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URINARY SYSTEM & EXCRETION URINARY SYSTEM & EXCRETION Excretion The removal of metabolic wastes from the body Kidneys are the primary organ of this process FUNCTIONS OF THE URINARY SYSTEM 1. Excretion of Metabolic Wastes Removing metabolic waste products, notably nitrogenous waste from breakdown of amino acids (aa): Urea Breakdown of amino acids releases ammonia which is toxic to cells) Liver converts the ammonia to urea so it be safely transported in the blood to the kidney where it is eliminated in urine Creatinine Uric acid if too much uric acid crystals can form in joints This is known as gout FUNCTIONS OF THE URINARY SYSTEM FUNCTIONS OF THE URINARY SYSTEM 2. Maintenance of Water-Salt Balance Blood volume is associated with salt balance in body Salt (NaCl) can cause water diffusion into blood ↑ salt = ↑ blood volume = ↑ blood pressure FUNCTIONS OF THE URINARY SYSTEM 3. Maintenance of Acid-Base Balance Kidneys regulate acid-base in blood Excretion of hydrogen ions and reabsorption of bicarbonate to keep pH around 7.4 Urine often has a pH of 6 FUNCTIONS OF THE URINARY SYSTEM 4. Secretion of Hormones Renin Leads to secretion of aldosterone Reabsorption of sodium ions Erythropoetin Stimulates Activates Helps tract. red blood cell production vitamin D from the skin promote calcium absorption from the digestive THE URINARY SYSTEM Fig. 16.1 16-9 ORGANS OF THE URINARY SYSTEM Kidneys Two bean-shaped organs Located near lumbar region on either side of vertebral column Has a depression called the hilum where the Renal artery Renal vein are located ORGANS OF THE URINARY SYSTEM Ureters Conduct urine from the kidneys to the bladder Small, muscular tube 25cm long, 5 mm thick ORGANS OF THE URINARY SYSTEM Urinary Bladder Stores urine until it is expelled from the body Located in the pelvic cavity 3 openings (orifices): 2 for the ureters 1 for urethera ORGANS OF THE URINARY SYSTEM Urinary Bladder con’t... Expandable Detrusor Muscle – bladder wall Sphincter Muscles – surround bladder neck and urethra ORGANS OF THE URINARY SYSTEM While the bladder is filling: the detrusor muscle is relaxed so the bladder wall can expand and the sphincter muscles are contracted to keep the urethra closed When the bladder empties: the detrusor muscle contracts to squeeze the urine out, and the sphincter muscles relax so the urethra can open up http://www.aboutkidshealth.ca/en/howthebodyworks/kidneysandbladderoverview/bladderfillingandempt ying/pages/default.aspx ORGANS OF THE URINARY SYSTEM Urethra Small tube that extends from the urinary bladder to an external opening females 4 cm long Increases likelihood of urinary tract infection Not connected to reproductive system Males 20 cm long Common pathway for reproductive and urinary tracts FEMALE & MALE URINARY SYSTEMS URINATION Micturition When the bladder fills to 250ml Stretch receptors in the bladder wall send sensory impulse to the spinal cord Motor impulses from spinal cord send a signal the bladder This Bladder contraction and sphinter to relax is called an involuntary reflex Present in infants and young children 16-17 URINATION In older children and adults the brain can control this reflex and delay urination until a suitable time Stretch receptors in the bladder send a sensory signal to micturition center in the pons If not appropriate it will send an inhibitory signal to keep the sphinter closed This is called a voluntary response https://www.youtube.com/watch?v=US0vNoxsW-k
