Presentation on theme: "Urinary System. Overall Functions Excretion – remove nitrogenous wastes from blood Osmoregulation – maintain proper balance of ions Volume regulation."— Presentation transcript:
Overall Functions Excretion – remove nitrogenous wastes from blood Osmoregulation – maintain proper balance of ions Volume regulation – maintain proper balance of water Regulation of pH Detoxify superoxides, free radicals and some types of drugs.
Why are nitrogenous wastes a problem? Ammonia is a moderately strong base (elevates blood pH). Urea is a weaker base made from ammonia and carbon dioxide in the liver – less toxic than ammonia (NH 3 ) Uric Acid is a waste produced from the metabolism of nucleic acids Creatinine is a waste product from creatine metabolism.
The kidneys only comprise about 0.5% of the total body weight, but they receive 1,200 mL of blood per minute; about 20% of the Total cardiac output. Kidneys are constantly cleaning, balancing ions and water, and adjusting the pH of the blood.
Tubule system (produces urine) Calyx (funnel-like Structure that Collects urine from Tubules) Pelvis of the Kidney ureter Cortex Medulla
The Nephron is the Functional Unit of the Kidney Glomerulus Afferent Arteriole Efferent Arteriole Bowman’s Capsule Proximal Convoluted tubule Loop of Henle Distal Convoluted Tubule Collecting Duct Urine is carried to Calyx, Pelvis and then the Ureter
Functions of the Nephron 1. Filtration The glomerulus is made of “fenestrated capillaries” that are unusually permeable. All of the following substances can easily filter out of the glomerulus and into Bowman’s capsule. water glucose (and other sugars) amino acids small organic molecules ammonia, urea, uric acid salts, H+, HCO 3 The only substances that are not usually filtered out are blood cells, proteins and larger organic molecules. Notice that several important nutrients are filtered out of the blood during the filtration process.
Functions of the Nephron 2. Reabsorption Reabsorption is a process that 1. Utilizes active transport pumps 2. Occurs in the proximal and distal tubules 3. Reclaims nutrients that were lost during the filtration process. 4. Returns the nutrients to the blood Examples of reabsorbed substances 1. glucose 2. amino acids 3. NaCl NOTE: water is reabsorbed passively by osmosis.
Functions of the Nephron 3. Tubular secretion Secretion is a process that 1. Utilizes active transport pumps 2. Occurs in the proximal and distal tubules 3. Adds wastes from the blood that were not effectively filtered at the glomerulus. 4. Increases the concentration of wastes in the urine Examples of secreted substances 1. Ammonia, H+ (smaller ionic) 2. histamine, creatinine (larger, organic) 3. penicillin
Glomerular Filtration Rate The two kidneys produce nearly 45 gallons (180 liters) of filtrate per day. Glomerular Filtration Rate (GFR) depends almost completely on hydrostatic pressure in the glomerulus. * dilation or constriction of afferent and efferent arterioles. * overall blood pressure What happens in exercise when blood pressure may increase up to 200 mm Hg or more? During exercise, the sympathetic nervous system comes into play. Symp. Nerves stimulate the afferent arteriole and it constricts.
Regulation of Na+ Reabsorption If blood pressure is low for an extended period of time, the kidney reacts by releasing an enzyme called renin. Renin is involved in a series of reactions that ultimately lead to the release of a hormone called Aldosterone from the adrenal gland. Aldosterone is a steroid that acts on the distal convoluted tubule and increases the rate of NaCl reabsorption. As the concentration of NaCl increases in the blood, water is reabsorbed at a faster rate (osmosis). With more salt and water in the blood, the volume of blood goes up and blood pressure goes up. Impact of diet and strenuous exercise....
Regulation of Urine Volume coordinate function of Loop of Henle and the Collecting Duct Na+ Four Times Saltier Than the Blood