Chapter 9 The Urinary System Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Urinary System Two kidneys and two ureters Urinary bladder & urethra Effector organ for Regulation of Plasma ion composition Regulation of Body water Volume (BP) Regulation of blood pH (with lung) Production of Hormones Excretion of waste Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Urinary System Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Kidney Divided into cortex –outer portion Medulla- inner portion Contain renal pyramids & renal columns Urine goes into renal pelvis Edges are made of major & minor calyces Then out ureter Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Kidney Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Renal Blood Supply 20-25% resting CO goes through kidneys  L. & R. renal arteries then Segmental  interlobar  arcuate  interlobular  afferent arterioles  glomerulus (capillary network)  efferent arterioles  peritubular capillaries  veins    renal vein Capillaris Units –nephrons grouped at pyramids Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Renal Blood Supply Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Renal Blood Supply Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Nephron Unit of renal function: corpuscle & tubule Corpuscle: forms filtrate Glomerulus & Glomerular capsule (cortex) Proximal convoluted tubule (cortex)  Descending Loop of Henle (into medulla) ascending Loop of Henle (into medulla)  Distal convoluted tubule (cortex)  Collecting duct minor calyx Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Nephron Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Basic Operation Glomerular filtration-filter plasma Tubular reabsorption Reabsorb needed compounds & water from filtrate Tubular Secretion Secrete some materials into filtrate Copyright 2010, John Wiley & Sons, Inc.

Glomerular Filtration Two layers of capsule surround glomerulus Between is capsular space Podocytes support capillary epithelium Form filtration membrane Permeable to water & solute but not most proteins & blood cells Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Filtration Pressure Blood pressure for filtration Opposed by colloid osmotic pressure and capsular pressure Efferent and afferent arteriole diameters adjust to maintain a net filtration pressure Even with small changes in blood pressure Copyright 2010, John Wiley & Sons, Inc.

Glomerular Filtration Rate = GFR 105-125 ml/min Determines net reabsorption because it determines filtrate flow ANP(Atrial natriuretic peptide) increases GFR Responds to increased blood volume Sympathetic stimulation  vasoconstriction  decreased GFR  Urine production a peptide hormone secreted by the myocytes cardiac atria that in pharmacological doses promotes salt and water excretion and lowers blood pressure Copyright 2010, John Wiley & Sons, Inc.

Glomerular Filtration Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Tubular Reabsorption Proximal tubule ~65% Na+ & H2O Normally 100% nutrients ~100% HCO3- (depends on blood pH) Active transport of solutes Osmosis moves water Cells distal to proximal tubule fine tune reabsorption under control Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Tubular Secretion Takes place all along tubule Major substances : H+, K+, ammonia, urea, creatine, drugs like penicillin Helps regulate plasma pH 7.35-7.45 Diet is acid  urine is typically acidic Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Urine Route Collecting ducts to calyces Calyces to ureter Ureter to bladder Bladder to urethra Copyright 2010, John Wiley & Sons, Inc.

Filtration, Reabsorption, Secretion Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormonal Regulation Angiotensin II & aldosterone Angiotensin II- stimulates NaCl in proximal tube Aldosterone- increases Na+ reabsorption & K+ secretion in DCT & CD More ions reabsorbed more water ANP-increases GFR & inhibits aldosterone action less Na+ reabsorbed ADH- responds to increased concentration of solute in blood + fall in BP Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormonal Regulation ADH: important to body water balance Increased concentration of solute in blood + fall in BP  ADH With no ADH: DCT & CD walls are impermeable to water dilute urine With ADH: water reabsorption occurs concentrated urine Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Components of Urine Urine = 1-2 l /day 95% water + urea, creatine, K+, ammonia, uric acid, Na+, Cl-, Mg2+, sulfate, phosphate & Ca2+ Depends on diet and state of health See table 21.3 Creatine (/ˈkriːətiːn/ or /ˈkriːətɪn/) is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body Copyright 2010, John Wiley & Sons, Inc.

Regulation of Water Reabsorption Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Urine Route Collecting ducts calyces Ureter Lined with mucus & transitional epithelium Pass under bladder Full bladder prevents backflow Bladder- directly in front of rectum Can stretch (700-800 ml) Smaller in females because of uterus Three layers of detrussor muscle  Urethra- internal urethral sphincter External urethral sphincter (voluntary) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Urine Route Copyright 2010, John Wiley & Sons, Inc.

Micturition = Urination Autonomic reflex- internal sphincter Responds to stretch like rectum Parasympathetic  detrusor muscle contraction Conscious control-external sphincter Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Aging Kidneys shrink- decrease in capacity Thirst decreases  dehydration  urinary tract infections Males: prostate enlargement frequent urination & slow flow Females: more prone to leakage of external sphincter (incontinence) Both: nocturia Nocturia (derived from Latin nox, night, and Greek [τα] ούρα, urine), also called nycturia (Greek νυκτουρία), is the need to get up in the night to urinate, Copyright 2010, John Wiley & Sons, Inc.

Fluid, Electrolyte and Acid-Base Balance Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fluid Compartments Total body water = 55-60% of lean body mass Remainder: solid parts of bone, muscles, tendons Major compartments (3): ICF, IF, plasma Intracellular fluid (ICF): inside cells= 2/3 Extracellular Fluid (ECF): outside cells = 1/3 Interstitial fluid (IF): 80% of ECF Includes: lymph; cerebrospinal, synovial, pericardial, pleural and peritoneal fluids; fluid in eyes and ears Blood plasma: 20% ECF Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fluid Compartments Copyright 2010, John Wiley & Sons, Inc.

Barriers Between Compartments Plasma membrane: between ECF and ICF Blood vessel walls: between plasma and interstitial fluid Fluid balance correct distribution of water & solutes Water redistributes rapidly by osmosis Thus fluid balance depends on solute (electrolyte) balance Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fluid Balance Fluid balance requires Appropriate total volume of body fluid Appropriate distribution of water and solutes Fluid balance depends on solute (electrolyte and nonelectrolyte) balance Fluids and electrolytes are closely linked Water redistributes rapidly by osmosis Copyright 2010, John Wiley & Sons, Inc.

Fluid Balance Interactions Animations Water and Fluid Flow You must be connected to the internet to run this animation. Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Water Gain and Loss Gain: ingestion + metabolic reactions Ingestion (food and drink): 2300 mL/day Metabolism: 200 mL/day Gain should = loss Daily intake = daily output. Both 2500 mL/day Loss: skin, lungs, kidneys, GI tract Kidneys: ~1500 mL/day Skin: sweat evaporates ~600 mL/day Lungs: 300 mL/day; more if fever GI tract: ~100 mL/day; more if diarrhea Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Water Balance Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Regulation of Gain Thirst center in hypothalamus ~2% dehydration will cause  BP Increase in body osmolality  dry mouth  thirst Hormonal responses High osmolality  hypothalamus releases ADH  water retention by kidneys  BP  renin released from kidney  angiotensin II  aldosterone  water retention by kidneys Sensation of thirst may be decreased, especially in elderly Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Regulation of Gain Copyright 2010, John Wiley & Sons, Inc.

Regulation of Salt and Water Loss Urinary NaCl loss mainly determines body fluid volume Na+ = main solute in ECF determining osmosis Fluid intake varies so loss must vary also ANP, angiotensin II and aldosterone regulate ADH regulates water loss Copyright 2010, John Wiley & Sons, Inc.

Regulation of Salt and Water Loss Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Movement of Fluid ICF and ECF are normally at the same osmolality Water moves freely  interstitial fluid osmolality  cell swelling and vice versa Most often due to Na+ change ADH responds rapidly: prevents significant cell change Copyright 2010, John Wiley & Sons, Inc.

Electrolytes in Body Fluids Functions of electrolytes Confined to compartments; control osmosis Help maintain acid-base balance Carry electrical currents Serve as cofactors for enzymes Copyright 2010, John Wiley & Sons, Inc.

Electrolyte Distribution Electrolyte content of ICF and ECF differ significantly ICF: K+ major cation; protein, HPO42-: anions ECF: Na+ major cation; Cl- major anion Na+/K+ pump maintains the cation difference The two ECF fluids are similar Electrolytes in plasma similar to those in IF One difference: plasma contains more protein than interstitial fluid (IF) Colloid osmotic pressure (due largely to plasma proteins) “holds onto” fluid in capillaries Copyright 2010, John Wiley & Sons, Inc.

Electrolyte Distribution Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Other Electrolytes K+ high in ICF, low in ECF Regulated by aldosterone Mg2+ and SO42- high in ICF, low in ECF Ca2+ high in ECF, low in ICF Regulated in plasma (PTH, calcitriol, and calcitonin) Bones serve as Ca2+ reservoir Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Acid- Base Balance Input: diet, products of metabolism Such as lactic acid, ketones Output Lungs: exhale CO2 Kidney: can eliminate H+ or HCO3- Regulatory mechanisms Buffers: fastest but incomplete Respiratory responses: fast but incomplete Renal responses: slowest but complete elimination Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 1: Buffer Systems Protein in cells or plasma Carboxyl and amino groups of amino acids Hemoglobin (protein) in red blood cells Carbonic acid-bicarbonate Especially important in plasma CO2 + H2O  H2CO3 ↔ HCO3- + H+ Phosphate H2PO4-  H+ + HPO42- HPO4 2 is a variation of phosphoric acid Copyright 2010, John Wiley & Sons, Inc.

2: Exhalation of Carbon Dioxide H+ + HCO3- ↔ H2CO3 ↔ CO2 + H2O Decrease of CO2 ↔ decrease of H+ Increase of CO2 ↔ increase of H+ Change of rate and depth of ventilation rapidly alters plasma pH Negative feedback loop regulates carbonic acid Copyright 2010, John Wiley & Sons, Inc.

2: Exhalation of Carbon Dioxide Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3. Renal Responses Kidney Excretion of H+ Slow but only way to actually eliminate acid or base Secrete H+ and replace with HCO3- Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Imbalances Acidosis: arterial blood pH < 7.35  Depresses CNS Below pH 7.0 can be fatal Alkalosis: arterial blood pH > 7.45  Overexcitation of CNS Muscle spasms, convulsions Compensation Respiratory or renal mechanisms Respiratory very rapid; renal slower Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Aging Decrease in control of water and electrolyte balance can lead to pH problems Decreases in respiratory and renal functioning Decreased capacity to sweat Copyright 2010, John Wiley & Sons, Inc.