ch 26 Urinary

Question 1

1. What are the organs of the urinary system?

2. Of these organs, which are the major excretory organs that also play many roles in metabolism?

Answer 1

1. 2 kidneys, 2 ureters, urinary bladder, and the urethra

2. the kidneys

Question 2

What are the functions of the urinary system?

Answer 2

regulates blood solute concentration, blood volume and pressure, pH and osmolarity, produces the hormone erythropoietin, and excretes wastes, drugs and toxins,

Question 3

1. What enters the kidney at the hilum?
2. What are the bases of the renal pyramids called, and where do they project into?
3. Describe what the renal pyramids are made of, and what they do.
4. trace the pathway of fluid through the kidney until it exits as urine.

Answer 3

1. renal artery and nerves (which enter the kidney)m and the renal vein and ureter (which exit the kidney).
2. Medullary rays, the cortex.
3. a collection of tubes and ducts that transport fluid throughout the kidney and modify it into urine
4. from the renal pyramids, urine goes to renal papillae, then to minor calices, major calices, renal pelvis and ureter.

Question 4

1. Nephrons are the ……….. units of the kidney. How many nephrons are in each kidney?
2. What do nephrons consist of?
3. Where are each of the structures of the nephron located?
4. What do the different parts of the nephron do?
5. Where does the renal tubule empty?

Answer 4

1. functional, over a million
2. The renal corpuscle, and renal tubule (consists of proximal convoluted tubule, loop henle (nephron loop), and distal convoluted tubule).
3. Renal corpuscle: in the cortex.
   Proximal Convoluted Tubule: in cortex.
   Loop of henle: sections in both cortex and medulla.
   Distal Convoluted Tubule: cortex.
4. Renal corpuscle makes a filtrate from blood. Renal tubule processes the filtrate.
5. Empties into a collecting duct.

Question 5

1. What are the 2 types of nephrons?

2. What is the difference between these 2 types of nephrons?

Answer 5

1. cortical nephrons, and juxtamedullary nephrons.
2. Juxtamedullary nephrons have loops of Henle that extend much deeper into the medulla than the loop of Cortical nephrons. The deeper in the medulla, the more water that they conserve.

Question 6

1. What does the renal corpuscle consist of?
2. what happens to fluid that flows out of the glomerulus?
3. How many layers does the bowman capsule have, and what are they composed of, and what is important about them?
4. What comprises the filtration membrane?
5. What does the filtration membrane prevent passage of?

Answer 6

1. a ball of capillaries (glomerulus) surrounded by a bowman capsule (glomerular capsule).
2. it is captured by the capsule.
3. 2 layers (parietal and visceral). Parietal: simple squamous epithelium. Forms a container for filtrate and continues into PCT. Visceral: epithelial cells called podocytes (adheres to glomerular capillaries).
4. The glomerular capillary endothelium (fenestrated), the basement membrane, and the podocytes (which have filtration slits).
5. molecules larger than the smallest proteins.

Question 7

1. Blood flows to the glomerulus by an …………….. arteriole, and an ………….. arteriole drains the glomerulus.
2. What sits between these two arterioles? What does it secrete and in response to what stimulus?
3. What surrounds the afferent arteriole?
4. What lines the DCT n the small section close to the juxtaglomerular apparatus??

Answer 7

1. afferent, efferent.
2. The juxtaglomerular apparatus. Renin. In response to low blood pressure and low urine output.
3. juxtaglomerular cells.
4. a group of specialized cells called macula densa.

Question 8

1. How long is the renal tubule? Is the PCT or DCT longer?
2. What is the epithelium of the PCT?
3. The loop of Henle has both ………… and ………….. parts
4. Why do juxtamedullary nephrons have a long part that appears thin?
5. The rest of the ascending limb is thick and lined by …………….. ………………. ………………. .
6. What type of epithelium are the DCT and collecting ducts lined with?

Answer 8

1. 50-55 mm long. PCT.
2. Simple cuboidal epithelium with microvilli
3. Ascending and descending
4. because cells are simple squamous (for more diffusion)
5. simple cuboidal epithelium
6. simple cuboidal epithelium

Question 9

1. What does the efferent arteriole form?

Answer 9

1. peritubular capillaries around both the PCT and DCT in the cortex, and vasa recta around the loop of henle in juxtamedullary nephrons in medulla.

Question 10

1. What is the main function of the kidneys?
2. What 3 processes make it possible for the kidneys to fulfill it’s function?
3. What is filtration?
4. What is tubular reabsorption?
5. What is Tubular secretion?

Answer 10

1. Filter the blood by allowing waste and toxin to go into filtrate and recover useful substances.
2. Filtration, tubular reabsorption, and tubular secretion.
3. forms filtrate from blood using blood pressure
4. removes useful substances from filtrate and returns it to blood in peritubular capillaries.
5. additional secretion of certain solutes to increase their loss from the blood.

Question 11

1. How does filtration force material through the filtration membrane?
2. What is the renal fraction?
3. What is the renal blood flow rate, and how do you calculate it?
4. What is GFR? And how much of the blood is it?
5. What is the benefit of this large volume?

Answer 11

1. With blood pressure.
2. The percentage of cardiac output that is routed to the kidneys. Typically 21% when body is at rest.
3. 1. it is a standard measure of blood flow through the kidney to determine if its working well.
      CO X Renal Fraction (remember this is 21%)
4. The glomerular filtration rate. It is the percentage of the plasma entering the glomerulus that becomes filtrate. 19%, 125ml/minute, or 180 liters per day.
5. Quick and easy removal of unwanted solutes.

Question 12

1. What are the 3 pressures that contribute to filtyration pressure?
2. What is GCP?
3. What is CHP?
4. What is BCOP?
5. How do you calculate Filtration Pressure?

Answer 12

1. Glomerular Capillary Pressure GCP, Capsular Hydrostatic Pressure CHP, and Blood Colloid Osmotic Pressure BCOP
2. Glomerular Capillary Pressure: outward pressure from blood pushing against capillary walls. Higher than systemic capillary blood pressure because afferent arteriole is bigger than efferent arteriole. approx 50 mmHg.
3. Capsular Hydrostatic Pressure: inward pressure exerted by capsule walls and resistance of fluid in tubule. approx 10 mmHg.
4. Blood Colloid Osmotic Pressure: inward pressure that opposes filtration. Due to proteins in blood. Approx 30 mmHg
5. GCP-(CHP + BCOP) = Filtration Pressure 10 mmHg

Question 13

1. T or F, GFR remains constant over a wide range of conditions? Why?
2. What happens if GFR is too high? If too low?
3. What are the names of the 2 mechanisms of autoregulation of GFR?
4. Describe each of these mechanisms.
5. What does sympathetic stimulation do to GFR during shock or exercise?

Answer 13

1. T because of autoregulation. Afferent arteriole constricts if high blood pressure, and dilates with low blood pressure.
2. materials can’t be reabsorbed quick enough. If too low, wastes can’t be secreted well.
3. myogenic mechanism and tubuloglomerular feedback mechanism
4. Myogenic mechanism: smmoth muscles in afferent arteriole contract when stretched and relax when wall diameter is reduce.

Tubuloglomerular Feedback Mechanism: macula densa cells detect flow rate in DCT and adjust diameter of afferent arteriole to maintain constant flow rate.

5. reduces GFR to allow blood flow to other tissues.

Question 14

1. How much water and other solutes are returned to the blood in tubular reabsorption?
2. What are the solutes?
3. How does water move between the tubules, interstitial fluid, and blood?
4. Why is reabsorption regulated and what is the result?

Answer 14

1. 99%
2. amino acids, sugars, Na+, K+, Ca+2, HCO3-, and Cl-
3. Osmosis
4. Regulated to produce either large volume of dilute urine or small volume of concentrated urine, depending on body’s needs.

Question 15

1. Where does the majority of reabsorption in the renal tubule occur and how is it driven?
2. Tubular cells have an ……….. membrane and a …………. membrane. Which one faces the lumen? Which one faces the interstitial fluid?
3. How does reabsorption of most solutes occur and with what ion?
4. Solute transport across the basal membrane is by what 2 mechanisms?
5. Why can a solute concentration not be removed if it’s too high?
6. What does water do when solutes are reabsorbed?
7. What happens to solutes that are not transported? Name these solutes.
8. At the end of the PCT, how much of the filtrate volume has been reabsorbed? What happens to the osmotic concentration?

Answer 15

1. In the PCT, driven by a steep Na+ gradient
2. Apical and basal. Apical faces lumen, basal faces interstitial fluid.
3. Symport with Na+ down its concentration gradient and the pumping of Na+ across the basal membrane.
4. facillitated diffusion and active transport
5. because the number of transport proteins is finite and their ability to to transport solutes is limited. So a concentration of solutes in excess cannot all be moved.
6. It follows by osmosis.
7. They increase in concentration and may leave the filtrate between the PCT cells by diffusion. K+, Ca+2, and Mg.
8. 65%, osmotic concentration is same as the interstitial fluid.

Question 16

1. Where is renin secreted from?
2. What stimulates the release of renin?
3. What does renin secretion lead to?
4. Where is aldosterone produced? What factors stimulate its secretion?
5. What does aldosterone do?

Answer 16

1. The juxtaglomerular apparatus
2. Reduced stretch of the afferent arterioles (signifies low blood pressure) and decreased Na+ concentration in the DCT filtrate (macula densa cells detect this).
3. renin activates angiotensin I from liver, which is activated by ACE from lungs into angiotensin II, a powerful vasoconstrictor. This raises BP and triggers the release of aldosterone.
4. produced by cortical cells of adrenal glands. Angiotensin II, Low levels of Na+ in interstitial fluid and increases of K+ in blood trigger its release.
5. Helps to raise BP and GFR by recovering Na+, Cl-, and water in DCT and collecting ducts.

Question 17

1. Where is ADH released from? What are its triggers?
2. ………………………. cells in the ……………….. …………….. of the hypothalmus detect ……………… in interstitial osmolarity and send action potentials to their axon terminals releasing ………… .
3. What happens without ADH?

Answer 17

1. Posterior pituitary. Increased blood osmolarity, and significantly decreased BP
2. osmoreceptor, supraoptic nucleus, increases, ADH
3. Large amounts of dilute urine are produced because little water is recovered in DCT and collecting tubules. This causes Dehydration and diabetes insipidus.

Question 18

1. When ADH is secreted where does it bind to?
2. ADH stimulates the insertion of ………………… molecules on the ………….. and …………….. membranes.
3. aquaporin increases or decreases the membranes permeability to water?
4. Water leaves the tubule by ……………. from the dilute filtrate to the ……………… ……….. and ………… …………… leaving a small amount of urine.
5. When ADH is not present, what happens to the aquaporins and the tubules? What does this result in?

Answer 18

1. cells of the DCT and collecting tubules
2. aquaporin, basal, and apical
3. increases
4. osmosis, interstitial fluid and vasa recta
5. they are removed from the membrane and the tubules become impermeable to water. Large volume of dilute urine.

Question 19

1. Where is Atrial Naturietic Peptide produced, and in response to what?
2. What does ANP reduce and how?
3. What hormone does ANP inhibit? What does is cause?

Answer 19

1. In the right atrial cardiac cells, stretch of the artia (high BP).
2. BP by reducing Na+ reabsorption and water recovery.
3. ADH. Widespread vasodilation

Question 20

1. What is plasma clearance?
2. How do you calculate plasma clearance?
3. If inulin is not reabsorbed, what does this mean?
4. Explain how plasma clearance can be used to estimate GFR.

Answer 20

1. its the volume of plasma (blood) cleared of a substance in a minute.
2. plasma clearance = urine produced (ml/min) X (concentration in urine/concentration in plasma)
3. It means that plasma clearance is equal to the GFR
4. By using a substance (such as inulin) that passes as freely as water thru the filtration membrane, is not reabsorbed, and is not secreted into the renal tubule, nor fabricated y the kidneys, then the plasma clearance for that substance is equal to the GFR.

Question 21

1. What is tubular load?
2. What is the tubular maximum? Does it differ depending on the substance?
3. What does tubular maximum depend on?
4. What happens if the tubular load exceeds the tubule maximum?

Answer 21

1. Tubular load of a substance is the amount of that substance that passes through the filtration membrane into the renal tubule each minute.
2. The maximum rate that a tubule can reabsorb a substance. Greatly differs depending on substance
3. The number of active transport carrier proteins for the particular substance and the rate they transport the substance.
4. The substance will end up in the urine.

Question 22

1. …………….. ………… push fluid through the urine tubule and ……………… …………. move urine down the ureters to the bladder.
2. what reflex produces urination?
3. Urine filling the bladder stimulates what? Where are action potentials sent? What happens as a result?
4. Action potentials ascend to the micturition center in the ……….. and ………… .
5. How do higher brain centers inhibit micturition?

Answer 22

1. hydrostatic pressure, peristaltic waves
2. micturition reflex
3. Stretch receptors. Sacral spinal cord region. Smooth muscle in the bladder contracts and the internal sphincter relaxes (women don’t have an internal sphincter)
4. pons and cerebrum
5. They inhibit the spinal micturition reflex and keep external urethral sphincter contracted.

Question 23

1. What happens to the kidneys as we age?
2. What happens to the glomeruli? The ability to concentrate urine?
3. responsiveness to ADH and aldosterone …………….. Ability to produce renin decreases, and ability to participate in vitamin D synthesis declines which leads to ……………..
4. How much of the kidney is required to maintain homeostasis?

Answer 23

1. They decrease in size (becomes obvious after age 50). The amount of blood flow thru the kidneys decreases about 10% per every 10 years after age 20.
2. the glomeruli become twisted ann non-functioning. By age 80 40% of glomeruli are non-functioning. Urine concentration declines.
3. declines. osteoporosis and fractures.
4. 1/3 of the kidney

Question 24

1. On what side of the renal tubule cell does active transport happen during reabsorption of materials, and what ion is exchanged with Na+?
2. How does symport work in the renal tubule?
3. Name the substances that move by active and passive transport and in what parts of the renal tubule does this movement take place.
4. What are the 3 ions that can diffuse between tubule cells when concentrations exceed the rate they can be symported out?

Answer 24

1. On the basal side, K+
2. more Na+ in the tubule (as compared to the epithelial cells) will cause Na+ to enter the cytoplasm of epitheleal cells taking other ions along for the ride. This piggy backing of ions with Na+ is symport
3. On the apical side of PCT most everything is symported in w/ Na+. On the apical side of thick ascending Henle and DCT, only K+ and Cl- symport w/ Na+.

On basal side of all renal tubules, Na+ is actively transported in exchange for K+.

On basal side of PCT all the ions that entered with Na+ exit by facilitated diffusion. On basal side of thick ascending Henle and DCT, only K+ and Cl- exit by facilitated diffusion.

4. K+, Ca2+, and Mg2+