The counter current mechanism involves the transport of …….....to maintain the concentration of……...in medullary interstitium.

Options

A. NaCI and urea
B. KCI and glucose
C. NaCl and water
D. Urea and water

Answer

To solve the question regarding the counter current mechanism, we need to fill in the blanks with the correct terms. Here’s a step-by-step breakdown:

### Step 1: Understand the Counter Current Mechanism
The counter current mechanism is a process that occurs in the kidneys, specifically in the juxtamedullary nephrons. It plays a crucial role in concentrating urine and maintaining the osmotic gradient in the renal medulla.

**Hint:** Remember that the counter current mechanism is primarily associated with the nephron structure and its function in urine concentration.

### Step 2: Identify the First Blank
The first blank asks for what is transported in the counter current mechanism. The primary substance involved in this mechanism is sodium chloride (NaCl). This is because NaCl is actively transported in the ascending limb of the loop of Henle, contributing to the osmotic gradient.

**Hint:** Think about the ions that are involved in creating osmotic gradients in the kidneys.

### Step 3: Identify the Second Blank
The second blank requires us to identify what is being concentrated in the medullary interstitium. The counter current mechanism helps maintain a high concentration of urea in the medullary interstitium, which is essential for the reabsorption of water and the production of concentrated urine.

**Hint:** Consider what waste product is involved in the concentration process within the kidney.

### Step 4: Combine the Answers
Now that we have identified both blanks, we can fill them in:
- The counter current mechanism involves the transport of **NaCl** to maintain the concentration of **urea** in the medullary interstitium.

### Final Answer
The complete statement is: "The counter current mechanism involves the transport of **NaCl** to maintain the concentration of **urea** in the medullary interstitium."

### Summary of Steps:
1. Understand the function of the counter current mechanism.
2. Identify that NaCl is transported.
3. Recognize that urea concentration is maintained.
4. Combine the answers to fill in the blanks.