To determine what the glomerular filtrate contains, we can break down the process of glomerular filtration and analyze the components involved.
### Step-by-Step Solution:
1. **Understanding Glomerular Filtration**:
- The first step in urine formation is the filtration of blood in the kidneys, specifically in the glomerulus. This process is known as glomerular filtration.
2. **Filtration Process**:
- Filtration occurs under the influence of glomerular capillary blood pressure. Blood is filtered through three layers:
- **Endothelium of Glomerular Blood Vessels**: The innermost layer.
- **Basement Membrane**: A thin layer that separates the endothelium from the podocytes.
- **Epithelium of Bowman's Capsule**: This layer contains specialized cells called podocytes that have filtration slits.
3. **Components of Blood**:
- During filtration, most constituents of blood plasma are filtered out, except for:
- **Proteins**: Such as albumin and globulin, which are too large to pass through the filtration slits.
- **Blood Cells**: Such as red blood cells (RBCs) and white blood cells, which are also too large to be filtered.
4. **Filtered Substances**:
- The glomerular filtrate typically contains:
- **Water**
- **Electrolytes** (like sodium and potassium)
- **Glucose**
- **Urea**
- **Uric Acid**
- These substances are small enough to pass through the filtration slits.
5. **Evaluating Options**:
- Now, we can evaluate the options given in the question:
1. **Urea, uric acid, and globulin**: Globulin is a protein and is not filtered.
2. **Urea, vitamin C, and RBC**: RBCs are blood cells and are not filtered.
3. **Urea, uric acid, and albumin**: Albumin is a protein and is not filtered.
4. **Urea, uric acid, glucose, and water**: All these substances can be filtered and are present in the glomerular filtrate.
6. **Conclusion**:
- The correct answer is option 4: **Urea, uric acid, glucose, and water**.
