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Example Questions
Example Question #1 : Excretory Anatomy
Which of the following statements about kidney structure and function is true?
No filtration occurs after Bowman's capsule, only reabsorbtion and secretion
Each kidney is composed of approximately one thousand nephrons
Cells and large proteins are filtered into urine from the glomerulus
All of the answer choices are correct
No filtration occurs after Bowman's capsule, only reabsorbtion and secretion
Cells and large proteins are too large to cross the capillary membranes of the glomerulus, and cannot be filtered into Bowman's capsule. After this initial step of filtration, urine in the nephron is only affected by secretion and reabsorbtion of water, ions, and other small molecules. Finally, each kidney is composed of about one million nephrons.
Example Question #1 : Excretory Anatomy
Where does blood go after it leaves the glomerulus?
It re-enters pulmonary circulation
It runs parallel to the nephron via the efferent venules
It returns to the heart via the inferior vena cava
It re-enters systemic circulation
It runs parallel to the nephron via the efferent arterioles
It runs parallel to the nephron via the efferent arterioles
The kidney-nephron system is one of the few portal systems in the human body. Portal systems link two arteriole or capillary systems together, in this case the afferent and efferent arterioles. The efferent arterioles leave the glomerulus after it has been filtered into Bowman's capsule, and follow along the nephron to pick up any reabsorbed material from the nephrons via the vasa recta capillary bed. Both the glomerulus and vasa recta are groups of capillaries, which qualifies the renal circulation as a portal system.
Example Question #2 : Excretory System
A patient is found to have abnormally high concentrations of glucose in his urine. Which of the following portions of the nephron is most likely the cause of this excess of glucose?
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Proximal convoluted tubule
The proximal convoluted tubule is incredible for its ability to reabsorb glucose at levels of nearly 100%. This function is due to specialized proteins that help transport the glucose out of the filtrate. Damage to the proximal convoluted tubule can lead to glucose in the urine. Another possible cause would be extremely high glucose levels in the filtrate, such that the proximal convoluted tubule is incapable of properly removing all of the solute. This condition is a trademark of diabetes.
The loop of Henle, the distal convoluted tubule, and, under special circumstances, the collection duct are responsible for the reabsorption of other nutrients (such as water and various ions).
Example Question #1 : Excretory System
Which of the following are located in the cortex of the kidney?
Ascending limb, descending limb, and collecting duct
Glomerulus, proximal tubule, and distal tubule
Glomerulus and proximal tubule
Loop of Henle
Glomerulus, proximal tubule, and distal tubule
The glomerulus, proximal tubule, distal tubule are all located in the cortex (outer portion) of the kidney, where the osmolarity of the interstitial fluid is relatively low. Both limbs of the loop of Henle and the collecting duct are located in the medulla (central portion) of the kidney, where the osmolarity of the interstitial fluid is much greater.
Filtrate movement through the nephron into different surrounding osmolarities is what allows water and sodium to be retained, if necessary, while other waste products are concentrated in the urine. The evolution of the loop of Henle is specifically designed to create the countercurrent multiplier system that allows for urine concentration and water retention in land animals. Water-based animals generally have shorter loops of Henle that may not intersect with the renal medulla, since water retention is less important.
Example Question #3 : Excretory Anatomy
What structure surrounds the glomerulus and serves as the site of filtrate production?
Proximal tubule
Renal pelvis
Bowman's capsule
Distal tubule
Bowman's capsule
Together, the glomerulus and Bowman's capsule form the structure known as the renal corpuscle. Blood in the capillaries of the glomerulus is forced against the walls of the vessels, where specialized epithelium and cell junctions allows fluids and small solutes to diffuse across the walls of the glomerulus and into Bowman's capsule. This process is highly dependent on pressure differentials; higher hydrostatic pressure in the glomerulus and greater solute concentration in Bowman's capsule will work to remove water and fluids from the capillary. Blood cells and large proteins are unable to pass through filtration and remain in circulation. Ions, small sugars, amino acids, and nitrogenous wastes pass through filtration, and are either reabsorbed back into the blood or excreted in the filtrate.
The proximal and distal tubules are regions of the nephron that are located in the renal cortex and specialize in ion reabsorption. The renal pelvis is located in the renal medulla and serves as the final collecting point for filtrate from multiple collecting ducts before transferring it to the ureter.
Example Question #1 : Excretory System
The nephron is the functional unit of the mammalian kidney. Which of the following structures is not considered part of the nephron?
Loop of Henle
All of these structures are part of the nephron
Glomerulus
Distal tubule
Proximal tubule
Glomerulus
The function of the kidney is to filter wastes out of the blood and concentrate them into a filtrate that can be excreted from the body. Nephrons are the functional unit of the excretory system, meaning that each nephron is capable of concentrating wastes into filtrate. Each nephron is made of a single long tubule, with different regions modified to transport different ions and wastes into or out of the filtrate. The proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule are the principle regions of the nephron.
The glomerulus and Bowman's capsule form the renal corpuscle, the site of blood filtration. While the nephron serves to concentrate filtrate, the renal corpuscle separates the filtrate from the blood. The glomerulus is a system of capillaries, and carries blood rather than filtrate. It is kept separate from the nephron by the barriers in the glomerulus walls and Bowman's capsule.
Example Question #1 : Understanding Kidney And Nephron Anatomy
What is the first structure encountered as blood interacts with a nephron?
Distal convoluted tubule
Collecting duct
Glomerulus
Proximal convoluted tubule
Loop of Henle
Glomerulus
Filtration of blood occurs in the renal corpuscle, which is composed of the glomerulus and Bowman's capsule. The glomerulus is a complex net of capillaries that carry blood adjacent to Bowman's capsule. Bowman's capsule collects fluid filtrate from the blood and transfers to the rest of the nephron. The glomerulus is the only portion of the nephron to contain blood rather than filtrate.
After entering Bowman's capsule, filtrate is passed to the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and finally the collecting duct.
Example Question #5 : Understanding Kidney And Nephron Anatomy
What is the functional unit of the kidney?
Nephrons
Renal corpuscles
Neurons
Renal medulla
Nephrons
The nephrons are the smallest functional unit in the kidney. They are responsible for the filtration and concentration of urine.
Neurons are the smallest functional unit of the nervous system. The renal medulla is the region on the interior of the kidney, as opposed to the renal cortex. Renal corpuscles are used to filter blood into the nephron, and consist of the glomerulus and Bowman's capsule.
Example Question #1 : Understanding Other Excretory Anatomy
Which of the following organs is involved in exocrine function?
All of these choices are correct
Kidneys
Skin
Pancreas
All of these choices are correct
The kidneys are responsible for the excretion of urine, while the skin secretes sweat from the body. The pancreas secretes digestive enzymes into glands and ducts. Exocrine function differs from endocrine function, in that exocrine excretions involve ducts that generally lead to the body's exterior. Endocrine functions, in contrast, will enter the blood stream and be distributed throughout the body.
Example Question #2 : Excretory System
What is a commonality between excretory systems of worms, insects, and vertebrates?
All of these answers
A large surface area
Reabsorption mechanisms for water and ions
A complex network of tubules
All of these answers
The overall organ systems that perform excretory functions are highly variable between animal groups. All animals, however, share some common features. Water and ion balances must be tightly regulated by reabsorption mechanisms, in order to maintain organismal homeostasis and functions. To assist in this process, the vessels for filtrate transport must have a large surface area. Proteins, pumps, and channels along this surface serve to moderate water and ion transport.
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