The excretory system eliminates wastes from the body while also maintaining water and chemical balances. The main organs of the excretory system are the kidneys, the ureters, the bladder, the urethra, the skin, and the lungs.
The main things that the body must excrete are nitrogen wastes and carbon dioxide. Nitrogen wastes are a byproduct of protein metabolism. Protein metabolism is the making of amino acids into proteins and the breaking-down of proteins into amino acids. Carbon dioxide is made when the lungs bring in oxygen and it is taken to cells for cellular respiration and as a byproduct carbon dioxide is made.
Humans have two kidneys that are kind of bean shaped. The kidneys are located one behind the stomach, and the other behind the liver. Together they regulate the chemical composition of the blood. The kidneys are made up of a bunch of different part starting with the cortex on the outside. The cortex is the outer wall that contains little structures that filter the blood brought in from the renal artery and makes up about one-third of the kidneys. (Towle, 1999)
The inner two-thirds is called the medulla. The medulla consists of 6 to 18 triangle shaped renal pyramids the bigger parts of the pyramids is next to the cortex and the tips, or renal papilla poke into the renal sinus. Each of the pyramids have grooves that meet at the papilla. The pyramids are separated by a tissue called renal columns. The columns have a texture that is very similar to the cortex. A renal lobe is made up of a renal pyramid, its area of cortex, and its columns. Urine production happens in the renal lobes. The renal papilla have small ducts that shoot urine into small cup-shaped drains called the minor calyx. Four or five minor calyces make up the major calyces and two or three combines major calyces make up the renal pelvis. The renal pelvis is a large, funnel shaped chamber that is connected to the ureter which drains the kidney. (Martini, Nath....
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