Histology

Question 1

Name the 3 major elastic arteries

Answer 1

Aorta, right and left pulmonary arteries.

Question 2

Where does the aorta terminate?

Answer 2

The aorta arches and then passes down through the thoracic and abdominal cavities. It bifurcated in the pelvis to become the right and left iliac arteries.

Question 3

What is the purpose of elastic arteries during diastole?

Answer 3

During systole the walls of the elastic arteries are stretched. These can recoil during diastole and ensure that pressure in the arteries is maintain to keep blood flow in the right direction.

Question 4

What is vasa vasorum?

Answer 4

These are small blood vessels which supply the walls of large arteries such as the aorta.

Question 5

What is dissection of aorta?

Answer 5

This is where the blood manages to push between the layers of the aorta wall causing damage.

Question 6

What is found in the tunica adventitia of muscular arteries?

Answer 6

Unmyelinated nerve endings

Question 7

Describe the action of the sympathetic nervous system on muscular arteries.

Answer 7

When neurotransmitter is released in tunica adventitia, this diffuses through fenestrations causing depolarisation of some smooth muscle cells and vasoconstriction.

Question 8

What difference is observed in artery walls as we get closer to arterioles?

Answer 8

The number of smooth muscle layers in the tunica media reduces.

Question 9

What is an end artery?

Answer 9

This is a terminal artery which supplies cells where there is no other blood supply. If this becomes occluded then blood supply to that tissue is insufficient.

Question 10

Describe the structure of an arteriole.

Answer 10

These have 1-3 layers of smooth muscle in their tunica intima. Tunica media is a single smooth muscle cell which completely encircles the endothelial cells.

Question 11

What is a metarteriole?

Answer 11

This is the vessel which supplies the capillary beds. They do not have a continuous layer of smooth muscle as it encircles the endothelium of the capillary - pre capillary sphincter.

Question 12

What is the effect of pre capillary aphid terms on blood flow?

Answer 12

When they are open blood flow is plentiful but when closed it is greatly reduced. They are able to remain constricted for a very long time.

Question 13

What is the main function of a capillary?

Answer 13

Diffusion of nutrients into the tissues. This is maximised by reducing diffusion distance as the rbc only just fits within the capillary and so is squashed against the walls.

Question 14

What is the difference between a continuous and a fenstrated capillary?

Answer 14

A continuous capillary has tight or occludin get junctions between cells whilst a fenestrated capillary has interruptions covered by a thin diaphragm.”

Question 15

Where might you find fenestrated capillaries?

Answer 15

Gut, endocrine glands, renal glomerolus.

Question 16

What type of capillaries are found in the liver, spleen and bone marrow?

Answer 16

Sinusoidal/ Discontinuous capillaries. The gaps allow whole cells to move between the blood and tissues.

Question 17

State a property of the walls of post capillary venules.

Answer 17

They are highly permeable and this means that fluid drains back into them ad the pressure is lower.

Question 18

In what circumstance will cells move out of post capillary venules?

Answer 18

During an inflammatory response. Leucocytes and fluids emigrate into tissues.

Question 19

What are pericytes and where are they found?

Answer 19

A branching network on the outside of the endothelium which can divide into muscle cells and fibroblasts. They are found in capillaries, post capillary venules and some venules.

Question 20

State a property of veins which distinguishes them from arteries.

Answer 20

They have valves. They also have less elastic fibres in their walls and less muscle.

Question 21

What two things help to return blood to the heart in veins?

Answer 21

Valves and skeletal muscle contraction

Question 22

What is a venae comitantes?

Answer 22

This is a sheath which contains a small artery and two veins. The pulsing of the blood through the artery aids venous return.

Question 23

Why do large veins in the leg have muscular walls?

Answer 23

This prevents distension due to gravity.

Question 24

How much does the lymphatic system drain into the blood and where does this occur?

Answer 24

Approximately 100ml/hour into the left subclavian vein.