Week 1 - CVS Histology

Question 1

List the 3 layers making up the walls of arteries and veins, from the innermost to outermost layers.

Answer 1

Tunica intima
Tunica media
Tunica adventitia

Question 2

The tunica media is thicker in veins. True or false?

Answer 2

False - thicker in arteries

Question 3

What are the components of the tunica intima?

Answer 3

Endothelium
Subendothelial layer
Internal elastic lamina

Question 4

Give one example of an elastic artery.

Answer 4

The aorta.

Question 5

What is contained within the walls of the tunica adventitia of elastic and muscular arteries?

Answer 5

Vasa vasorum

Question 6

What is the function of vasa vasorum? Why are they needed?

Answer 6

Supply the artery wall with blood.

Wall too thick to rely on diffusion from the blood in the lumen.

Question 7

What is the tunica media of elastic arteries made up of?

Answer 7

40 - 70 elastic membranes

Question 8

How do arteriole walls differ from elastic lamina walls?

Answer 8

Arterioles - tunica media has just 1 - 3 layers, and there is very little adventitia.
Elastic arteries - thick tunica media and significant adventitia with vasa vasorum.

Question 9

What is the key feature of metarterioles?

Answer 9

Pre-capillary sphincters

Question 10

What is a pre-capillary sphincter?

Answer 10

Smooth muscle cell encircles capillary at the point at which it branches off from the metarteriole. Contracts and relaxes to control blood flow into the capillary.

Question 11

RBCs are almost as large as a capillary lumen. What benefit does this have?

Answer 11

Reduces path length for diffusion

Question 12

Is blood through capillaries fast or slow? Why?

Answer 12

Slow - allows longer time for nutrient exchange

Question 13

Describe a capillary wall

Answer 13

Endothelium and basement membrane only

Question 14

What are the 3 types of capillary?

Answer 14

1. Continuous
2. Fenestrated
3. Discontinous/sinusoidal

Question 15

What feature leads a capillary to be referred to as a “continuous” capillary?

Answer 15

The endothelium in the wall is continuous

Question 16

What does it mean if a capillary is fenestrated?

Answer 16

There are interruptions in the endothelium, bridged by a thin membrane

Question 17

Where may you find discontinuous capillaries? Why?

Answer 17

Liver, spleen and bone marrow

Large gaps in the endothelium which allow whole cells through

Question 18

What sort of cell may surround continuous or fenestrated capillaries?
What is their function?

Answer 18

Pericytes

Divide into myocytes or fibroblasts

Question 19

In which vessels do valves begin to appear?

Answer 19

Venules

Question 20

What are valves formed from?

Answer 20

Extensions of the tunica intima

Question 21

What are venae commitantes?

Answer 21

Pairs of veins which lie either side of an artery.

The pulsating of the artery aids venous return.

Question 22

Are venae commitantes wrapped in a single sheath, or is each vessel individually wrapped?

Answer 22

Single sheath

Question 23

Compare and contrast the structure of large veins and elastic arteries.

Answer 23

Veins:
Wall thinner - thin tunica intima and thin tunica media
Lumen wide and irregular
Valves

But generally similar in size and structure

Question 24

Veins have a thin tunica media. Which are the exceptions, and why?

Answer 24

The superficial veins of the legs - need muscle to resist gravity

Question 25

List the vessels in order of size, starting with the elastic arteries and ending with the large veins.

Answer 25

``` Elastic arteries Muscular arteries Arterioles Metarterioles Capillaries Post-capillary venules Venules Medium veins Large veins ```