Three of the Systems of the Body

Circulatory System

• The atria are the chambers that fill with the blood returning to the heart from the body and lungs.
• The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs.
• Running down the middle of the heart is a thick wall of muscle called the septum. The septum's job is to separate the left side and the right side of the heart.

Circulatory System Continued

• Two of the heart valves are the mitral valve and the tricuspid valve, they let blood flow from the atria to the ventricles.
• The other two are called the aortic valve and pulmonary valve, and they're in charge of controlling the flow as the blood leaves the heart.

Respiratory System

• The nose and the nasal cavity filter, warm, and moisten the air you breathe. The nose hairs and the mucus produced by the cells in the nose catch particles in the air and keep them from entering the lungs.
• Behind the nasal cavity, air passes through the pharynx , a long tube. Both food and air pass through the pharynx.

Respiratory System Continued

• The larynx , also called the "voice box," is found just below the pharynx. Your voice comes from your larynx. Air from the lungs passes across thin tissues in the larynx and produces sound.
• The trachea is a long tube that leads down to the lungs, where it divides into the right and left bronchi . There is small flap called the epiglottis that covers your trachea when you eat or drink.

Respiratory System Continued

• The bronchioles lead to the alveoli. Alveoli are the little sacs at the end of the bronchioles. They look like little bunches of grapes. Oxygen is exchanged for carbon dioxide in the alveoli. That means oxygen enters the blood, and carbon dioxide moves out of the blood. The gases are exchanged between the blood and alveoli by simple diffusion.

Respiratory System Continued

• The diaphragm is a sheet of muscle that spreads across the bottom of the rib cage. When the diaphragm contracts, the chest volume gets larger, and the lungs take in air. When the diaphragm relaxes, the chest volume gets smaller, and air is pushed out of the lungs.

Digestive System

• The saliva in your mouth and your teeth help break up the food into smaller pieces
• The esophagus is a narrow tube that carries food from the throat to the stomach.

Digestive System

• The stomach is a sac-like organ at the end of the esophagus. The muscles contract and relax, this moves the food around and helps break it into smaller pieces. Mixing the food around with the enzyme pepsin and other chemicals helps digest proteins. The stomach stores food until the small intestine is ready to receive it.

Digestive System

• The small intestine a is narrow tube that starts at the stomach and ends at the large intestine.The small intestine is also where most nutrients are absorbed into the blood. The later sections of the small intestines are covered with tiny projections called villi. Villi contain very tiny blood vessels. Nutrients are absorbed into the blood through these tiny vessels. There are millions of villi, so, altogether, there is a very large area for absorption to take place.

Digestive System

• The large intestine is a wide tube that connects the small intestine with the anus. Waste enters the large intestine from the small intestine in a liquid state. As the waste moves through the large intestine, excess water is absorbed from it.

Digestive System

• Then the waste leaves the body through the anus