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51 Cards in this Set
- Front
- Back
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Which organs constitute the urinary system?
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Kidneys, Ureters, Urethra, Urinal Bladder, Rectum,
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Why are the kidneys said to be retroperitoneal?
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Becuase their position is posterior to the peritoneum of the abdominal cavity.
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What are the three layers of the kidney their histology and their functions?
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1. Renal Capsule -deepest layer -sheet of dense irregular connective tissue -a barrier against trauma and maintains shape. 2. Adipose capsule - fatty tissue - protect from trauma- hold in place 3. Renal Fascia -superficial layer - thin dense irregular tissue -anchors kidney to other structures
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What structures pass through the renal hilum?
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Hilum extends into the renal sinus which contains parts of the renal artery and vein, renal pelvis, the calyces and branches of nerves.
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What amount of blood per minute flows through the renal arteries? How much of this is resting cardiac output?
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Renal blood flow is about1200ml/min and is 20% of the resting cardiac output.
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List the path of blood through the kidneys
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1.Renal artery 2. Segmental arteries 3. Interlobular arteries 4. Arcuate arteries 5. Interlobular arteries 6. Afferent arterioles 7. Glomerular capillaries 8. Efferent arterioles 9. Peritubular capillaries 10. Interlobular veins 11. Arcuate veins 12. Interlobular veins 13. Renal vein
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List the path of urine drainage
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In the nephron;
1. Papillary duct in renal pyramid 2. Minor Calyx 3. Major Calyx 4. Renal Pelvis 5. Ureter 6. Urinary Bladder. |
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What are the basic differences between cortical and juxtamedullary nephrons?
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Cortical nephrons 80%, outer portion of cortex, short loops of Henle &lie in the cortex Juxtamedullary nephrons,15 - 20%, long loops of henle that penetrate deep into the medulla, thin followed by thick ascending limb
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What are podcytes where are they found and what is their function?
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Podcytes are cells found in the visceral layer of the Bowman's capsule that wrap their pedicels around gomerular capillaries. The spaces between them are called slit membranes which permit the passage of small molecules (0-006-0.007um)e.g. plasma proteins, glucose vitamins ammonia urea & ions
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What is glomerular filtrate and what is the filtrate fraction?
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Fluid that enters the capsular space is termed filtrate. The fraction of blood plasma in the afferent arterioles that becomes filtrate is the filtrate fraction usually 0.16-0.20 (16%-20%)
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What is the deepest layer of the filtration membrane composed of and what is its function?
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Glomerular endothelial cells- Fenestration pores -permits solutes exit from glomerular & prevents filtration of RBC & platelets. Contractile mesingal cells help regulate glomerular filtration
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What is the basal lamina? What is its function?
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The middle layer of the filtration membrane. A layer of acellular material between the podcytes and the endothelium of the filtration membrane consiting of minute collagen fibers & proteglycans in a glycoprotein matrix, to prevent filtration of larger plasma proteins
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What is the principal of filtration?
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The use of pressure to force solutes and fluid through a membrane.
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Why is the volume of fluid filtered by the glomerular capillaries larger than in other capillaries of the body?
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Thre reasons;
1. Larger surface area provided by relaxed mesingal cells 2. Membrane is thin & pourous,3 layers 0.01um thick. Also GC 50X leakier than other capillaries due to fenestrations 3. Glomerular capillary BP is high due to the efferent arteriole being smaller in diameter than the afferent arteriole. |
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What is net filtration pressure?
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NFP is the sum of glomerular blood hydrostatic pressure GBHP, capsular hydrostatic pressure CHP an opposing force & blood colloid osmotic pressure BCOP also an opposing force. NFP = GBHP - CHP- BCOP
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What is the equation for NFP?
When would filtration cease? What could cause this? |
NFP =
55mm Hg - 15mm Hg - 30mm Hg = 10mm Hg A minimum pressure of 10mm Hg causes filtration. Pressure below 10mm Hg ceases filtration, this could be caused by hemorrhage |
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What happens if GFR is too high?
Too low? |
Too High can cause loss of needed solutes by fluid moving to fast and not being reabsorped, too low and nearly all filtrate can be reabsorped & waste products will not be adequately excreted
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Describe the myogenic mechanisim in renal autoregulation.
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Elevated sytemic blood pressure stretches the walls of the afferent arterioles causing the smooth muscle to contract narrowing the lumen. Renal blood flow is then decreased returniing GFR to homeostatic levels within seconds.
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Describe tubuloglomular feedback in renal autoregulation
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Elevated systemic BP causes fluid to flow too rapidly through renal tubule and Na+ and Cl- arent reabsorbed. The macula densa detects extra Na and Cl and h2O from cells in the JA and inhibits release of NO, (NO=vasodialator) causing afferent arterioles to constrict and as a result less blood flows through the capillaries and GFR is decreased
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What is the juxtamedullary apparatus (JA)?
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juxtamedullary cells + macula densa = JA
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How does filtered glucose enter and leave a PCT cell?
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Na-glucose symporters in the APICAL membrane transport glucose.It attaches to a symporter protein which carries it from the tubular fluid into the cell. They then exit via the basoleteral membrane by facilitated diffusion, diffusing into peritubular capillaries
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What do the secondary active transport Na/H antiporters do?
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Carry filtered Na down its concentration gradient into a cell as H is moved from the cytosol into the tubule. This causes Na to be rabsorped and H to be secreted into tubular fluid.
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How do PCT cells keep antiporters operational?
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CO produced by metabolic reaction or diffuse from peritubular blood and react with water in the presence of carbonic anhydrase to form carbonic acid which the dissociates into H and HCO3 and reabsorbed mostly in the PCT recycling HCO3 in a buffer system
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By what mechanisim is water reabsorbed from tubular fluid?
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Osmotic gradient produced by reabsorption of solutes promotes reabsorption of water via osmosis
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Write the chemical formula for the reaction of CO
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CO2 + H2O -in the presence of CA - H2CO3 ___H + HCO3
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Where does passive reabsorption occur and what solutes are involved?
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Occurs in the 2nd half of the PCT caused by the elctrochemical gradients of Cl, K, Ca Mg & urea
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Which ion makes ISF electronegativity higher than tubular fluid promoting passive reabsorption of which cations (+ions)?
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Negatively charged chlorine promotes paracellular reabsorption of K+ Ca2+ & Mg+
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What is ammonia? How is it formed and how and where is it secreted?
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NH3 is produced by the liver when it deminates proteins. Most is converted into urea. NH3 & urea are filtered @ glomerulus and secreted in the PCT
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Which hormone stimulates reabsorption & secretion by principal cells and how does this hormone exert its effect?
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In principal cells aldosterone stimulates secretion of K & reabsorption of Na by increasing the activity of Na/K pumps & number of leakage channels for Na & K
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If a tumor is presing on the right ureter what effect might this have on CHP and thus NFP in both kidneys?
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Obstruction would cause higher CHP and thus would decrease NFP in the right kidney. The left kidney would not be effected
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What is reabsorped in the Loop of Henle?
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20-30% of filtered K Na Ca2 & HCO3; 35% of filtered Cl A 15% filtered water.
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What and how does the DCT absorb ions?
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The DCT reabsorbs Na & Cl ions via Na/Cl symporters
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What occurs in the collecting duct?
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Intercalated cells reabsorb K & principal cells reabsorb a & secrete K
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Which symporters are located in the apical membrane of the thick descending limb of the Loop of Henle? What is the main effect?
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Leaky K channels & Na-K -2Cl symporters that reclaim 2 chloride ions and 1 potassium and 1 sodium ion from the tubular lumen via active transport. Most K moves down its gradient & returned to tubular fluids, thus Na & Cl reabsorption are the main functions.
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Why is the osmolarity of fluid in the LOH similar to blood plasma? What does this set the stage for?
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Because many nutrients as well as 65% of water were reabsorbed in the PCT setting the stage for independant regulation of volume and osmolarity of body fluids
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Describe the basic reabsorption process in the DCT
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95% of all solutes are already reabsorbed.10-15% more water reabsorbed. PTH stimulates reabsorption of Ca. Principal cells secrete K & reabsorb Na. Intercaleted cells reabsorb K & HCO3 & secrete H
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How do principal cells function?
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Reabsorb sodium and secrete a variable amount of potassium according to dietry needs. In contrast to other segments of the tubule sodium enters cell via leakage channels not symporters
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How does the renin-angiotensin-aldosterone pathway function?
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1. BP or BV is decreased
2.afferent arterioles constrict 3. juxtaglomerular cells release renin. Sympathetic stimulation also stimulates renin release. 4.Renin clips off angiotensin I from angiotensinogen 5. then clips off ACE 6. ACE converts angiotensin to its active form (A2) 7.A2 then a) decreases GFR b)stimulates Na/H antiporters c) release aldosterone which stimulate principal cells in CD to reabsorb more Na & CL & secrete more K 8 Resulting in osmotic increase in BV by excreting less water |
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What is aquaporin 2?
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A water channel protein that in the presence of ADH increases the permeability of the DCT to water. When ADH is removed channels are removed from the apical membrane via endocytosis
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Which portions of the renal tubule and collecting duct reabsorb more solutes than water to produce dilute urine?
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Dilute urine is produced in the thick ascending limb of the LOH. The DCT & the collecting duct(CD) reabsorb more solutes than water.
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What causes the high osmolarity of interstitial fluid in the renal medulla?
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The high osmolarity of ISF is mainly due to Na Cl and urea.
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What is dilute urine? What is the milliosmoles of dilute urine?
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Dilute urine is 300 mOsm/L
It is filtrate that has a lower osmolarity of solutes than blood plasma. |
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Define Renal Plasma Clearance
What does high and low clearance indicate? |
Renal Plasma Clearance is the volume of blood cleaned of a substance expressed as ml/min High clearance indicates effecient excretion of a substance and low clearance indicates inefficient excretion
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Why is the plasma creatinine a good measurement of kidney function?
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Cretainine results from catabolisim of creatine phosphate in skeletal muscle and is usually cleared via urine at the same rate as it is discharged from muscle
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What is the equasion used to calculate renal clearance?
What is the typical flow per minute? |
S = ( U x V) / P
650mL/min 55% of 1200mL renal blood flow |
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What are the charecteristics of urine?
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1 -2 L per day but variable, Yellow or amber in colour, Transparent, mildly aromatic but becomes like NH3 upon standing, a pH bw 4.6 - 8.0 avg 6.0, Specific Gravity ranges from 1.001 - 1.035. High solutes = high Specifc Gravity
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Describe the micturition reflex
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When volume exceeds 200mL - 400mL in the bladder, stretch receptors in the walls transmit impulses to S2 & S3 in the spinal cord and trigger a reflex arc. This causes contraction of the detrusor muscle and relaxation of sphincters & urination takes place
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What forces propel urine from the renal pelvis to the urinary bladder?
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Peristaltic waves pass from the renal pelvis to the urinary bladder varying in frequency from 1 - 5 minutes depending on how fast urine is formed
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Compare the urethra among males and females
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Male - also discharges sperm about 20cm long passes through the prostate, perenium then penis to the external urethral orifice
Female - 4cm long opens to the outside via EUO b/w clitoris & vaginal opening |
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Where and what is the lamina propia composed of in the femal urethra?
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In the deep mucosa wall.
Areolar connective tissue with elastic fibers and a plexus of veins |
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How does the superficial muscularis differ in males and females? Name any subdivions.
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In females it consists of circularly arranged smooth muscle fibers.
In males it is divided into the prostatic urethra, membranous urethra and spongy urethra consiting of same arrangement |
