Overview
This lecture introduces the basics of the human circulatory system, focusing on blood composition, heart anatomy, and the pathway of blood through the heart.
Functions and Components of Blood
- Blood transports nutrients, gases (oxygen, carbon dioxide), hormones, and helps regulate pH, temperature, and osmotic pressure for homeostasis.
- Blood is composed of plasma (liquid with water, proteins, salts, lipids) and cellular components (red and white blood cells, platelets).
- Red blood cells contain hemoglobin, an iron protein that carries oxygen and gives blood its red color.
- White blood cells fight infections; platelets help blood clot after injury.
Vessels and Circulatory Pathways
- Arteries carry blood away from the heart (usually oxygen-rich); veins carry blood toward the heart (usually oxygen-poor).
- Capillaries are small vessels where oxygen is delivered to tissues and carbon dioxide is picked up for removal.
Heart Anatomy and Blood Flow
- The heart has two sides: right (deoxygenated) and left (oxygenated).
- Heart contains four chambers: right atrium, right ventricle, left atrium, left ventricle (atria on top, ventricles on bottom).
- Valves (tricuspid, pulmonary, mitral/bicuspid, aortic) prevent backflow and keep blood moving one way.
Pathway of Blood through the Heart
- Deoxygenated blood returns from the body via the inferior vena cava to the right atrium.
- Blood moves from right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery → lungs.
- In the lungs, blood gains oxygen, loses carbon dioxide, and returns via the pulmonary vein to the left atrium.
- Blood moves from left atrium → mitral (bicuspid) valve → left ventricle → aortic valve → aorta → body.
Heart's Own Blood Supply
- The heart receives oxygen and nutrients through coronary arteries branching from the aorta.
- Coronary veins return deoxygenated blood to the right atrium.
Heart Defects and Conditions
- Septal defects (holes in the heart's septum) can cause mixing of oxygen-rich and oxygen-poor blood, potentially leading to health problems.
- Treatments for heart defects include medications or surgery; research is ongoing in cardiology.
Key Terms & Definitions
- Plasma — the liquid portion of blood containing water, proteins, salts, and lipids.
- Hemoglobin — an iron-containing protein in red blood cells that binds oxygen.
- Atria — the upper chambers of the heart that receive blood.
- Ventricles — the lower chambers of the heart that pump blood out.
- Valve — a structure preventing backflow of blood in the heart.
- Aorta — the largest artery carrying oxygenated blood from the heart to the body.
- Coronary arteries — vessels supplying the heart muscle with oxygen-rich blood.
- Septal defect — an opening in the wall separating the right and left sides of the heart.
Action Items / Next Steps
- Review the pathway of blood through the heart by tracing each step.
- Explore further reading on heart physiology and cardiology as suggested in the lecture details.