Cardiovascular System Overview

General Structures and Functions of the Cardiovascular System

• Composed of the heart, blood vessels, and blood, forming a closed circulatory loop.
• Transports oxygen, nutrients, hormones, and waste products throughout the body.
• Regulates body temperature, pH levels, and fluid balance.

Location of the Heart in the Thoracic Cavity

• Positioned in the mediastinum, between the lungs and posterior to the sternum.
• Base of the heart is located at the level of the second rib, while the apex points towards the left, at the fifth intercostal space.

Layers of the Heart Wall

• Composed of three main layers: epicardium, myocardium, and endocardium.
• Epicardium: Outermost layer, also known as the visceral pericardium; reduces friction during heartbeats.
• Myocardium: Thick, muscular middle layer; responsible for the heart's contraction and pumping action.
• Endocardium: Innermost layer; provides a smooth lining for the heart chambers and valves.

Major Structural Features of the Heart

• Chambers: Four chambers - right atrium, right ventricle, left atrium, left ventricle.
  • Right atrium receives deoxygenated blood from the body.
  • Right ventricle pumps blood to the lungs for oxygenation.
  • Left atrium receives oxygenated blood from the lungs.
  • Left ventricle pumps oxygenated blood to the body; has the thickest wall.
• Valves: Four key valves prevent backflow of blood.
  • Atrioventricular valves (tricuspid and mitral) control flow between atria and ventricles.
  • Semilunar valves (pulmonary and aortic) regulate blood flow out of the ventricles.
• Great Vessels: Major blood vessels include:
  • Superior and inferior vena cava (return deoxygenated blood to the right atrium).
  • Pulmonary arteries (carry deoxygenated blood from the right ventricle to the lungs).
  • Pulmonary veins (bring oxygenated blood from the lungs to the left atrium).
  • Aorta (distributes oxygenated blood from the left ventricle to the body).

Pathway of Blood Through the Adult Heart

• Blood enters the right atrium from the body via vena cavae.
• Passes through the tricuspid valve into the right ventricle.
• Ejected into the pulmonary arteries through the pulmonary valve to the lungs.
• Oxygenated blood returns via pulmonary veins to the left atrium.
• Flows through the mitral valve into the left ventricle.
• Pumped into the aorta through the aortic valve to supply the body.

Coronary Vessels and Their Functional Significance

• Coronary arteries supply oxygenated blood to the heart muscle itself.
• Major arteries include the right coronary artery and left coronary artery (which branches into the anterior interventricular and circumflex arteries).
• Coronary veins collect deoxygenated blood from the heart muscle and drain into the coronary sinus, which empties into the right atrium.
• Importance of coronary circulation: ensures adequate oxygen supply to the myocardium, preventing ischemia and heart attacks.