The Eight Major Systems
The digestive systemThe excretory system The muscular system The respiratory system
The skeletal system The nervous system The circulatory system The immune system
The Excretory System
Closely associated with the digestive system is the excretory system. Its primary purpose is to help the body dispose of unneeded materials. This is important for the body because there are some things that could kill the individual if their body didn't slowly get rid of it. The four major components of the excretory system are the skin, kidneys, lungs, and liver. The skin is primarily responsible for disposing of salt, which it does when you sweat.
The kidneys are the major components of the excretory system, and are responsible for cleaning the blood. The most important component of the kidney is the nephron, where the blood is actually filtered. The nephron works by changing the concentration of the fluid outside the tube of the nephron, which causes different materiels to flow out of the blood. This results in a highly concentrated solute, which then flows to the bladder for storage before it leaves the body. The liver is responsible for processing alchohol in the blood supply so that it doesn't stay in circulation, where it can damage cells and organs. The lungs help the body dispose of carbon dioxide which is produced during cell respiration. The body uses two kinds of cleaning processes when it is disposing of waste: filtration and reabsorption. Filtration is when something like the blood is filtered so that the undesired substances aren't in it anymore. Reabsorption involves recovering molecules that the body needs from a solution that has lots of unwanted molecules in it.