Blood Vessels L9

Question 1

Draw out the wigger’s diagram

Answer 1

Question 2

Function of elastic artery

Answer 2

Very large arteries
near the heart which have
elastic walls. During systole
they expand to store the bolus of blood leaving the ventricle; then during diastole they push
blood out into the arterial tree by elastic recoil. Thus they smooth the pulsatile flow of blood leaving
the ventricles.

Question 3

Structure of elastic artery

Answer 3

Many thin sheets of
elastin in the middle tunic

Question 4

Vasoconstriction

Answer 4

When smooth muscle cells contract

Question 5

Vasodilation

Answer 5

When smooth muscle cells relax, and diameter of the vessel increases

Question 6

Which one first - elastic or muscular?

Answer 6

Elastic

Question 7

Function of muscular artery

Answer 7

Distribute blood around the body at high pressure (and lungs at medium pressure) Rate of blood flow is adjusted by using smooth muscle to vary the radius of the vessel.
Flow is proportional to the fourth power of radius.
A small change in radius has a large effect on flow rate.

Question 8

Structure of the muscular artery

Answer 8

Many layers of circular smooth muscle wrapped around the vessel in the middle tunic

Question 9

Which has a thicker wall - artery or vein?

Answer 9

Artery - greater pressure

Question 10

Function of the arteriole

Answer 10

Control blood flow into capillary beds. They have
a thicker muscular wall relative to their size than any other blood vessel. These are the vessels in the circulation where
the greatest pressure drop occurs, and where there is the
greatest resistance to flow. The degree of constriction of
arterioles throughout the body determines:
total peripheral resistance
which in turn affects
mean arterial blood pressure

Question 11

Structure of arteriole

Answer 11

Between one and three layers of circular smooth muscle wrapped around the vessel in the middle tunic.

Question 12

Function of the capillary

Answer 12

Tiny vessels which are thin-walled to allow
exchange of gases, nutrients and wastes between
blood and the surrounding tissue fluid. Blood flow is
slow to allow time for exchange to occur. Capillaries
are leaky vessels; plasma escapes (but not blood
cells). Most of the lost plasma is immediately
recovered due to an osmotic gradient.

Question 13

Oedema

Answer 13

When you have too much pressure at the beginning of your capillaries you are forced to have too much fluid out and your tissue fluids get saturated. Stopped by osmosis.

Question 14

Structure of the capillary

Answer 14

The diameter is just wide enough to admit
one red blood cell. The capillary wall is a single
layer of endothelium (with an external basement
membrane). No smooth muscle is present within the
wall, (therefore no ability to adjust diameter), and no
connective tissue.

Question 15

Function of the venule

Answer 15

Low-pressure vessels which drain capillary beds.
During infection and inflammation, venules are the site where
white blood cells leave the blood circulation to attack bacteria
in the tissue alongside. The drawing shows a neutrophil which,
having first adhered to the endothelium, is now squeezing its
way between two endothelial cells to exit the vessel.

Question 16

Structure of the venule

Answer 16

Small venules (like the one shown at left) have the
usual endothelium plus a little connective tissue. Larger ones have a single layer of smooth muscle.

Question 17

Function of the vein

Answer 17

Thin-walled, low-pressure vessels which drain blood back to the atria (except portal veins which drain blood to another capillary bed). Their walls are thin and soft; they stretch easily (ie.
they are compliant). A small change in venous blood pressure causes a large change in venous
volume. Therefore veins act as a reservoir which stores blood, (64% of blood volume occurs in
systemic veins and venules compared to 13% in systemic arteries and arterioles)

Question 18

Structure of the vein

Answer 18

Similar to a muscular artery but much thinner-walled for their size, (much less muscle
and connective tissue). Larger veins (especially in the legs) have valves which prevent backflow.
As leg muscles alongside the vein alternately contract and relax during walking, the system acts
as a venous pump which returns blood to the right atrium.

Question 19

Altherosclerosis

Answer 19

When you eat too much cholesterol or high lipid diets, and they start to line the wall of our vessels starting to close off the lumen.

Question 20

What are coronary arteries?

Answer 20

Arteries that arise from the aorta just downstream from the aortic valve
and supply the muscle of the heart (myocardium). They are ordinary
small muscular arteries but critically important because of the tissue
they supply. They are named from their resemblance to a coronarius.

Question 21

How is deoxygenated blood is drained from the myocardium?

Answer 21

By cardiac veins - they return the blood back to the right atrium.

Question 22

What happens if a coronary artery is narrowed to about 20% of its normal cross-section by atheroma? (the fatty material which clogs your arteries)

Answer 22

Significant
obstruction to blood flow occurs. During exercise the myocardium supplied by the diseased artery
runs low on oxygen (ischemia) causing chest pain (angina). Severe ischemia results in death
(infarction) of a local area of myocardium.

Question 23

Why do artery-to-artery junctions (anastomoses)
between small penetrating branches of the main coronary arteries widen slowly?

Answer 23

For an ischaemic area of muscle to be supplied by a distant artery.

Question 24

Principles of the cardiac cycle

Answer 24

1. Blood flows from higher to lower pressure
2. Contraction increases the pressure within a chamber, while relaxation lowers the pressure
3. AV valves open when atrial pressures (atriums) are higher than ventricular pressures (ventricles), and close when ventricular pressures are higher
4. Semilunar valves open when ventricular pressures are higher then atrial pressures, and close when atrial pressures are higher than ventricular pressures

Question 25

AV valves

Answer 25

Tricuspid and bicuspid (mitral) valves

Question 26

Semilunar valves

Answer 26

Pulmonary and aortic valves

Question 27

What is the cycle initiated by?

Answer 27

The firing of the SA node which stimulates the atria to depolarise.

Question 28

What does the first heart sound mark?

Answer 28

Systole

Question 29

What does the second heart sound mark?

Answer 29

Diastole