Overview
This lecture introduces the basics of the human circulatory system, focusing on blood components, heart anatomy, and the pathway of blood through the heart.
Functions and Components of Blood
- Blood transports glucose, gases (O₂ and CO₂), hormones, and nutrients throughout the body.
- Blood helps regulate pH, temperature, and osmotic pressure, maintaining homeostasis.
- Blood consists of plasma (liquid with water, proteins, salts, and lipids) and cellular components.
- Red blood cells (RBCs) carry gases using hemoglobin, which gives blood its red color.
- White blood cells (WBCs) fight infections.
- Platelets are fragments that help blood clot.
Blood Vessels and Circulation
- Arteries carry blood away from the heart, usually oxygen-rich except for pulmonary arteries.
- Veins carry blood to the heart, usually oxygen-poor except for pulmonary veins.
- Capillaries are small vessels where oxygen is delivered to tissues and CO₂ is picked up.
Heart Anatomy and Chambers
- The heart has four chambers: right atrium, right ventricle, left atrium, left ventricle.
- Atria are the upper chambers with thinner walls; ventricles are the lower chambers with thicker walls.
- Valves (tricuspid, pulmonary, mitral/bicuspid, aortic) are one-way and prevent blood backflow.
- The right side of the heart handles deoxygenated blood; the left side handles oxygenated blood.
Blood Flow Pathway Through the Heart
- Deoxygenated blood enters right atrium via inferior vena cava.
- Right atrium contracts, pushing blood through tricuspid valve to right ventricle.
- Right ventricle contracts, sending blood through pulmonary valve to pulmonary artery and then lungs.
- Oxygenated blood returns from lungs via pulmonary vein to left atrium.
- Left atrium contracts, blood passes through mitral valve to left ventricle.
- Left ventricle contracts, pumping blood through aortic valve to aorta for distribution.
- Aorta delivers oxygen-rich blood to body; cycle repeats as blood returns via vena cava.
Coronary Circulation
- Heart’s own blood supply comes from coronary arteries branching off the aorta.
- Coronary capillaries deliver oxygen and glucose to heart tissue.
- Coronary veins return deoxygenated blood to right atrium.
Heart Conditions
- Septal defects (e.g., atrial septal defect) allow oxygen-rich and oxygen-poor blood to mix.
- These defects may lead to abnormal heartbeat, stroke, or heart failure; treatments include medication or surgery.
Key Terms & Definitions
- Plasma — Liquid component of blood containing water, proteins, salts, and lipids.
- Hemoglobin — Iron-containing protein in RBCs that transports oxygen.
- Atrium/Atria — Upper chambers of the heart.
- Ventricle — Lower chambers of the heart.
- Valve — Structure preventing backflow of blood in the heart.
- Aorta — Main artery delivering oxygenated blood from heart to body.
- Coronary arteries — Vessels supplying the heart muscle with oxygenated blood.
- Septal defect — An opening in the wall between the heart’s right and left sides.
Action Items / Next Steps
- Review the pathway of blood through the heart and be able to trace each step.
- Suggested further reading on cardiovascular conditions and cardiology (see video details).
- Stay tuned for detailed lectures on the cardiac cycle.