Lab assignment 10- Urinary Anatomy

Blood flows from the peritubular capillary to the renal vein through this sequence of vessels.

Cortical radiate vein, arcuate vein, interlobar vein

What is the function of the renal pelvis?

Collects newly formed urine. The minor calyces of the renal pelvis collect newly formed urine as it exits the renal papillae.

The outermost portion of the kidney is called the renal ________.

Cortex

Where does the ureter penetrate the kidney?

Hilum

Where are the renal columns located?

Renal medulla. The renal columns are located between the renal pyramids in the renal medulla.

Which structure is highlighted?

Renal pelvis

Of the following urinary system organs, major homeostatic functions are performed by the ________.

Kidneys

Tracey had been slightly concerned about the trace glucose that was found in Max's urine six hours after his exercise until she discovered that he had eaten an entire large pizza an hour before the urinalysis. Explain why glucose might show up in Max's urine after a particularly heavy meal.

Glucose passes easily through the glomerular filtration membrane, and normally 100% of it is reabsorbed in the proximal convoluted tubule (PCT). The reabsorption of glucose is accomplished by secondary active transport and requires a transport protein in the membrane to facilitate the movement of glucose across the membrane. Typically, there are more than enough of these transport proteins, but they do have an upper limit beyond which no more glucose can be transported. This is called the transport maximum (Tm) for glucose. Generally, the Tm for glucose is not reached until blood levels of glucose exceed 180 mg/dL, which is known as the renal threshold. The most common cause of hyperglycemia (high blood glucose) is diabetes mellitus. So, if the renal threshold is exceeded for glucose in the PCT, it will "spill" into the filtrate and be eliminated in urine. Without further testing, it's unknown whether Max has a lower-than-normal renal threshold for glucose, or has exceeded the normal renal threshold of 180 mg/dL with his heavy meal.

The renal artery enters the kidney at this indented area.

Hilum

Antidiuretic hormone (ADH) regulates the formation of concentrated or dilute urine. In which time period is Max's body secreting its highest amount of ADH? Explain your answer.

ADH is going to be highest when the body is most dehydrated. In Max's case, this is right after his 2-hour run. During his run, Max loses water via sweat and exhalation , and does not effectively replace it. The osmolality of his blood increases, singnaling the posterior pituitary to release ADH. ADH targets the principle cells in the collecting ducts of the kidney tubules, causing them to increase reabsorption of water from the filtrate. This negative feedback mechanism attempts to conserve water in order to decrease blood osmolality and restore body fluid homeostasis

Based on Max's urinalysis data, should he drink more water prior to exercise to ensure that he doesn't dehydrate during intense activity? Explain your answer.

ADH is going to be highest when the body is most dehydrated. In Max's case, this is right after his 2-hour run. During his run, Max loses water via sweat and exhalation, and doesn't effectively replace it. The osmolality of his blood increases, signaling the posterior pituitary to release ADH. ADH targets the principle cells in the collecting ducts of the kidney tubules, causing them to increase reabsorption of water from the filtrate. This negative feedback mechanism attempts to conserve water in order to decrease blood osmolality and restore body fluid homeostasis.

The vessel that supplies blood to the nephron is called the ________.

Afferent arteriole

Max's regular exercise regimen has reduced his high blood pressure, allowing him to achieve normal blood pressure on a single antihypertensive medication. The medication he takes is called an angiotensin converting enzyme inhibitor, or ACE inhibitor, which blocks the activation of angiotensin II. Describe at least two mechanisms by which angiotensin II targets the kidneys to increase extracellular fluid volume and, therefore, increase blood pressure.

Angiotensin II directly signals the renal tubules to reabsorb sodium. Where sodium goes, water follows by osmosis, causing blood volume and pressure to increase. Angiotensin II signals the release of ADH from the posterior pituitary. ADH acts on the principle cells of the collecting ducts to cause reabsorption of water from the filtrate into the blood. Blood volume and pressure are increased. Angiotensin II is a potent vasoconstrictor, which leads to a decline in peritubular capillary hydrostatic pressure and more fluid reabsorption. Blood volume and pressure are increased. Angiotensin II prompts the release of aldosterone from the adrenal medulla. Aldosterone stimulates renal tubules to reabsorb sodium (with water following) and this leads to an increase in blood volume and pressure. Angiotensin II stimulates the glomerular mesangial cells to contract and reduce glomerular filtration rates. Less filtrate is produced, less fluid is lost in urine, and blood volume and pressure are increased. Angiotensin II triggers thirst by acting at the hypothalamus. This increases blood volume and blood pressure.

The functions of the urinary system include ________.

Excreting nitrogenous wastes, maintaining electrolyte balance, and maintaining acid base and fluid balance.

The medullary pyramids contain collecting tubules (ducts) that travel towards the renal cortex, carrying urine to exit the kidney.

False

Max needs to drink more water before exercise to avoid dehydration.

False. Max's urinalysis data indicate that his urine is already dilute (pale yellow with low specific gravity). If he drinks more water, the kidneys will simply eliminate it, further diluting the urine and possibly causing him to stop to urinate during the race.

The fibrous capsule is a layer of adipose tissue that surrounds the kidney.

False. The fibrous capsule is a strong sheet of dense fibrous connective tissue. There is a layer of adipose tissue superficial to the fibrous capsule, called the perirenal fat capsule. Provide Feedback Next Correct. Followup. The fibrous capsule is a strong sheet of dense fibrous connective tissue. There is a layer of adipose tissue superficial to the fibrous capsule, called the perirenal fat capsule. End of followup.

Max is curious about the protein content of his urine. Which of these statements provides an accurate basis for Tracey's response, explaining normal conditions?

Fewer proteins are small enough to pass through the glomerular membrane, but the few that do are reabsorbed. So, proteins are not usually present urine. Under normal conditions, only small proteins can make it through the glomerular membrane. When they do, they are reabsorbed in the proximal convoluted tubule by endocytosis. So, proteins are not a typical finding in urine.

Name the strong transparent covering that encases the kidney.

Fibrous capsule

A fenestrated squamous epithelium can be observed in this structure within the kidney.

Glomerulus

This structure is a capillary bed from which blood is filtered into the nephron.

Glomerulus

List the parts of the nephron in correct sequential order: ________.

Glomerulus, proximal convoluted tubule, nephron loop.

Antidiuretic hormone (ADH), which regulates urine concentration and dilution, is __________.

Lowest before Max exercises. ADH is secreted in response to dehydration, as signaled by high blood osmolality. Max's data indicate that his body is well hydrated before exercise so ADH secretion is lowest at that time.

Lactic acid accumulation can be a consequence of intense exercise. Tracey notes that Max's kidneys are working to defend his body against acidosis. How can she tell? Describe this mechanism.

Max's pH is more acidic right after his run. This is evidence of a higher hydrogen concentration in urine. When pH drops, the tubule cells secrete hydrogen into the filtrate, allowing it to be lost in urine. They also reabsorb bicarbonate (a base) to help buffer the body fluids. The result is a restoration of normal pH.

Given the correlation between urine color and urine concentration, which of the following statements is true about Max's urine?

Max's urine is most dilute before exercise. the pale yellow and low specific gravity before exercise indicate that the kidneys are producing larger quantities of dilute urine

As urine is formed it flows through the collecting ducts to enter, in order, the following structures.

Minor calyces, major calyces, renal pelvis, ureter.

Name the structures in the kidney that produce urine.

Nephrons

During strenuous exercise, Max's body produces lactic acid and his blood pH begins to decline. His kidneys go to work to preserve acid-base balance by doing all of the following EXCEPT __________.

Reabsorbing hydrogen. The kidneys secrete, not reabsorb hydrogen when body pH declines, as happens with lacttic acid accumulation. This elimination of acid raises and restores pH

Tracey explains to Max that his transiently elevated blood glucose leads to "spilling" of glucose into his urine. Why does this happen?

Reabsorption of glucose is limited by transport proteins. Glucose passes freely through the glomerular filter and is usually 100% reabsorbed in the proximal convoluted tubules via transport proteins. However, the transporters have a set cumulative transport maximum beyond which they cannot reabsorb glucose. So, when blood glucose levels are high, too much glucose enters the tubules and some remains in the filtrate to be eliminated in urine.

What is a function of the highlighted organ?

Removal of toxins of new red blood cells.

Which structure is highlighted?

Renal Vein

Which blood vessel is highlighted?

Renal artery

Which structure is found separating the renal pyramids?

Renal columns. The renal columns are extensions of cortical tissue located in between the renal pyramids. Provide Feedback Next Correct. Followup. Correct. The renal columns are extensions of cortical tissue located in between the renal pyramids. End of followup.

Which of the following regions of the kidney is in contact with the fibrous capsule?

Renal cortex he fibrous capsule encloses the kidney. It is in contact with the renal cortex.

Where does filtration of the blood occur within the kidneys?

Renal cortex. Filtration takes place within the renal corpuscles located in the renal cortex.

Which region of the kidney is the most superficial?

Renal cortex. The renal cortex is the most superficial region of the kidney. Renal corpuscles are found in the renal cortex. They are microscopic structures, so they can't be observed on a kidney specimen. The renal corpuscles are responsible for the bumpy texture of the renal cortex that can be visualized.

A major calyx is a component of which of the following anatomical structures?

Renal pelvis The major branches of the renal pelvis are the major calyces, and the smaller branches that contact the renal papillae are the minor calyces.

Which structure is highlighted?

Spongy urethra

Tracey knows that proteinuria (protein in the urine) after intense exercise is physiological (normal). However, protein is typically not present in urine. Why is that?

The glomerulus is a passive filter that acts as a barrier to larger molecules, such as most plasma proteins. also, because most proteins carry a net negative charge, they are repelled by the membrane thereby hindering their passage. However, some smaller proteins can and do pass through the filtration membrane.Most of them are reabsorbed in the proximal convoluted tubule by endocytosis and then broken down into amino acids to be returned to the blood in the peritubular capillaries. The mechanism of exercise-induced proteinuria is unclear, but it is typically a transient, occurrence. Any kidney disease can render the glomerulus dysfunctional, leading to a more sustained proteinuria. In fact, Max's hypertension, if left unchecked, could damage the filtration membrane of the glomerulus. The proteinuria will increase the specific gravity of his urine. (along with his relative dehydration)

Tracey knows that the large pizza Max consumed just prior to collecting his third urine sample caused a transient increase in his blood glucose levels. What can be accurately said about the relationship between glucose in the blood and the amount of glucose filtered through the glomerular membrane?

The higher the blood glucose concentration, the more glucose is filtered through the glomerular membrane. Glucose passes freely through the glomerular membrane

What is true about the urethral sphincters?

The internal urethral sphincter is under involuntary control.

What does the color of Max's urine tell Tracey about how concentrated or dilute it is? How does Max's urine color/concentration compare to the urine specific gravity at the same time?

The pale urine is dilute, the yellow urine is more concentrated , and the dark yellow urine is very concetrated. Specific gravity is the ratio of the density of a substance compared to the density of an equal volume of distilled water. Urine, with its various solutes, has a greater specific gravity than water. (1.001-1.035), which varies depending on the concentration of solute. The more concentrated the urine, the darker its color and the higher its specific gravity.

The ureter, blood vessels, and nerves penetrate the kidney on its medial surface.

True. The ureter, blood vessels, and nerve supply penetrate the kidney at its concave medial surface at the hilum. Part D The fibrous capsule is a layer of adipose tissue that surrounds the kidney. View Available Hint(s) The fibrous capsule is a layer of adipose tissue that surrounds the kidney. True False Submit Provide Feedback Next Correct. Followup. Correct. The ureter, blood vessels, and nerve supply penetrate the kidney at its concave medial surface at the hilum. End of followup.

Urine is formed by three processes. In which process do filtrate components that are useful to the body move from the nephron into the blood?

Tubular reabsorption

Based on the urine color and specific gravity, what might Tracey conclude about the hydration status of Max's body at the three different times?

When Max's urine is pale with a low specific gravity, his body is likely to be well hydrated; the kidney are reabsorbing less water, allowing it to be eliminated in urine. When his urine is dark yellow with a higher specific gravity, his kidneys are concentrating urine and reabsorbing more water in an attempt to maintain body fluid homeostasis (defend plasma osmolality). Dehydration will trigger this response. The yellow urine signals dehydration; the corresponding high-normal specific gravity is likely due to the small amount of glucose in the urine.

Identify the correct direction of urine flow from formation to exiting the kidney.

cortex, medulla, renal pelvis, ureter. Filtration occurs in the renal cortex, processing of the filtrate occurs within the renal tubules. Urine exits the renal pyramids into the renal pelvis, where it will be conveyed to the urinary bladder by the ureter.

Which of the following directly enclose the papilla of the renal pyramid?

o Minor Calyx

Where does the kidney filter the blood?

renal corpuscle The renal corpuscle is an interface between the blood supply and the kidney. It consists of the glomerulus, which is a capillary bed, and the glomerular (bowman's) capsule, which is part of the nephron. Filtration is the exit of small substances from the blood in the glomerulus into the glomerular capsule of the nephron.