Functions of the Cardiovascular System
Thecardiovascular systemshown inFigure18.1is the organ system that is made up of
the heart, the blood vessels, and the blood. Your cardiovascular system has many important
roles in maintaining homeostasis. It moves nutrients, hormones, gases (such as oxygen) and
wastes (such as carbon dioxide) to and from your body cells. It also helps to keep you warm
by moving warm blood around your body. To do these tasks, your cardiovascular system
works with other body systems such as the respiratory, endocrine, and nervous systems.
The Movement of Gases
It could be said that the movement of gases, especially oxygen and the waste product of
cellularrespiration, carbondioxide, isoneofthemostimportantaspectsofthecardiovascular
system. But the cardiovascular system cannot do this alone. It must work with other organ
systems, especially the respiratory system (discussed in a later chapter), to move these gases
throughout your body.
Oxygen is needed by every cell in your body as it is the final electron acceptor during aerobic
cellular respiration. You breath oxygen in and carbon dioxide out through your respiratory
system. Once oxygen enters your lungs, it must diffuse into your blood stream for transport
around your body.
Oxygen is transported in your blood by attaching to the hemoglobin protein. The oxygen
diffusesfromthebloodintothetissues,whilecarbondioxidediffusesintheoppositedirection.
Carbon dioxide is transported back to the lungs, where it diffuses out of the blood and into
your lungs for release from your body.
Parts of the Cardiovascular System
Your heart pushes the blood around your body through the blood vessels. The heart, shown
inFigure18.2, is made of cardiac muscle (refer to theSkin, Bones, and Muscleschapter).
The heart is connected to many blood vessels that bring blood all around the body. The
cardiac muscle contracts and pumps blood through the heart and blood vessels.
Blood Vessels
The job of these blood vessels is to channel the blood around the body. There are three
main types of blood vessels in the body; arteries, veins, and capillaries.
Arteriesare blood vessels that carry blood away from the heart. Arteries have thick walls
that have a layer of smooth muscle, as shown inFigure18.3. Arteries usually carry oxygen-
rich blood around the body. The blood that is in arteries is under pressure. The contractions