Kidney Function & Structure PDF

Structure of the Kidney  The Nephron There are 1.2 million nephrons per kidney! - They are the functional unit of the kidney - What would be the functional unit of the lung?? - Bowman's Capsule; where the Glomerulus resides - Blood flows through the glomerulu...

Structure of the Kidney  The Nephron There are 1.2 million nephrons per kidney! - They are the functional unit of the kidney - What would be the functional unit of the lung?? - Bowman's Capsule; where the Glomerulus resides - Blood flows through the glomerulus & filters out wastes and water into the tubule  The Nephron Tubular reabsorption and secretion - Forms a filtrate of protein-free fluid - Regulates the filtrate to maintain fluid volume, electrolytes, and pH Renal Blood Flow Glomerular Filtration Rate (GFR) - The rate at which the glomeruli filter blood - Normal GFR is 87-139 mL/minute Creatinine Clearance - The most accurate measure of glomerular filtration, as creatinine is filtered by the glomeruli but not reabsorbed by the tubules - The volume of blood (mL) that the kidney can clear of creatinine in 1 minute - Creatinine is a waste product of skeletal muscles The higher the blood creatinine level, the lower the estimated GFR Urinary Structures Ureters: bring urine from kidneys to bladder Bladder: muscular container for urine, holds 300-500 mL (urge to urinate at 250-300 mL) Urethra: a narrow passageway from the bladder to the outside of the body, it has internal and external sphincters; 3-4 cm in females, 18-20 cm in males Urine Composition Urine is normally clear yellow of amber in colour Cloudiness may indicate presence of bacteria, cells, or high solute concentration pH ranges from 4.6 - 8.0, but is normally acidic providing protection against bacteria Normal urine does not contain glucose of blood cells, and only occasionally contains trace protein; usually in association with rigorous exercise A healthy human should create 0.5 - 1 cc of urine/ kg per hour (average 30 cc/hr) Functions of the Kidneys Maintaining fluid & electrolyte concentration ○ Hormones such as ADH & Aldosterone Maintaining acid-base balance ○ Secreting H+ ions (if in a state of alkalosis) or reabsorbing HCO3 ions (if in a state of acidosis) Detoxifying the blood and eliminating wastes Regulating blood pressure (RAAS system) Aiding RBC production (erythropoiesis) Regulating vitamin D and calcium formation Hormones and Renal Function Antidiuretic hormone (ADH): produced by your pituitary gland; alters the tubules’ permeability to water ○ ↑ADH means increased permeability to water (reabsorbed) resulting in a concentrated low volume of urine ○ ↓ or no ADH means there is less permeability to water, causing more water to be excreted creating a larger volume of less concentrated urine Aldosterone: produced by the adrenal cortex; regulates water and sodium reabsorption ○ ↑Aldosterone increases H2O & Na reabsorption ○ ↓Aldosterone promotes H2O & Na reabsorption Renin: secreted in response to decreased extracellular volume; step one of the renin-angiotensin-aldosterone system Vitamin D: the kidneys help vitamin D convert into its active form! Necessary for the absorption of calcium and phosphate Erythropoietin: released when decreased oxygen to the kidney; stimulates RBC production Renin-Angiotensin-Aldosterone System https://www.youtube.com/watch?v=tiirLoa5jK0 For review of RAAS Tests of Renal and Bladder Function Renal Function Tests Blood Studies ○ Blood Urea Nitrogen (BUN) → urea is a cellular waste product removed from the blood ○ Creatinine → waste product of skeletal muscles ○ Electrolytes (K+, Na+) Glomerular filtration rate (GFR) ○ If your GFR < 60 this indicates renal injury! Urinalysis ○ Appearance: Colour, turbidity (cloudiness), pH, specific gravity (density of water), blood ○ Microscopic Urine: bacteria, RBC, WBC, crystals, fat, casts ○ Urinary Chemistry: bilirubin, ketones, glucose, sodium, potassium, protein Bladder Function Tests Cystometry: measures bladder pressure by using a pressure-measuring catheter Uroflowmetry: measures the time it takes to empty a full bladder (faster with urge incontinence or slower with prostatic obstruction) Post Void Residual (PVR): measures residual urine in the bladder after voiding (usually with US--bladder scanner). >200ml is abnormal! Direct visualization tests ○ Cystoscopy: camera inserted through the urethra and visualizes inside of the bladder ○ Ureteroscopy: camera inserted through the urethra and bladder directly into ureter to visualise upper urinary tract Age-Related Renal Function Pediatric Geriatric Decreased ability to remove excess water and Decrease in renal blood flow and GFR solutes Altered sodium and water balance Decreased concentrating ability Number of nephrons decrease due to renal Narrow margin for fluid and electrolyte vascular and perfusion changes balance Response to acid–base changes delayed Increased risk of medication toxicity Increased risk for medication toxicity Alterations in thirst and water intake