During embryonic development of human, limbs, and digits are formed during

Options

A. First month of pregnancy
B. Second month of pregnancy
C. Third month of pregnancy
D. Seventh month of pregnancy

Answer

To determine when limbs and digits are formed during human embryonic development, we can follow these steps:

### Step 1: Understand the Germ Layers
- The human embryo consists of three germ layers: ectoderm, mesoderm, and endoderm. The limbs and digits develop from the mesoderm layer.

**Hint:** Remember that the mesoderm is responsible for forming muscles, bones, and limbs.

### Step 2: Identify Limb Development Timeline
- Limb development begins with the formation of limb buds. These limb buds appear as small elevations on the embryo.

**Hint:** Focus on the timeline of limb bud appearance in relation to pregnancy weeks.

### Step 3: Limb Bud Formation
- Limb buds start to appear at the end of the fourth week of gestation. This is when the initial structures for limbs begin to form.

**Hint:** Keep track of the specific week when limb buds first appear.

### Step 4: Development Progression
- Most of the significant development of the limbs occurs around the sixth week of gestation. By this time, the basic structure of the limbs is being formed.

**Hint:** Note that the sixth week is crucial for limb development.

### Step 5: Differentiation of Limbs and Digits
- By the end of the eighth week of gestation, the limbs and digits can be distinguished, although they may still appear webbed.

**Hint:** Understand that differentiation occurs over a few weeks, culminating around the eighth week.

### Step 6: Conclusion
- Based on the above information, we conclude that the formation of limbs and digits occurs primarily during the second month of pregnancy, specifically by the end of the second month.

**Final Answer:** The correct option is the second month of pregnancy.

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