The Digestive System Ureters, Urinary Bladder, and Urethra o Ureters carry urine from the renal pelvis to the urinary bladder. o The urethra carries urine from the urinary bladder to the outside of the body. o The ureters and urinary bladder are lined with transitional epithelium and have smooth muscle in their walls. o The internal and external urinary sphincter muscles regulate the flow of urine through the urethra. Urine Production • Urine is produced by the processes of filtration, reabsorption, and secretion. Filtration o The renal filtrate passes from the glomerulus into Bowman's capsule and contains no blood cells and few blood proteins. o Filtration pressure is responsible for filtrate formation. Reabsorption o About 99% of the filtrate volume is reabsorbed; 1% becomes urine. o Proteins; amino acids; glucose; fructose; and sodium, potassium, calcium, bicarbonate, and chloride ions are among the substances reabsorbed. o
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