RENAL SYSTEM
approximately 99% of water is absorbed in a normal, healthy person. If a person is chronically not reabsorbing the appropriate amount of water, they may have a condition known as:
diabetes
. Vasoconstriction of the efferent arteriole would lead to the release of renin from the JG apparatus: t or f
f
Nephrogenic form of diabetes insipidus results when there is a problem with the production or release of ADH from the hypothalamus/pituitary: t or f
f
The hormone renin is secreted by JG cells into the blood in response to a fall in the blood pressure within the efferent arteriole: t or f
f
t or f; loop diuretics inhibit ncc symporters
f
The transporter mechanism for the reabsorption of sodium in the TAL is
facilitated diffusion
what type of capilaries make up the floerules
fenestrated
18. Suppose a patient has high blood pressure, but cannot use beta blockers because of a low heart rate. With your understanding of renal physiology, what are some other medications that could be employed to treat this individual's hypertension?
i. Thiazide diuretics. ii. Angiotensin-converting enzyme (ACE) inhibitors. iii. Angiotensin II receptor blockers (ARBs). iv. Calcium channel blockers. v. Renin inhibitors.
The transport protein for the reabsorption of sodium in the DCT is:
na/k pump
what is the principal funtional unit of the kidney
nephron
the transporter protein for the reabsorption of soedium in teh tal is
nkcc2
Which of the following is not a part of the glomerular filtration membrane:
parietal layer of bowman's capsule
The majority (60 - 70%) of water is reabsorbed from the filtrate in the _______ of the nephron:
pct
________ are the cells that cover the capillaries of the glomerulus. They have many feet that interdigitate with the pedicels of their neighbors. They compose the ________ layer of Bowman's capsule:
podocytes ; visceral
The method of transport for the transporter protein for the reabsorption of sodium in the DCT is:
primary active transport
__________ is released in response to _____________ blood pressure in the heart:
renin ; decreased
The method of transport for reabsorption of glucose in the nephron:
secondary active transport
The transporter protein for reabsorption of glucose in the nephron is:
sglt
Vasodilation of the afferent arteriole will cause an increase in the glomerular filtration rate: t or f
t
t or f; acp regulates teh reabsorption of water in the collecing duct
t
tubular secreation
the active movement of solutes from teh capillariesinto the nephron
tubular reabsorption
the movement of important filtered solutes (like nutrients) back into the capillaries
describe flomerular filtration
the movement of plasma and dissolved solutes from the blood into the bowmans space
excretion
the relase of wastes from teh body
Loop diuretics carry out their pharmaceutical action at which portion of the nephron:
thick ascending limb of the loop of henle
14. What is the term given to the fluid that has entered Bowman's capsule and will run through the length of the nephron:
ultrafiltrate, glomerular filtrate, glomerular unltrafiltrate
______ of filtered glucose is reabsorbed by the kidneys. Failure to do so indicates a disease state (like diabetes mellitus). This reabsorption occurs in the ___________ of the nephron:
100% ; pct
Which of the following is incorrect: a. the kidneys are connected to the bladder via two ureters, down which, urine travels c. the renal corpuscle consists of a Bowman's capsule and a glomerulus b. the functional parts of the kidney have an outer portion called the cortex and an inner portion called the medulla d. cortical nephrons have glomeruli in the cortex while juxtamedullary nephrons have glomeruli in the medulla
D
11. How much water is reabsorbed by the PCT? Why is glucose normally not detected in the urine? Under what circumstances would it be?
a. 60-70% reabsorption of sodium and water. b. Because there is 100% reabsorption of glucose, along with amino acids. c. Diabetic or kidney failure.
35. Which of the following is correct: a. renal corpuscles of juxtamedullary nephrons are located in the cortex c. proximal convoluted tubules are solely found in the cortex b. the apex of a renal pyramid is adjacent to cortical tissue d. peritubular capillaries arise from the afferent arteriole
c
16. Can you explain how ADH works on the kidney to help regulate blood volume and pressure? What is central diabetes insipidus? Nephrogenic? What happens if tissue osmolarity is high? Low?
a. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absence of antidiuretic hormone, the collecting ducts are virtually impermeable to water, and it flows out as urine, which decreases BV and BP. b. Central diabetes insipidus is a lack of vasopressin (antidiuretic hormone) that causes excessive production of very dilute urine (polyuria). c. Nephrogenic is a rare disorder that occurs when your kidneys are unable to concentrate urine. d. Dilute urine. e. Concentrated urine.
7. Can you use your knowledge of the anatomy of a nephron and the renal vasculature to describe where these renal processes occur? What is hemodialysis and which of these processes does this clinical treatment replicate? How does secretion differ from excretion?
a. Basic renal processes per nephron segment: 1. Proximal convoluted tubule (PCT): - 60-70% reabsorption of sodium and water. - 100% reabsorption of glucose and amino acids. - Secretion of ions (e.g., ammonium, H+, HCO3-), drugs and toxins caffeine and theophylline cause diuresis by enhancing Na+ and H2O excretion 2. Loop of Henle: - 3 regions: descending limb, Henle's loop, ascending limb. - The loop of Henle and the vasa recta work together to concentrate the medullary tissue with solute (salt and urea). 3. Distal Convoluted Tubule (DCT) - Reabsorbs sodium ions (regulated by aldosterone). - Reabsorbs calcium ions (regulated by PTH and calcitriol). - Secretion of drugs and toxins. 4. Collecting Duct - Reabsorbs sodium ions (regulated by aldosterone). - Reabsorbs water (regulated by ADH/AVP and aldosterone). - Reabsorbs urea and bicarbonate. - Secretes proton. b. Hemodialysis: artificial kidney to filter wastes out of the blood. c. A secretion is a substance that is moved into a body space or onto the surface of the body (e.g., mucus in the lungs, fluid in the kidney and sweat). An excretion is a waste removed entirely from the body (e.g., urine and feces).
5. How does a glomerulus differ from a renal corpuscle? Can you describe the organization of a renal corpuscle? Can you describe the structure and location of the juxtaglomerular (JG) apparatus?
a. Bowman's capsule + the glomerulus = renal corpuscle. b. The renal corpuscle consists a fenestrated capillary bed (glomerulus) surrounded by a double-walled capsule (Bowman's capsule). c. The JG apparatus is a specialized structure formed by modified distal convoluted tubule cells and modified smooth muscle cells of the afferent arteriole.
19. What are the primary functions of the collecting duct? What is the effect of ADH on collecting duct? What effect does ADH have on the solute concentration and volume of urine? What is the effect of alcohol on ADH? How does this affect urinary output?
a. Collecting Duct reabsorbs sodium ions (regulated by aldosterone), reabsorbs water (regulated by ADH/AVP and aldosterone), reabsorbs urea and bicarbonate, and secretes proton. b. When ADH is present, the collecting duct becomes permeable to water. The high osmotic pressure in the medulla (generated by the counter-current multiplier system/loop of Henle) then draws out water from the renal tubule, back to vasa recta. c. Increase in ADH will cause a decrease in urine volume but a increase in solute concentration. d. Alcohol inhibits the pituitary secretion of anti-diuretic hormone (ADH), which acts on the kidney to reabsorb water. e. When ADH levels drop due to alcohol, the kidneys do not reabsorb as much water; consequently, the kidneys produce more urine.
3. What are the two different types of nephrons? Can you compare and contrast the structure and function of the two types of nephrons?
a. Cortical nephrons (80%) and juxtamedullary nephrons (20%). b. Cortical nephrons have their loops of Henle in the renal medulla near its junction with the renal cortex, while the loops of Henle of juxtamedullary nephrons are located deep in the renal medulla. Both are surrounded by peritubular capillaries and the juxtamedullary nephrons have special peritubular capillaries around their loops of Henle referred to as the vasa recta.
15. What renal processes occur in the DCT? How much water is reabsorbed by the DCT? Can you mechanistically describe the functions of ADH, aldosterone, PTH, calcitriol and thiazides on the DCT?
a. Distal Convoluted Tubule (DCT) reabsorbs sodium ions (regulated by aldosterone), reabsorbs calcium ions, and secrets drugs and toxins. b. ADH increases permeability to water. c. aldosterone increases the number of sodium-potassium pumps. d. PTH enhances the synthesis of all transporters within the distal convoluted tubule where it activates calcium absorption. e. Calcitriol inhibits PTH synthesis therefore inhibits calcium absorption. f. Thiazide diuretics increases calcium reabsorption at the distal tubule.
6. What is glomerular filtration? What is its purpose? What is tubular absorption? What is its purpose? What is tubular secretion? What is its purpose?
a. Glomerular filtration is the process by which the kidneys filter the blood, removing excess wastes and fluids from blood plasma. b. Its purpose is to filter the blood so that waste products (e.g., urea, uric acid and creatinine) are removed from the circulation. c. Tubular reabsorption is the process by which water and solutes (e.g., glucose, amino acids, fatty acids) are moved from the tubular fluid back into the circulating blood. d. Since filtration is only a selective process based on size, the purpose of reabsorption is to reabsorb all of the water, ions and nutrients lost during filtration. e. Tubular secretion is the transfer of materials from peritubular capillaries to the renal tubular lumen and occurs by active transport and passive diffusion. f. Its purpose is the opposite process of reabsorption. This secretion is thought of as a "back-up" to filtration, and typically involves the removal of waste products and toxins not removed via the filtration process.
20. What is natriuresis? Where is atrial natriuretic hormone (ANH) produced? Under what circumstances it is secreted?
a. Natriuresis is the excretion of sodium in the urine. b. Atrial natriuretic hormone secreted by heart muscle cells. c. Secretion of ANH is triggered by increased stretch of the atrial wall, due to raised blood pressure or increased blood volume. It acts to inhibit sodium reabsorption in the kidneys and the secretion of aldosterone by the adrenal glands.
2. What is the smallest structural and functional unit of the kidney? How many are there per kidney? Can you draw and label all of the segments of a nephron?
a. Nephron. b. ~1 million
Which of the following is incorrect regarding the effects of Angiotensin II: a. it causes increased aldosterone secretion c. it causes leads to decreased water secretion b. it causes vasoconstriction d. it causes the secretion of ADH
c
10. What renal processes occur in the PCT? Can you describe how the tubular concentrations of water, ions, nutrients and wastes are altered as they pass through the PCT? How do caffeine and theophylline cause diuresis in the PCT?
a. Proximal Convoluted Tubule (PCT) - 60-70% reabsorption of sodium and water, 100% reabsorption of glucose and amino acids, and of ions (ammonium, H+, and HCO3) drugs and toxins caffeine and theophylline cause diuresis by enhancing Na+ and H2O excretion. b. Cells in the hypothalamus detect low water content in blood. ADH is released into blood by the hypothalamus, acting on the distal tubule and collecting duct. This causes more water to be reabsorbed into the peritubular capillary. Therefore, blood volume increases. As the blood becomes more dilute, this is detected by the hypothalamus, causing ADH secretion to stop. So, in other words, the concentration shift is what causes the filtering to happen with ADH helping. c. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine.
4. Can you diagrammatically describe the vasculature associated with a nephron? What vessel feeds the glomerulus? What vessel drains it? What are the functions of peritubular capillaries? The vasa recta?
a. Renal artery segmental artery interlobar artery arcuate artery interlobar artery afferent arteriole glomerulus efferent arteriole peritubular capillaries interlobar vein arcuate vein interlobar vein segmental vein renal vein. b. Afferent arteriole. c. Efferent arteriole. d. First, these vessels deliver oxygen and nutrients to the epithelial cells. Second, they are responsible reabsorption of tubular fluid and secretion of solutes into the tubular fluid. e. Peritubular capillaries are responsible reabsorption of tubular fluid and secretion of solutes into the tubular fluid. Vasa recta prevent the solute gradient created in the renal medulla from being washed out (i.e., diluted).
14. What is the NKCC2? Where is it located? What is its function? What drugs are designed to inhibit it? Clinically, why would we want to inhibit the NKCC2? Physiologically, what happens when the NKCC2 is inhibited?
a. The Na-K-Cl cotransporter (NKCC) is a protein that aids in the active. transport of sodium, potassium, and chloride into and out of cells. b. Located in the apical membrane of the epithelial cells of the thick ascending limb of the loop of Henle. c. Transport sodium, potassium, and chloride into and out of cells through the loop of Henle. d. Dilute the urine more to reduce BV and thus reduce BP. e. Impairment of sodium reabsorption in the thick ascending limb of the loop of Henle.
9. Can you explain, in detail, the determinant of glomerular filtration pressure (i.e., explain the Starling forces of the glomerulus)? What is filtered by the glomerulus into Bowman's space? What remains behind in the blood? How much plasma is filtered per day? How much plasma is reabsorbed per day? How much urine is formed per day? What is polyuria? What can conditions can cause this phenomenon?
a. The forces that favor filtration (movement out of the glomerulus and into Bowman's space) are glomerular hydrostatic pressure (which is essentially blood pressure in the glomerulus; 60 mmHg) and capsular osmotic pressure (which is negligible; 0 mmHg). The forces that favor reabsorption (movement out of the Bowman's space and back into the glomerulus) are glomerular osmotic pressure (which is primarily as the result of plasma albumin; 29 mmHg) and capsular hydrostatic pressure (15 mmHg). If you subtract the forces favoring reabsorption from the forces favoring filtration, you end up with the effective filtration pressure, 16 mmHg. b. The blood plasma is filtered through the capillaries of the glomerulus into the capsule. The Bowman's capsule empties the filtrate into the proximal tubule that is also part of the duct system of the nephron. A glomerulus receives its blood supply from an afferent arteriole of the renal circulation. c. The glomerulus filters proteins and cells (i.e., does not let them pass), which are too large to pass through the membrane channels of this specialized component, from the blood. These large particles remain in the blood vessels of the glomerulus, which join with other blood vessels so that the proteins remain circulating in the blood throughout the body. The small particles like ions, nutrients and nitrogenous wastes pass through the membranes of the glomerulus into Bowman's capsule. These smaller components then enter the membrane-enclosed tubule in essentially the same concentrations as they have in the blood. Hence, the fluid entering the tubule is identical to the blood, except that it contains no proteins or cells. d. The heart pumps about 5 L blood per min under resting conditions. Approximately 20 percent or one liter enters the kidneys to be filtered. On average, this liter results in the production of about 125 mL/min filtrate produced in men (range of 90 to 140 mL/min) and 105 mL/min filtrate produced in women (range of 80 to 125 mL/min). This amount equates to a volume of about 180 L/day in men and 150 L/day in women. Ninety-nine percent of this filtrate is returned to the circulation by reabsorption so that only about 1-2 liters of urine are produced per day. e. Look at answer to D. f. Look at answer to D. g. Production of abnormally large volumes of dilute urine. h. Drinking excessive amounts of fluids (polydipsia), particularly water and fluids that contain caffeine or alcohol. It is also one of the major signs of diabetes mellitus. When the kidneys filter blood to make urine, they reabsorb all of the sugar, returning it to the bloodstream.
8. Can you list the components of the glomerular filtration membrane and describe its anatomical organization? What type of capillaries make up the glomerulus?
a. The glomerular capillary endothelial cells, the glomerular filtration membrane and the filtration slits (podocyte pedicels) between the podocytes perform the filtration function of the glomerulus, separating the blood in the capillaries from the filtrate that forms in Bowman's capsule. The glomerular filtration membrane is a fusion of the endothelial cell and podocyte basal laminas. b. Fenestrated capillaries.
17. Where is the JG apparatus located? How does it function in regulating RBC numbers? Blood pressure? Under what circumstance is renin secreted from JG cells? What is the function of renin? Can you diagrammatically describe the renin-angiotensin-aldosterone system (RAAS)? What are all of the functions of angiotensin II? Suppose you had severely low blood pressure, how would you expect the JG apparatus to respond?
a. The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole. It is located near the vascular pole of the glomerulus. b. Juxtaglomerular apparatus cells secrete a hormone called erythropoietin, which is critical for the production of red blood cells. c. When systemic blood pressure decreases, there is decreased stretch of JG cells, which leads to their release of renin. Renin release causes the activation of renin-angiotensin mechanism, which ultimately leads to an increased blood pressure. d. Look at answer of C. e. Look at answer of C. f. Three step system for its release: i. Sympathetic nerve activation (acting through β1-adrenoceptors). ii. Renal artery hypotension (caused by systemic hypotension or renal artery stenosis). iii. Decreased sodium delivery to the distal tubules of the kidney. g. Angiotensin II constricts resistance vessels thereby increasing systemic vascular resistance and arterial pressure. Stimulates sodium transport (reabsorption) at several renal tubular sites, thereby increasing sodium and water retention by the body. Acts on the adrenal cortex to release aldosterone, which in turn acts on the kidneys to increase sodium and fluid retention. Stimulates the release of vasopressin (antidiuretic hormone, ADH) from the posterior pituitary, which increases fluid retention by the kidneys. h. Juxtaglomerular apparatus cells would secrete a hormone called erythropoietin, release renin, and activate of renin-angiotensin mechanism, which ultimately leads to an increased blood pressure.
role of antidiuretic hormone in the nephrom
causes insertion of aquaporins into the apical membrane of the collecting duct (and some of the DCT)
12. Can you draw and identify the different regions of the loop of Henle? How much water is reabsorbed by the ascending limb of the loop of Henle? The descending limb?
a. The loop of Henle forms a hair-pin structure that dips down into the medulla. It contains four segments: the pars recta (the straight descending limb of proximal tubule), the thin descending limb, the thin ascending limb, and the thick ascending limb. The turn of the loop of Henle usually occurs in the thin segment within the medulla, and the tubule then ascends toward the cortex parallel to the descending limb. The end of the loop of Henle becomes the distal convoluted tubule near its original glomerulus. The loops of Henle run in parallel to capillary loops known as the vasa recta. Recall that the loop of Henle serves to create high osmotic pressure in the renal medulla via the counter-current multiplier system. Such high osmotic pressure is important for the reabsorption of water in the later segments of the renal tubule. b. Ascending limb of the loop of Henle is impermeable to water. c. Descending limb of the loop of Henle reabsorbs majority of water.
13. Can you explain, in detail, how the loop of Henle and the vasa recta work in concert to generate solute in the medulla of the kidney (i.e., countercurrent multiplication)?
a. The movement of fluid through the tubules causes the hyperosmotic fluid to move further down the loop. Repeating many cycles causes fluid to be near isosmolar at the top of Henle's loop and very concentrated at the bottom of the loop. Interestingly, animals with a need for very concentrated urine (such as desert animals) have very long loops of Henle to create a very large osmotic gradient. Animals that have abundant water on the other hand (such as beavers) have very short loops. The vasa recta have a similar loop shape so that the gradient does not dissipate into the plasma. The mechanism of counter current multiplication works together with the vasa recta's counter current exchange to prevent the wash out of salts and maintain a high osmolarity at the inner medulla.
21. Can you explain why drinking too much water can be dangerous? What symptoms would an individual exhibit if they were "water intoxicated"?
a. This can cause a dangerous influx in sodium levels. Sodium balances the fluids in and around your cells. Drinking too much water causes an imbalance, and the liquid moves from your blood to inside your cells, making them swell and sometimes burst. b. Symptoms i. Whole body: water-electrolyte imbalance, dizziness, fatigue, or lightheadedness. ii. Gastrointestinal: nausea, vomiting, or water retention. iii. Muscular: abnormality walking, cramping, or muscle weakness. iv. Also common: excess urination, mental confusion, headache, or sleepiness.
1. Can you describe the anatomical organization of the urinary system? The cross-sectional anatomy of a kidney?
a. Two kidneys, two ureters, urinary bladder and urethra. b. Cortex: Bowman's capsule, PCTs and DCTs. Medulla: composed of 6-7 renal pyramids containing loops of Henle and collecting ducts. Collecting ducts open into minor calyces which open into major calyces which open into the renal pelvis.
The reabsorption of Na+ in the DCT is regulated by ________ while the reabsorption of Ca++ is regulated by ________:
aldosterone: pth (or calcitriol)
Which of the following is not a solute found in glomerular ultrafiltrate: a. albumin c. glucose b. sodium d. amino acids
almbumin
. The active form of angiotensin is ____________, which is primarily produced in the _________:
angiotensin II : lungs
Which of the following is an incorrect way to increase glomerular filtration rate: a. drinking a gallon of water (over one hour) c. vasoconstriction of efferent arterioles b. vasoconstriction of afferent arterioles d. acute hypertension
b
how loop diuretics (Like furosemide) work
block NKCC2 symporters resulting in decreased solute reabsorption (and thus water reabsorption) leading to increased urine volume