BMS - Cardiovascular System

The Heart

• A muscular organ, about the size of a clenched fist
• Located in the thoracic cavity between the lungs
• Contains four chambers: two upper atria (right and left), and two lower ventricles (right and left)
• The right side pumps deoxygenated blood to the lungs for oxygenation
• The left side pumps oxygenated blood to the rest of the body

Structure of the Heart

• Composed of three main layers
• The epicardium (outer layer) provides protection
• The myocardium (middle layer) consists of thick cardiac muscle for contraction
• The endocardium (inner layer) is a smooth lining that covers the chambers and valves
• Contains valves, including the tricuspid, mitral, pulmonary semilunar, and aortic semilunar, which ensure one-way blood flow

Flow of Blood Through the Heart

• Deoxygenated blood returns to the right atrium from the body via the superior and inferior vena cava
• It moves through the tricuspid valve into the right ventricle
• The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary arteries and then to the lungs for oxygenation
• Oxygenated blood returns to the left atrium via the pulmonary veins
• It passes through the mitral valve into the left ventricle
• The left ventricle pumps blood through the aortic semilunar valve into the aorta, delivering oxygenated blood to the body

Conduction System of the Heart

• Consists of specialized cardiac tissue that controls the heartbeat
• The components are:
• The sinoatrial (SA) node, the primary pacemaker in the right atrium, initiates electrical impulses
• The atrioventricular (AV) node delays impulses to allow atrial contraction before ventricular contraction
• The Bundle of His conducts impulses from the AV node to the ventricles
• Purkinje fibers distribute electrical impulses throughout the ventricles, triggering contraction

Blood Supply to the Heart

• The heart receives its own blood supply through the right and left coronary arteries
• These arteries branch off from the aorta and deliver oxygenated blood to the myocardium
• Deoxygenated blood is returned to the right atrium via cardiac veins that drain into the coronary sinus

Components and Vessels of the Circulatory System

• The circulatory system includes:
• Arteries, which carry oxygenated blood away from the heart (except pulmonary arteries)
• Veins, that return deoxygenated blood to the heart (except pulmonary veins)
• Capillaries, where gas and nutrient exchange occurs
• Major vessels include the aorta, pulmonary arteries and veins, as well as the superior and inferior vena cava