Vascular Structure/Function, Vascular Anomalies, and Vascular Response to Injury

Question 1

There are 3 concentric layers to a blood vessel. What are they?

Answer 1

Intima
Media
Adventitia

Question 2

Describe the 3 layers of blood vessels (intima, media, and adventitia). Make sure to mention differences in arteries vs. veins.

Answer 2

Intima = single layer of endothelial cells

Media:

• arteries = well organized concentric layers of smooth muscle
• veins = haphazard

Adventitia = external to media, often separated from media by wide external elastic lamina

Question 3

What layer separates intimate from media?

Answer 3

Internal elastic lamina

Question 4

What are the 3 types of arteries?

Answer 4

Elastic arteries
Muscular arteries
Arterioles

Question 5

Describe elastic arteries. What are they predominantly made up of and how does this affect its function?

Answer 5

They have a high elastin content which allows expansion during systole and recoil during diastole

Propels blood toward organs

Question 6

How are elastic arteries affected by age?

Answer 6

Increasing age leads to less compliance leading to increased blood pressure

Question 7

Describe muscular arteries.

Answer 7

Circumferentially oriented smooth muscle

Arteriolar smooth muscle contraction = vasoconstriction
relaxation = vasodilation

Question 8

Describe arterioles.

Answer 8

Principal point of physiologic RESISTANCE to blood flow

Question 9

How do you calculate resistance?

Answer 9

Resistance to fluid flow is INVERSELY proportional to 4th power of diameter

R ~ nL/r^4

Question 10

What is vasa vasorum?

Answer 10

“vessels of the vessels”, small arterioles supply O2 to outer media of large arteries

Question 11

Where might you see Large Elastic Arteries?

Answer 11

Aorta and its major branches (common carotid, iliac, pulm art)

Question 12

Where might you see Medium Sized Muscular Arteries?

Answer 12

Smaller branches of the aorta (coronary and renal)

Question 13

Where might you see Arterioles?

Answer 13

Within tissues and organs

Question 14

Describe capillaries.

Answer 14

Diameter of an RBC, no media, pericytes (resemble smooth muscle cells)

Question 15

Describe veins. How are they structured compared to arteries?

Answer 15

Most inflammatory reactions, vascular leakage, and leukocyte exudation

Larger lumens, thinner and less organized walls; contains about 2/3 of total blood volume

Less rigid = susceptible to dilation and compression, as well as infiltration by tumors and inflamm. processes

Question 16

What are venous valves?

Answer 16

Valves in the extremities to prevent venous reverse flow due to gravity

Question 17

Describe lymphatics. How are they structures? What is their function?

Answer 17

Thin walled, lined by specialized endothelium

Return intestinal tissue fluid and inflammatory cells to bloodstream

Transport bacteria and other materials
Tumor cells = pathway for disease dissemination

Question 18

What are the pressure differences between arteries and veins?

Answer 18

Arteries have a HIGH pressure system

Veins have a LOW pressure system

Question 19

What are the 3 vascular anomalies?

Answer 19

Aneurysms
Arteriovenous malformation (AVM)
Fibromuscular dysplasia

Question 20

What are aneurysms? When do they occur?

Answer 20

Localized abnormal dilation of blood vessel or the heart

Not present at birth, but develop over time due to underlying defect in the media of vessel

Question 21

What are arteriovenous malformations (AVMs)?

Answer 21

Tangle, worm-like vascular channels with prominent PULSATILE arteriovenous shunting with high blood flow

Arteriovenous shunting = arteries –> veins WITHOUT intervening capillaries

Question 22

What can AVMs ultimately lead to?

Answer 22

Large or multiple AVMs may shunt blood from arterial to venous circulation, forces heart to pump additional volume leading to high-output cardiac failure

Question 23

What is fibromuscular dysplasia? When does this occur?

Answer 23

Focal irregular thickening in medium and large muscular arteries (renal, carotid, splanchnic, and vertebral vessels)

Usually developmental defect, but can arise form trauma, etc.

Question 24

What is HTN a consequence of?

Answer 24

Increase tone in small muscular arteries and arterioles

Question 25

What is the defining characteristic of a berry aneurysm?

Answer 25

"The WORST headache I've ever had"

Question 26

Where do Berry aneurysms typically occur, what part of this area is the most common site? What disease could they be characteristic of?

Answer 26

Circle of Willis 90% of berry aneurysms found near major branch points of the ANTERIOR circulation AD polycystic kidney disease

Question 27

What is most clinically significant of berry aneurysms?

Answer 27

It is the most frequency cause of subarachnoid hemorrhage 1/3 of ruptures associated with acute increases in intracranial pressure

Question 28

How can mycotic aneurysms arise? Can you give me an example of when you may get a mycotic aneurysm?

Answer 28

Embolization of a septic embolus, usually complication of infective endocarditis Extension of adjacent suppurative process Circulating organisms directly infecting the arterial wall EX: Pts with cardiac disease may get these aneurysms

Question 29

What are fusiform and giant aneurysms?

Answer 29

Fusiform aneurysms bulge from all sides of an artery and do not have a neck (unlike berry) Giant aneurysms will involve more than one artery and be over 2.5 cm wide

Question 30

How can AVMs form?

Answer 30

Result from rupture of an arterial aneurysm into adjacent vein Penetrating injuries that pierce arteries and veins Inflammatory necrosis of adjacent vessels

Question 31

When is an AV fistula useful?

Answer 31

Surgically generated AV fistulas provide vascular access for chronic hemodialysis. Joining the artery and vein together makes the vein stronger by thickening it due to the high pressure system of the artery. It also provides better access to the blood as it will get taken from the vein, cleaned, and put directly back into the artery.

Question 32

What is fibromuscular dysplasia?

Answer 32

Focal IRREGULAR thickening in medium and large muscular arteries (renal, carotid, splanchnic, and vertebral vessels) Can develop aneurysms that may rupture

Question 33

What is the cause of fibromuscular dysplasia? In who is it most likely seen?

Answer 33

Unknown, probably developmental Young women First degree relatives have increased incidence

Question 34

What conditions may arise form fibromuscular dysplasia?

Answer 34

Medial and intimal hyperplasia leading to luminal stenosis Renovascular HTN due to fibromuscular dysplasia of renal arteries

Question 35

What is the marked appearance of fibromuscular dysplasia? What imaging is needed to confirm dx?

Answer 35

String of beads | Seen in Angiography - needed

Question 36

Describe the normal expression of vascular endothelial cells.

Answer 36

Non-thrombogenic surface = maintains blood in fluid state Modulate medial smooth muscle tone = influence vascular resistance ``` Metabolize hormones (angiotensin) Regulate inflammation Affect growth of other cell types (esp smooth muscle cells) ```

Question 37

What is endothelial activation? Explain in detail.

Answer 37

When an injury (turbulent flow, HTN, cigarette smoke, lipid products, etc) leads to change in expression of endothelial cells. Increased expression of procoagulants, adhesion molecules, and pro inflammatory factors Altered expression of chemokine, cytokines, and growth factors

Question 38

What is the initial event following vascular injury?

Answer 38

Endothelial activation

Question 39

What is endothelial dysfunction?

Answer 39

Alteration in phenotype of endothelial cells leading to pro inflammatory and prothrombogenic states Initiation of thrombus formation, atherosclerosis, and vascular lesion of HTN

Question 40

Describe the conditions that vascular smooth muscle cells are responsible for.

Answer 40

Vascular Repair and atherosclerosis

Question 41

What is the function of vascular smooth muscle cells?

Answer 41

Ability to proliferate Synthesize collagen, elastin, and proteoglycans Elaborate growth factors and cytokines Vasoconstriction/vasodilation

Question 42

What is intimal thickening?

Answer 42

Stereotypical response of vessel wall to any insult/injury

Question 43

Describe the process of intimal thickening.

Answer 43

Associated with endothelial cell dysfunction or loss Stimulates smooth muscle cell recruitment and proliferation and associated matrix synthesis Neointimal smooth muscle cells are motile, undergo cell division, acquire new biosynthetic capabilities They can return to nonproliferative state with normalization of endothelial layer The healing response results in intimal thickening that may impede blood flow

Question 44

In a step wise fashion, describe the response to vascular injury.

Answer 44

1. Recruitment of smooth muscle cells or smooth muscle precursor cells to intimal 2. Smooth muscle cell mitosis 3. Elaboration of extracellular matrix