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70 Cards in this Set
- Front
- Back
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What is the main function of the kidneys?
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Maintaining extracellular electrolytes and tonicity (300mosm)
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Where are the kidneys located?
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Retroperitoneal--outside of the peritoneal cavity
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What do kidneys filter?
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Blood
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What is the functional unit in the kidney?
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A multicellular nephron
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What are capillaries that pass by the kidneys called?
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Capillary tuft
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Explain bulk flow in the renal system.
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Pushes out protein-free plasma under force of blood pressure for filtration in the tubular system.
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What is filtrate?
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Pre-urine; can either become urine or be reabsorbed
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What is located in the renal corpuscle of the kidney?
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Bowman's capsule, which contains the glomeruli
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How many nephrons are in the kidney?
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1 million
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What happens in the renal pelvis?
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Has become urine at this point, and leaves the system.
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Explain tonicity changes in the kidney.
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Forms an osmotic gradient in the medullary region. Goes from 300mosm to 1400mosm toward the inside of the kidney. This is caused by juxtomedullary nephrons, and it allows us to vary the concentration of our urine.
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What are the two types of nephrons?
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Juxtamedullary nephron: closest to the medulla, but the corpuscle is still in the cortex, have long loops of Henle, form the osmotic gradient
Cortical nephron: further into the cortex than the juxtamedullary |
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What are the two types of tubules?
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Proximal tubule: closer to the renal corpuscle and convoluted
Distal tubule: closer to the cortical collecting duct, sometimes convoluted |
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How many nephrons come into the collecting duct?
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About 8
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Most nephrons (~80%) are
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Cortical nephrons
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What do we call the capillaries that surround the loops of Henle?
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Peritubular capillaries: allow for secretion and absorption
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Where do filtration, secretion, and absorption take place?
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Filtration: glomerular capillaries
Secretion and absorption: peritubular capillaries |
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What connects transport epithelia?
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Tight junctions: prevent proteins from moving around the cell. For example, the Na/K pump stays on the baso-lateral membrane.
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How does the Na/K pump work to filter in the kidneys?
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It aids in reabsorption by creating a sodium gradient that causes sodium in the tubular lumen to move back through the epithelial cells back into the blood. Amino acids and glucose are moved by secondary active transport back with sodium through the lumen back into the blood. The decreased osmolarity in the lumen allows water to travel through aquaporins back into the blood.
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What types of cells make up the juxtaglomerular apparatus?
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Juxtaglomerular: activates the enzyme renin that senses blood pressure
Macula densa: act as chemoreceptors to control rate of filtration, has some active substances as well Mesangial cells: Modified smooth muscle cells that vasodilate or vasoconstrict arterioles |
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How does renin regulate blood pressure in the renal system?
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Stimulates vasoconstriction of the afferent arteriole under low blood pressure and vasodilation under high blood pressure.
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How do the macula densa cells of the renal system control rate of filtration?
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Respond to high osmolarity with vasoconstriction and low osmolarity with vasodilation.
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How do blood vessels regulate glomerular filtration rate (GFR)?
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Decrease: constrict afferent or dilate efferent
Increase: constrict efferent or dilate afferent Dilation in response to sympathetic nervous system. |
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Examples of bulk flow:
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1) Cardiac output (MAP/TPR=5L/min)
2) Ventilation (Difference in alveolar and environmental pressure/resistance to flow in airway)(Tidal volume x respiratory rate)=6L/min 3) Capillaries (difference in blood pressure/proteins in the capillaries) 4) Glomerular filtration rate (GFR) (60mmHg blood pressure in the Bowman's capsule/29mmHg pulling in) 125mL/min or 180L/day |
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What is RAAS?
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Renin angiotensin aldosterone system
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What is different about the filtrate from plasms?
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Filtrate is protein-free
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Where is the filtrate considered urine?
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In the renal pelvis
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Review Table 14-5
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A
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What are podocytes?
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Cells with feet that extend over the glomeruli, can change shape to increase resistance to bulk flow.
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Explain glomerular filtration rate.
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(60mmHg bloodP-29mmHg osmoticP)/(capillary pores, basement membrane (repels proteins), podocyte slits in the Bowman's capsules)
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What is reabsorbed in the renal system?
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Na+ (1ry active), Cl- (follows Na+)
Glucose (2ry active, has tubular maximum (saturation)) Amino acids (2ry active, has Tm) Po42-, Ca2+ both active H2O (passive, follows NaCl) Urea (reabsorbed and secreted) |
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What is the main role of urea?
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To contribute to the osmotic gradient?
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What is secreted in the renal system?
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K+ (active NaK pump)
H+ (active) Prostaglandins, food additives, drugs, pollutants |
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How does vasopressin work?
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Protein kinase A phosphorylates snares to cause insertion of aquaporons in the luminal membrane.
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Explain what tubular maximum is in active transport.
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When tubular maximum is reached, glucose appears in the urine.
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Where does vasopressin work?
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In the collecting ducts
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Where does no sodium reabsorption take place? No water reabsorption?
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Descending branch of the loop of Henle, Ascending branch
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How is the medullary gradient created?
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By the countercurrent multiplier in the long loop of Henle. No sodium reabsorption on the descending loop and no water reabsorption in the ascending loop.
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Where is the amount of sodium and water reabsorption finally regulated?
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In the medullary collecting duct, under hormonal control
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What do the macula densa do?
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Can release vasoactive substances that can change the radius of the afferent arteriole.
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What does renin do in the renal system?
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Cleaves angiotensinogen into angiotensin I. Converted by ACE (angiotensin converting enzyme) into angiotensin II. ATII releases aldosterone, which inserts more NaK pumps in the basolateral membrane and more channels in the luminal membrane, increasing sodium reabsorption.
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Where does extrinsic regulation of H20 and sodium take place?
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In the collecting ducts
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What does the renin-angiotensin-aldosterone system (RAAS) regulate?
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Regulates MAP long term via regulation of blood volume. Uses the countercurrent multiplier in the long loops of Henle in juxtamedullary nephrons to achieve this.
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What does the enzyme renin do?
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Turns preprohormone angiotensinogen into prohormone angiotensin I.
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What does angiotensin converting enzyme (ACE) do?
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Converts prohormone angiotensin I to active enzyme angiotensin II.
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What does angiotensin II do? How is it produced?
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It is a potent vasoconstrictor. It also goes to the adrenal cortex and stimulates the release of aldosterone. Cut from angiotensinogen produced in the liver to angiotensin II to angiotensin I.
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What does aldosterone do? Where does it target?
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Aldosterone acts on the cortical collecting ducts to cause salt and H2O retention. It accomplishes this by adding more NA/K pumps to the BL membrane, more sodium channels and fewer K+ channels to the luminal membrane. It is a steroid and can diffuse through the lipid bilayer.
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What does vasopressin do?
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Increases permeability to H2O in the collecting ducts by adding aquaporins, increasing reabsorption of H2O.
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What three main factors respond to a decrease in blood pressure?
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1) Sympathetic nervous system UP
2) Baroreceptors in the juxtaglomerular cells 3) Chemoreceptors in the macula densa |
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How much urine must be excreted per day?
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500mL
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Explain the micturation response.
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Detrusor muscle contracts in response to parasympathetic nervous system during micturation. Internal sphincter is inhibited by sympathetic motor system during micturation, and external sphincter is inhibited by somatic motor. Bladder control comes from the external sphincter.
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Why do the effects of aldosterone take longer than that of vasopressin?
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There are more steps in aldosterone--steroid hormones take longer to act.
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What are the three basic functions of the renal system?
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Filtration, secretion, and reabsorption
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Where does glomerular filtration take place? Secretion and reabsorption?
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Glomerular filtration occurs at the junction of the glomerular capillary and the (Bowman's capsule)? Secretion and absorption occur at the junction of the tubule with the peritubular capillaries.
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Describe the general anatomy of a nephron.
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The body of the nephron is called the renal corpuscle, and contains the Bowman's capsule and the glomerulus. The macula densa lies between the glomerulus and the glomerular capillaries. Proximal and distal convoluted tubules extend upward, and the loop of Henle (with ascending and descending limbs) extends down toward the medulla.
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What is the vasa recta of the renal system?
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???
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Describe the anatomical and functional differences between the two types of nephron.
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Cortical:
Juxtamedullary: |
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What are the two ducts of the renal system called?
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Cortical and medullary collecting ducts
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Describe the anatomy of the renal corpuscle.
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Inside of the renal corpuscle is Bowman's capsule, which has visceral (podocyte) and parietal layers. The visceral layers contain the glomerular capillaries, and has filtration slits and fenestrae. At the junction with the afferent arteriole is the juxtaglomerular apparatus, composed of the macula densa cells and juxtaglomerular cells. The distal tubule ends at this point.
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Describe the flow of urine through the renal system.
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Begins in the renal cortex, enters the medulla through loops of Henle, exits through collecting ducts into the renal pelvis, then to the ureters, the bladder, and finally the urethra.
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Describe how diarrhea can cause alteration of GFR.
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Loss of Na+ and H2O cause lower blood volume, which means lower blood pressure. Baroreceptors detect this change and constrict the afferent arterioles, decreasing filtration pressure, and consequently, GFR.
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Describe how Na+ reabsorption is controlled by the renin-angiotensin system.
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1. Decrease in plasma volume stimulates renin secretion from juxtaglomerular cells.
2. Renin cleaves angiotensin I from liver-produced angiotensinogen. 3. Angiotensin I is cleaved into II by ACE. 4. Angiotensin II mediates vasoconstriction of (afferent) arterioles. 5. It also stimulates aldosterone secretion. 6. Aldosterone acts to increase reabsorption of Na+. |
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What is tubular reabsorption of urea dependent on?
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Reabsorption of water
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Tubular reabsorption of glucose is __ and __.
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Active and saturable
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The tubular fluid is ________ to plasma as it enters Bowman's space, ______ to plasma at the beginning of the loop of Henle, ______ to plasma at the tip of the loop and ________ to plasma as it leaves the loop to enter the distal convoluted tubule.
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Isoosmotic, isoosmotic, hyperosmotic, hypoosmotic
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What does the countercurrent multiplier system of the kidneys allow for?
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Allows the kidneys to form hypertonic urine
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The rate-limiting (regulated) step for stimulating the secretion of aldosterone is
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Conversion of angiotensinogen to angiotensin I in the blood
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What cells secrete renin?
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Juxtaglomerular cells in renal afferent arterioles
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How do baroreceptors affect vasopressin secretion?
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Decreased firing causes increased secretion
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What stimuli lead to aldosterone secretion?
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Both increased potassium ion concentration in adrenal cortical arterial blood and increased angiotensin II concentration in adrenal cortical arterial blood
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