Question

Which one of these is not a part of uriniferous tubule? (a) Loop of Henle (b) Collecting duct (c) Bowman's capsule (d) Distal convoluted tubule

Short answer

The option (b) Collecting duct is not a component of the uriniferous tubule.

Step-by-step solution

Identify the Components of the Uriniferous Tubule

The Uriniferous tubule is composed of parts of the nephron, namely Bowman's capsule, proximal convoluted tubule, Loop of Henle, and distal convoluted tubule.

Check the options

Check each option against the known components of the uriniferous tubule.

Identify the Incorrect Option

From the given options, the Collecting duct is part of the kidney nephron but not considered a part of the uriniferous tubule as it collects urine from multiple nephrons.

Key concepts

Nephron

The nephron is the fundamental structural and functional unit of the kidney. It's responsible for filtering blood, reabsorbing nutrients, and excreting waste products as urine. Each kidney contains over a million nephrons working together in harmony.

A nephron is comprised of several key components, including:

• Bowman's Capsule: This is where the filtration of blood begins.
• Proximal Convoluted Tubule: Reabsorbs water, ions, and nutrients back into the bloodstream.
• Loop of Henle: Concentrates the urine by reabsorbing water.
• Distal Convoluted Tubule: Further regulates potassium, sodium, and calcium levels.

Typically, nephrons help regulate blood pressure, electrolytes, and waste products. They are your body’s internal filtration system, working continuously to maintain balance.

Loop of Henle

The Loop of Henle is a critical part of the nephron that plays a significant role in concentrating urine and conserving water. It is a U-shaped structure that extends into the inner part of the kidney.

The Loop of Henle consists of:

• Descending Limb: Here, water is reabsorbed from the filtrate into the bloodstream, meaning it becomes more concentrated.
• Ascending Limb: This part is impermeable to water, but allows ions like sodium and chloride to be reabsorbed.

Its unique shape and properties allow the Loop of Henle to create a concentration gradient within the medulla of the kidney. This gradient is essential for the kidney to produce urine that is more concentrated than blood, which helps conserve water in the body and limit urine volume.

Collecting Duct

The Collecting Duct is not actually part of the nephron but plays a critical role in processing and transporting urine. Once the urine moves out of the nephron, it reaches the collecting ducts, which gather urine from multiple nephrons.

The main functions of the Collecting Duct include:

• Transporting urine through the kidney to the renal pelvis.
• Regulating water and electrolyte balance through hormone-controlled reabsorption.

The Collecting Ducts converge to form larger ducts that eventually lead to the ureter, carrying the finally processed urine away from the kidneys. Through processes controlled by hormones like vasopressin, the Collecting Duct can make final adjustments to the urine concentration.

Bowman's Capsule

Bowman's Capsule forms the beginning part of the nephron, where filtration actually starts. It acts like a funnel, collecting the fluid filtered out of the blood by the glomerulus, which it surrounds.

The role of Bowman's Capsule is crucial for:

• Housing the glomerulus: A cluster of capillaries where blood filtration occurs.
• Transferring the filtered liquid (glomerular filtrate) into the proximal convoluted tubule.

Bowman's Capsule ensures that large molecules like proteins and blood cells remain in the bloodstream, while smaller molecules and excess ions move into the nephron to be processed into urine. This selective filtration is the first step in urine formation, setting the stage for further processing down the nephron.