Cardiovascular System: Heart and Blood Vessels

• The heart, roughly fist-sized, is a muscle that pumps blood.
• Blood vessels are tube-like structures carrying blood throughout the body and heart.
• The heart and blood vessels form the cardiovascular system.

Heart Structure

• The heart contains four chambers.
• The upper two are the right and left atrium.
• The lower two are the right and left ventricle.
• The atrial septum is the wall between the two atria.
• The ventricular septum is the wall between the two ventricles.
• Arteries carry blood away from the heart.
• Veins carry blood to the heart.
• The superior vena cava and inferior vena cava are the two main veins returning blood to the heart.
• The pulmonary artery and aorta are the main arteries carrying blood to the lungs and the rest of the body, respectively.
• Valves control blood flow through blood vessels and chambers.

Heart Valves

• Tricuspid valve separates the right atrium from the right ventricle.
• Pulmonary valve separates the right ventricle from the pulmonary artery.
• Mitral valve separates the left atrium from the left ventricle.
• Aortic valve separates the left ventricle from the aorta.

Blood Flow Through the Heart

• Body returns oxygen-poor blood to the heart through the superior and inferior vena cavae, which enters the blood into the right atrium.
• Blood flows from right atrium through the tricuspid valve into the right ventricle.
• Right ventricle pumps oxygen-poor blood through the pulmonary valve into the main pulmonary artery.
• Blood flows through the right and left pulmonary arteries into the lungs.
• Blood entering the lungs picks up oxygen and unloading carbon dioxide, becoming oxygen-rich.
• Oxygen-rich blood flows from the lungs back to the heart through four pulmonary veins.
• Blood flows from the pulmonary veins into left atrium.
• Blood flows from the left atrium through the mitral valve into the left ventricle.
• The left ventricle pumps oxygen-rich blood through the aortic valve into the aorta and out to the rest of the body.

Detailed Blood Flow

• Blood enters the right atrium from the superior and inferior vena cavae.
• Blood flows from the right atrium through the right AV valve (tricuspid) into the right ventricle.
• Contraction of the right ventricle forces the pulmonary semilunar valve to open.
• Blood flows through the pulmonary valve into the pulmonary trunk.
• Blood is distributed by the right and left pulmonary arteries to the lungs, unloading CO2 and loading Oxygen.
• Blood returns from the lungs through pulmonary veins to the left atrium.
• Blood flows from the left atrium through the left AV valve (mitral) into the left ventricle.
• Contraction of the left ventricle forces the aortic semilunar valve to open.
• Blood flows through the aortic valve into the ascending aorta.
• Blood in the aorta is distributed to every organ, unloading O and loading CO2.
• Blood returns to the heart from the venae cavae.

Blood Properties

• The heart pumps blood providing oxygen and nutrients, also removing carbon dioxide and wastes.
• Blood picks up oxygen from the lungs.
• Oxygenated blood is called oxygen-rich.
• Deoxygenated blood is called oxygen-poor.

The heart, a muscular pump, and blood vessels, which transport blood, make up the cardiovascular system. The heart has four chambers: two atria and two ventricles, separated by septa. Arteries carry blood away, and veins return blood to the heart; valves control blood flow through the heart.