B3.2 Transport

Question 1

What are some adaptations of the arteries?

Answer 1

Arteries have an overall thick wall to withstand high blood pressure and to prevent rupture of the artery wall. They also have a thick layer of elastic tissue to even out and maintain blood pressure, and lastly with increasing distance from the heart, the tunica media (middle layer) progressively contains more smooth muscle fibres and less elastic tissues, because less stretching and recoiling is eeded due to the smaller differences in blood pressure. By varying constriction and dilaltion of arteries, blood flow is maintained. Muscle fibres stretch and recoil, tending to even out the pressure, but a pulse can still be detected.

Question 2

What are some adaptations of veins for the return of blood to the heart

Answer 2

In the vein, there are varying thickness of the walls. Veins generally have thin walls however, the middle layer (tunica media) contains few elastic fibres and muscle fibres because of low pressure. The wall of the vein is also flexible, which allows surrounding muscle to compress the vein, helping in keepng the blood moving.

Blood flows into veins from smaller vessels called venules

Question 3

Name a cause of coronary heart disease

Answer 3

Caused by a build up of plaque under the endothelium in the artery. A “thrombus” or a blood clot is formed where the atheroma hhas broken through the endothelium.

Caused of atherosclerosis (occlusion of the arteries)

Initiall caused by
Diets high in saturates fatty acids which lead to abnormally high blood-cholesterol levels. Excess blood cholesterol may cause atheroschloresis- a progressive degenraton of the artery walls aused by build up of plaque under the endothelium ehich csn turn into a thrombus and break of to become an embolus.

caused by….

1) damage to the artery wall. As fatt tissue is deposited under the endothelium, these atheromas (fatty deposits) significantly reduce the diamater of the lumen.

2) raused blood pressure causes coronary heart disease. Raised blood pressure follows the damage to the artery walls as the fatty tissue starts to impede blood flow. And this damages the vessel wall.

3) Lesion formation

Lesion formation occurs when the smooth lining of the arteries breaks down, lesions are known as atherosclerotic plaques.

4) If the plaque ruptures, blood clotting is triggered. A blood clot is formed within a blood vessel called a thrombus. When a thrombus breaks free and begins to circulate in the blood stream, it is called an embolus.

Question 4

Consequences of atheroschlerosis

Answer 4

Embolus (thrombus; blood clot tht breaks off) is swept into a small artery or arteriole, which is narrower than the diameter of the clot which causes a blockage. Hence, blood supply to tissue downstream is impacted. Tissue downstream does not receie oxygen and dies.

Atheroschlorosis can also cause a myocardial infarction as the heart muscle in this way, reducing its ability to act as an effective pump.

Question 5

What are the advantages of transpiration?

Answer 5

Cooling effect

Firstly, evaporation of water in the sunlight has a strong cooling effect for the plant.

Dissolved Ions

Secondly, the stream of water travelling up from the xylem vessel carries dissolved ions that have been absorbed from soil solutio that are necessary for the plant to grow.

Turgor pressure

Lastly, all cells of a plant receive water by lateral movements of water from xylem vessels. This water is received through pits in the wall. This allows living cells to be fully hydrated.

Additionally- it is the turgor pressure that is created from this hydration and that provides support for the whole leaf and enables leaf blade to receive maximum exposure to sunlight.

Question 6

List the features of root cells that facilitate absorption of water from soil

Answer 6

Mass flow, diffusion through the symplast pathway, osmosis through vauuolar pathway.

(of water occuring through the interconnecting free spaces between cellulose fibres and plant cells), Diffusion occuring through the cytoplasm of cells through plasmodesmata. Osmosis occuring through symplast pathway (living cell pathway, in contrast to apoplast pathway, non living things pathway).

Question 7

What are some adaptations of xylem vessels for transport o water?

Answer 7

Firstly, xylems have thickened walls stregthened by lignin. As lignin is waterproof, it stops water from escaping the vessels.

Secondly, pits in the walls allow for entry of water and lateral movement between vessels.

OR

Adaptations of xylem allow for

unimpeded flow of water and mineral due to lack of cell contents or absent cell walls

Ability to wishstand tension through lignified walls as they are waterproof also preventing loss of water from vessel

Xylem vesses also have pits which allow entry and exit of water.