Urinary (lecture and lab)

When systemic blood pressure decreases, the result is that the ___________ arterioles change diameter by undergoing ______________

afferent; vasodilation

Glucose that is reabsorbed into tubular cells travels __________ its concentration gradient through sodium-glucose symport channels at the luminal membrane. Glucose in tubular cells exits the basolateral membrane into interstitial fluid through the process of ______________________.

against; facilitated diffusion

If both the glomerular and capsular hydrostatic pressures remain unchanged, an increase in the blood colloid osmotic pressure results in a(n) _____________ in the net filtration pressure.

decrease

The nephron loop is responsible for approximately 25% of the reabsorption of sodium. Loop diuretics cause an overall __________________ in the reabsorption of sodium in this region resulting in a(n) ________________________ in the osmolarity of the tubular filtrate.

decrease; increase

The major calices merge to form a single, funnel-shaped

Renal pelvis

Filtration is a ________________ process that depends on a ___________________ gradient.

passive; pressure

Put the following portions of the nephron in order, beginning at the renal corpuscle and heading toward the collecting tubules.

1 Glomerular capillaries 2 Proximal convoluted tubules 3 Nephron loop 4 Distal convoluted tubules

What percentage of glomerular filtrate becomes urine?

1%

Diabetes mellitus is a metabolic condition that results in hyperglycemia, or abnormally high blood glucose levels. There are three types of diabetes mellitus; type 1, type 2, and gestational diabetes. Type 1 and type 2 diabetes are sometimes referred to as "insulin-dependent" and "insulin independent" respectively. Gestational diabetes is usually a temporary condition present during pregnancy. Individuals with untreated diabetes mellitus have higher glucose levels within the tubular filtrate due to the high blood glucose levels. Normally, 100% of the filtered glucose gets reabsorbed as it passes into the tubular cells through the sodium-glucose symport SGLT2 found at the luminal membrane, and enters the interstitial fluid through the facilitative glucose transporter GLUT2 found at the basolateral membrane. When glucose levels exceed normal values these transport proteins become saturated, unable to reabsorb all of the glucose within the tubular filtrate. This causes glucosuria, in which glucose remains within the tubular filtrate and thus is present within the urine. The increased osmolarity of the glucose-rich tubular filtrate causes water to move into the tubular filtrate by osmosis. This is referred to as osmotic diuresis. The result of this action is an increase in the frequency and volume of urine, and subsequent excessive thirst. An emerging class of drugs is being tested that seeks to lower blood glucose levels by inhibiting the reabsorption of glucose. These drugs target and inhibit the sodium-glucose symport SGLT2, disrupting glucose reabsorption and increasing urinary glucose secretion. Although these drugs are still undergoing clinical trials, they may potentially assist in controlling blood glucose levels of individuals with type 2 diabetes.

1. Inactivating the sodium-glucose symport SGLT2 inhibits the reabsorption of glucose by ____________________________. preventing glucose from entering the tubular cells 2. Inhibiting the sodium-glucose symport SGLT2 is expected to cause a(n) __________________________ in the osmolarity of the tubular filtrate, and would thus _____________________ the risk of dehydration. increase; increase

1. Each nephron is composed of two parts: a renal corpuscle and a renal tubule. 2. The renal corpuscle is composed of a glomerulus and a Bowman's capsule. 3. This area is where the filtrate is formed from the plasma.

4. Leading away from the corpuscle is the renal tubule, which consists of three regions. 5. The regions include the proximal and distal convoluted tubules and the loop of Henle.

Blood pH adjustment occurs at the distal convoluted tubule, collecting tubule, and collecting duct through the reabsorption and secretion of HCO3- and H+. Type A and type B intercalated cells transport both HCO3- and H+, but in opposite directions. Type A cells secrete H+ through H+ ATPases located at the luminal membrane, and reabsorb bicarbonate through Cl-/HCO3- exchangers at the basolateral membrane. Type B cells secrete bicarbonate through Cl-/HCO3- exchangers at the luminal membrane, and reabsorb H+ through H+ ATPases found at the basolateral membrane. The Cl-/HCO3- exchanger found at the luminal membrane of Type B intercalated cells has been identified as Pendrin (SLC26A4). In these cells, the Cl-/HCO3-ion transporter moves bicarbonate into the tubular filtrate in exchange for a Cl- ion moving in the opposite direction. Animal studies have shown that Pendrin transport proteins may be upregulated (increased) or down-regulated (decreased) in response to specific conditions such as metabolic alkalosis and metabolic acidosis, respectively. Upregulation and downregulation allows the nephron to dynamically adjust to changes in blood pH and maintain homeostasis.

1. Pendrin is found in __________ intercalated cells where it allows for the ________________ of bicarbonate. type B; secretion 2. The expected response to metabolic alkalosis is the ___________________ of Pendrin. Type _____________ also assist in buffering the alkaline blood through its transport of H+. upregulation; B

1. The cortex is the outer part that functions in blood filtration.

2. The medulla is the inner part kidney tissue that functions in tubular reabsorption and secretion. 3. The renal sinus is the medial most portion that is filled with vessels and the renal calyces.

1. The glomerular capsule leads into the proximal convoluted tubule, the longest and most coiled of the four regions of the renal tubule. 2. From there, the filtrate flows into the descending limbof the nephron loop, the first part of the U-shaped portion of the tubule found mostly in the medulla.

3. Next, the flitrate makes a 180 degree turn into the ascending limb, returning to the renal cortex. 4. The filtrate is funnelled into the distal convoluted tubule, the end of the nephron. 5. The collecting duct receives the filtrate from the DCTs of several nephrons and funnels it toward the medullary pyramid.

1. There are four major stages in the formation of urine. 2. The first stage involves creating a filtrate in the glomerulus.

3. Second, the filtrate flows through the tubules and useful substances are reabsorbed. 4. Waste products will then be secreted by the tubules. 5. The last stage is water conservation occuring in the renal tubule.

The cell type in the distal tubule and collecting duct that is responsible for Na⁺ and water reabsorption is the principal cell. The hormone aldosterone acts in this part of the nephron and has a big impact on sodium and potassium levels in the filtrate. Overconsumption of alcohol can cause the hypothalamus to sense that the blood is too dilute, resulting in a decrease in the production of antidiuretic hormone thus reducing the reabsorption of water leading to dehydration.

A person who experiences higher than normal levels of phosphate in their blood and higher than normal levels of Ca²⁺ in their urine probably suffers from a deficiency in the production of parathyroid hormone. When the level of the hormone atrial natriuretic peptideincreases, a person will experience an increase in Na⁺ excretion in their urine.

Indicate whether each of the following is a characteristic of the ascending limb or the descending limb of the nephron loop.

Ascending limb: Tubular fluid osmolarity decreases as it passes through Permeable to solutes Impermeable to water Descending limb: Tubular fluid osmolarity increases as it passes through Impermeable to solutes Permeable to water

Identify the three components of the filtration membrane.

Basement membrane Fenestrated endothelium Podocytes with filtration slits

Choose the correct order of urine formation and flow through the kidney.

Collecting tubules Collecting ducts Papillary duct Renal papilla

Match the component of a nephron with its description.

Contains podocytes, pedicels, and filtration slits Glomerulus Secretes ions into the tubular fluid; reabsorption of water Distal convoluted tubule Contains a descending limb and an ascending limb Nephron loop Cuboidal cells with tall microvilli; active reabsorption Proximal convoluted tubule

Name the arteries that supply the kidney, in sequence from largest to smallest.

Cortical radiate arteries Afferent arteries Peritubular capillaries Glomerulus

List the veins through which blood leaves the kidney in sequence from smallest to largest.

Cortical radiate veins, Arcuate veins, Interlobar veins, Renal vein

he junction of the renal medulla and renal cortex is called the

Corticomedullary junction

Indicate whether the provided renal function results from the creation of urine or through other mechanisms.

Directly Resulting From Urine Formation: Filtration of blood Reduction of blood acidity Blood pressure regulation Removal of nitrogenous waste Electrolyte regulation Blood volume regulation Not Resulting From Urine Formation: Calcitrol (vitamin D) conversion Erythropoiesis stimulation

Hypertension affects approximately 20% of the adult population in the U.S., and is classified into 'primary hypertension' and 'secondary hypertension.' Primary hypertension has no specific, single identifiable factor and is the most common cause of hypertension. Secondary hypertension can be attributed to a specific cause, such as chronic volume overload. For patients in which modified diet and exercise plans do not significantly improve hypertensive symptoms, diuretics may be prescribed.

Diuretics increase urine output and decrease fluid volume by reversibly inhibiting Na+ reabsorption at specific sites of the nephron, and increasing the excretion of both Na+ and water. This results in decreased blood volume and blood pressure, improving hypertension. Diuretics work at different sites on the nephron. Loop diuretics (ex. Furosemide, Bumetanide, and Torsemide) act at specific sites along the nephron loop, and specifically inhibit the Na+/K+/2Cl- symport (NKCC2) found at the luminal membrane of the thick ascending loop, thereby preventing the reabsorption of sodium, chloride, and potassium. Thiazides (ex. Chlorothiazide and hydrochlorothiazide) act on the Na+/Cl- cotransporter at the distal convoluted tubule (DCT) and inhibit Na+ and water reabsorption in this region.

Correctly label the forces involved in glomerular filtration.

HPc 18 in OPg 32 in NFP 10 out HPg 60 out

Blood vessels, nerves and the renal pelvis enter/exit the kidney at the

Hilum

The renal corpuscle consists of a capillary called the glomerulus and a capsule of epithelial cells. A virus that specifically attacks podocytes would damage the visceral layer of the glomerular capsule . Glomerular filtrate collects in the capsular spacebefore entering the first portion of the renal tubule, called the proximal tubule. A blockage in the distal tubule would prevent filtrate from reaching the collecting duct.

If an electron micrograph of a nephron segment revealed very highly developed microvilli, then you are most likely looking at cells of the proximal tubule. Nephrons that have very long loops are classified as juxtamedullary nephrons.

Indicate whether each factor on the left would increase or decrease urine volume.

Increase: Blood pressure Atrial natriuretic peptide (ANP) Decrease: Antidiuretic hormone (ADH) Aldesterone

Indicate whether each of the following would increase or decrease filtration.

Increase: an increase in blood pressure Constriction of the efferent arteriole Decrease: An increase in capsular pressure An increase in plasma protein concentration An obstruction i the proximal tubule

Which of the following are primary organs of the urinary system?

Kidneys Ureters Urinary Bladder Urethra (Small intestine and gall bladder are not)

Place the following structures in order as urine passes through them. (cadaver)

Kidneys, ureter, urinary bladder, urethra

Explain the order of kidney structures (and thus urine flow) leaving the renal papilla until reaching the urinary bladder.

Minor calyces, Ureter, Major calyces, Renal pelvis

Label the midsagittal male pelvis using the hints provided.

Nephrons

Indicate the pathway of urine formation to urine output by placing each of the structures in the correct sequential order from left to right.

Nephrons, collecting tubules, collecting duct, papillary duct, minor calyx, major calyx, renal pelvis, ureters, bladder, urethra

Put the labels in order based on the blood vessels blood passed through from the blood supply of the kidney to blood draining the kidney.

Renal artery Interlobular artery Arcuate artery Cortical radiate artery Afferent arteriole Glomerular capillary Efferent arteriole Peritubular capillaries Cortical radiate vein Arcuate vein Interlobular vein Renal vein

Name the arteries that supply the kidney, in sequence from largest to smallest.

Renal artery Segmental arteries Arcuate arteries Afferent arterioles

What is the correct branching sequence of arteries in the kidney?

Renal artery, segmental arteries, interlobar arteries

Indicate whether each of the following substances is reabsorbed from the filtrate or secreted into the filtrate.

Secreted: NH4- Drugs H+ Reabsorbed: Glucose Water Mg2+ HCO3- Amino acids Vitamins

During renal autoregulation, the kidneys maintain a relatively constant GFR despite changes in blood pressure, and without the input of nervous or hormonal control. The process whereby the flow of filtrate through the distal tubule results in changes in GFR is termed tubuloglomerular feedback. The three components of the juxtaglomerular apparatus are the JG cells, the macula densa, and the mesangial cells. Epithelial cells found where the distal tubule passes between the afferent and efferent arterioles are called the macula densa.

The afferent arteriole contains cells called juxtaglomerular cells that secrete the enzyme renin. The afferent arteriole reflexively contracts in response to a rise in blood pressure, thus preventing a rise in GFR. This form of regulation is called the myogenic mechanism. An increase in the rate of filtrate flow through the distal tubule results in contraction of the afferent arteriole and a decrease in GFR. When blood pressure drops, renin is released into the blood, resulting in an increase in the hormone angiotensin II, which acts to decrease GFR while simultaneously raising blood pressure.

The preprostatic urethra is connected to the urinary bladder. The prostatic urethra passes through a reproductive organ and receives two ejaculatory ducts.

The membranous urethra passes through the pelvis floor. The spongy urethra is the longest part of the male urethra.

The countercurrent multiplier is a phenomenon that occurs in the nephron loop. Countercurrent exchange occurs as both solutes and water move freely in and out of the vasa recta. The increase in osmolarity as filtrate moves down the descending limb is due to water moving out of the tubule. The decrease in osmolarity of the filtrate as it moves up the ascending limb is due to solutes moving out of the tubule.

The osmolarity of the filtrate is approximately 100 mOsm/L at the end of the ascending limb and around 1200 mOsm/L at the end of the descending limb. The recycling of urea out of the collecting duct and back into the nephron loop contributes significantly to the medullary osmotic gradient.

An obstruction in the renal pelvis would prevent urine from leaving the kidney. Urine directly exits the body via the urethra. The minor calyx receives urine from the renal pyramid.

The portion of the kidney in direct contact with the renal capsule is the renal cortex. The ureter and the renal artery and vein enter the kidney through the opening known as the hilum.

Low blood pressure causes the kidneys to increase the secretion of renin from the JG cells. The activation of angiotensin II stimulates widespread vasoconstriction, release of ADH from the posterior pituitary, as well as the adrenal cortex to release aldosterone. Aldosterone acts on the DCT of the kidney tubules to reabsorb greater amounts of sodium from the tubular fluid.

The release of ADH directly stimulates the collecting ducts of the kidney to increase water reabsorption from the tubular filtrate. The net result of angiotensin II, aldosterone, and ADH cooperatively is a(n) increase in blood pressure resulting largely from increased blood volume.

Negatively charged proteoglycans found in the basement membrane prevent most proteins in the blood from exiting the glomerular capillaries. Filtrations slits are formed by podocytes. Small openings in the capillary endothelium called fenestrations are too small to allow cells to leave the glomerulus.

The volume of blood that enters the afferent arteriole is not equal to the volume of blood that travels through the efferent arteriole due to the process termed glomerular filtration. A kidney infection or injury that results in damage to the filtration membrane may result in proteinuria (protein in the urine).

Match the component of urine formation with its description.

Water and solutes passively move out of the glomerulus Filtration Active transport or diffusion of substances into the blood Tubular reabsorption Active transport of solutes into the tubular fluid Tubular secretion

Place each of the labels in the proper position to denote whether they would pass through the filtration membrane or not.

Will Pass Through: sodium water urea thyroid hormone (TH) glucose Will Not Pass Through: RBCs lymphocytes Platelets Albumin TH bound to a plasma protein

Indicate whether each of the following would result in a more dilute urine or a more concentrated urine.

Would Result in a More Concentrated Urine: Working outside in the heat without access to water Overespression of aquaporins Increasing the permeability of the collecting duct to water Would Result in a More Dilute Urine: Drinking a large volume of water on a day when you rested and stayed insife Overdosing on Losartan, a drug that blocks action of angiotensin II. Overproduction of aldosterone A new virus that attacks and damages the pituitary gland.

1. Aldosterone enhances the reabsorption of sodium through the upregulation of the sodium-potassium pump found at the ________________. 2. In addition to enhancing the reabsorption of sodium, aldosterone also enhances the __________________ of potassium. 3. Antidiuretic hormone enhances water ______________ by _______________ the number of aquaporins at the tubular cell membrane.

basolateral membrane secretion reabsorption; increasing

Which of the following forces oppose glomerular filtration?

capsular hydrostatic pressure (HPc) and blood colloid osmotic pressure (OPg)

Place the following parts of the kidney in order of urine flow.

collecting duct, renal papilla, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, urethra

The vasa recta is a specialized capillary that branches from the ___________ arteriole. The blood flow in the vasa recta runs _______________ to the flow of tubular filtrate within the nephron loop.

efferent; parallel, but in the opposite direction

Tubular secretion involves the movement of substances

from capillary blood to tubular fluid.

The interstitial fluid within the medulla has a __________________ osmolarity than the interstitial fluid within the cortex.

higher

Treatment with Probenecid® results in _________________ levels of uric acid in the urine and __________________ levels of uric acid in the blood.

increased; decreased

Individuals with Bartter syndrome have a defective gene coding for Na+/K+/2Cl- symport (NKCC2) that disables it from functioning. These individuals are expected to have ___________ than normal blood potassium levels. This response is the ___________ what is expected from individuals taking prescribed loop diuretics.

lower; same as

The majority of sodium reabsorption occurs at the proximal convoluted tubule. During this process sodium enters the tubule cells at the ___________________ and exits the tubule cells at the ____________________.

luminal membrane by facilitated diffusion; basolateral membrane through the sodium potassium pump

Urine is formed in the

nephrons

Which of the following substances utilizes paracellular transport in order to cross the basolateral membrane of the tubule cell during the process of reabsorption?

potassium

Most of the water in tubular fluid is reabsorbed in the

proximal convoluted tubule

Under normal conditions the majority of uric acid reabsorption occurs at the _______________________.

proximal convoluted tubule

Which of the following is one of the processes in urine formation?

tubular secretion

Tubular reabsorption and tubular secretion differ in that __________________________.

tubular secretion adds materials to the tubular filtrate while tubular reabsorption removes materials from the tubular filtrate