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The Excretory System Honors Biology Facilitator: Mr. Lee Room 320 Objectives • Describe the function of the kidneys • Identify the functional unit of the kidney • Describe the role of the liver in the excretory system Functions of the Excretory System • Every cell in our bodies produce metabolic wastes, such as: – Excess salts – Carbon dioxide – Urea • The excretory system removes the metabolic wastes Organs of the Excretory System • Skin: – Excretes excess water, salts, and some urea in our sweat • Lungs: – Excretes carbon dioxide • Liver: – Converts excess amino acids into useful compounds – Converts nitrogen waste into urea Organs of the Excretory System… • Kidneys (main organ): – Filter blood • Nitrogenous wastes are eliminated by the kidneys • Waste laden blood enters from the renal artery • Clean blood leaves through the renal vein – Maintain blood pH – Regulates water content of blood Organs of the Excretory System… • Kidney Structure- There are three main parts of the: – Cortex: • Outermost portion – Medulla: • Inner portion – Renal pelvis: • Funnel-shaped structure in the center Organs of the Excretory System… • Ureter: – Carries urine to the urinary bladder • Bladder: – Stores urine • Urethra: – Where urine is excreted Kidney Structure • Nephrons are the functional units of the kidney – Stretched out, they would extend for 50 miles – They remove toxins, urea, water, and salts from the blood to form urine – Blood enters the nephrons through the arteriole, impurities are filtered out and emptied into the collecting duct Kidney Structure … • The filtered blood (filtrate) exits the nephrons through the venule • Blood purification involves: – Filtration – Reabsorption Anatomy of a Kidney.mp4 Filtration • Filtration of the blood takes place in the glomerulus • The glomerulus is a network of capillaries that at the top of the nephrons that is enclosed by the Bowman’s capsule • Blood pressure forces smaller molecules out of the blood Reabsorption & Secretion • The kidneys filter all our blood in about 45 minutes • Most reabsorption takes place in the proximal convoluted tubule • About 75% of the water is reabsorbed through osmosis • Glucose and minerals are returned to the blood by active transport Urine Formation • Materials that is left is called urine • Urine is primarily concentrated at the Loop of Henle • Urine is stored in the urinary bladder until it is released through a tube called the urethra Control of Kidney Function • Activity of the kidneys are mainly controlled by the composition of blood • Regulatory hormones are also released Review • Describe the function of the kidneys: – Filter blood – Maintain blood pH – Regulates water content of blood • Identify the functional unit of the kidney: – Nephrons are the functional units of the kidney Review… • Describe the role of the liver in the excretory system: – Converts excess amino acids into useful compounds – Converts nitrogen waste into urea