The circulatory system is the body’s transport system. It is made up of a group of organs that transport blood throughout the body. The heart pumps the blood and the arteries and veins transport it. Oxygen-rich blood leaves the left side of the heart and enters the biggest artery, called the aorta.
The aorta branches into smaller arteries, which then branch into even smaller vessels that travel all over the body. When blood enters the smallest blood vessels, which are called capillaries, and are found in body tissue, it gives nutrients and oxygen to the cells and takes in carbon dioxide, water, and waste. The blood, which no longer contains oxygen and nutrients, then goes back to the heart through veins. Veins carry waste products away from cells and bring blood back to the heart , which pumps it to the lungs to pick up oxygen and eliminate waste carbon dioxide. Digestive System The digestive system is made up of organs that break down food into protein, vitamins, minerals, carbohydrates, and fats, which the body needs for energy, growth, and repair. After food is chewed and swallowed, it goes down the esophagus and enters the stomach, where it is further broken down by powerful stomach acids.
From the stomach the food travels into the small intestine. This is where your food is broken down into nutrients that can enter the bloodstream through tiny hair-like projections. The excess food that the body doesn’t need or can’t digest is turned into waste and is eliminated from the body. Endocrine System The endocrine system is made up of a group of glands that produce the body’s long-distance messengers, or hormones. Hormones are chemicals that control body functions, such as metabolism, growth, and sexual development.
The glands, which include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, thymus gland, pineal body, pancreas, ovaries, and testes, release hormones directly into the bloodstream, which transports the hormones to organs.