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7. CVS > 2. Histology of the Cardiovascular System > Flashcards

2. Histology of the Cardiovascular System Flashcards

1
Q

How are flow rate of blood and cross-sectional area of the vessels linked? Give an example demonstrating this relationship.

A

Blood flows fastest where the total cross-sectional area is least. For example, the capillaries have a huge total cross sectional area so their flow rate is very slow.

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2
Q

What are arteries?

A

Blood vessels that carry blood away from the heart to the capillary beds.

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3
Q

What is the major artery from the right ventricle and what does it bifurcate into?

A

The pulmonary trunk. It bifurcates into the right and left pulmonary arteries that enter the lungs.

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4
Q

What is the major artery arising from the left ventricle?

A

The aorta, it courses in a posteriorly oblique arch to descend in the thoracic cavity.

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5
Q

What are the three major arterial trunks of the heart?

A

The brachiocephalic artery, left common carotid artery and the left subclavian artery (arise from the arch of the aorta).

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6
Q

What happens to the aorta as it enters the abdominal cavity?

A

It terminates by bifurcation get into the left and right common iliac arteries in the pelvis.

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7
Q

What are the three major types of artery?

A

Elastic conducting arteries (widest), muscular distributing arteries (intermediate diameter) and arterioles (narrowest).

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8
Q

What are the three layers of the walls of arteries and veins?

A

Tunica intima, next to the lumen.
Tunica media, in the middle.
Tunica adventitia, outer layer.

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9
Q

Give the main features of the layers in the walls of large arteries.

A

Walls may be yellow when fresh due to abundant elastin.
Tunica intima - endothelial cells with long axes orientated parallel to long axis of artery. Narrow subendothelium of connective tissue with discontinuous internal elastic lamina.
Tunica media - 40-70 finest rated elastic membrane, smooth muscle and collagen between lamellae, thin external elastic lamina.
Tunica adventitia - thin layer of fibroelastic connective tissue containing vasa vasorum, lymphatic vessels and nerve fibres.

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10
Q

What is dissection of the aorta?

A

The tunica media is breached so blood forces it’s way between and separates the elastin.

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11
Q

Give the features of the wall of elastic arteries.

A

Tunica intima - internal elastic lamina.
Tunica media - many elastic lamellae.
Tunica adventitia - connective tissue with neurovascular supply and some elastin.

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12
Q

Give the details of the wall of small elastic arteries.

A

Tunica intima - in distinct endothelial cells.
Tunica media - elastin lamellae.
Tunica adventitia - collagen.

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13
Q

Give the details of the walls of muscular arteries.

A

Tunica intima - endothelium, subendothelial layer and thick internal elastic lamina.
Tunica media - 40 layers of smooth muscle cells, prominent external elastic lamina.
Tunica adventitia - thin layer of fibroelastic connective tissue containing vasa vasorum, lymphatic vessels and nerve fibres.

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14
Q

How is vasoconstriction of muscular arteries stimulated?

A

By sympathetic nerve fibres. Neurotransmitter is release at them nerve endings and diffuse in the external elastic lamina into the tunica media so the superficial smooth muscle cells are depolarised. All the cells of the tunica media then depolarise.

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15
Q

How are the diameter and layers of smooth muscle of arteries linked?

A

As diameter decreases, so does the number of smooth muscle layer.

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16
Q

What is an end artery?

A

A terminal artery that supplies all or most of the blood to a body part without significant collateral circulation.

17
Q

What are some example of end arteries?

A

Coronary artery, splenic artery and renal artery.

18
Q

In which part of the cardiac cycle do coronary arteries fill with blood?

A

In diastole.

19
Q

What is classed as an arteriole?

A

Arteries with a diameter less than 0.1mm.

20
Q

Give the details of the wall layers of arterioles.

A

Tunica intima - layer of endothelial cells and a very thin layer of sub endothelial connective tissue.
Tunica media - single layer of smooth muscle cells.
Tunica adventitia - layers of fibroblasts.

21
Q

What are metarterioles?

A

Arteries that supply blood to capillary beds.

22
Q

How do metarterioles differ from arterioles?

A

The smooth muscle layer is not continuous in metarterioles.

23
Q

What is the role of precapillary sphincters?

A

They allow arterioles and metarterioles to serve as flow regulators for the capillary beds.

24
Q

What is the role of lymphatic capillaries?

A

Drain away excess extracellular fluid, returning it to the blood at the junctions of the internal jugular and subclavian veins.

25
Q

Why is blood velocity at its lowest through the capillaries?

A

To allow time for gas and nutrient exchange with surrounding tissues.

26
Q

What’s the diameter of capillaries?

A

7-10um.

27
Q

How long are most capillaries?

A

1mm.

28
Q

What are capillaries made of?

A

A single layer of endothelium and its basement membrane.

29
Q

What are the three types of capillaries?

A

Continuous capillaries - most common, in nervous, muscle and connective tissues, exocrine glands ands the lungs. The endothelial layer is continuous, with cells joined by tight occluding junctions.
Fenestrated capillaries - in parts of gut, endocrine glands and renal glomerulus. Little interruptions across thin parts of the endothelium that are bridged by a thin diaphragm.
Sinusoidal/discontinuous capillaries - larger diameter and slower blood flow. In the liver, spleen and bone marrow. Gaps in the walls to allow whole cells to move between blood and tissue.

30
Q

What possible routes of transport are allowed through the endothelial wall of fenestrated capillary?

A

Direct diffusion, diffusion through intercellular cleft or diffusion through fenestration

31
Q

What is the diameter of venules?

A

50um-1mm.

32
Q

What is the wall of a venule made of?

A

Endothelium or thin smooth muscle cells.

33
Q

What structure restricts retrograde transport of blood through venules?

A

Valves.

34
Q

How do vein walls differ from artery walls?

A

Vein walls are thinner and have more connective tissue and fewer elastic and muscle fibres.

35
Q

What is the composition of small and medium sized vein walls?

A

Tunica intima - thin.
Tunica media - thin, 2/3 layers of smooth muscle.
Tunica adventitia - well developed.

36
Q

What is the composition of large vein walls?

A

Tunica intima - thicker.
Tunica media - not prominent, unless in superficial veins of the legs.
Tunica adventitia - well developed.

37
Q

What are venae comitantes?

A

Deep paired veins that accompany one of the smaller arteries on each side of the artery. The three vessels are wrapped in one sheath together.

38
Q

How is blood distributes around the body?

A

Peripheral veins - 65%
Heart and lungs - 20%
Peripheral arteries - 10%
Capillaries - 5%

7. CVS (21 decks)

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