Which part doesn't constitute internal part of kidney ?

Question

Accepted Answer

The correct option is 4:
The part that does not constitute the internal part of the kidney is the **Alveoli**. The internal structure of the kidney, known as the renal parenchyma, is systematically divided into two main regions: the outer renal cortex and the inner renal medulla. The functional units, the nephrons, span both these regions. Alveoli, however, are tiny, grape-like air sacs located within the **lungs** at the terminal ends of the respiratory system's bronchial tree. Their sole physiological role is the exchange of gases, specifically the diffusion of oxygen into the blood and carbon dioxide out of the blood. They have absolutely no structural or functional relationship with the kidney, which is the organ responsible for filtering blood and producing urine in the excretory system.

The incorrect option is 1:
The **Cortex** is, in fact, the outermost and one of the two major parenchymal regions of the kidney. It is situated directly beneath the kidney's fibrous renal capsule. Structurally, the renal cortex is crucial as it houses the starting sections of every nephron, including the renal corpuscle (glomerulus and Bowman's capsule) and the proximal and distal convoluted tubules. The cortex also forms the renal columns that dip down between the renal pyramids of the medulla. As the main site for initial blood filtration, the cortex is undeniably a key internal component of the kidney.

The incorrect option is 2:
The **Medulla** is the inner region of the kidney parenchyma, located deep to the cortex. This internal section is organized into cone-shaped structures called renal pyramids. The medulla contains vital parts of the nephron not found in the cortex, specifically the loops of Henle and the collecting ducts. Its function is essential for the kidney's ability to concentrate urine by establishing a high solute gradient. Without the medulla, the kidney would be unable to perform its crucial function of water and electrolyte balance.

The incorrect option is 3:
**Nephrons** are not only internal parts but are also the definitive functional units of the kidney. It is estimated that each kidney contains about one million of these microscopic structures. The entire apparatus of the nephron—which includes the renal corpuscle (in the cortex) and the renal tubule (spanning both cortex and medulla)—is contained within the kidney parenchyma. The nephrons perform the essential tasks of filtration, reabsorption, and secretion that create urine. Therefore, a nephron is the most important structural and functional internal element of the kidney.