Renal Physiology

In this task you must be guided by the PDF attachment in order to answer the following questions:

There are four parts to this set. Please type your answers in the text

box below, using no more than 250 words for the whole set.

About 60% of the fluid filtered into the nephron is reabsorbed back into

the circulation by the time the tubular fluid enters the loop of Henle.

1) How does the osmolality of tubular fluid in Bowman’s capsule

compare with the osmolality of tubular fluid at the beginning of the

descending thin limb of the loop of Henle?

2) If inulin had been injected into the organism and time had been

allowed for equilibration, how would the concentration of inulin in

Bowman’s capsule compare with the concentration of inulin at the

beginning of the descending thin limb of the loop of Henle?

3) If the protein content of the blood were to double, what would be the

effect on glomerular filtration? What would be the immediate effects and long term effects?

4) In muscle capillaries, plasma oncotic pressure is constant all along

the length of the capillary, but in the glomerulus, the plasma oncotic

pressure increases along the length of the capillary. What causes the

capillaries in these two tissues to differ in this way?

NOTE: DO NOT USE THE ANSWERS BELOW THIS AD AS POSSIBLE ARGUMENTS.

1- The osmolality of the tubular fluid in Bowman’s capsule is lower than the osmolality of the tubular fluid at the beginning of the descending thin limb of the loop of Henle. This is due to the reabsorption of water and other substances from the glomerular filtrate, as it travels through the tubules of the nephron. The osmolality continues to decrease as the fluid travels through the loop of Henle.

2- The concentration of inulin in the tubular fluid is affected by both reabsorption and secretion, as well as by the concentration of inulin in the blood. So, the concentration of inulin in Bowman’s capsule and in the beginning of the descending thin limb of the loop of Henle will depend on the balance of these processes.

So, by the time the tubular fluid reaches the beginning of the descending thin limb of the loop of Henle, the concentration of inulin in Bowman’s capsule would be essentially the same as it was when it was initially filtered at the glomerulus. This behavior of inulin makes it a valuable substance for measuring the glomerular filtration rate (GFR) because it is not subject to reabsorption or secretion within the nephron.

3- if the protein content of the blood were to double, this would cause an increase in glomerular filtration, at least in the short term. This is because the increased protein concentration in the blood would cause an increase in the osmotic pressure of the blood, which would lead to an increase in the filtration pressure in the glomerulus. In the long term, however, the increased filtration rate would lead to damage to the glomerular filtration barrier, which could eventually lead to decreased filtration and even kidney failure.

4- The difference in the plasma oncotic pressure between muscle capillaries and glomerular capillaries is the presence or absence of a basement membrane. In muscle capillaries, the plasma oncotic pressure is constant because there is a basement membrane present, which prevents fluid from passing from the capillary into the interstitial fluid. However, in the glomerulus, there is no basement membrane, so fluid can pass freely from the capillary into the tubule, which leads to an increase in the plasma oncotic pressure along the length of the capillary.