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Difficulty: MediumHuman Anatomy and Body Systems

Microscopic physiological exchange between the circulating bloodstream and surrounding interstitial tissues requires a vessel wall thin enough to facilitate rapid diffusion. Which blood vessels possess walls consisting of only a single layer of endothelial cells to allow this exchange of gases and nutrients?

  1. A
    Muscular arteries
  2. B
    Arterioles
  3. CapillariesAnswer
  4. D
    Systemic veins

Answer

Capillaries are the microscopic vessels with single-layered endothelial walls that enable the exchange of gases and nutrients with surrounding tissues.
Capillaries are the narrowest blood vessels in the human circulatory system. Their walls consist exclusively of a single layer of endothelial cells and an underlying basement membrane, creating a minimal barrier that allows oxygen, glucose, carbon dioxide, and cellular wastes to diffuse rapidly between the blood and tissue cells.

Step-by-Step Solution

1
Identify the functional requirement described in the scenario
The vessel must permit rapid diffusion of gases and nutrients across its boundary into interstitial fluid.
Efficient passive and active transport across tissue boundaries requires minimal wall thickness according to Fick's law of diffusion.
2
Evaluate the histological structure of the vessel types
Arteries, arterioles, and veins possess multiple tissue tunics including muscular and fibrous layers, whereas capillaries consist solely of a single layer of squamous endothelium.
Only capillaries have the ultra-thin structure necessary for direct gas and metabolic exchange.

Key Concept

Microvascular functional anatomy and capillary exchange in the circulatory system
Estimated Time:45s
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Topics

Human Anatomy and Body Systems

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