Question

If the loop of Henle is absent from the mammalian nephron, which of the following is expected?
A)Urine will be more concentrated
B)Urine will be more diluted
C)No urine formation
D)No change in quality and quantity

Answer 1

The human kidney is made of a couple of million nephrons. Each nephron consists of a coiled tubule, one end of which forms a cup-shaped structure. Inside this cup may well be a tuft of capillaries called glomerulus, with fenestrated basement membrane. Glomerulus filters out water as well as solutes from blood passing through it into the surrounding space, which is a cavity between the two walls of the cup. This part is wholly within the cortex. The next part of the tubule is extremely coiled and empties into a U-shaped loop which carries the filtered fluid inside into the medulla then back again into the cortex. This is termed the loop of Henle.

Complete answer:
Loop of Henle, a long U-shaped portion of the tubule that conducts urine within each nephron of the kidney of reptiles, birds, and mammals. The principal function of the loop of Henle is within the recovery of water and customary salt from urine. This function allows production of urine that's far more concentrated than blood, limiting the amount of water needed as intake for survival. The loop of Henle is split into- descending limb, ascending limb, and thick ascending limb.

The loop of Henle is critical to the ability of the kidney to concentrate urine. High concentration of salt within medullary fluid is achieved by countercurrent exchange multiplication. This works similarly to the principle applied within the conduction of hot exhaust gases past cold incoming gas so as to warm it and conserve heat. That exchange could be a passive one, but within the kidney the countercurrent multiplier system uses energy to “pump” sodium and chloride out of the ascending limb of the loop into the medullary fluid. From there it enters the filtrate entering the descending limb from the proximal tubule, thus raising its concentration above that of plasma. When the luminal fluid reaches ascending limb, and distal tubule, it provides sodium to be pumped out into encircling fluid or blood, if necessary, and transported back to descending limb; this concentrating process continues until the pressure of the fluid is sufficient to balance the resorptive power of the collecting ducts within the medulla, through which all of the ultimate urine must pass. This resorptive capacity within the ducts is regulated by antidiuretic hormone (ADH), which is secreted by the hypothalamus and stored within the ductless gland gland at the bottom of the brain. Within the presence of ADH, the medullary collecting ducts become freely permeable to solute and water. As a consequence, the fluid entering the ducts acquires the concentration of the extracellular fluid of the medulla; i.e., the urine becomes concentrated. On the opposite hand, within the absence of ADH, the collecting ducts are impermeable to solute and water, and, thus, the fluid within the lumen, from which some solute has been removed, remains less concentrated than plasma; i.e., the urine is dilute.

Hence, the correct answer is option (B)

Note: The urine leaving the kidney differs in composition from the plasma entering it. The study of renal function must account for differences such as absence of protein, glucose from the urine, a change in the pH, and also the high levels of ammonia and creatinine within the urine, while sodium and calcium remain at similar low levels in both urine and plasma. An outsized volume of ultrafiltrate is produced by the glomerulus into the capsule. As this liquid traverses the proximal convoluted tubule, most of its water and salts are reabsorbed, a number of the solutes completely and others partially; i.e., there's a separation of drugs that has to be retained from those due for rejection. Subsequently the loop of Henle, distal convoluted tubule, and collecting ducts are mainly concerned with the concentration of urine to produce fine control of water and electrolyte balance.