Dlh Mi

descending limb of the loop of Henle (DLH) by the osmotic gradient and there is some urea diffusion from the medullary interstitium into the DLH. NaCl diffuses passively down its concentration gradient from the thin ascending limb of the loop of Henle into the medullary interstitium, leaving water and urea behind because they are impermeable. Thus, the tubular fluid flowing to the thick ascending limb (TAL) has the same urea concentration as at the tip of the medulla, but the NaCl concentration is progressively reduced.

descending limb of the loop of Henle (DLH) by the osmotic gradient and there is some urea diffusion from the medullary interstitium into the DLH. NaCl diffuses passively down its concentration gradient from the thin ascending limb of the loop of Henle into the medullary interstitium, leaving water and urea behind because they are impermeable. Thus, the tubular fluid flowing to the thick ascending limb (TAL) has the same urea concentration as at the tip of the medulla, but the NaCl concentration is progressively reduced.

of Henle and, in antidiuresis, in the connecting tubules and collecting ducts, urea reaches a high concentration by the time the tubular fluid reaches the inner medulla.

The collecting duct of the inner medulla is, however, permeable to urea, and this permeability is increased by vasopressin. Because of the higher urea permeability in antidiuresis, the urea that has been concentrated in the tubular fluid can diffuse from the concentrated tubular fluid into the inner medulla. In the presence of vasopressin, when there is considerable water reabsorption, the urea concentration equilibrates at about 600 mmol/L in both the urine and the medulla.

In diuresis, the tubular fluid flowing into the inner medulla has a lower urea concentration because less water reabsorption has occurred in the cortex and in the outer medulla. Thus, there is a gradient for urea to diffuse from the medullary interstitium into the urine. This is prevented to some extent by the lower urea permeability in the absence of vasopressin. But the loss

FIGURE 15 Sites of urea reabsorption along the nephron. Urea is reabsorbed passively in the proximal tubule; some urea diffuses into the thin descending limb of the loop of Henle (i.e., secreted; not shown). The nephron segments beyond the tip of the loop of Henle, with the exception of the inner medullary collecting duct, are impermeable to urea. Consequently, the urea concentration rises because of water reabsorption from the thin descending limb of the loop of Henle, and in the connecting tubule and collecting duct. This is shown by the increasing size of the letters "Urea." The inner medullary collecting duct is permeable to urea and that permeability is increased by vasopressin, therefore, in antidiuresis, urea diffuses passively into the medullary interstitium.

FIGURE 15 Sites of urea reabsorption along the nephron. Urea is reabsorbed passively in the proximal tubule; some urea diffuses into the thin descending limb of the loop of Henle (i.e., secreted; not shown). The nephron segments beyond the tip of the loop of Henle, with the exception of the inner medullary collecting duct, are impermeable to urea. Consequently, the urea concentration rises because of water reabsorption from the thin descending limb of the loop of Henle, and in the connecting tubule and collecting duct. This is shown by the increasing size of the letters "Urea." The inner medullary collecting duct is permeable to urea and that permeability is increased by vasopressin, therefore, in antidiuresis, urea diffuses passively into the medullary interstitium.

of urea into the tubular fluid, in combination with the increased water entry from the collecting duct and the increased medullary blood flow discussed earlier, is responsible for the fall in the inner medullary hyper-osmolality during diuresis.

Get Rid of Gallstones Naturally

Get Rid of Gallstones Naturally

One of the main home remedies that you need to follow to prevent gallstones is a healthy lifestyle. You need to maintain a healthy body weight to prevent gallstones. The following are the best home remedies that will help you to treat and prevent gallstones.

Get My Free Ebook


Post a comment