Module 3: Transport in Animals

Question 1

Open circulatory system

Answer 1

Blood not always held in blood vessels but instead blood fluid circulates through the body cavity

Question 2

Closed circulatory system

Answer 2

The blood is maintained inside vessels

Question 3

Single circulatory system

Answer 3

Blood passes through the heart once for each circuit of the body

Question 4

Double circulatory system

Answer 4

Blood passes through the heart twice for each circuit of the body

Question 5

Structure and function of arteries

Answer 5

Function
Carry blood away from the heat
Structure
Thick artery wall to withstand pressure
Small lumen to maintain high pressure
Inner wall folded to allow Lumen to expand as blood flow increases

Question 6

Structure and function of arterioles

Answer 6

Function
Distribute blood from arteries to capillaries
Structure
Contains smooth muscles which when it contracts, can divert the flow of blood to regions of the body demanding more oxygen

Question 7

Structure and Function of Capillaries

Answer 7

Function
Allow exchange of materials between blood and tissue fluid
Structure
Walls consist of flattened endothelium cells- reduces diffusion distance for materials being exchanged
Walls are leaky- allow blood plasma and dissolved substances to leave the blood
Lumen is narrow- helps transfer of oxygen as it reduces diffusion path to tissues

Question 8

Function of venules

Answer 8

Collect blood from the capillary bed and lead into the veins

Question 9

Structure and function of Veins

Answer 9

Function
Carry blood  back to the heart
Structure
Lumen is large to ease flow of blood
Contain valves to prevent the back flow of blood

Question 10

Formation of tissue fluid

Answer 10

1. At the arteriole end of the capillary water moves out the plasma and into the tissue fluid due to high hydrostatic pressure
2. When water moves out of blood plasma, it takes dissolved molecules with it. Proteins and erythrocytes too large
3. Neutrophils can move into the tissue fluid through the small gaps between the cells of the capillary endothelium
4. At the venous end of the capillary, the water moves out of the tissue fluid and back into the plasma due to high oncotic pressure

Question 11

Events in Diastole

Answer 11

Both atria and ventricles relax
Pressure in arteries is higher than the pressure in ventricles so semi-lunar valves close
Blood flows into the atria

Question 12

Events in atrial systole

Answer 12

Both the atria contract at the same time
Pressure in atria is higher than the pressure in the ventricles
Blood flows through open AV valves into the ventricles

Question 13

Events in ventricular systole

Answer 13

Both ventricles contract at the same time
Pressure in the ventricles is higher than pressure in atria and arteries leaving heart causing AV valves to close and semi-lunar valves in artery to open
Blood leaves heart

Question 14

How is heart action initiated

Answer 14

SAN sends a wave of excitation across both of the atria, causing them to contract at the same time.
At the top of the septum the AVN, after a short delay, sends the wave of excitation along the purkyne tissue in the septum to the apex
This causes ventricles to contract from apex upwards