Overview
This lecture introduces the cardiovascular system, focusing on the heart's structure, blood vessels, and the flow of blood through systemic and pulmonary circulation.
Components of the Cardiovascular System
- The cardiovascular system includes the heart and blood vessels (arteries, veins, capillaries).
- Major blood vessels: superior vena cava, inferior vena cava, aorta (with its branches), pulmonary artery, and pulmonary veins.
Structure of the Heart
- The heart is divided into right and left sides, each with an atrium and a ventricle (four chambers: right atrium, right ventricle, left atrium, left ventricle).
- Valves control blood flow between chambers: tricuspid (right), pulmonary (right outflow), mitral/bicuspid (left), and aortic (left outflow).
- The tricuspid and mitral/bicuspid valves have cusps (tricuspid: 3, mitral: 2).
Circulation Pathways
- Systemic circulation delivers oxygen-rich blood from the left ventricle through the aorta to the body and returns oxygen-poor blood to the right atrium via the vena cavae.
- Pulmonary circulation sends oxygen-poor blood from the right ventricle to the lungs via pulmonary arteries and returns oxygen-rich blood to the left atrium via pulmonary veins.
Heart Function and Cardiac Cycle
- Blood enters ventricles during relaxation (diastole) and is pumped out during contraction (systole).
- Valve closures cause heart sounds: louder ("lub") from tricuspid and mitral valves, softer ("dub") from aortic and pulmonary valves.
Major Blood Vessels and Branches
- The aorta arches and branches into: brachiocephalic artery (arms, head), left common carotid artery (head), and left subclavian artery (shoulder).
- Pulmonary arteries branch left and right to the lungs; pulmonary veins return blood to the heart.
Blood Vessel Structure
- Blood vessel walls have three layers: tunica intima (inner), tunica media (middle, muscle/elastic), tunica externa (outer).
- Veins have larger lumens and thinner walls than arteries and contain valves to prevent backflow.
- Valves in veins and heart prevent backflow; papillary muscles and tendinous cords anchor heart valves.
Key Terms & Definitions
- Aorta — Main artery carrying blood from the heart to the body.
- Vena cava (superior/inferior) — Large veins returning deoxygenated blood to the right atrium.
- Pulmonary artery — Vessel carrying deoxygenated blood from the right ventricle to the lungs.
- Pulmonary vein — Vessel carrying oxygenated blood from the lungs to the left atrium.
- Atrium — Upper chamber of the heart.
- Ventricle — Lower chamber of the heart.
- Tricuspid valve — Valve with three cusps between right atrium and ventricle.
- Mitral (bicuspid) valve — Valve with two cusps between left atrium and ventricle.
- Systole — Heart muscle contraction phase.
- Diastole — Heart muscle relaxation phase.
- Systemic circulation — Blood flow from heart to body and back.
- Pulmonary circulation — Blood flow from heart to lungs and back.
Action Items / Next Steps
- Review the structure and function of heart valves and major blood vessels.
- Prepare a list of structures involved in systemic and pulmonary circulation.
- Read about the respiratory system for the next session.