What is the difference between continuous and fenestrated capillaries?

• A. Continuous capillaries have a complete endothelial lining; fenestrated capillaries have windows or pores.
• B. Continuous capillaries have pores; fenestrated capillaries have a complete lining.
• C. Fenestrated capillaries have no endothelium.
• D. Fenestrated capillaries are thicker and stronger than continuous Capillaries.

Answer: (A)

The main idea here is how the lining of the capillary wall determines what can pass through. Continuous capillaries have a complete endothelial lining with tight junctions, so they are relatively less permeable and substances mainly move through the cell membranes or by small vesicles. Fenestrated capillaries, on the other hand, have small pores (fenestrae) in the endothelial layer, sometimes with diaphragms, which create more open pathways for rapid exchange of smaller molecules. This structural difference makes fenestrated capillaries especially suited for areas that require quick transfer of substances, like the kidneys, the intestinal lining, endocrine glands, and the choroid plexus. So, the defining contrast is the presence of window-like pores in fenestrated capillaries versus the continuous, pore-free lining in the others.