thickest tunic

Question 11

What is special about the medium artery layers?

Answer 11

Adventitia: Nothing special
Media: Prominent, has 40 layers of SMC, almost no elastin
Intima: Internal elastic lamina as a unique marker

Question 12

What is the function of middle vessels?

What is a clinical finding for this vessel, and what is the pathophys of this finding?

Answer 12

SMC regulate Blood Pressure

Athrosclerosis are intimal plaques from foam cells (macrophages and SMCs)
These plaques calcify, have platelets attach, form a thrombus, and lead to an MI/Stroke

Question 13

What is different between middle arteries and veins?

Answer 13

Veins have much less media and lack an internal elastic lamina

Question 14

What is the composition of the small arteries and arterioles?

Answer 14

T. media: 8 layers of SMC in small artery down to 2 layers of SMC in arterioles

Question 15

What is the function of small vessels?

What is the clinical finding for these vessels?

Answer 15

SMC regulates bloodflow to capillary beds

Lipid uptake by SMCs narrows the lumen

Question 16

What is the structure of a capillary?

Answer 16

The diameter of the lumen accepts 1 RBC: 7.5 μm
Single endothelial cell can make up a tube
Simple squamous endothelium with basal lamina (no media, no adventitia)

Question 17

What are the types of capillaries and their structures?

Answer 17

Type I: Continuous
10 μm diameter
Tight junctions which admit proteins smaller than 10 kDa and pinocytotic vesicles which permit passage of proteins > 10 kDa

Type II: Fenestrated
10 μm diameter
100 nm windows which serve as permanent pinocytotic vesicles

Type III: Sinusoidal
30 μm diameter
Discontinuous walls

Question 18

Where are continuous capillaries located and what do they transport?

Answer 18

CNS, Heart, Skeletal Muscle, Lung

Oxygen

Question 19

Where are fenestrated capillaries located and what do they transport?

Answer 19

Endocrine Glands - Hormones
GI Tract - Nutrients
Kidneys - Ions

Question 20

Where are sinusoidal capillaries located and what do they transport?

Answer 20

Bone marrow, spleen, liver

Whole cells

Question 21

What are the function of endothelial cells?

Answer 21

1. Exchange gases & nutrients
   Gases thru cell membrane, nutrients thru pinocytotic vesicles, fenestrations, discontinuities
2. Secrete regulatory molecules
   Vasoactive factors: Endothelin (vasoconstrictor), NO (vasorelaxant)
   Growth factors: FGF, PDGF, VEGF to activate angiogenesis

Question 22

Angiogenic activating factors (w/ receptors) and inhibiting factors

Answer 22

Activating: VEGF (VEGFR), FGF (FGFR), Angiopoietin-1 (TIE-2)
Inhibitors: Angiostatin, Endostatin

Question 23

What diseases are there clinical therapies for using angiogenic factors? (Pro-angiogenic vs anti-angiogenic)

Answer 23

Pro-angiogenic: Ischemia in heart & extremities

Anti-angiogenic: Combat tumors (Single endothelial cell can support 50 tumor cells)

Question 24

What is an anti-VEGF monoclonal antibody?

Answer 24

Bevacizumab