Heart and Circulatory System
About the Cardiovascular System
The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues. With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to all of our cells.
Every day, the approximately 10 pints (5 liters) of blood in your body travel many times through about 60,000 miles (96,560 kilometers) of blood vessels that branch and cross, linking the cells of our organs and body parts. From the hard-working heart, to our thickest arteries, to capillaries so thin that they can only be seen through a microscope, the cardiovascular system is our body's lifeline.
The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries.
Our bodies actually have two circulatory systems:
1. pulmonary circulation is a short loop from the heart to the lungs and back again. 2. systemic circulation (the system we usually think of as our circulatory system) sends blood from the heart to all the other parts of our bodies and back again.
What the Heart & Circulatory System Do
The circulatory system works closely with other systems in our bodies. It supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body. Hormones — produced by the endocrine system — are also carried through the blood. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another.
Lungs and Respiratory System
Whether you're wide awake and getting ready for a big date or asleep during your most snooze-worthy afternoon class, you don't have to think about breathing. It's so important to life that it happens automatically. If you didn't breathe, you couldn't live.
Lungs & Respiratory System Basics
Each day we breathe about 20,000 times. All of this breathing couldn't happen without help from the respiratory system, which includes the nose, throat, voice box, windpipe, and lungs. With each breath, you take in air through your nostrils and mouth, and your lungs fill up and empty out. As air is inhaled, the mucous membranes of the nose and mouth warm and humidify the air.
Although we can't see it, the air we breathe is made up of several gases. Oxygen is the most important for keeping us alive because body cells need it for energy and growth. Without oxygen, the body's cells would die.
Carbon dioxide is the waste gas that is produced when carbon is combined with oxygen as part of the body's energy-making processes. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out.