Questions: Touchstone 4 Sophia - Critical Thinking.. Paraphrasing Tool (Ad-Free and No Sign-... UNIT 1 - CHALLENGE 1.3: Blood Vessels anc 3 - Blood Vessels: Capillaries LEARNING OBJECTIVE: Determine the structure and function of capillaries. What properties make a sinusoid capillary especially leaky? a.) Extensive intercellular gaps, large pores, and incomplete basement membranes b.) Complete endothelial linings and basement membranes c.) Extensive intercellular gaps and complete basement membranes. d.) Large pores and tight junctions in their endothelial linings.

The answer is the first one (or A): Extensive intercellular gaps, large pores, and incomplete basement membranes.

Explanation for each option:

a.) Extensive intercellular gaps, large pores, and incomplete basement membranes - This is the correct answer. Sinusoid capillaries are characterized by their high permeability, which is due to the presence of large intercellular gaps, large pores (fenestrations), and an incomplete or absent basement membrane. These features allow for the easy passage of large molecules and even cells between the blood and surrounding tissues.

b.) Complete endothelial linings and basement membranes - This is incorrect. Capillaries with complete endothelial linings and basement membranes are typically continuous capillaries, which are much less permeable than sinusoid capillaries.

c.) Extensive intercellular gaps and complete basement membranes - This is incorrect. While extensive intercellular gaps contribute to permeability, the presence of a complete basement membrane would reduce the overall leakiness, which is not characteristic of sinusoid capillaries.

d.) Large pores and tight junctions in their endothelial linings - This is incorrect. Although large pores contribute to permeability, the presence of tight junctions would limit the passage of substances, which is not a feature of sinusoid capillaries.

Summary: Sinusoid capillaries are especially leaky due to their extensive intercellular gaps, large pores, and incomplete basement membranes, which facilitate the movement of large molecules and cells.