NEET Practice Questions (MCQs) with Answers & Solutions

The process of urine formation in the nephron includes three main mechanisms: ultrafiltration, reabsorption, and secretion. Ultrafiltration occurs in the glomerulus, reabsorption occurs primarily in the proximal tubule, and secretion happens in the distal tubule and collecting duct.

Deamination is the process by which amino acids are broken down in the body to release ammonia (NH4) and carbon dioxide (CO2). This process primarily occurs in the liver. The ammonia released is then converted into urea, which is less toxic and is excreted from the body via the kidneys.

Transamination is a process that occurs primarily in the liver. It involves the transfer of an amino group from one amino acid to a keto acid, forming a new amino acid and a new keto acid. This process is crucial for the synthesis of non-essential amino acids.

The solubility of substances in water can be ranked as follows: NH3 (ammonia) > urea > uric acid. Ammonia is highly soluble in water, followed by urea, and uric acid is the least soluble among the three.

The correct passage of urine involves the following sequence: Duct of Bellini, calyces, ureters, and finally the urinary bladder. Here is a brief explanation of each term:

1. Duct of Bellini: Collects urine from the nephrons.
2. Calyces: Collect urine from the ducts of Bellini.
3. Ureters: Transport urine from the kidneys to the urinary bladder.
4. Urinary bladder: Stores urine until it is excreted through the urethra.

The Loop of Henle and the collecting ducts are primarily located in the medullary pyramids of the kidney. The medulla is the innermost part of the kidney and contains the renal pyramids, which house these structures.

1. Loop of Henle: Extends into the medulla and is crucial for the concentration of urine.
2. Collecting ducts: Pass through the medulla and carry urine to the renal pelvis.

The urine produced by the human kidney is concentrated up to 4 times more than the initial filtrate formed in the nephron. This concentration process occurs mainly in the Loop of Henle and the collecting ducts, where water reabsorption is regulated to produce concentrated urine.

The Renin-Angiotensin-Aldosterone System (RAAS) involves the hormones renin, angiotensin, and aldosterone. Renin is an enzyme that converts angiotensinogen to angiotensin I, which is then converted to angiotensin II. Angiotensin II stimulates the release of aldosterone. Together, these hormones regulate blood pressure and fluid balance.

Atrial Natriuretic Factor (ANF) decreases blood pressure. It is a hormone secreted by the heart's atria in response to high blood pressure. ANF promotes the excretion of sodium and water by the kidneys, leading to a reduction in blood volume and blood pressure.

Renin is secreted by the Juxtaglomerular (JG) cells of the kidney. These cells are located in the walls of the afferent arterioles, which supply blood to the glomerulus. Renin plays a crucial role in the RAAS, regulating blood pressure and fluid balance.