Which of the following structures play a significant role in maintaining osmolarity in mammals?

Options

A. Henle's loop and vasa recta
B. Vasa recta and renal pelvis
C. Vesa recta and glomerulus
D. Renal pelvis and collecting duct

Answer

To determine which structures play a significant role in maintaining osmolarity in mammals, we can analyze the options provided in the question.

### Step-by-Step Solution:

1. **Understanding Osmolarity**: Osmolarity refers to the concentration of solutes in a solution. In mammals, maintaining osmolarity is crucial for homeostasis, especially in the kidneys, which play a key role in regulating body fluids.

2. **Identifying Key Structures**:
- **Loop of Henle**: This structure is part of the nephron in the kidney. It consists of a descending limb and an ascending limb. The descending limb is permeable to water but not to solutes, while the ascending limb is impermeable to water and actively transports ions out, which helps in creating a concentration gradient in the medulla.
- **Vasa Recta**: This is a capillary network that surrounds the Loop of Henle. It helps in maintaining the osmolarity by allowing the exchange of water and solutes without disrupting the concentration gradient established by the Loop of Henle.

3. **Analyzing the Options**:
- **Option 1: Loop of Henle and Vasa Recta**: This combination is correct as both structures are involved in maintaining osmolarity.
- **Option 2: Vasa Recta and Renal Pelvis**: The renal pelvis does not play a significant role in osmolarity maintenance.
- **Option 3: Vasa Recta and Glomerulus**: The glomerulus is primarily involved in filtration, not osmolarity maintenance.
- **Option 4: Renal Pelvis and Collecting Duct**: While the collecting duct does play a role in water reabsorption, it is not as significant as the Loop of Henle and Vasa Recta in terms of osmolarity.

4. **Conclusion**: The correct answer is **Option 1: Loop of Henle and Vasa Recta**. These structures work together to maintain osmolarity in mammals by regulating the concentration of solutes and water in the kidney.