The Urinary System Functions of the urinary system Anatomy of the kidney Urine formation glomerular filtration tubular reabsorption water conservation Urine and renal function tests Urine storage and elimination Urinary System Kidneys Ureters bladder urethra Kidney Functions Filters blood plasma ? separates and eliminates waste; returns useful chemicals to blood Regulates blood volume and pressure eliminates or conserves water as needed Regulates osmolarity of body fluids Controls amounts of water and solutes eliminated Secretes renin, activates angiotensin, aldosterone controls BP, electrolyte balance Secretes erythropoietin - controls RBC count Regulates PCO2 and acid base balance (pH) Detoxifies ? eliminates free radicals and drugs Promotes gluconeogenesis - during starvation periods Partially regulates blood calcium levels ? excrete phosphate Wastes Any substance that is useless to the body Toxins Drugs Hormones Salts Hydrogen ions Excess water Metabolic wastes ? produced by the body CO2 ? most expelled by lungs, but some in urine Nitrogenous wastes Nitrogenous Wastes Urea 50% of nitrogenous wastes protein catabolism proteins?amino acids ?NH2 removed ?forms ammonia, liver converts to urea Uric acid nucleic acid catabolism Creatinine creatinine phosphate catabolism Renal Failure Kidneys fail to eliminate wastes from the blood azotemia ? build up of nitrogenous wastes in the blood uremia - toxic effects as wastes accumulate Diarrhea, vomitting, dypsnea, cardiac arrythmia, convulsions, coma, death If kidneys fail, dialysis must be started to artificially remove wastes from the blood Excretion Separation of wastes from body fluids and eliminating them respiratory system: CO2 integumentary system: water, salts, lactic acid, urea digestive system: water, salts, CO2, lipids, bile pigments, cholesterol urinary system: many metabolic wastes, toxins, drugs, hormones, salts, H+ and water Anatomy of Kidney Position, weight and size retroperitoneal, level of T12 to L3 Right kidney slightly lower due to liver about size of a bar of soap (12x6x3 cm) Shape ? kidney bean lateral surface - convex; medial ? concave hilum ? point of entry/exit for nerves, blood vessels, lymphatic vessels and ureter Adrenal Glands located on superior surface Connective Tissue 3 layers for protection Renal fascia Tough, fibrous outer layer binds to kidney, ureters and bladder to abdominal wall Adipose capsule fatty middle layer cushions kidney Renal capsule fibrous inner sac encloses kidney like cellophane wrap Renal Parenchyma Kidney tissue that forms the urine 2 Zones cortex ? outer 1 cm medulla - encircles the renal sinus Renal sinus ? cavity within the kidney contains blood & lymphatic vessels, nerves, urine collecting ducts and fat Renal columns ? extensions of the cortex that project toward the renal sinus divide medulla into renal (medullary pyramids) Lobe ? a pyramid and its overlying cortex Anatomy of Kidney Renal cortex: outer 1 cm Renal medulla: renal columns, pyramids - papilla Lobe of kidney: pyramid and it?s overlying cortex Lobe of Kidney Broad side faces cortex Papilla (pointy end) faces the renal sinus Nestled in the minor calyx Lobes, etc. 1 pyramid and its overlying cortex 6-10 lobes in each adult kidney ? 2 or 3 pyramidal papilla empty into a minor calyx ? 2 or 3 minor calyxes empty into a major calyx ? Major calyxes empty into the renal pelvis ? Renal pelvis empties into the ureter Kidney: Frontal Section Minor calyx: cup over papilla collects urine Path of Blood Through Kidney Renal artery ? interlobar arteries (up renal columns, between lobes) ? arcuate arteries (over pyramids) ? interlobular arteries (up into cortex) ? afferent arterioles ? glomerulus (cluster of capillaries) ? efferent arterioles (near medulla ? vasa recta) ? peritubular capillaries ??interlobular veins ??arcuate veins ??interlobar veins Renal vein Blood Supply Diagram Blood Supply Nephron Functional unit of kidney 1.2 million nephrons per kidney Each nephron contains Renal Corpuscle Glomerulus enclosed in a 2-layer sac Bowman?s capsule or ______________ Glomerular filtrate collects in capsular space and flows into renal tubule Renal Tubule Duct from glomerulus to tip of medullary pyramid Proximal Convoluted Tubule Nephron Loop (Loop of Henle) Distal Convoluted Tubule Collecting Duct #s 1-3 only one each per nephron #4 ? collects from several nephrons Renal (Uriniferous) Tubule Proximal convoluted tubule (PCT) longest, most coiled, simple cuboidal with brush border Nephron loop - U shaped; descending + ascending limbs ______________(simple cuboidal) initial part of descending limb and part or all of ascending limb, active transport of salts ______________(simple squamous) very water permeable Distal convoluted tubule (DCT) - cuboidal, minimal microvilli Collecting duct: several DCT?s join Collecting duct PCT DCT Nephrons True proportions of nephron loops to convoluted tubules shown ______________ nephrons (85%) short nephron loops efferent arterioles branch off peritubular capillaries ______________ nephrons (15%) very long nephron loops, maintain salt gradient, helps conserve water Nephron Diagram Flow of Urine glomerular capsule PCT nephron loop DCT collecting duct papillary duct minor calyx major calyx renal pelvis ureter urinary bladder urethra Urine Formation Preview 4 Processes: Blood Plasma ? Urine plasma-like filtrate returns solutes to the bloodstream removes additional wastes from the blood returns water to the bloodstream ____% of glomerular filtrate is reabsorbed into the bloodstream Filtration Membrane Diagram Filtration Membrane Most any unbound molecule smaller than 3 nm can pass water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, vitamins - 70-90nm pores like other fenestrated capillaries Pores are small enough to exclude blood cells - proteoglycan gel excludes molecules > 8nm a few large particles may penetrate, but most are held back negatively charged blood plasma 7% protein, glomerular filtrate 0.03% podocyte arms have pedicels with negatively charged filtration slits to exclude large anions Filtration Pressure Blood pressure is higher in the glomeruli of the kidneys than in other body capillaries Afferent arteriole is larger than the efferent arteriole large inlet, smaller outlet Lots of filtration, little or no reabsorption Kidneys are especially vulnerable to _____________ Glomerular Filtration Rate (GFR) Filtrate formed per minute GFR = NFP x Kf ?125 ml/min or 180 L/day, male GFR = NFP x Kf ?105 ml/min or 150 L/day, female NFP = net filtration pressure filtration coefficient (Kf) depends on permeability and surface area of filtration barrier 99% of filtrate reabsorbed Effects of GFR Abnormalities ?GFR urine output rises ? ?GFR ______________________ (azotemia possible) GFR controlled by adjusting glomerular blood pressure autoregulation sympathetic control hormonal mechanism - renin and angiotensin Renal Autoregulation of GFR If constrict afferent arteriole, dilate efferent If dilate afferent arteriole, constrict efferent Stable for BP range of 80 to 170 mmHg (systolic) Cannot compensate for extreme BP Negative Feedback Control of GFR Sympathetic Control of GFR Strenuous exercise or acute conditions (circulatory shock) stimulate afferent arterioles to constrict ? GFR and urine production, redirecting blood flow to heart, brain and skeletal muscles Hormonal Control of GFR -efferent arterioles Tubular Reabsorption and Secretion Proximal Convoluted Tubules (PCT) Reabsorbs 65% of GF to peritubular capillaries Great length, prominent microvilli and abundant mitochondria for active transport Reabsorbs greater variety of chemicals than other parts of nephron transcellular route - through epithelial cells of PCT paracellular route - between epithelial cells of PCT __________________ - when transport proteins of plasma membrane are saturated ie. glucose > 220 mg/dL remains in urine (glycosuria) Tubular Secretion of PCT and Nephron Loop urea, uric acid, bile salts, ammonia, catecholamines, many drugs secretion of hydrogen and bicarbonate ions regulates pH of body fluids Primary function of nephron loop also involved in electrolyte reabsorption DCT and Collecting Duct Effect of ? BP causes angiotensin II formation angiotensin II stimulates adrenal cortex adrenal cortex secretes aldosterone aldosterone promotes Na+ reabsorption Na+ reabsorption promotes water reabsorption water reabsorption ? urine volume BP drops less rapidly DCT and Collecting Duct 2 Effect of atrial natriuretic factor (ANF) ? BP stimulates right atrium atrium secretes ANF ANF promotes Na+ and water excretion Effect of ADH dehydration stimulates hypothalamus hypothalamus stimulates posterior pituitary posterior pituitary releases ADH ADH ? water reabsorption Collecting Duct Concentrates Urine Osmolarity 4x as high deep in medulla Medullary portion of CD is permeable to water but not to NaCl Control of Water Loss Producing NaCl reabsorbed by cortical CD water remains in urine Producing GFR drops tubular reabsorption ? less NaCl remains in CD ADH ? CD?s water permeability more water is reabsorbed urine is more concentrated Countercurrent Multiplier Recaptures NaCl and returns it to renal medulla Descending limb reabsorbs water but not salt concentrates tubular fluid Ascending limb reabsorbs Na+, K+, and Cl- maintains high osmolarity of renal medulla impermeable to water tubular fluid becomes hypotonic Recycling of urea: collecting duct-medulla urea accounts for 40% of high osmolarity of medulla Countercurrent Multiplier of Nephron Loop Diagram Countercurrent Exchange System Formed by provide blood supply to medulla do not remove NaCl from medulla Descending capillaries water diffuses out of blood NaCl diffuses into blood Ascending capillaries water diffuses into blood NaCl diffuses out of blood Maintenance of Osmolarity in Renal Medulla Summary of Tubular Reabsorption and Secretion Composition and Properties of Urine Appearance Odor Specific gravity Osmolarity Lower than blood when hydrated Higher than blood when dehydrated pH - range: 4.5 - 8.2 usually 6, which is slightly acidic Chemical composition Appearance Clear to deep amber is normal Urochrome - yellow pigment produced from breakdown of hemoglobin of dead erythrocytes Pink, green, brown, black food, vitamins, drugs, metabolic disease Cloudy ? bacterial growth Pyuria ? pus present due to kidney/bladder infection Hematuria ? blood present caused by infection, trauma, kidney stones Odor Should normally have little odor Pungent odor ? bacteria bacteria convert urea to ammonia Foods may cause odor ie. asparagus Sweet, fruity odor ? glucose present diabetes Foul odor - infection Specific Gravity 1.001-1.035 Distilled water is 1.000 1.001 urine is very dilute 1.035 is very concentrated dehydration The more solutes you have in the urine, the higher the specific gravity will be. Chemical Composition 95% water, 5% solutes Normal solutes urea, NaCl, creatine, uric acid, phosphates, sulfates calcium, magnesium, bicarbonate, H+ Abnormal solutes Glucose Free hemaglobin or whole RBCs Albumin Ketones (ok during pregnancy) Bile pigments Urine Volume Normal volume - 1 to 2 L/day Polyuria - excess of 2L/day disease long term (ie. Diabetes) drugs - temporary Oliguria ? less than 500 mL/day Anuria - 0 to 100 mL disease dehydration circulatory shock enlarged prostate gland (males only) Diuretics Effects ? Increased urine output ? blood volume Uses Hypertension and congestive heart failure Mechanisms of action ? GFR ? tubular reabsorption Urine Storage and Elimination Ureters Muscular tube from renal pelvis of kidney to bladder passes dorsal to bladder and enters it from below about 25 cm long 3 layers adventitia - CT muscularis - 2 layers of smooth muscle urine enters, it stretches and contracts in peristaltic wave mucosa - transitional epithelium lumen very narrow, easily obstructed Urinary Bladder Muscular sac on floor of pelvic cavity 3 layers Parietal peritoneum on flat superior surface Fibrous adventitia everywhere else Muscularis (detrusor muscle) - smooth muscle Mucosa with rugae (wrinkles) relaxed bladder in wrinkled ? highly distensible Trigone - triangular area on floor where ureters enter and urethra exits Normally holds up to 500 mL before urination, but can hold 700 - 800 ml maximum Urinary Bladder and Urethra - Female Female Urethra 3 to 4 cm long External urethral orifice between vaginal orifice and clitoris Internal urethral sphincter thickened smooth muscle involuntary control External urethral sphincter skeletal muscle voluntary control Male Bladder and Urethra 18 cm long Internal urethral sphincter External urethral sphincter 3 regions Prostatic urethra during orgasm receives semen Membranous urethra passes through pelvic cavity Penile urethra ~15 cm through the penis Micturition in Infants Micturition ? voiding the bladder Micturition reflex 1) 200 ml urine in bladder - stretch receptors send signal to spinal cord 2) parasympathetic reflex arc from spinal cord - stimulates contraction of detrusor muscle 3) relaxation of internal urethral sphincter 4) voids bladder Note: The signal does not go all the way to the brain! Voluntary Control of Micturition Children/Adults Bladder stretches Receptors send stretch signals via pelvic nerves to micturition center in pons of brain Micturition center receives stretch signals and integrates cortical input (voluntary control) If urination is appropriate, pons sends signal for stimulation of detrussor and relaxes internal urethral sphincter If urination is inappropriate, impulses sent to external urethral sphincter keep it contracted When urination becomes appropriate, the impulses are inhibited and the external urethral sphincter will relax Valsalva maneuver aids in expulsion of urine by ? pressure on bladder activates micturition reflex voluntarily when there is no urge to void bladder Micturition Reflex Diagram Kidney Stones Renal Calculi Calcium, phosphate, uric acid and protein crystallize Form in the renal pelvis Most are small, but some can be several centimeters Causes blockages that destroy nephrons Jagged ? pain and hematuria Causes hypercalcemia dehydration PH imbalances frequent urinary infections enlarged prostate (males only) Treatments ? stone-dissolving drugs, surgery and/or lithotripsy (ultrasonic vibrations) Renal Disorders/Disease Acute Glomerularnephritis ? destruction of glomeruli autoimmune disease may follow an infection usually temporary ? most recover hydronephrosis ? increased fluid pressure due to blockage in kidney nephroptosis ? floating kidney too little body fat to hold kidney in place (ie anorexia) prolonged vibration ? truck drivers, jackhammer operators Nephrotic Syndrome ? glomerular injury causes large amounts of protein to be excreted in urine leads to hypotension, edema, increased susceptibility to infection Renal Failure Acute Renal Failure ? sudden onset traumatic damage to nephrons great blood loss Chronic Renal Failure slow, progressive irreversible loss of nephrons trauma metal poisoning glomeruli blocked by protein atherosclerosis Hemodialysis Urinary Incontinence Inability to control urination Causes: Incompetence of urethral sphincters Bladder irritation due to infection Pressure during pregnancy Obstruction Stress incontinence uncontrollable urination due to brief surges in bladder pressure laughter, coughing, sneezing Diabetes Chronic polyuria of metabolic origin With hyperglycemia and glycosuria Diabetes mellitus I & II- insulin hyposecretion/insensitivity gestational diabetes - 1 to 3% of pregnancies Pituitary diabetes - hypersecretion of GH adrenal diabetes - hypersecretion of cortisol With glycosuria but no hyperglycemia renal diabetes - hereditary deficiency of glucose transporters With no hyperglycemia or glycosuria Diabetes insipidus - ADH hyposecretion; CD ? water reabsorption CPS Which of these structures lies closest to the renal cortex? a) parietal peritoneum b) renal fascia c) renal capsule d) adipose capsule e) renal pelvis Increased ADH secretion should cause urine to have a) a lighter color b) a higher pH c) a higher specific gravity d) a lower urea concentration e) a lower glucose concentration CPS
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