Which are derivatives of endoderm?

Options

A. Muscles and blood
B. Alimentary canal and respiratory organs
C. Excretory and reproduction organs
D. Skin and nerve cord.

Answer

To determine the derivatives of the endoderm, we can follow these steps:

### Step 1: Understand the three germ layers
The human embryo has three primary germ layers: ectoderm, mesoderm, and endoderm. Each layer gives rise to different tissues and organs in the body.

### Step 2: Identify the derivatives of the endoderm
The endoderm primarily forms the lining of the gastrointestinal tract and associated organs. It also contributes to the formation of the respiratory system. Key derivatives include:
- Elementary canal (which includes the stomach and intestines)
- Respiratory organs (such as lungs)

### Step 3: Evaluate the options given in the question
Now, let’s analyze the options provided:
- **Option A**: Muscles and blood - These are derived from the mesoderm, not the endoderm.
- **Option B**: Elementary canal and respiratory organs - These are indeed derivatives of the endoderm.
- **Option C**: Excretory and reproductive organs - The excretory organs are derived from the mesoderm, while reproductive organs also originate from the mesoderm.
- **Option D**: Skin and nerve cord - Both of these are derived from the ectoderm.

### Step 4: Conclusion
Based on the analysis, the only option that correctly lists the derivatives of the endoderm is **Option B: Elementary canal and respiratory organs**.

### Final Answer:
**Option B: Elementary canal and respiratory organs.**

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