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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: – 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 – 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 – • internal urethral sphincter: – • Involuntary smooth muscle, keeps closed when urine is not being passed External urethral sphincter: – • Double function: passageway for sperm ejaculation 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