Intro

Question 1

Why do we need a cardiovascular system?

Answer 1

• All living cells are metabolically active
– use O2 and produce CO2
• Single-celled or tiny organisms can get O2 and nutrients directly by diffusion from environment
• Larger organisms need a system for getting the oxygen and nutrients close to the cells

Question 2

What happens if left ventricle uncle walls are damaged?

Answer 2

• The left ventricle is filled with oxygenated blood
• BUT - The distance of the cells from the source of O
means that the muscle wall of the left ventricle will be seriously damaged if the vessels supplying it are blocked

Question 3

What is the purpose of the CVS?

Answer 3

• The cardiovascular system carries oxygen and
nutrients to the capillaries to allow diffusion to
take place

Question 4

What is the structure of capillaries?

Answer 4

• Capillaries are composed of a single layer of

endothelial cells surrounded by basal lamina

Question 5

What factors affect diffusion?

Answer 5

• Rate of diffusion depends on:
– Area available for exchange
– Diffusion ‘resistance’ - nature of the barrier
– Concentration gradient

Question 6

What does area available for diffusion depend on?

Answer 6

• Area for exchange between capillaries and tissues is generally very large
– it depends on capillary density
- not all tissues have the same density

• A tissue which is more metabolically active will have more
capillaries
– Higher capillary density

Question 7

What does the conc gradt depend on?

Answer 7

• A substance which is used by the tissues will have a lower concentration in capillary blood than arterial blood capillary blood flow venous end arterial end
• How much lower depends on
– rate of use by the tissue
– rate of blood flow through the capillary bed
• The lower the blood flow, the lower the capillary concentration
• Blood flow must be high enough to maintain a sufficient concentration gradient
• The rate of blood flow determines the concentration gradient driving O2 diffusion into the cells

Question 8

What increases the demand for O2 and what is the rate of blood flow known as?

Answer 8

• Blood flow must match the tissues’ metabolic needs
– the higher the rate of metabolism the greater the demand for O2 and nutrients
– increases in metabolism must be met by increases in blood flow
– the rate of blood flow is known as the perfusion rate

Question 9

Describe the blood flow to brain, heart, kidneys and skeletal muscle

Answer 9

Blood flow to different tissues

• Brain needs high, constant flow - if cut off, lose consciousness, if cut off for a long time then neurones can die
– 0.5 ml.min-1.g-1

• Heart muscle needs high flow which increases during exercise
– 0.9 to 3.6 ml.min-1.g-1

• Kidneys need high, constant flow
– 3.5 ml.min-1.g-1

• Blood flow to skeletal muscle can be very high during exercise and gut blood flow is high after a meal

Question 10

What is the in and max flow in lmin^-1

Answer 10

70kg man
Min 5lmin^-1
Max 24lmon^-1 - eg during exercise

Question 11

Name some coronary arteries and veins and describe their position

Answer 11

See slide