Excretory System Excretion involves the removal of wastes that pass through a membrane or wastes that are results of metabolic processes. (Undigested food that is eliminated is NOT excreted.) Kidney: excretion of nitrogenous wastes, excess water, salts, and spicesKidney: excretion of nitrogenous wastes, excess water, salts, and spices Lungs: carbon dioxide, spices, and waterLungs: carbon dioxide, spices, and water Skin: water and saltsSkin: water and salts

Urinary System Kidneys: main organs of the urinary system that regulate the excretion of water, solutes, and nitrogenous wastes.

Parts of the Kidney Parts of the Kidney Cortex: outermost portion (1/3) Medulla: inner 2/3 of the kidney Renal pelvis: funnel-shaped structure in the center of the kidney where the renal vein and renal artery meet the kidney Nephrons: functional units of kidneys where urine is formed

In the Nephron Nephron Bowman’s capsule: cup-shaped structure enclosing a bed of capillaries where filtration occurs Glomerulus: capillary bed that receives blood from the renal artery Renal tubule: further exchange of materials occur here in the processes of reabsorption and secretion Loop of Henle: part of the renal tubule that ensures the reabsorption of water

Formation and Composition of Urine From the renal tubules of nephrons urine collects Urine is composed of urea, salts, water, and other metabolic wastes –Nitrogenous wastes are in the form of ammonia (toxic) which the liver converts to urea. Thus, the liver contributes to both digestion and excretion.

Elimination of Urine Elimination of Urine Urine travels from the renal pelvis through a narrow tube called a ureter. It is then stored in the urinary bladder. Elimination occurs when urine is forced through the urethra