Question

During the embryonic development, on which day does the human heart starts beating?

• A. 11
• B. 21
• C. 7
• D. 15

Hint:

Important embryological fact: \[ \text{Human embryonic heart begins beating around day } 21 \] The heart is one of the earliest functioning organs in the embryo.

Answer 1

The Correct Option is B

Concept:
Embryonic development is the process by which a fertilized egg develops into a complete human body. During this development, different organs begin forming at different stages. One of the earliest organs to begin functioning is the: \[ \text{Heart} \] The heart is extremely important because it starts circulating blood and nutrients throughout the developing embryo. In humans, the embryonic heart starts beating approximately on the: \[ \boxed{21^{st} \text{ day}} \] after fertilization.

Step 1: Understand embryonic development.
After fertilization:
• Zygote forms
• Cell division begins
• Embryo develops gradually As development progresses:
• Nervous system begins forming
• Heart tube develops
• Circulation begins

Step 2: Identify when heartbeat starts.
Scientific observations show that: \[ \text{Heartbeat starts around the } 21^{st} \text{ day} \] This is approximately: \[ 3 \text{ weeks after fertilization} \] At this stage, the primitive heart starts pumping blood.

Step 3: Analyze all options carefully.
Option (A): 11
Too early for heart development. Incorrect. Option (B): 21
Correct timing of first heartbeat. Correct. Option (C): 7
Embryo is still at very early developmental stage. Incorrect. Option (D): 15
Heart has not fully started beating at this stage. Incorrect.

Step 4: Choose the correct answer.
Therefore, human heart starts beating on: \[ \boxed{21^{st} \text{ day}} \] Hence, \[ \boxed{(2)\ 21} \]