Outline the function of a nephron and its associated blood vessels, limited to: (a) the role of the glomerulus in the filtration from the blood of water, glucose, urea and ions (b) the role of the nephron in the reabsorption of all of the glucose, some of the ions and most of the water back into the blood (c) the formation of urine containing urea, excess water and excess ions (details of these processes are not required)
Outline the function of a nephron and its associated blood vessels, limited to: (a) the role of the glomerulus in the filtration from the blood of water, glucose, urea and ions (b) the role of the nephron in the reabsorption of all of the glucose, some of the ions and most of the water back into the blood (c) the formation of urine containing urea, excess water and excess ions (details of these processes are not required)
Answer
The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine. It consists of a glomerulus and a renal tubule, with associated blood vessels playing crucial roles in these processes.
(a) Role of the Glomerulus in Filtration
The glomerulus is a network of capillaries located at the beginning of each nephron. Its primary function is to filter blood under high pressure, allowing water, glucose, urea, and ions to pass into the Bowman’s capsule, while retaining larger molecules such as proteins and blood cells. This filtration process produces a fluid known as glomerular filtrate, which contains essential substances needed by the body as well as waste products like urea. The specialized structure of the glomerular capillaries, combined with their high blood pressure, facilitates this efficient filtration process.
(b) Role of the Nephron in Reabsorption
After filtration, the nephron continues to process the filtrate through its tubular components. In particular, the proximal convoluted tubule (PCT) reabsorbs nearly all glucose, a significant portion of ions (such as sodium and potassium), and most of the water back into the bloodstream. This reabsorption occurs through both passive and active transport mechanisms, ensuring that vital nutrients are returned to circulation while waste products remain in the tubule for excretion. The remaining segments of the nephron, including the loop of Henle and distal convoluted tubule (DCT), further adjust the composition of the filtrate by selectively reabsorbing additional ions and water based on the body’s needs.
(c) Formation of Urine
The final stage in urine formation occurs as the filtrate passes through the nephron’s collecting ducts. Here, any remaining urea, excess water, and excess ions are concentrated into urine. The urine then flows from the collecting ducts into the renal pelvis and eventually to the bladder for storage before excretion. This process ensures that waste products are effectively eliminated from the body while maintaining fluid and electrolyte balance.
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