Question

Which of the following is the functional unit of the kidney?

• A. Nephron
• B. Neuron
• C. Axon
• D. Neurilemma

Hint:

Remember to differentiate between similar-sounding biological terms. Nephron relates to the kidney (excretory system), while neuron relates to the nervous system.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the fundamental structural and functional unit of the kidney.

Step 3: Detailed Explanation:
- Nephron: The nephron is the microscopic structural and functional unit of the kidney. It is responsible for filtering blood, reabsorbing essential substances, secreting waste products, and forming urine. Each human kidney contains about one million nephrons.
- Neuron: A neuron is the basic functional unit of the nervous system.
- Axon: An axon is a long, slender projection of a nerve cell (neuron) that typically conducts electrical impulses away from the neuron's cell body.
- Neurilemma: This is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of some nerve cells.
Based on these definitions, the nephron is clearly the functional unit of the kidney.

Step 4: Final Answer:
The functional unit of the kidney is the nephron.

Answer 2

A quick way to sort these four options is to first notice which ones belong to the nervous system and which one belongs to the excretory system, and then look at the nephron's own structure in more depth.

1. Nephron: The nephron is the microscopic structural and functional unit of the kidney, made up of a Bowman's capsule surrounding a glomerulus (a tuft of capillaries), followed by the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and a collecting duct. Together these parts carry out filtration of blood, selective reabsorption of useful substances, secretion of wastes, and concentration of urine. Each human kidney contains roughly a million nephrons working in parallel.
2. Neuron: A neuron belongs to the nervous system, not the excretory system. It is the basic unit responsible for generating and transmitting electrical impulses, and has nothing to do with blood filtration in the kidney.
3. Axon: An axon is just one part of a neuron, the long fibre that carries impulses away from the cell body. It is a component of the nervous system, again unrelated to kidney function.
4. Neurilemma: This is the thin outer sheath of Schwann cells that wraps around the axons of peripheral neurons, helping in impulse conduction and nerve fibre regeneration. Like the other two wrong options, it belongs to the nervous system, not the kidney.

Three of the four options are all parts of the nervous system, leaving the nephron as the only structure connected to the kidney, and it is indeed the kidney's basic structural and functional unit.

Therefore, the correct answer is Nephron.