Problem 98 - Objective Biology for NEET

Question

The number of nephrons in a kidney is equal to the (a) Number of Bowman's capsules (b) Sum of Bowman's capsules and glomeruli (c) Double the number of Bowman's capsules (d) Sum of Bowman's capsules and Malpighian corpuscles

Step-by-Step Solution

Answer

The correct answer is (a) Number of Bowman's capsules

Step 1: Understanding the structure of a Nephron

Each nephron in the human kidney consists of a glomerulus and a Bowman's capsule. The glomerulus is a network of capillaries that perform the filtration of blood. The filtered blood (filtrate) is collected in the Bowman's capsule.

Step 2: Relation between number of Nephrons and Bowman's capsules

Since each nephron consists of one Bowman's capsule, it's logical to conclude that the number of nephrons in a kidney is equal to the number of Bowman's capsules.

Key Concepts

Kidney structure

The kidney is a vital organ that plays an essential role in filtering waste products from the blood and excreting them in the form of urine. Each kidney contains a myriad of microscopic structures called nephrons, which are the basic functional units responsible for the kidney's filtration work. The kidney's internal structure is specifically designed to optimize this filtration process.

• The cortex is the outer part of the kidney, where most of the nephrons are located.
• Deeper within lies the medulla, which hosts the renal pyramids and helps conduct filtered substances toward the ureter.
• The renal pelvis acts as a funnel to direct the urine from the kidneys into the ureters.

Each kidney typically contains around one million nephrons, highlighting the efficiency and capacity of this organ. The sophisticated arrangement of the kidney's structure allows it to regulate blood pressure, electrolyte balance, and the body's overall fluid balance effectively.

Bowman's capsule

Bowman's capsule is a critical component of the nephron's filtering mechanism. It's a cup-like sac that surrounds the glomerulus within the nephron. Positioned in the kidney's cortex, it plays a crucial role in the initial stages of filtration.

The primary function of Bowman's capsule is to collect the filtrate that drips out of the glomerulus. This filtrate includes waste products, salts, glucose, and other small molecules, but not large proteins or cells. Here's how the filtration process works:

• The blood enters the nephron via an afferent arteriole.
• Inside, the glomerulus acts as a fine filter, where blood pressure forces water and dissolved substances into Bowman's capsule.
• The collected filtrate then passes into the proximal tubule for further processing.

This design ensures that only necessary substances are kept while unwanted material is expelled as urine, making the Bowman's capsule a pivotal structure in kidney function.

Glomerulus

The glomerulus is a tiny, yet fascinating part of the nephron situated inside Bowman's capsule. It consists of a tuft of microscopic blood vessels or capillaries, where the filtration of blood actually takes place. The arrangement of these capillaries is akin to a finely woven net, designed to maximize the surface area available for filtration.

Filtration in the glomerulus is driven by blood pressure, allowing small molecules, such as water, ions, and waste products, to pass through while retaining larger molecules and blood cells within the circulation. Here's a closer look at the glomerulus:

• It receives incoming blood from the afferent arteriole.
• Blood pressure is crucial here, as it propels the plasma through the glomeruli's walls.
• The filtered fluid, now known as glomerular filtrate, enters Bowman's capsule.
• The remaining blood exits via the efferent arteriole, continuing onward within the renal circulation.

The glomerulus acts as the initial step in the process of removing waste products from the bloodstream, making it indispensable to the body’s ability to maintain homeostasis.