CVS- Types of Vessels

Question 0

What are the three things diffusion is affected by?

Answer 0

Area available for exchange
Movement through barrier (resistance)
Concentration gradient

Question 1

How does blood exchange with tissues?

Answer 1

At capillaries via diffusion

Question 2

How is the area available for exchange determined?

Answer 2

By capillary density (how many per unit volume)

Highest in metabolically active tissues.

Question 3

How is resistance through a barrier determined?

Answer 3

Nature of the barrier (diffusion distance) and types of molecule diffusing

Question 4

What type of molecules are O2 and CO2?

Answer 4

They are lipophilic so easily pass through capillary membrane

Question 5

How is concentration gradient determined?

Answer 5

Affected by flow of blood

Fast flow maintains conc gradient but must be slow enough to allow exchange.

Question 6

What kind of blood supply does the brain require?

Answer 6

A constant Hugh blood flow

0.5ml/min/g

Question 7

What blood flow does the heart require at rest?

And at working hard?

Answer 7

At rest high 0.9ml/min/g

But at work this can increase 4x

Question 8

What blood flow does the kidney require?

Answer 8

Constant high supply needed

3.5ml/min/g

Question 9

How much blood does the CVS as a unit need to deliver to the whole body?

Answer 9

5-25l/min-1

Question 10

What is the form of blood storage (or capacity) in the CVS

Answer 10

The veins

Question 11

What is the distribution of blood in the CVS (as figures)

Answer 11

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

Question 12

What is the rate of blood flow known as?

Answer 12

Perfusion rate

Question 13

Where is blood flow fastest?

Answer 13

Where total surface area is smallest

Question 14

What are the features of arteries?

Answer 14

They carry blood away from the heart
Some are elastic, some are muscular
They have a thicker wall and narrower lumen than veins

Question 15

Describe the anatomy of an elastic artery?

Answer 15

These are the widest artery (e.g aorta, PA)
The tunica intima - has endothelial cells with axes in parallel (to reduce friction) it also contains internal elastic lamina
The tunica media - smooth muscle cells and collagen, thin external elastic lamina
Tunica adventitia - thin layer of fibroelastic CT containing vasa vasorum (blood vessels), lymph vessels and nerves

Question 16

Describe the features of muscular arteries

Answer 16

They are narrower than elastic ones
The tunica intima - endothelium + thick internal elastic lamella
Tunica media - 40 layers of SM. Cells connected by gap junctions to allow for coordinated contraction
Tunica adventitia - thin layer of fibroelastic CT

Question 17

Explain how vasoconstriction occurs in muscular arteries

Answer 17

Noradrenaline realised at nerve endings diffuses through fenstratioms in external lamina into tunica media.
Depolarisation is propagated to all cells via gap junctions.

Question 18

What are end arteries?

Name an example

Answer 18

These are the terminal arteries that supply blood directly to a body part.
E.g coronary arteries

Question 19

What are arterioles?

Answer 19

Arteries with a diameter >0.1nm
Only 1-3 layer of SM
EEL is absent
They direct blood flow by vasoconstriction/dilation

Question 20

What are metarterioles?

Answer 20

These supply blood to capillary bed.

Smooth muscle is not continuous

Question 21

What are precapillary sphincters?

Answer 21

This is when the smooth muscle on the arteriole is present at the endothelium of the capillary only.
When contracted this prevents blood flow to the capillary bed.

Question 22

What a capillaries?

Answer 22

These are narrow vessels (7-10um)

Allowing for the diffusion of metabolic substrates from blood.

Question 23

What are the 3 types of capillary?

Answer 23

Continuous
Fenestrated
Sinusoidal

Question 24

What are the features of continuous capillaries?

Answer 24

Most common type
Present in nervous, muscle and connective tissue
Continuous endothelial layer - cells joined by occlusion junctions

Question 25

Features of fenestrated capillaries …

Answer 25

Little windows (interruptions) across thin parts of endothelium 
Bridged by a thin diaphragm 
Present in parts of the gut, endocrine glands etc

Question 26

Features of Sinusoidal capillaries…

Answer 26

Larger in diameter
Caps exist in walls allowing while cells to move between blood and tissue .
Liver, spleen and bone marrow

Question 27

What are venules?

Answer 27

These are post capillary transport vessels

As they increase in size they gain smooth muscle layer

Question 28

Describe features of veins?

Answer 28

Small and medium veins have well developed adventitia but thin initial and media.
Large veins have thick intima and well developed longitudinal muscle in adventitia.
Superficial veins of the leg have a well defined muscular wall to resist distension caused by gravity.

Question 29

What is a venae comitantes?

Answer 29

Deep paired veins accompanying arteries

3 vessels one sheath