Biology Circulation / Transport NUMS 2024
PMDC Verified Question 7 of 54
Which of the following set of characteristics are related to veins?

A. Present, Thick, \(7-9\mu m\)
B. Absent, Thick, \(40-50\mu m\)
C. Present, Thinner, \(40-50\mu m\)
D. Absent, Thinner, \(40-50\mu m\)
A
Present, Thick, 7-9μm
B
Absent, Thick, 40-50 μm
C
Present, Thinner, 40-50 μm
D
Absent, Thinner, 40-50 μm
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Present, Thinner, 40-50 μm
Concept:

Veins are structurally adapted for low-pressure blood return to the heart.

Formula:

None

Solution:

  • Valves: Veins must fight gravity under low pressure, so internal valves are universally present.


  • Wall Thickness: Without high systolic pressure, veins do not need massive muscle layers, rendering their walls thinner than arteries.


  • Diameter: To act as a blood reservoir, veins have large internal lumens, typically ranging from \(40-50\text{ }\mu m\) (or larger in macroscopic veins) compared to microscopic capillaries.


Why other options are incorrect:

  • Options claiming absent valves define arteries. Thick walls define arteries. \(7-9\text{ }\mu m\) perfectly describes the diameter of a single capillary.

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