Review sheet Ch 23 Urinary system PDF

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Review sheet: Chapter 23: the urinary system Define excretion. What organs or organ systems are involved? Excretion is defined as separating and removing was, or separation and elimination of body fluids. The urinary system eliminates many metabolic waste, toxins, drugs, hormones and water Know the approximate proportion of cardiac output, oxygen used by kidneys at rest (as a measure of how hard the kidneys are working!). Kidneys are about 1% of total body mass, give ¼-1/5 of cardiac output, the total volume goes through the kidneys about every 4 to 5 minutes. About 20% of resting oxygen consumption. Overview of anatomy of urinary system: kidneys, ureters, urinary bladder, urethra. Location of kidneys; definition of retroperitoneal. Kidneys have high blood supply, produce urine, leaves through ureters goes to urinary bladder and leaves through the urethra. Kidney structure: capsule, medulla, cortex, lobe, columns, pyramids, papillae, the nephron and all its parts, calyces, pelvis, renal sinus etc. Outer fibrous capsule, cortex and inner medulla. The medulla has renal pyramids, the tissue is separated and forms column, the pyramids produce urine, and drips lose the tip is called the renal papillae, and to the ureter. Minor calyx drains into major calyx, and drain into the renal pelvis, becoming the ureter. Renal sinus hollow place. List and understand kidney functions. Has numerous number of kidneys: 1) Filters blood plasma, eliminates waste, returns useful chemicals to the blood. 2) Adjusts water and ion recovery, regulating blood volume, pressure and osmolality. 3) Secretes renin, which forms angiotensin 2. Involved in control of BP, and electrolyte balance. 4) Secretes erythropoietin stimulating RBC formation, comes from kidneys 5) Regulates acid-base balance. 6) Detoxifies free radicals and drugs 7) Preforms gluconeogenesis during starvation. Know the anatomy of the nephron, and role(s) of each portion of the nephron in urine formation. Nephrons drain into collecting ducts. Afferent larger than efferent. Define nitrogenous wastes. What are the main ones, which one is most toxic. Catabolism of what molecules create them? Where is urea formed and what chemical is it formed from? Basically, waste products of metabolism, most toxic is ammonia it is formed from the breakdown of proteins and amino acids, Urea comes from ammonia and that takes place in the live. Uric acid, is from the breakdown of nucleic acids. Breakdown of creatine phosphate is creatinine. Take ammonia to urea. Ammonia is highly toxic and can diffuse through membranes. Definite azotemia, uremia, and BUN. Describe the clinical significance of BUN and define renal insufficiency. Blood urea nitrogen (BUN) amount of nitrogenous waste in the blood Urea is normally 10-20mg/dl. Evaluated amount is renal insufficiency. Azotemia is called elevated BUN. Sickness and toxic effects are called uremia, convulsions, coma, and death if not corrected. Treated by hemodialysis or kidney transplant. 1

Describe glomerular filtration (what, where, why, how). Know the structure of the glomerulus, glomerular capsule, filtration membrane, podocytes, afferent and efferent arteriole, vasa recta. Blood vessels, the afferent arteriole brings blood in, glomerulus, the afferent has larger diameter than the efferent, causing higher blood pressure, flood is forced out and collects in the renal corpuscle, proximal convoluted tubule feeds to the nephron loop, distal convoluted tubule, feeds into the collecting duct which received from multiple distal convoluted tubules. Vasa recta, collects and goes back into the blood. Cortical and juxtamedullary nephrons – describe differences in structure and function; describe the role of juxtamedullary nephrons in forming concentrated urine. Two types of nephrons, cortical nephron, who’s nephron loop doesn’t dip into medulla, compared to juxtamedullary nephrons, who’s nephron loop goes way down into the medulla, lets us produce a concentrated urine. A urine that is more concentrated than our body fluid. What are the steps in urine formation, and where does each occur in the nephron? (i.e. Filtration, reabsorption and secretion, water conservation). 1) Glomerular filtration 2) tubular reabsorption and secretion and 3) water conservation before leaving the pyramid. Adjusting and removing water, leaving other materials behind. Define, describe glomerular filtrate, tubular fluid. Describe the forces driving and opposing filtration in the glomerulus, contributing to the net filtration pressure. Driven by blood pressure, higher in glomerulus higher than elsewhere. Similar to plasma but normally no cells or protein. Filtrate becomes the tubular fluid as enters the PCT. Net hydrostatic pressure drives filtration, colloid osmotic pressure, and capsular pressure all drives the fluid out. 10mmHG Where in the system would you find the glomerular filtrate (capsule), tubular fluid (tubule), and urine (calyces – urethra)? Filtrate in glomerulus, tubular fluid, is PCT, and urine, is in GFR – (glomerular filtration rate): definition, know approximate amounts filtered/day, and the significance of reabsorption. Why is it critical to reabsorb the vast majority of the materials that have been filtered? What would happen if you didn’t? GFR is how much filtrate both kidneys form per minute, 125ml/min or 180/L in males 150/L in females. The body has 5-6 liters of blood, if it wasn’t recovered we would have enough. Filter blood 30x a day, 99% of filtrate is reabsorbed, 1-2 L Urine excreted a day. Describe the regulation of GFR: Know the 3 main mechanisms. Autoregulation: know the myogenic mechanism and tubuloglomerular feedback. Describe each. What are the roles of macula densa, mesangial and granular cells, how does this response regulate GFR? Myogenic mechanism, smoot muscles of arterioles. Smooth muscle contracts when stretched. If MAP changes, it changes how much efferent and afferent arterioles are stretched. MAP goes anywhere from 90-180 mmHG without changing GFR. Elevated blood pressure: the afferent arteriole constricts, and efferent arterioles dilate. Decreased: afferent arteriole dilates, efferent arteriole constricts, adjust glomerulus. Tubuloglomerular feedback, tubule communicates with glomerulus, sensory cells produce a signal that adjust afferent tubule. The chemical environment is detected by sensory cells, or 2

macula densa, that produce a signal that constrict mesangial and granular cells, and slows down blood flow to reduce GFR, and sodium levels drop because we can recover more sodium. 2. Sympathetic NS: What effect does the sympathetic NS have on GFR, urine formation? When would this occur? Reduces urine formation by constricting afferent arterioles, 3. Describe the Renin-angiotensin-aldosterone system: Roles of angiotensinogen and renin in regulation of blood volume, vasoconstriction, and blood pressure. What is angiotensinogen, angiotensin I and angiotensin II? Where is renin formed and what does it do? What is ACE and where is it found? What are the roles of the kidneys, liver, and lungs in this system? What effects does it have on the brain? Describe the actions of angiotensin II on the brain, vasculature, and adrenal cortex and kidneys. What is aldosterone and where is it from, and what does it do? Actions of angiotensin 2 include: 1) Widespread vasoconstriction, raising MAP 2) Constriction of afferent and efferent arterioles decreasing GFR and water loss 3) Stimulation of NaCl and water recovery by vasa recta due to low BP in Peritubular capillaries 4) Stimulates secretion of aldosterone 5) Stimulates secretion of ADH 6) Stimulates thirst sensations. Blood pressure drops, and when kidney senses it produces renin, and when renin hits angiotensinogen, it makes angiotensin 1, when it flows through capillaries, ACE makes it angiotensin 2, which brings up blood pressure. It causes vasoconstrictions, makes kidneys produce aldosterone, and hypothalamus, to produce thirst, and ADH helping us recover more water, and acts on blood volume. Angiotensin 2, causing constriction and constricts afferent and efferent arterioles, and basic water intake, maintain blood pressure. Define reabsorption, secretion. Materials moving out of tubular movement, back into the blood. And materials added to tubular fluid. Secretion includes acid, all along the tubule. List the 4 nephron regions in order. What are the roles of each in urine formation? Where does most solute and water recovery occur? Where do ADH and aldosterone act? Where is acid secretion occurring? Nephron Regions: renal corpuscle + tubule. Tubule regions: Proximal convoluted tubule, nephron loop, distal convoluted tubule. Roles of PCT, loop of Henle (nephron loop), DCT, collecting duct in reabsorption, secretion, water recovery. Proximal Convoluted Tubules (PCT) where tubular fluid goes after been filtered, reabsorbs 65% of volume of Glomerular filtrate, Reabsorbs a greater variety of chemicals than the rest of the nephron. Mechanisms contributing to reabsorption by PCT. Define transcellular and paracellular routes. Routes of reabsorption: transcellular route: through epithelial cells of PCT, recovery by active and passive transport, and Para cellular route between epithelial cells of PCT, recovery by water flow and solvent drag. (Osmotic gradient) Na/K ATPase in basal membrane provides primary motive force. Na or sodium recovery is key, reabsorption is driven by Na+ recovery, crating osmotic and 3

electrical gradients. Include Symports: couple Na+ with our solutes, Na/H antiport secretes H+ in exchange for Na+ and aquaporin and tight junctions in allow for water flow. Describe the role of the sodium glucose transporter (SGLT) of the PCT. It allows you to pull glucose. Driving more acid out. Define the glucose transport maximum of the PCT. Why is there a transport mechanism – how is this related to the transporter? High glucose causes harm to tissues, Normoglycemia, glucose levels are low enough that when we get out of PCT there is no glucose left in the urine. If you have Diabetes we have hyperglycemia, all pumps are used up and no more glucose can be recovered, glucose will appear in the urine, creating a osmotic gradient which prevents water from being recovered, and higher urine volume Why does glucose remain in the urine if plasma glucose concentrations are >220 mg/dl? Why does urine volume increase under this circumstance? How does the glucose remaining in the urine under this circumstance create an osmotic gradient at the collecting duct that prevents recovery of water? The amount you can recover is dependent on how many transported you have, Transport maximum at 220mg/dl, here none will appear in the urine. Anything above transport maximum, it will be excreted in the urine. Making large urine volume and harming other tissues throughout the tubule. Secretion includes urea, uric acid, bile salts, ammonia, catecholamines, many drugs such as penicillin are added to the tubular fluid, removed faster than allowed by filtration aloud. Loop of Henle: how does it contribute to water reabsorption? What are the differences in properties of the descending and ascending limbs, and how does this allow formation of concentrated ECF in the medulla? What is the role of the NaK2Cl transporters? Why does their inhibition lead to diuresis? Sets up osmotic gradient for water conservation by collecting duct, add solutes to do this. Transporter revolvers Na, K, and Cl) Descending and ascending limbs, with thick segment with simple cuboidal and thin segment of simple squamous. The descending and ascending have different transport properties. Descending lets water through but not salt, ascending lets salt in but not water. Forms a countercurrent multiplier allowing high solute concentration. Salt is continually added by the PCT, the higher the osmolality of the ECF, the more water leaves the descending limb by osmosis, the more water that leaves the saltier the fluid is that remains in the tube, the saltier the tube in the, the more salt the tubule pumps into the ECF, and the more salt that is pumped out of the ascending limb the saltier the ECF is in the renal medulla. Describe the peritubular capillaries and vasa recta: what are they, what do they do? Flows parallel and delivers oxygen and blood without washing out osmotic gradient. Procides blood supply to the medulla without removing high medullary NaCl and urea concentration needed for recovery of water. DCT and CD: Roles of DCT – site where aldosterone acts, and adjustable H+ secretion or reabsorption. It regulates acid/base balance via H+ excretion and NH4 formation to let us get rid of additional acid. Also, regulation of aldosterone of Na+ and water reabsorption and K+ 4

excretion. Recover more sodium and pump more potassium into the fluid of the tubule. Water follows sodium. Principal cells: salt and water balance and Intercalated cells: acid/base balance. Maintain PH by adjusting Co2/HCO3 buffering system is primary responsible for regulation of ECF ph. 1) excretion of CO2 from the long, for short term changes in ph. Adjusting ventilation. 2) Excretion of additional acid or HCO by the kidney, slow but effect. Collecting duct: adjustable water recovery. Hormones acting on the kidneys: Norepinephrine Aldosterone from cortex, ADH Atrial and Brain Natriuretic hormones, one from the atria, is released when it is stretched, and causes you to dump blood volume, get rid of sodium and water. Angiotensin 2 elevated blood pressure Parathyroid hormone: stimulates excretion of phosphate by PCT and recovery of Ca by DCT. List and know the effects of each (we will get back to these in the next chapter). ANH, aldosterone, renin, angiotensin, ADH: overall effects and mechanism of action of each. Aldosterone: actions on Na+, K+, and water retention and secretion. On what part of the nephron does it act? What gland releases it? Stimulates uptake of Na+ (and water) and secretion of K+ from DCT and collecting duct. ADH acts on collecting duct by triggering insertion of aquaporin into membranes, released during dehydration and increases osmotic recovery of water from the tubular fluid. ADH: What does it do, how does it do this? Relate to actions of CD, salt and urea concentrations in renal medulla. Why does elevated blood glucose interfere with its actions? What gland is it released from? Controls how much water is pulled out. Sensors in Hypothalamus detect BP and in brain stem, detect osmotic concentration, can make you thirsty. Adjust how fast you lose water, posterior pituitary releases ADH, add aquaporin, and recover water back into the body. Atrial natriuretic hormone (ANH): Where is it released from, what effect does it have on plasma water and Na+ and thus blood volume and pressure? Released from heart, brain in response to high BP (stretch of atrial wall), inhibits of aldosterone, renin and ADH. Increases GFR and inhibits NaCl reabsorption by collecting duct. Net effect: increase excretion of Na+ and water reducing blood and pressure. Renal clearance- define. Volume of blood plasma cleared of a waste in one minute. Determined by assessing blood and urine samples. C= UV/P where C= Renal Clearance U= waste concentration in urine V= Rate of urine output P= waste concentration in plasma Know the normal urine volumes, define diuresis, polyuria, oliguria, anuria. 5

Define and compare diabetes insipidis and mellitus. Normal urine volume” 1-2L/day, More than 2L a day: diuresis or polyuria Less than 500ml/day: oliguria 0-100ml/day: anuria Describe the mechanism of water recovery by CD- describe the role of the nephron loop in setting up osmotic gradients, the role of differences in transport properties of the ascending and descending limbs of the nephron loop in creating the osmotic gradient that drives water recovery. How (by what mechanism) does ADH increase water recovery? Medulla has osmotic concentration: recovery of water is driven by osmotic gradient, water picked up and removed by vasa recta. Solution around tubule is really concentrated, the further you get towards the pelvis, the higher the osmotic concentration, as tubular fluid flows down collecting duct it is pulled out, we can choose how much it leaks out by antiporons. What is the difference between diabetes mellitus and diabetes insipidis? How do they cause diuresis? What hormone is at issue with each? Excess urine production: Diabetes mellitus (sweet), type 1 caused by immune system attacking beta cells which produce insulin, type 2 loss of sensitivity of insulin and gestational developed during pregnancy. Elevated plasma glucose, too much to be recovered, spilled out in urine, and can’t recover as much water. Diabetes insipidis: not caused by sugar. Caused by block of ADH, don’t get aquaporin’s, and loose water very rapidly. Define diuretics. What do they do? What medical conditions are they used to treat? Describe the different mechanisms that loop diuretics, caffeine, and alcohol cause diuresis? Used to decrease blood volume, increase urine output, treats hypertension and congestive heart failure. Caffeine increases GFR, don’t recover as much sodium and water. Or low tubular reabsorption by loop diuretics, inhibit, don’t recover ions, and don’t recover water from collecting duct. Alcohol inhibits ADH release, destroys brain cells, causes dehydration from prevention of ADH. Know the anatomy of the bladder, urethra, internal and external sphincters and their control (which one is voluntary and which involuntary?). Why can’t an infant or a person with a spinal cord injury control urination voluntarily? The stretch leads to contractions, brain sends voluntary signals down to control voluntary sphincter. The sensory neurons send up to the brain, and local reflex arc to internal sphincter and when stretched we get contraction and voiding of the urine. Overwritten by external. Micturition: urinating. If you have a spinal injury, local reflex works fine, but can’t voluntary control or when 6 mo olds don’t have pathways for control. What is the detrusor muscle? Describe the roles of sympathetic, parasympathetic, and voluntary actions in control of micturition. The smooth muscle. Compare the anatomy of the male and female urethra. Female urethra is shorter than male, 3-4 cm long. Females can get more UTI compared to men. 6

What is hemodialysis and how does it work? What medical condition requires it? Kidney disease and failure associated with obesity, diabetes mellitus, high blood pressure, CV disease. Glomerulus and tubules are becoming damaged. Hemodialysis, fluid is pulled out. Cells and proteins stay in tubing. Fluid is sent back into the blood.

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