In each nephron of the kidney, the glomerulus and Bowman's capsule
a. Filter the blood and capture the filtrate.
b. Reabsorb water into the blood.
c. Break down harmful toxins and poisons.
d. Refine and concentrate the urine for excretion.

Verified step by step guidance

1. Understand the structure and function of the nephron, which is the functional unit of the kidney. The nephron is responsible for filtering blood, reabsorbing essential substances, and excreting waste products.
2. Focus on the glomerulus and Bowman's capsule, which are the initial components of the nephron. The glomerulus is a network of capillaries, and Bowman's capsule is a cup-shaped structure surrounding the glomerulus.
3. Learn the process of filtration: Blood enters the glomerulus under pressure, and small molecules like water, ions, glucose, and waste products are filtered out of the blood into Bowman's capsule. Larger molecules like proteins and blood cells remain in the bloodstream.
4. Clarify that the filtrate collected in Bowman's capsule is the starting point for further processing in the nephron, including reabsorption and secretion, but the glomerulus and Bowman's capsule themselves do not reabsorb water or refine urine.
5. Eliminate incorrect options by understanding that the glomerulus and Bowman's capsule are specifically involved in filtration, not toxin breakdown, water reabsorption, or urine concentration. This aligns with option 'a' as the correct description of their function.

Key Concepts

Nephron Structure

The nephron is the functional unit of the kidney, consisting of a glomerulus and Bowman's capsule, among other components. The glomerulus is a network of capillaries that filters blood, while Bowman's capsule surrounds it, collecting the filtrate. This structure is essential for the initial stage of urine formation.

Filtration Process

Filtration in the nephron occurs when blood enters the glomerulus, where pressure forces water, ions, and small molecules through the capillary walls into Bowman's capsule. This process separates waste products from the blood, creating a filtrate that will undergo further processing in the nephron.

Reabsorption and Secretion

After filtration, the nephron reabsorbs essential substances like water, glucose, and ions back into the bloodstream, while secreting additional waste products into the filtrate. This process is crucial for maintaining homeostasis and ensuring that valuable nutrients are not lost in urine.