High School Biology : Understanding Nephron Structure

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Nephron Structure

What adaptation do desert animals exhibit that allows them to retain and reabsorb lots of water for survival in the dry environment?

Possible Answers:

Long loops of Henle

Sweat glands

The ascending limb of the loop of Henle is permeable to water

Short loops of Henle

Correct answer:

Long loops of Henle

Explanation:

Many desert animals have adapted physiologically with certain mechanisms to retain more water and survive the in a dry, desert environment. Such desert animals have long loops of Henle, allowing greater opportunity to reabsorb water in the medulla in the descending loop of Henle.

Example Question #2 : Understanding Nephron Structure

In the nephron, where does filtration take place?

Possible Answers:

Glomerulus

None of the other answers

Proximal convoluted tubule

Bowman's capsule

Loop of Henle

Correct answer:

Glomerulus

Explanation:

The correct answer is the glomerulus, a convoluted capillary bed that is directly adjacent to the nephron. Solutes from the blood are filtered in the glomerulus and enter the nephron, specifically, Bowman's capsule. Both blood pressure and oncotic force (pressure in the glomerulus due to proteins) affect filtration rate. Together, the glomerulus and Bowman's capsule are known as the renal corpuscle.

Example Question #2 : Understanding Nephron Structure

What is the purpose of the glomerular basement membrane in filtration?

Possible Answers:

Allow filtration of large molecules and red blood cells

Prevent filtration of negatively charged proteins

It is comprised of aquaporins that allow water to filter quickly 

Prevent filtration of glucose into the nephron

It is selectively permeable to only calcium and chloride

Correct answer:

Prevent filtration of negatively charged proteins

Explanation:

The glomerular basement membrane—which sits between capillary endothelial cells and the selectively permeable podocytes that line Bowman's capsule—is comprised of negatively charged proteins that repel other negatively charged proteins. This helps prevent these compounds from entering the nephron with the filtrate.

Example Question #3 : Understanding Nephron Structure

How does glucose leave the tubule lumen and enter proximal tubule cells during reabsorption?

Possible Answers:

Glucose travels via simple diffusion

Glucose does not get reabsorbed because the epithelia between the glomerulus and the Bowman's capsule prevent filtration of glucose

Glucose enters the proximal tubule through a sodium-dependent glucose cotransporter

Glucose travels though a Glut-2 transporter from the tubule lumen to the proximal tubule cells

Aquaporins facilitate the transport of glucose from the tubule lumen to the proximal tubule cells

Correct answer:

Glucose enters the proximal tubule through a sodium-dependent glucose cotransporter

Explanation:

Sodium is coupled with glucose via a cotransporter, allowing it to enter the proximal tubule cells from the tubule lumen. Once in the proximal tubule cells, glucose then passes through a Glut-2 transmembrane carrier protein, but only on the basolateral membrane of the proximal tubule cells (from proximal tubule cells to the interstitual fluid). 

Example Question #4 : Understanding Nephron Structure

Which of the following nephron segments reabsorbs water exclusively?

Possible Answers:

Collecting duct

The ascending loop of Henle

The descending loop of Henle

Proximal convoluted tubule

Correct answer:

The descending loop of Henle

Explanation:

Kidneys contain small structures called nephrons that function to create urine. Urine is created by filtering the incoming blood. The blood enters the nephron via the glomerulus. It enters the Bowman’s space and then is transported through a series of nephron segments. Each segment has varying permeabilities for ions and water. The nephron segment that is only permeable to water is the descending loop of Henle. As urine travels down this segment, water gets reabsorbed back into the blood whereas the solutes remain in the urine (because the descending loop of Henle is impermeable to solutes). This makes the urine very concentrated.

The ascending loop of Henle has opposite permeabilities. Solutes, such as ions, are permeable and can cross the wall and be reabsorbed into the blood; however, water is impermeable. The proximal convoluted tubule is the site of most of the reabsorption and secretion of molecules; therefore, both water and solutes are permeable here. The collecting duct is not part of the nephron. Multiple nephrons drain into a collecting duct. Collecting ducts are sites of further reabsorption and secretion; therefore, both water and ions are permeable.

Note that reabsorption is the process of moving substances (solutes or water) from urine to the blood whereas secretion is the process of moving substances from the blood to urine.

Example Question #6 : Understanding Nephron Structure

The __________ receives filtered blood and the __________ reabsorbs and secretes substances in the filtered fluid.

Possible Answers:

renal corpuscle . . . renal tubule

renal corpuscle . . . renal corpuscle

renal tubule . . . renal corpuscle

renal tubule . . . renal tubule

Correct answer:

renal corpuscle . . . renal tubule

Explanation:

Blood from afferent arterioles enter the Bowman’s space via glomerulus. The filtered blood in the Bowman’s space traverses through different nephron segments before being excreted as urine. The glomerulus and Bowman’s space together are called the renal corpuscle; therefore, blood is first filtered here.

The urine gets processed (reabsorption or secretion) in different nephron segments before being ultimately excreted. During this process, the urine (also called tubular fluid) is transported via tubes called renal tubules; therefore, this is the site of reabsorption and secretion.

Example Question #7 : Understanding Nephron Structure

Which of the following is FALSE regarding nephrons?

            I. A nephron includes the glomerulus and the collecting duct.

            II. Most of reabsorption and secretion happens in the latter third of the nephron.

            III. Most of the urine is created inside a nephron.

Possible Answers:

II

I and II

II and III

III

Correct answer:

I and II

Explanation:

A nephron begins at the renal corpuscle and ends at the distal convoluted tubule. The renal corpuscle consists of the glomerulus and the Bowman’s capsule; therefore, the glomerulus is a part of the nephron. The collecting duct, on the other hand, is not part of a nephron. Multiple nephrons drain their tubular fluid into a single collecting duct. The tubular fluid is further filtered in the collecting duct and is ultimately excreted as urine. The distal convoluted tubule (last part of a nephron) is connected to the collecting duct.

Most of the reabsorption and secretion of ions and water happens in the proximal tubule, which is the nephron segment located right next to the Bowman’s space. This means that most of the fluid that enters the Bowman’s space is immediately processed in the proximal tubule. The latter third of a nephron also processes the fluid; however, it is negligible when compared to the proximal tubule.

Most of the urine is created in the nephron. The tubular fluid traverses each nephron segment, where it is processed. The final fluid that enters the collecting duct is processed further, but most of the urine that is excreted comes from the nephron.

Example Question #8 : Understanding Nephron Structure

The proximal convoluted tubule is found in the __________ of the kidneys and the distal convoluted tubule is found in the __________ of the kidneys.

Possible Answers:

medulla . . . medulla

medulla . . . cortex

cortex . . . medulla

cortex . . . cortex

Correct answer:

cortex . . . cortex

Explanation:

Kidneys can be divided into two parts: renal cortex and renal medulla. The cortex is the outer part of the kidneys that contains the renal corpuscles (glomerulus and Bowman’s space) and most of the renal tubules (except the loop of Henle). The medulla is the inner part; it contains the ascending and descending limbs of the loop of Henle, and the portion of renal tubule that descends into the medulla. The proximal convoluted tubule and the distal convoluted tubule are not part of the loop of Henle and, therefore, are found in the renal cortex.

Note that the nephron begins at the renal corpuscle in the cortex, becomes the proximal tubule (in the cortex), descends into the medulla as loop of Henle, and rises back into the cortex as the distal tubules. The tubular fluid in distal tubules drains into the cortical collecting duct (the region of the collecting duct found in the cortex), which eventually enters the medullary collecting duct and leaves the kidney as urine.

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