To supply oxygen and nutrients efficiently to cells, the mammalian mass transport system branches from a single large aorta into a vast network of capillaries. Which of the following correctly describes how the total cross-sectional area and the velocity of blood flow change from the aorta to the capillaries, and explains the primary physiological benefit of this change for supplying cells?
Total cross-sectional area increases, and velocity of blood flow decreases. This slower flow rate provides sufficient time for the diffusion of gases and nutrients across the capillary walls to supply the cells.
Total cross-sectional area decreases, and velocity of blood flow increases. This rapid flow rate ensures a constant, rapid delivery of oxygenated blood directly to tissues with high metabolic demands.
Total cross-sectional area increases, and velocity of blood flow increases. This maintains high hydrostatic pressure throughout the capillary bed, maximizing ultrafiltration and nutrient delivery.
Total cross-sectional area remains constant, and velocity of blood flow decreases. This stabilizes the blood pressure, preventing the thin capillary walls from rupturing under high mechanical stress.
82 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.