MCAT Biology : Kidney and Nephron Physiology
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Example Questions
Example Question #31 :Excretory System
Which of the following structures will be found in the renal medulla?
I. Glands that secrete aldosterone
II. Loop of Henle
III. Distal convoluted tubule
I and III
II only
I only
I and II
II only
Recall that the renal medulla is the inner portion of the kidney. A nephron spans both the renal cortex and the renal medulla. Structures such as the glomerulus (capillary bed), Bowman's capsule, and the proximal and distal convoluted tubules are found in the renal cortex, whereas the loop of Henle is found in the renal medulla. The collecting duct (the structure that transports urine to the renal pelvis) spans both the renal cortex and the renal medulla.
As mentioned above, distal tubules are found in the renal medulla and function to reabsorb sodium ions. Reabsorption of sodium ions inside the nephron (for example in the distal tubules) is facilitated by the hormone aldosterone. Aldosterone is a steroid hormone that is produced in glands inside the adrenal cortex (in the adrenal gland, rather than the kidney).
Example Question #32 :Excretory System
Which of the following is true regarding a nephron?
Filtration begins in nephrons’ capillary beds, called the collecting duct
Nephrons are only found in the adrenal medulla
A nephron is the functional unit of a neuron
Nephrons create urine, but they cannot store urine
Nephrons create urine, but they cannot store urine
A nephron is the functional unit of kidneys. It is the site of filtration, secretion, and reabsorption (processes essential for urine production).
Nephrons contain several structures that facilitate the proper excretion of waste through urine. A nephron contains structures that are found in both the adrenal medulla (inner region) and the adrenal cortex (outer region) of the kidneys; therefore, a single nephron spans both the adrenal medulla and the adrenal cortex. The first step in urine production occurs at the capillary beds of nephrons. Blood arrives at these capillary beds, known as the glomerulus, and initiates filtration. Filtration is the process by which potential waste products in the blood are filtered into the nephron, where they will ultimately become urine.
Remember that nephrons are the site of urine production; they do not store the urine. Once complete, urine exits the kidneys and is stored in the bladder. The bladder stores urine until it reaches the maximum capacity, causing smooth muscle around the organ to stretch. Once this maximum is reached the individual feels the urge to urinate, and the urine is excreted via the urethra.
Example Question #33 :Excretory System
In the urinary system, the ureter is most directly associated with the__________.
adrenal gland
liver
renal vein
renal pelvis
renal pelvis
The renal pelvis (hollow structure within the kidney) narrows to become the ureter, which leads to the bladder.
Example Question #34 :Excretory System
Which components of the nephron can be found in the renal medulla?
The loop of Henle and the glomerulus
The entire nephron can be found within the cortex of the kidney
The loop of Henle and the collecting duct
The proximal and distal convoluted tubules
The loop of Henle and the collecting duct
The loop of Henle descends into the medulla before ascending back into the cortex. The collecting duct, which ends the nephron, extends into the medulla.
Example Question #35 :Excretory System
Which of the following is true of a functioning kidney?
Macromolecules, such as proteins, do not enter Bowman's capsule due to the impermeability of the podocyte membrane
Only water can enter into Bowman's capsule by passive diffusion
Glucose, water, and ions permeate the visceral layer of Bowman's capsule to enter the blood vessels of the glomerulus
All blood solutes pass from the glomerulus into Bowman's capsule, adding to the volume of the filtrate
Macromolecules, such as proteins, do not enter Bowman's capsule due to the impermeability of the podocyte membrane
肾小球囊是permeabl的脏层e to small blood solutes. Blood cells and most macromolecules remain in the blood stream.
One answer choice is nearly correct: "Glucose, water, and ions permeate the visceral layer of Bowman's capsule to enter the blood vessels of the glomerulus." While these solutes do in fact permeate the membrane, theyexitthe blood vessels of the glomerulus to enter Bowman's capsule.
Example Question #36 :Excretory System
Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Which of the following statement(s) will contradict carbonic anhydrase inhibitors' usefulness in patients with hypertension?
The reabsorption of
The reabsorption of
Water is only reabsorbed in the collecting tubule of the kidneys
None of these
All of these
Water is only reabsorbed in the collecting tubule of the kidneys
In patients with hypertension, the blood volume is too high resulting in high blood pressure. carbonic anhydrase inhibitors will prevent water absorption by preventing sodium chloride reabsorption. As described from the passage, without sodium reabsorption at the proximal tubule, there will be no electrochemical drive for the reabsorption of water. carbonic anhydrase inhibitors mainly work on the proximal tubule where the majority of water reabsorption occurs.
Example Question #37 :Excretory System
Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:
A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.
In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride
When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more
Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.
Based on the passage, which of the following statements, if true, would contradict the effectiveness of carbonic anhydrase inhibitors as a treatment?
Even in a basic environment, sometimes an acidic molecule is able to retain it's proton
The proximal tubule of the kidney is impermeable to water
The distal tubule of the kidney is impermeable to water
None of these
When sodium chloride is absorbed, the electric force created will pull magnesium with greater force than water
The proximal tubule of the kidney is impermeable to water
The proximal tubule has a high permeability for water. In patients with hypertension and/or heart failure, blocking the reabsorption of water at the proximal tubule will lower the blood's volume and blood's pressure. Therefore, if the proximal tubule is impermeable to water, then regulating the site with a carbonic anhydrase inhibitor has no purpose.
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