Question

Arrange the following in sequence of blood entering and leaving the fish heart
A. Bulbus arteriosus
B. Sinus venosus
C. Ventricle
D. Atrium
Choose the correct answer from the options given below:

• A. A - C - B - D
• B. B - D - C - A
• C. B - A - C - D
• D. D - C - B - A

Hint:

Fish Heart Chambers in Series: Sinus Venosus (B) $\rightarrow$ Atrium (D) $\rightarrow$ Ventricle (C) $\rightarrow$ Bulbus arteriosus (A).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Branchial single-circuit circulatory path through the four chambers in series of the teleost branchial heart.
Key Formula or Approach:
\[ \text{Deoxygenated Blood} \longrightarrow \text{Sinus Venosus (B)} \longrightarrow \text{Atrium (D)} \longrightarrow \text{Ventricle (C)} \longrightarrow \text{Bulbus Arteriosus (A)} \longrightarrow \text{Ventral Aorta (Gills)} \]

Step 2: Detailed Explanation:
The single-circuit flow of venous deoxygenated blood through the fish heart:
1. 1. Sinus Venosus (B): Thin-walled chamber collecting deoxygenated systemic venous return from the Ducts of Cuvier and hepatic veins.
2. 2. Atrium (D): Thin-walled muscular chamber receiving blood through the sinoatrial valve.
3. 3. Ventricle (C): Heavily muscular, thick-walled pumping chamber with trabeculae creating systolic pressure.
4. 4. Bulbus Arteriosus (A): Elastic, non-contractile chamber (or conus arteriosus in elasmobranchs) that damps systolic pressure pulses before blood enters the ventral aorta to the gills.
Sequence: B $\rightarrow$ D $\rightarrow$ C $\rightarrow$ A.

Step 3: Final Answer:
Thus, the correct sequence is B - D - C - A, matching option (B).