Overview
This lecture covers the structure and function of the heart and circulatory system, including blood vessel types, circulatory loops, and the flow of blood through the heart.
Structure and Function of the Circulatory System
- The heart is a muscular organ that pumps blood throughout the body.
- The circulatory system transports blood using a network of blood vessels.
- Red blood cells carry oxygen via hemoglobin and remove carbon dioxide waste.
- Every cell in the body needs a constant oxygen supply to survive.
Circulatory Loops
- The pulmonary circuit circulates blood through the lungs for oxygenation.
- The systemic circuit delivers oxygenated blood to the entire body.
- The coronary circuit supplies blood to the heart muscle itself.
Types of Blood Vessels
- Arteries carry blood away from the heart, usually oxygenated, and have thick, muscular walls.
- Veins bring blood back to the heart, usually deoxygenated, and have valves to prevent backflow.
- Capillaries are tiny vessels where oxygen, nutrients, and waste exchange occurs with thin walls.
Pathway of Blood Through the Heart
- De-oxygenated blood enters the right atrium via the superior and inferior vena cava.
- Blood moves to the right ventricle through the tricuspid valve.
- From the right ventricle, blood goes through the pulmonary valve to the pulmonary artery.
- Blood becomes oxygenated in the lungs and returns via pulmonary veins to the left atrium.
- Oxygenated blood passes through the mitral (bicuspid) valve to the left ventricle.
- The left ventricle pumps blood through the aortic valve into the aorta and systemic circulation.
- The valve order in blood flow: Tricuspid, Pulmonary, Mitral, Aortic (T.P.M.A.).
Heart Anatomy and Special Structures
- The left ventricle has thicker walls to pump blood throughout the body.
- Coronary arteries supply oxygen to the heart muscle; blockage causes a heart attack (myocardial infarction).
Electrical Coordination of the Heartbeat
- The SA node (in right atrium) initiates the heartbeat, causing the atria to contract.
- The AV node delays and relays the impulse so the ventricles contract after the atria.
- The heartbeat’s coordinated activity is detectable with an electrocardiogram (EKG).
Key Terms & Definitions
- Hemoglobin — A protein in red blood cells that binds and carries oxygen.
- Pulmonary circuit — The pathway of blood between the heart and lungs.
- Systemic circuit — The route of blood from the heart to the body and back.
- Coronary circuit — The blood vessels supplying the heart muscle.
- Artery — Vessel carrying blood away from the heart.
- Vein — Vessel carrying blood toward the heart.
- Capillary — Smallest blood vessel; site of gas and nutrient exchange.
- Sinoatrial (SA) node — Heart’s natural pacemaker initiating contractions.
- Atrioventricular (AV) node — Relays and delays electrical impulse to ventricles.
- Systole — Heart chamber contraction phase.
- Diastole — Heart chamber relaxation/refill phase.
Action Items / Next Steps
- Review the corresponding study guide handout linked with the video.