transport in animals

Question 1

Artery structure and function

Answer 1

Function: carry blood away from the heart under high pressure (so they have to withstand this pressure and force).

Structure: (Thicker) elastic layer / elastin, enables them to withstand, pressure / force.

(Thicker) elastic layer / elastin, enables them to, stretchrecoil. Ref . elastic layer evens out surges from the pumping of the heart and allows a continuous flow of blood (Windkessel effect).

Collagen provides, structure / support.Collagen maintains shape and volume (limiting stretch).

Smooth muscle contracts and relaxes to, change the size of the lumen / control blood pressure.Smooth muscle provides strength to withstand the pressure

Question 2

Outline the three ways in which carbon dioxide can be transported around the body, ready for excretion.

Answer 2

Dissolved in plasma

Carried as hydrogen carbonate; In erythrocytes;
Carbon dioxide + water = hydrogen carbonate;
Hydrogen carbonate dissociates; H+ combines with haemoglobin to form haemoglobinic acid;

Causes oxygen to dissociate / chloride shift Combined with haemoglobin; As carbaminohaemoglobin;

Question 3

Describe how the action of the heart is initiated and coordinated

Answer 3

SAN generates a wave of excitation
spreads over the atrial walls and atrial systole occurs
there is then an delay due to the non conductive tissue layer allowing atria to fully contract
AVN then sends a wave of excitation down the bundle of his to the apex
spreading across the ventricle walls to allow ventricle systole and for them to fully contract

Question 4

vein structure and function

Answer 4

Function: Veins carry blood back to the heart.No, pulse / surge from heart. Blood in veins is under less pressure (than in arteries). Needs to move against gravity.

Structure: Thinner elastic layer (no, stretch / recoil / pulse).
Have valves to prevent backflow of blood.
More collagen than arteries to give structural support as they carry large volumes of blood.

Question 5

capillary structure and function

Answer 5

Function: Allow substances, to be exchanged / diffuse, between blood and, tissue fluid / surrounding cells.

Structure:
Walls are one cell thick. Short diffusion distance.

Only large enough to allow red blood cells to travel through in single f ile (to increase contact of RBCs with capillary wall).

Small enough to form network needed to exchange substances.