Excretory Products and Their Elimination MCQs for NEET — Zoology Questions with Answers

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.

Angiotensinogen, which is converted to angiotensin I, is secreted by the liver. This protein plays a key role in the renin-angiotensin system, which helps regulate blood pressure and fluid balance.

Secretion of renin from Juxtaglomerular (JG) cells is stimulated by a fall in glomerular blood flow, glomerular blood pressure, and Glomerular Filtration Rate (GFR). Therefore, all these factors contribute to the secretion of renin.

ADH, also known as Antidiuretic Hormone or vasopressin, is secreted by the neurohypophysis, which is the posterior part of the pituitary gland. The neurohypophysis releases ADH in response to signals from the hypothalamus when the body needs to conserve water. This hormone acts on the kidneys to reduce water loss.