Explain why red blood cells can be kept intact when they are placed in a normal saline solution.
In blood, red blood cells are suspended within plasma. The chief constituent of blood plasma is water. Suggest one further plasma component that may enter red blood cells and describe the way it would pass through the cell surface membrane.
The true diameter of the capillary lumen at point X-Y in Fig. 3.2 is $9.5\,\mu\text{m}$. Calculate the magnification of the image shown in Fig. 3.2. Show your working.
With reference to Fig. 3.2, explain one feature that allows the surrounding body cells to receive a sufficient supply of oxygen from the blood carried by the capillary.
Some regions of the brain, called blood-brain barriers, contain a capillary type that is relatively impermeable to substances. Suggest one way in which the structure of a capillary in the blood-brain barrier is different from the capillary shown in Fig. 3.2.