1. excretion is the removal of toxic materials, the waste products of metabolism, and substances in excess of requirements from organisms.
2. kidneys remove nitrogenous waste products, water, salt, hormones and drugs.
3. structure
3.1. kidney
3.1.1. Two fairly solid oval structures. They are red-brown enclosed in a transparent membrane at the back of the abdominal cavity.
3.1.2. cortex
3.1.2.1. a dark outer region.
3.1.3. medulla
3.1.3.1. lighter inner zone.
3.2. Renal vein
3.2.1. branvhes off from the aorta and brings oxigenated blood to them.
3.3. Renal artery
3.3.1. takes deoxygenated blood away from the kidneys to the vena cava.
3.3.2. divides up' into many arterioles, making a knot of vessels
3.3.2.1. glomerulus
3.3.2.1.1. each glomerulus is surrunded by a cup-shaped otgan called a renal capsule, which leads to a renal tubule. the joins a collecting duct which passes to the medulla to open into the pelvis
3.4. ureter
3.4.1. runs from each kidneys to the bladder in the lower part of the abdomen.
3.5. bladder
3.5.1. is where the urine is store
3.6. sphincter muscle
3.6.1. when it contract,it is shut off and do not let the urine get through. When it relax, the urine passes.
3.7. pelvis
3.7.1. where the ureter joins the kidney.