Problem 53 - Objective Biology for NEET

Question

Blood vessel draining the glomerulus in a mammalian nephron is called (a) Afferent arteriole and is narrower than the vessel entering it. (b) Efferent venule and is narrower than the vessel entering it. (c) Efferent arteriole and is narrower than the vessel entering it. (d) Renal artery and is wider than the vessel entering it.

Step-by-Step Solution

Answer

The blood vessel that drains the glomerulus in a mammalian nephron is the efferent arteriole and is narrower than the vessel entering it. (Option c)

Step 1: Understanding the Function of a Mammalian Nephron

In the context of the mammalian urinary system, the nephron acts as the functional unit of the kidney, which filters blood to produce urine. It consists of blood vessels and tubules.

Step 2: Identifying the Blood Vessel Draining the Glomerulus

The glomerulus is a tiny cluster of blood vessels where the filtration of blood occurs. The blood vessel that drains the glomerulus and carries filtered blood away from this cluster is the efferent arteriole.

Step 3: Comparing the Relative Widths

The width of the efferent arteriole as compared to the vessel entering it, which is the afferent arteriole, is narrower. This constriction creates high pressure within the glomerulus, facilitating filtration.

Key Concepts

Glomerulus Filtration

Understanding how our kidneys cleanse our blood is crucial to appreciating our overall health. Let's dive into one of the core functions: glomerulus filtration. This is a sophisticated process that occurs in the nephrons, the kidney’s microscopic functional units.

In this process, blood flows into the glomerulus, a tiny ball-shaped cluster of capillaries, through the afferent arteriole. The glomerulus acts like a sieve, thanks to its semi-permeable membrane. It filters out waste, excess salts, and water from the blood, while preventing large molecules like proteins and blood cells from passing through.

Imagine squeezing a sponge full of water; that's akin to what happens when blood pressure forces these substances out of the bloodstream and into the Bowman's capsule, the next stage in the filtration journey.

Efferent Arteriole

The efferent arteriole is a critical blood vessel in the nephron's filtration squadron. Following the filtration in the glomerulus, this vessel is the exit route for the remaining blood that didn't become part of the urine.

It's narrower than the afferent arteriole, which is important because the size difference between the efferent and afferent arterioles ensures a greater pressure in the glomerulus. This high pressure is essential for effective filtration. Additionally, after the efferent arteriole carries blood away from the glomerulus, it branches out to form a network around the nephron tubules for further exchange of substances, underlining its role in efficient kidney function.

Afferent Arteriole

The afferent arteriole serves as the kidney nephron's entrance for blood to be filtered. It's wider than the efferent arteriole and is responsible for bringing blood into the glomerulus. The width of the afferent arteriole allows a substantial volume of blood to enter the glomerulus under high pressure, which is necessary for the filtration process.

Adjustments in the diameter of the afferent arteriole can regulate blood flow and pressure into the nephron, thus controlling the efficiency of glomerular filtration. This adjustability is a testament to the dynamic nature of kidney function and its ability to respond to the body's changing needs.

Kidney Function in Mammals

The mammalian kidney is an architectural marvel when it comes to maintaining homeostasis - the body's balanced internal state. Essentially, kidneys perform several vital functions beyond just creating urine.

They regulate blood pressure, balance electrolytes, and manage the body's fluid levels. They also act as a natural filter of the blood, ensuring that wastes and toxins are excreted while valuable substances like glucose and amino acids are reabsorbed.

These functions are all made possible through the harmonious work of millions of nephrons, where the glomerulus filtration marks the beginning of the urinary formation process. Without this intricate system, mammals - including humans - could not sustain life, as the accumulation of wastes would be detrimental to their health.