The Urinary System Organs: Kidneys (creates urine), ureters (transport), urinary bladder (stores), urethra (transport)

Kidney Function Filter fluids from bloodstream and maintain homeostasis in body Rids body of wastes, excess ions, toxins, and drugs in urine Regulate blood volume, pH, salt content Secretes renin – regulates blood pressure Secretes erythropoietin – increases rbc production

Kidney Anatomy 5” long, 2.5” wide Renal capsule: Renal cortex: encloses kidney Renal cortex: outer region Renal medulla: deep to cortex w/ medullary pyramids separated by renal columns Renal hilus: medial indentation Rich Blood Supply Renal artery  segmental arteries  lobar arteries  interlobar artery  afferent arteriole  glomerulus capillaries  efferent arteriole  peritubular capillaries  interlobular vein  arcuate vein  interlobar vein  renal vein

Nephrons Nephrons form urine Glomerulus: knot of capillaries Renal tubule w/ enlarged bowman’s capsule at end Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting ducts: receive urine from many nephrons; deliver urine to renal pelvis

Urine Formation Filtration Tubular reabsorption Tubular Secretion Water and solutes smaller than proteins are forced thru capillary walls and pores of glomerular capsule into the renal tubule Tubular reabsorption Water, glucose, amino acids, and needed ions are transported out of the filtrate into the tubule cells and then enter the capillary blood Tubular Secretion Urea, H+, K+, creatinine, and drugs are removed from the peritubular blood and secreted by the tubule cells into the filtrate Urine: 1-2 L produced every 24 hrs

Ureters 10-12” long tubes Carry urine from kidneys to bladder Peristalsis propels urine transport Valve-like folds prevent back flow from bladder

Urinary Bladder Smooth, collapsible muscular sac Temporarily stores urine Empty: 2-3” long Full: 5”long and stores 1-2 pints urine

Urethra Thin walled tube Carries urine (by peristalsis) from bladder to outside the body Females: 3-4” long, opening is anterior to vaginal opening Males: 8” long, opening at tip of penis Double function: passageway for sperm ejaculation internal urethral sphincter: Involuntary smooth muscle, keeps closed when urine is not being passed External urethral sphincter: Voluntary skeletal muscle through pelvic floor Micturition – emptying the bladder 200mL urine collects and activates stretch receptors and cause bladder to contract to force open internal urtheral sphincter…feel urge to void

Fluid and Electrolyte Balance 2/3 water in intracellular fluid (ICF) 1/3 water in extracellular fluid (ECF) Electrolytes: charged ions that conduct electrical current, alters blood volume and blood pressure Ex. sodium, potassium, calcium ions Electrolyte balance maintained by hormones Antidiuretic hormone (ADH) Aldosterone

Acid-Base Balance Proper function, blood pH between 7.35-7.45 Alkalosis rise in blood pH above 7.45 Acidosis drop in pH below 7.35 Blood Buffers Respiratory System Renal Mechanisms Excreting bicarbonate ions Reabsorbing or generating new bicarbonate ions