Lecture Notes: Introduction to the Heart and Circulatory System

Overview

• Circulatory System: Also known as the cardiovascular system, consists of the heart, arteries, veins, and capillaries.
• Function: Circulates blood to deliver oxygen and nutrients throughout the body.

Anatomy of the Heart

• Location: The heart is located in the mediastinum of the thorax.
• Function: Serves as a pump to circulate blood.

Circuits of the Heart

• Pulmonary Circuit:
  • Blood enters the right side of the heart.
  • Sent to the lungs for oxygenation.
  • Returns to the left side of the heart.
• Systemic Circuit:
  • Oxygenated blood is pumped from the left side of the heart.
  • Delivers oxygen and nutrients to body tissues.
  • Returns to the right side of the heart.

Chambers of the Heart

• Right Atrium: Receives oxygen-poor blood via superior vena cava, inferior vena cava, and coronary sinus.
• Left Atrium: Receives oxygen-rich blood from the pulmonary veins.
• Right Ventricle: Pumps blood to the pulmonary trunk.
• Left Ventricle: Pumps blood into the aorta.

Heart Structure

• Pericardium: Protective dense connective tissue covering the heart.
  • Fibrous Pericardium
  • Serous Pericardium: Parietal and visceral layers (epicardium).
• Heart Wall Layers:
  • Epicardium: Outermost layer.
  • Myocardium: Main cardiac muscle layer, contains cardiac skeleton.
  • Endocardium: Inner lining of heart chambers.

Heart Valves

• Atrioventricular (AV) Valves:
  • Right AV Valve (Tricuspid): Three flaps.
  • Left AV Valve (Mitral/Bicuspid): Two flaps.
• Semilunar Valves:
  • Aortic Valve
  • Pulmonary Valve: Prevents blood backflow into ventricles.

Cardiac Muscle

• Cardiac Muscle Fibers:
  • Striated, but shorter, branched, and interlocked.
  • Intercalated discs with desmosomes and gap junctions.
• Contraction:
  • Automaticity: Some cells can self-excite.
  • Coordinated contraction due to gap junctions.
  • Longer refractory period ensures proper functioning.

Intrinsic Cardiac Conduction System

• Specialized pacemaker cells distribute impulses.
• Unstable resting potential leads to continuous depolarization.
• Issues can cause arrhythmias and fibrillation.

Coronary Circulation

• Coronary Arteries and Veins: Supply blood to the heart.

Conclusion

• This lecture provided a basic introduction to the heart and its functioning.
• Further exploration into heart rate and other phenomena will be discussed in future lectures.