Pa of the kidney unit involved in As. Poisoning-
**Core Concept**
The kidney plays a crucial role in the excretion of various toxins, including arsenic (As). The renal unit involved in As poisoning involves the glomeruli and the renal tubules, particularly the proximal convoluted tubules (PCTs). The PCTs are responsible for the reabsorption and secretion of various substances, including ions and small molecules.
**Why the Correct Answer is Right**
Arsenic poisoning occurs when the body accumulates excessive amounts of arsenic, which can be due to environmental exposure or ingestion of contaminated food and water. The renal system is responsible for the elimination of arsenic from the body. In the glomeruli, arsenic is filtered from the blood and enters the nephron. The PCTs then play a key role in the reabsorption and secretion of arsenic. The PCTs contain specific transporters, such as the sodium-dependent arsenite transporter (AQP9), which facilitate the movement of arsenic across the cell membrane. The proximal convoluted tubules also contain enzymes, such as glutathione S-transferase, which help to detoxify arsenic.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the medulla does not play a direct role in the excretion of arsenic.
**Option B:** This option is incorrect because the distal convoluted tubules (DCTs) are not primarily responsible for the excretion of arsenic.
**Option C:** This option is incorrect because the collecting ducts are not directly involved in the excretion of arsenic.
**Clinical Pearl / High-Yield Fact**
The kidneys are the primary organs responsible for the elimination of arsenic from the body. Prolonged exposure to arsenic can lead to renal damage and increased risk of kidney disease.
**Correct Answer: C. Proximal Convoluted Tubules (PCTs)**