8: Transport in Humans - Problems Flashcards
Suggest one major role of plasma in our bodies.
As medium for transporting substances.
Explain why the blood cell layer of centrifuged human blood appears dark red. (2)
Y contains red blood cells,
which are red in colour due to the presence of haemoglobin.
The photomicrographs show the cross-sections of two blood vessels X and Y.
Suggest how blood vessels X and Y are adapted to their functions. Support each answer with one observable feature. (4)
The wall of blood vessel X (capillary) is made up of one-cell thick endothelium,
which provides a short distance for rapid diffusion of materials between the blood inside the capillary and the body cells.
Blood vessel Y (artery) has a thick wall
to withstand a high blood pressure.
The photomicrographs show the cross-sections of two blood vessels X and Y.
Cell P can be observed in both blood vessels X and Y. Explain how P is adapted to its function. (3)
Cell P has a biconcave disc shape,
which provides a higher surface area to volume ratio
to facilitate the diffusion of oxygen and carbon dioxide.
The photomicrographs show the cross-sections of two blood vessels X and Y.
Blood vessel Y is found on the surface of the heart wall. Predict the possible effects on heart function if Y is blocked.
The blood supply to the cardiac muscles decreases.
Therefore, the amount of nutrients and oxygen delivered to the cardiac muscles reduces.
The heart fails to pump blood properly. This can lead to coronary heart diseases.
CE 2010 I Q3
The graph below shows the changes in blood pressure and rate of blood flow along different blood vessels.
Compare the blood pressure at X and Y. Suggest three possible reasons for the difference. (4)
The blood pressure at X is much higher than that at Y.
The blood at X is under the pumping action of the heart whereas the blood at Y is not.
The blood at Y has overcome great resistance of the blood vessel walls after travelling a long distance away from the heart.
Some fluid is lost from the blood during the formation of tissue fluid.
The graph below shows the changes in blood pressure and rate of blood flow along different blood vessels.
Describe the rate of blood flow in capillaries, and explain the significance of the rate of blood flow. (3)
The rate of blood flow drops to nearly zero in the capillaries.
This provides more time
for the exchange of materials between the blood in the blood capillaries and body cells.
The graph below shows the changes in blood pressure and rate of blood flow along different blood vessels.
Explain why the blood pressure is the lowest in veins, but a relatively fast rate of blood flow is maintained. (4)
The blood pressure in the vein is the lowest as compared to that in other blood vessels because blood has overcome great resistance as it travels a long distance from the heart.
The rate of blood flow is maintained by the contraction of skeletal muscles lying next to the veins.
The total cross-sectional area of the veins is smaller than that of the capillaries.
Since the volume of blood passing through each section of the blood vessel per unit time is the same, the rate of blood flow increases.
The photograph below shows a dissected human heart.
Explain how structures P and Q maintain a unidirectional blood flow in the heart. (2)
P (tricuspid valves) separates the right atrium from the right ventricle and it closes to prevent the backflow of blood from the right ventricle to the right atrium when muscles in the right ventricle contact.
Q holds P in place to prevent P from turning inside out when the ventricle contracts.
The photograph below shows a dissected human heart.
Compare and explain the thickness of the wall of chambers X and Y. (3)
The muscular wall of chamber Y is thicker than that of chamber X,
which ensures that chamber Y can provide a greater force to pump blood to travel a very long distance to all parts of the body except the lungs,
whereas chamber X pumps blood for only a short distance to the lungs.
The photograph below shows a dissected human heart.
Predict the possible effect on heart function if there is a hole in structure T. (2)
If there is a hole in structure T, oxygenated blood and deoxygenated blood in the two sides of the heart will mix together. The oxygen content in the blood pumped out of the heart will decrease.
The heart has to pump harder to meet the oxygen demand of body cells.
DSE 2015 IB Q11
Although both arteries and veins are blood vessels, they are very different in their structure. Discuss how their structural differences are related to her different wats of maintaining blood flow inside the blood vessels. (8+3)
The table below shows the concentrations of proteins and sodium ions in plasma and tissue fluid.
Describe and explain the difference in concentration of proteins in plasma and that in tissue fluid. (3)
Proteins are found in plasma but not in tissue fluid.
This is because proteins are too large in size,
so they cannot pass through the capillary wall.
The table below shows the concentrations of proteins and sodium ions in plasma and tissue fluid.
Describe and explain the difference in concentration of sodium ions in plasma and that in tissue fluid. (2)
The concentrations of sodium ions in plasma and tissue fluid are the same.
Sodium ions are very small. They are being forced out of the capillary wall into the tissue fluid.
State two importances of tissue fluid. (2)
Tissue fluid provides a constant environment for body cells.
Tissue fluid serves as an important link for the exchange of materials between capillaries and body cells.
The diagram below shows a capillary and the surrounding body cells.
State and explain how protein concentrations differ the following positions: P and R, P and Q. (4)
P and R: The blood at P has a higher protein concentration than the tissue fluid at R.
Plasma proteins in blood are too large to pass through the capillary walls. They cannot enter the tissue fluid, therefore they are not present in position R.
P and Q: The blood at Q has a higher protein concentration than the blood at P.
It is because at Q, some water in the blood is forced out of the capillary walls due to the difference in blood pressure in the capillary and hydrostatic pressure of the tissue fluid, but plasma proteins remain in the capillary.
The diagram below shows a capillary and the surrounding body cells.
Suggest the role of plasma proteins in the return of tissue fluid to capillaries. (3)
The presence of plasma proteins lowers the water potential of the blood in the capillary at the venule end.
There is a net movement of water from the tissue fluid into the blood through the capillary wall
by osmosis, which causes the return of tissue fluid to the capillaries.
Explain why body tissues may swell as tissue fluid accumulates under prolonged starvation. (3)
Starvation leads to a lower protein concentration in the blood because protein is being broken down to release energy to support body activities.
Water potential of the blood is higher than normal, so the water potential gradient between the blood and the tissue fluid becomes less steep. Thus, there is less net movement of water from the tissue fluid to blood inside of the capillary by osmosis.
The rate of formation of tissue fluid exceeds the rate of return of tissue fluid. Therefore, tissue fluid accumulates and the body swells.
The diagram below shows certain structures in the human lymphatic system.
Explain how structure X helps protect our body against diseases. (2)
White blood cells in X kill germs that enter the lymphatic system.
Germs are filtered out from the lymph before the lymph is returned to the blood.
The diagram below shows certain structures in the human lymphatic system.
Suggest how a continuous flow of fluid is maintained in vessel Y. (2)
Lymph is kept flowing very slowly by the contraction of skeletal muscles which surround vessel Y.
Valves are present in vessel Y to prevent the backflow of lymph.
Suggest how blockage of lymph vessels may cause swelling in the legs. (3)
Tissue fluid forms continuously as blood flows along capillaries.
If lymph vessels are blocked, tissue fluid in surrounding tissues cannot be transported away.
The accumulation of tissue fluid results in swelling of legs.
DSE 2017 IB Q11
