Session 1

Question 1

What factors affect the rate of diffusion in the CVS?

Answer 1

Area available for exchange - determined by the capillary density
Diffusion resistance - the difficulty of movement through the barrier. Determined by the nature of the barrier, the molecules that are diffusing and the path length of diffusion.
Concentration gradient - this gradient mostly depends of the flow of blood through the capillaries. This is usually the limiting factor.

Question 2

List typical blood flows to major organs of the body

Answer 2

Brain - 750ml/min
Heart - 300 to 1200 ml/min
Kidney - 1200ml/min (most not nutritive)
Gut & liver - 1400 to 2400 ml/min (short term flow reduction tolerable)
Skin - 200 to 2500 ml/min

Question 3

What is the typical range of cardiac output the heart can provide?

Answer 3

5 to 25 L/min

Question 4

What are the main functional components the CvS requires?

Answer 4

A pump
Distribution vessels
Flow control - via resistance vessels (arterioles and pre capillary sphincters) allowing the cardiac output to be distributed appropriately
Capacitance - ability to cope with changes to the cardiac output this store is in the veins.

Question 5

What is the distribution in blood volume over the main parts of the CVS?

Answer 5

67% in veins
17% in heart and lungs
11% in arteries and arterioles
5% in capillaries

Question 6

What are the two main circulations in the body?

Answer 6

Systemic - left heart

Pulmonary - right heart

Question 7

Where in the thorax does the heart lie?

Answer 7

Middle mediastitium - between the left and right pleural cavities

Question 8

Where do the coronary arteries originate from and where do the veins drain in to?

Answer 8

Originate from left and right aortic sinus, drain into coronary sinus

Question 9

Describe the branches of the left coronary artery and the regions they supply

Answer 9

Left anterior descending/anterior interventricular artery - supplies left and right ventricles and interventricular septum. Runs towards the apex of the heart
Circumflex artery - left atrium and ventricle
Left marginal artery - left ventricle

Question 10

Describe the branches of the right coronary artery and the regions they supply

Answer 10

Right coronary artery - right atrium and right ventricle
Right marginal artery - right ventricle and apex
Posterior interventricular artery - right and left ventricles and interventricular septum

Question 11

Where do the coronary arteries originate from and where do the veins drain in to?

Answer 11

Originate from left and right aortic sinus, drain into coronary sinus

Question 12

Describe the branches of the left coronary artery and the regions they supply

Answer 12

Left anterior descending/anterior interventricular artery - supplies left and right ventricles and interventricular septum. Runs towards the apex of the heart
Circumflex artery - left atrium and ventricle
Left marginal artery - left ventricle

Question 13

Describe the branches of the right coronary artery and the regions they supply

Answer 13

Right coronary artery - right atrium and right ventricle
Right marginal artery - right ventricle and apex
Posterior interventricular artery - right and left ventricles and interventricular septum
Also supplies SAN and AVN

Question 14

What are the main coronary veins?

Answer 14

Great cardiac vein - runs in line with the LAD up to the coronary sulcus.
Coronary sinus - main vein located on the posterior surface in the coronary sulcus

Question 15

Describe the interior surface to the right atrium

Answer 15

A smooth part (sinus venarum) derives from the sinus venosus and a rough part (atria proper) derived from the primitive atrium

Question 16

What are the rough ridges in the right ventricle called?

Answer 16

Trabeculae carnae

Question 17

What are the main borders of the heart?

Answer 17

Superior - left and right atria and great vessels of the heart
Inferior - left and right ventricles
Left - left ventricle
Right - right atrium

Question 18

What are the main surfaces of the heart?

Answer 18

Anterior - right ventricle
Posterior - left atrium
Inferior - left and right ventricles 
Left - left ventricle
Right - right atrium

Question 19

What nerve innervates the pericardium?

Answer 19

Phrenic nerve (C3-5)

Question 20

What are the major elastic arteries of the CVS?

Answer 20

Right and left pulmonary arteries
Aorta
Three main arterial trunks - brachiocephalic, left common carotid and left subclavian
Left and right common iliac arteries

Question 21

Describe the structure of large elastic arteries

Answer 21

Tunica intima - endothelial cells with narrow subendothelium of connective tissue with discontinuous internal elastic lamina

Tunica media - 40 to 70 fenstrated elastic membranes with smooth muscle and collagen in between.

Tunica Adventitia - thin layer of fibroelastic connective tissue containing vasa vasorum (vessels of vessels), lymphatic vessels and nerves. (Same in all arteries)

Question 22

Describe the structure of muscular arteries

Answer 22

Tunica intima - epithelium, subendothelial layer and thick internal elastic lamina.

Tunica media - ~40 layers of smooth muscle cells connected by gap junctions. Prominent external elastic lamina.

Question 23

How is vasoconstriction stimulated in muscular arteries?

Answer 23

By sympathetic nerve fibres releasing noradrenaline which diffuses through fenestrations in the external elastic lamina into the tunica media to depolarise some of the superficial SMCs. Depolarisation is propagated to all cells via gap junctions.

Question 24

What is an end artery?

Answer 24

A terminal artery supplying all/most of the blood to a body part without significant collateral circulation.

Question 25

Describe the structure of arterioles

Answer 25

Diameter

Question 26

What is the structure and function of metarterioles?

Answer 26

Supplies blood to the capillary beds.
The smooth muscle layer is not continuous. Individual smooth muscle cells are spaced out and encircle the endothelium of an arising capillary to form a precapillary sphincter.

Question 27

Describe the structure of capillaries

Answer 27

Single layer of epithelium with basement membrane

Question 28

Describe the three types of capillary:

Answer 28

Continuous - most common, joined by tight junctions
Fenstrated - little interruptions exist between thin parts of the epithelium. Bridged by a diaphragm.
Sinusoidal - larger diameter and slower blood flow. Gaps exist in the walls to allow whole cells to move between blood and tissue.

Question 29

What are pericytes?

Answer 29

Cells that form a branching network on the outer surface of the endothelium of capillaries. They are capable of dividing to form smooth muscle cells or fibroblasts during angiogenesis, tumour growth and wound healing.

Question 30

What is the structure and function of post-capillary venules?

Answer 30

Wall is similar to capillaries but larger and even more permeable. Fluid drains into them due to pressure differences (except in inflammatory responses).

Question 31

What happens to venules once they reach >50micrometres?

Answer 31

Tunica media containing smooth muscle appears. They contain valves to prevent retrograde transport.

Question 32

What is the difference between a vein and its accompanying artery?

Answer 32

Larger diameter with a thinner wall containing more connective tissue and fewer elastic & muscle fibres. Exception is the superficial veins of the leg which have a well defined muscular wall to resist distension by gravity.

Question 33

What are venae comitantes?

Answer 33

Deep paired veins accompanying arteries in one sheath. The pulsing of the artery promotes venous return.