It's made of bones, tendons, and ligaments.

You already know these steps: mouth, esophagus, stomach, small intestine, large intestine.

Be sure to also know what each of these do: pancreas, liver, villi, anus.

Digestive system remove the waste food from our bodies, but we have other wastes that also need to be removed.

For humans, waste leaves as sweat or urine.

See the website below for the basics of the excretory system. You also need to know 2 more details involved:

1. the liver converts nitrogen waste in the blood to urea, which it sends right back into the blood.

2. Nephron are tiny filters in the kidney that collect waste and send useful substances back to the blood.

For fish, the gills pull oxygen into the body. We're focusing on human respiratory system, which consists of lungs and all the tubes leading to them. Air travels through the nose or mouth and trachea to the lungs. Once it's in the lungs, it goes through smaller tubes called bronchi. Inside the alveoli are tiny thin-walled sacs called alveoli. Alveoli are thin enough that oxygen can pass through them into the circulatory system. These tiny pockets are the connector between the 2 body systems.

Parts: hear, arteries, veins, capillaries

As blood travels through the body, it's dropping off oxygen and digested food to each individual cell. It constantly travels away from the heart- to the cells- then back to the heart. By the time it gets back to the heart, it's almost out of its oxygen. That's OK, though, because half-way through the heart, it pitstops at the lungs and loads up through the alveoli.  

The capillaries are tiny vessels that allow oxygen and food to pass through them to the cells.

It has 2 parts that work together;

1. Central Nervous System - brain and spinal cord

2. Peripheral Nervous System- all other nerves (besides the ones in CNS) and the sense organs

Nerve cells are called neurons. There are 3 kinds of neurons: sensory, motor, and associative. Each type does a different job.

Three types of muscles are:

*skeletal: These are voluntary (we have to think about moving them) and they move the skeleton.

* smooth: These are involuntary (brain moves them automatically) and control the organs.

* cardiac: This is another name for the heart muscle. It works automatically, but it's structure is very different from smooth muscles.