The heart is an iconic organ often associated with love, though it primarily functions as a pump.
It powers the circulatory system, moving nutrients, oxygen, waste, heat, hormones, and immune cells throughout the body.
Heart Functionality
The primary role of the heart: maintaining pressure gradients for blood flow.
Blood flows from high to low-pressure areas, analogous to a squirt gun or shaken soda can.
Anatomy of the Heart
Average adult heart size: similar to two fists clasped together.
Location: center of the chest, angled towards the left hip and right shoulder.
The heart is housed in the mediastinum cavity, nestled in a double-walled sac called the pericardium.
Fibrous Pericardium: Dense connective tissue protecting and anchoring the heart.
Serous Pericardium: Contains a fluid film for lubrication, allowing frictionless movement.
Heart Wall Layers
Epicardium: Outer layer.
Myocardium: Middle layer, composed of cardiac muscle tissue.
Endocardium: Innermost layer, made of squamous epithelial tissue.
Heart Chambers and Valves
The heart is divided by the septum into:
Atria: Two superior, low-pressure chambers.
Ventricles: Two inferior, high-pressure chambers.
Valves
Function as one-way passages:
Blood flows to the next chamber when open, stops backward flow when closed.
Heart Sounds:
"Lub-DUB" are the sounds of valves opening and closing.
Circulatory System
Arteries carry blood away from the heart; veins carry it back.
Arteries are typically shown in red in diagrams, veins in blue.
Blood Circulation
Pulmonary Circulation Loop:
Right ventricle pumps deoxygenated blood to lungs via pulmonary arteries.
Blood picks up oxygen in lung capillaries and returns via pulmonary veins to the left atrium.
Atria contract, passing blood to the left ventricle.
Systemic Circulation Loop:
Left ventricle pumps oxygenated blood through the aorta to the body.
Blood returns, oxygen-depleted, through vena cavae to the right atrium.
Blood Pressure
Systolic: High pressure during ventricular contraction.
Diastolic: Pressure in arteries when ventricles are relaxed.
Measured as two numbers (e.g., 120/80).
Importance in homeostasis and potential damage from prolonged high blood pressure.
Conclusion
The heart’s role in maintaining blood flow through pressure gradients is crucial for oxygen distribution.
The lecture explored the anatomy and function of heart components and how they contribute to systemic and pulmonary circulation.
Additional Credit
Presented by Thomas Frank, supported by Patreon patrons.
Written by Kathleen Yale, directed by Nicholas Jenkins. Further contributions by Dr. Brandon Jackson, Nicole Sweeney, Michael Aranda, and Thought Cafe.