D. C. Mikulecky Faculty Mentoring Program Virginia Commonwealth Univ. 10/6/2015

 Water balance  Electrolyte balance  Plasma volume  Acid-base balance  Osmolarity balance  Excretion  Hormone secretion 10/6/2015

 Kidneys  Blood supply: Renal arteries and veins  Ureter  Urinary bladder  Urethra 10/6/2015

Bowman’s Capsule Glomerulus Proximal Convoluted Tubule Distal Convoluted Tubule Loop of Henle Cortex Medulla Artery Vein Peritubular Capillaries Collecting Duct

 Glomerular Filtration: Filtering of blood into tubule forming the primitive urine  Tubular Reabsorption: Absorption of substances needed by body from tubule to blood  Tubular Secretion: Secretion of substances to be eliminated from the body into the tubule from the blood 10/6/2015

GF TR TA Urine Excreted Efferent Arteriole Afferent Arteriole Glomerulus Kidney Tubule Peritubular Capillary

 First step in urine formation  180 liters/day filtered  Entire plasma volume filtered 65 times/day  Proteins not filtered 10/6/2015

Glomerular Capillary Blood Pressure + 55 Plasma Colloid Osmotic Pressure Bowman’s Capsule Hydrostatic Pressure - Net Filtration Pressure+

 Water: 99% reabsorbed  Sodium: 99.5% reabsorbed  Urea: 50% reabsobed  Phenol: 0% reabsorbed 10/6/2015

 By passive diffusion  By primary active transport: Sodium  By secondary active transport: Sugars and Amino Acids 10/6/2015

Lumen Plasma Cells

10/6/2015 Lumen Plasma Cells PUMP: Na/K ATPase Sodium Potassium Chloride Water

 Stimulates Sodium Reabsorption in distal and collecting tubules  Naturetic peptide inhibits  In absence of Aldosterone, 20mg of sodium/day may be excreted  Aldosterone can cause 99.5% retention 10/6/2015

Fall in NaCl, extracellular fluid volume, arterial blood pressure Juxtaglomerular Apparatus ReninLiver Angiotensin + Aldosterone Lungs Converting Enzyme Adrenal Cortex Increased Sodium Reabsorption Helps Correct

 ACE Inhibitors (Angiotensin Converting Enzyme): Cause loss of salt---> water follows  Atrial Naturetic Peptide (ANP) also inhibits sodium reabsorption  Osmotic diuretics: Are not reabsorbed 10/6/2015

 They are actively transported across the apical cell membranes of the epithelial cells  Their active transport depends on the sodium gradient across this membrane  All other steps are passive 10/6/2015

Renal threshold (300mg/100 ml) Plasma Concentration of Glucose Glucose Reabsorbed mg/min Filtered Excreted Reabsorbed

 Protons (acid/base balance)  Potassium  Organic ions 10/6/2015

Lumen Plasma Cells PUMP: Na/K ATPase Sodium Potassium Chloride Water

10/6/2015 Fall in sodium ECF Volume Blood Pressure Increased Plasma Potassium Increased Aldosterone secretion Increased Tubular Potassium Secretion Increased Urinary Potassium Secretion Increased Tubular Sodium Reabsorption Fall in Urinary Sodium Excretion

 Glucose and Amino Acids  67% of Filtered Sodium  Other Electrolytes  65% of Filtered Water  50% of Filtered Urea  All Filtered Potassium 10/6/2015

 Variable Proton secretion for acid/base regulation  Organic Ion secretion 10/6/2015

 Variable Sodium controlled by Aldosterone  Chloride follows passively  Variable water controlled by vasopressin 10/6/2015

 Variable Proton for acid/base regulation  Variable Potassium controlled by aldosterone 10/6/2015

 Variable water reabsorption controlled by vasopressin  Variable Proton secretion for acid/base balance 10/6/2015

 Medullary countercurrent system  Vasopressin 10/6/2015

 Osmotic gradient established by long loops of Henle  Descending limb  Ascending limb 10/6/2015

 Highly permeable to water  No active sodium transport 10/6/2015

 Actively pumps sodium out of tubule to surrounding interstitial fluid  Impermeable to water 10/6/2015

From Proximal Tubule To Distal Tubule Cortex Medulla Active Sodium Transport Passive Water Transport Long Loop of Henle

10/6/2015 From Distal Tubule Cortex Medulla Interstitial Fluid Collecting Duct Pores Open Passive Water Flow

10/6/2015 From Distal Tubule Cortex Medulla Interstitial Fluid Collecting Duct Pores Closed No Water Flow Out of Duct

 Acute: Sudden onset, rapid reduction in urine output - usually reversible  Chronic: Progressive, not reversible  Up to 75% function can be lost before it is noticeable 10/6/2015

 Gravity and peristaltic contractions propel the urine along the ureter  Parasympathetic stimulation contracts the bladder and micturition results if the sphincters (internal and external urethral sphincters) relax  The external sphincter is under voluntary control 10/6/2015

 Bladder filling reflexively contracts the bladder  Internal Sphincter mechanically opens  Stretch receptors in bladder send inhibitory impulses to external sphincter  Voluntary signals from cortex can override the reflex or allow it to take place 10/6/2015