Question

arrange the structures in the following list in the order that blood will encounter as it flows from the output side of the heart to the input side of the heart.

1. venules
2. arterioles
3. capillaries
4. elastic arteries
5. medium veins
6. large veins
7. muscular arteries

a) 7,4,2,3,1,5,6
b) 6,5,1,3,2,7,4
c) 5,6,1,3,2,7,4
d) 2,7,6,3,1,5,6
e) 4,7,2,3,1,5,6

Explanation:

Trace the arterial outflow

Blood leaves the heart's output side (ventricles) via large, highly distensible vessels. These are the elastic arteries (4). From there, blood flows into medium-sized distributing vessels, known as muscular arteries (7).

Trace the microcirculation

From muscular arteries, blood enters smaller resistance vessels called arterioles (2). Arterioles deliver blood directly to the exchange network, which consists of capillaries (3).

Trace the venous return

After exchange occurs in the capillaries, blood is collected by the smallest venous vessels, the venules (1). Venules merge into medium veins (5), which then drain into large veins (6) returning blood to the input side of the heart (atria).

Synthesize the complete sequence

Combining these stages in order from output to input yields:

1. Elastic arteries (4)
2. Muscular arteries (7)
3. Arterioles (2)
4. Capillaries (3)
5. Venules (1)
6. Medium veins (5)
7. Large veins (6)

This corresponds to the sequence: 4, 7, 2, 3, 1, 5, 6.

Match with options

Comparing our sequence \(4, 7, 2, 3, 1, 5, 6\) to the choices:

• Option A: 7, 4, 2, 3, 1, 5, 6
• Option B: 6, 5, 1, 3, 2, 7, 4
• Option C: 5, 1, 3, 2, 7, 4
• Option D: 2, 7, 6, 3, 1, 5, 6
• Option E: 4, 7, 2, 3, 1, 5, 6

Option E is the correct match.

Answer:

• A) 7,4,2,3,1,5,6
• B) 6,5,1,3,2,7,4
• C) 5,1,3,2,7,4
• D) 2,7,6,3,1,5,6
• E) 4,7,2,3,1,5,6 (Correct answer)