What are the different steps that are involved in formation of urine?

Explanation

To understand the formation of urine, we can break it down into three main steps:

### Step 1: Ultrafiltration
- The first step in urine formation is ultrafiltration, which occurs in the glomerulus of the nephron. Blood enters the glomerulus under high pressure, and this pressure forces water, ions, and small molecules (like glucose and urea) through the glomerular membrane into the Bowman's capsule. Larger molecules, such as proteins and blood cells, are retained in the blood.

### Step 2: Selective Reabsorption
- The second step is selective reabsorption, which primarily takes place in the proximal convoluted tubule (PCT). In this step, essential substances such as glucose, amino acids, and a significant amount of water and ions (like sodium) are reabsorbed back into the bloodstream. This process ensures that valuable nutrients are not lost in urine.

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