Problem 40 - Objective Biology for NEET

Question

Each kidney has (nearly) how many nephrons? (a) 1 million (b) 2 million (c) \(1 / 2\) million (d) 3 million

Step-by-Step Solution

Answer

(a) 1 million

Step 1: Identifying the question

Recognize that the question is asking for the number of nephrons in a single human kidney. Thus, the focus will be on factual knowledge about nephrons in human anatomy.

Step 2: Using biological knowledge

Apply biological knowledge. It is a well known fact in biology that each human kidney contains approximately 1 million nephrons.

Step 3: Choosing the correct answer

Match the fact known from step 2 with the options provided in the question. The correct answer should be (a) 1 million, as this correctly approximates the number of nephrons per kidney in human anatomy.

Key Concepts

Human Anatomy and the Kidneys

Human anatomy is a complex and detailed study of the structure of the human body. A critical part of this study is understanding the renal system, of which the kidneys are a central component. The kidneys are remarkable bean-shaped organs located on either side of the spine, just below the rib cage. Their main function is to filter and remove waste products and excess fluids from the blood through urine production.

Each kidney contains an intricate network of structures that aid in filtration and waste removal. The nephrons, which are the functional units of the kidney, play a pivotal role in this process. Through a series of tubules and associated blood vessels, nephrons filter blood, reabsorb needed substances, and secrete waste. Understanding the intricacy of nephrons and their function is critical in comprehending how the kidneys maintain homeostasis within the body.

Kidney Function and Nephron Activity

The primary function of the kidney is homeostasis—regulating the balance of water, electrolytes, and organic solutes. This is achieved through the filtration of blood plasma and the selective reabsorption and secretion of substances. Central to this function are the nephrons, the micro-machines of the kidneys that make urine formation possible.

A nephron begins with a structure called the Bowman's capsule, which encases a network of capillaries known as the glomerulus. The Bowman's capsule collects the filtrate—fluid containing waste and other substances. This filtrate passes through various segments of the nephron, including the proximal tubule, the loop of Henle, the distal tubule, and finally, the collecting duct. During this passage, a complex interaction of reabsorption and secretion occurs, allowing the body to retain necessary nutrients and eliminate waste. It's these microscopic processes carried out by each nephron that are crucial for the kidneys' life-sustaining tasks.

Nephron Count in Human Kidneys

The number of nephrons within an individual's kidneys is a remarkable testament to the complexity and efficiency of human anatomy. A common textbook exercise is to identify the approximate count of nephrons in a human kidney. Through the biological consensus, we understand that each kidney typically harbors around 1 million nephrons.

It is a fascinating fact that the nephron count remains constant from birth; humans do not produce more nephrons as they grow older. Rather, the body must maintain kidney function throughout life with the nephrons it is born with. The large number of nephrons ensures that the kidneys have a considerable amount of redundancy and resilience. Even if some nephrons become nonfunctional, others can compensate to maintain overall kidney function. This is a fine example of the body's adaptability and the robustness of human anatomy. Notably, the variation in nephron count can influence susceptibility to various kidney diseases, making this information not just a factoid, but also a significant consideration in medical studies and practices.