Which of the following statements (s) regarding the cardiac system is/are correct ?
(i) Human heart is an ectodermal derivative
(ii) Mitral valve guards the opening between the right atrium and left ventricle
(iii) SAN is located on the left upper corner of the right atrium
(iv) Stroke volume `xx` Heart rate = Cardiac output.

Options

A. A) (i) only
B. B) (i) and (ii)
C. C) (ii) and (iii)
D. D) (iv) only

Explanation

To determine which statements regarding the cardiac system are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement (i)
**Statement:** Human heart is an ectodermal derivative.
**Analysis:** The human heart is not derived from the ectoderm; it is derived from the mesoderm. The heart forms during embryonic development from the mesodermal layer. Therefore, this statement is **incorrect**.

### Step 2: Analyze Statement (ii)
**Statement:** Mitral valve guards the opening between the right atrium and left ventricle.
**Analysis:** The mitral valve, also known as the bicuspid valve, is located between the left atrium and the left ventricle, not between the right atrium and the left ventricle. Thus, this statement is also **incorrect**.

### Step 3: Analyze Statement (iii)
**Statement:** SAN is located on the left upper corner of the right atrium.
**Analysis:** The Sinoatrial Node (SAN) is located in the right atrium, but it is not specifically in the left upper corner; it is generally positioned at the upper wall of the right atrium. Therefore, this statement is **incorrect**.

### Step 4: Analyze Statement (iv)
**Statement:** Stroke volume × Heart rate = Cardiac output.
**Analysis:** This statement is correct. Cardiac output is defined as the volume of blood pumped by the heart per minute, and it is calculated by multiplying the stroke volume (the amount of blood ejected by each ventricle per contraction) by the heart rate (the number of heartbeats per minute). Therefore, this statement is **correct**.

### Conclusion
After analyzing all the statements:
- Statement (i) is incorrect.
- Statement (ii) is incorrect.
- Statement (iii) is incorrect.
- Statement (iv) is correct.

Thus, the only correct statement is (iv).

### Final Answer:
The correct answer is **(iv) only**.

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