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The Urinary and Respiratory Systems Urinary system Parts of the urinary system: Aorta Kidneys Ureters Bladder Urethra Function of the kidneys Main function is to maintain water and mineral balance In 24 hours – all the blood passes through the kidneys about 400 times. Function of the kidneys Nephrons are the functional ‘filters’ of the blood Reject blood cells and proteins Accept fluid salts and other chemicals Also filter nitrogenous waste (Urea) Function of the kidneys Also act in reverse – return water to bloodstream All but about 2 gallons of water are returned to bloodstream, kidneys filter approximately 200 gallons of water daily. Salts (and some liquid) are passed from the nephron to the glomeruli and on to a collecting duct. From the collecting duct, the urine enters the ureter and on to the bladder. Bladder Simply defined – a sac to hold urine When the bladder is full, nervous impulse signals indicate the bladder needs to be emptied Excretion of the urine Urine is excreted through the urethra Mares, urethra is relatively short, empting into the vagina. Stallions or geldings, much longer because it must past through the penis. Respiratory system Parts: Nostril Turbinates Nasopharnyx Trachea Lungs Bronchus Bronchiole alveoli Lungs The lungs are the organ of respiration – the other parts act as transport mechanisms. The average horse lungs hold 1.5 cubic feet of air At resting respiration, about 250 cubic inches of air are inhaled Resting respiration rate is approximately 8 – 16 times per minute. When called for by initiation of the Kreb’s cycle, respiration increases to supply oxygen needed for muscular action. Breathing process Air is drawn into the nostrils, passes through the turbinates and on to the trachea. At the juncture of the trachea and the lungs the air is directed into the bronchia where it is evenly distributed to the bronchioles and eventually to the alveoli. Physiology if respiration Respiration is the act of breathing Exchange of Oxygen and Carbon Dioxide Internal External In internal respiration, the diaphragm contracts, and an outward rotation of the ribs. effectively acting like a piston to draw in air External respiration, the process is reversed, the diaphragm relaxes and the ribs contract. Gas exchange Gas exchange takes place in the alveoli. The epithelial cells of the alveoli act by diffusion. Diffusion is a form of passive transport (no energy required) in which substances flow from an area of high concentration to an area of low concentration. Substances such as O2 and CO2, are small enough to pass through the walls of the capillaries in the alveoli.
