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Urinary system Ch. 28,29,30 Consists of: • 2 kidneys that filter blood • 2 ureters • Urinary bladder • urethra Kidneys Reddish brown, bean shaped, 12 cm long, enclosed in fibrous capsule Location Either side of vertebral column Between 12th thoracic and 3rd lumbar Left kidney slightly higher Kidney structure Medial depression – sinus (entrance of blood vessels, nerves, lymphatic vessels and ureter.) Divided into major and minor calyces Renal papillae project inward 2 regions Renal medulla Renal cortex – contains nephrons (functional regions of the kidney) Kidney function Regulate volume composition, and ph of body fluids Remove metabolic wastes Control rate of red blood cell formation (erythropoietin secretion) Regulate blood pressure (renin secretion) Renal blood vessels Abdominal aorta gives rise to renal arteries leading to kidneys Branch into smaller arteries Venous blood returned through vessels that generally correspond to arterial pathways. Nephrons Structure Renal corpuscle Renal tubule Urine formation Glomerular filtration, tubular reabsorption, tubular secretion Glomerular filtration Urine forms when fluid portion of blood leaves glomerulus and enters glomerular capsule Filtration pressure – hydrostatic pressure of blood Filtration rate factors Filtration pressure, glomerular osmotic pressure, and hydrostatic pressure in capsule. Sympathetic nervous system – filtration declines Parasympathetic – filtration increases Average filtration rate: 125 ml per minute, 180 liters in 24 hours (most is reabsorbed) Tubular reabsorption Most reabsorption – promimal convoluted tubule Glucose and amino acids reabsorbed by active transport, water by osmosis, proteins by pinocytosis. Sodium by active transport Water – osmosis Presence of ADH causes kidneys to retain water Ureters and Urinary bladder Ureters move urine to bladder Bladder is hollow, distensibe, muscular Floor of bladder called trigone – openings to urter and urethra Muscular wall Internal sphincter controls release to urethra urethra Tubes that takes urine from bladder to outside Peristalisis moves urine out Secretes mucus for lubrication Urine composition Urea and uric acid – product of amino acid metabolism Uric acid - nucleic acid metabolism Varies – reflects amount of water and solutes Urea 95% water, urea, uric acid, amino acids, electrolytes. Urine elimination Path - nephron, renal papillae, calyces, renal pelvis, ureter, bladder, urethra Ureters – muscular tubes. From kidneys to bladder Peristaltic waves take urine to bladder Micturation Muscle contracts and sphincter relaxes Stretching triggers micturation reflex Strong contractions open sphincter Under some conscious control Water, Electrolyte, and AcidBase Balance To be in balance, quantities of fluids and electrolytes leaving body should be equal to quantities entering body. Fluids occur in compartments Intracellular Extracellular Transcellular (fluid of eye, cerebrospinal etc.) Female – 52% water Male – 63% water