Lecture 1 Part 1 - Chapter 18 Part A

The heart serves as a transport system consisting of two side-by-side pumps.
Right Side Functionality:
- Receives oxygen-poor blood from tissues.
- Pumps blood to the lungs to release carbon dioxide (CO2) and absorb oxygen (O2).
- Blood flow route: Right Atrium → Right Ventricle → (via Pulmonary Circuit) → to lungs.
Left Side Functionality:
- Receives oxygenated blood from lungs.
- Pumps blood to body tissues.
- Blood flow route: Left Atrium → Left Ventricle → (via Systemic Circuit) → to body.

Pulmonary Circuit Components:
- Heart:
- Right Atrium (receives deoxygenated blood)
- Right Ventricle (pumps blood to lungs)
- Major Vessels:
- Pulmonary Arteries (carry blood to lungs)
- Pulmonary Veins (carry oxygen-rich blood back to the heart)
Systemic Circuit Components:
- Heart:
- Left Atrium (receives oxygenated blood)
- Left Ventricle (pumps blood to body)
- Major Vessels:
- Aorta (distributes oxygen-rich blood to the body)
- Venae Cavae (return deoxygenated blood to the heart)

Pericardium:
- A double-walled sac surrounding the heart that reduces friction during heartbeats.
- Composed of two layers:
- Fibrous Pericardium: tough outer layer.
- Serous Pericardium: inner layer that reduces friction.
Heart Wall Layers:
- Epicardium:
- Visceral layer of the serous pericardium.
- Myocardium:
- Composed of circular or spiral bundles of contractile cardiac muscle cells, responsible for contraction.
- Endocardium:
- Innermost layer that lines heart chambers and covers heart valves; continuous with endothelial lining of blood vessels.

Pericarditis:
- Inflammation of pericardium; roughens membrane surfaces leading to a pericardial friction rub (a creaking sound). It can be diagnosed using a stethoscope.
Cardiac Tamponade:
- Condition resulting from excess fluid leaking into the pericardial space, compressing the heart and impairing its ability to pump blood.
- Treatment involves drawing out the excess fluid from the pericardial cavity, usually done with a syringe.

Cardiac muscle in the myocardium is arranged in circular and spiral bundles which aid in effective contraction and pumping action.

Four Heart Chambers:
- Atria (2):
- Right Atrium:
  - Receives blood from systemic circuit via:
  - Superior Vena Cava (returns blood from above the diaphragm)
  - Inferior Vena Cava (returns blood from below the diaphragm)
  - Coronary Sinus (returns blood from coronary veins)
- Left Atrium:
  - Receives oxygen-rich blood from lungs through four pulmonary veins.
- Ventricles (2):
- Right Ventricle:
  - Pumps blood into pulmonary trunk to be sent to lungs.
- Left Ventricle:
  - Pumps blood into the aorta, delivering oxygen-rich blood to the body.

General Function:
- Ensure unidirectional blood flow through the heart, opening and closing in response to pressure changes.
Types of Valves:
- Atrioventricular (AV) Valves:
- Located between atria and ventricles; prevent backflow into atria when ventricles contract.
- Tricuspid Valve: (Right AV Valve)
  - Composed of three cusps; located between right atrium and ventricle.
- Mitral Valve: (Left AV Valve or Bicuspid Valve)
  - Composed of two cusps; located between left atrium and ventricle.
- Chordae Tendineae:
  - Structures that anchor the cusps of AV valves to papillary muscles to prevent inversion into atria during ventricular contraction.
- Semilunar Valves:
- Prevent backflow from major arteries into ventricles with three cusps resembling a half-moon.
- Pulmonary Semilunar Valve: located between the right ventricle and pulmonary trunk.
- Aortic Semilunar Valve: located between the left ventricle and aorta.

Right Side of the Heart: Flow order is:
1. Superior Vena Cava (SVC)
2. Inferior Vena Cava (IVC)
3. Coronary Sinus
4. Right Atrium
5. Tricuspid Valve
6. Right Ventricle
7. Pulmonary Semilunar Valve
8. Pulmonary Trunk
9. Pulmonary Arteries → to lungs (to be oxygenated).
Left Side of the Heart: Flow order is:
1. Four Pulmonary Veins (oxygenated blood)
2. Left Atrium
3. Mitral Valve
4. Left Ventricle
5. Aortic Semilunar Valve
6. Aorta
7. Systemic Circulation (to body).
Blood is pumped equally to both pulmonary and systemic circuits.
Differences between Pulmonary and Systemic Circuits:
- Pulmonary circuit: short, low-pressure; designed for gas exchange.
- Systemic circuit: long, high-friction circulation; designed to supply body tissues.

Right Ventricle:
- Thinner walls than the left ventricle; crescent shape; wraps around the left ventricle.
Left Ventricle:
- Thicker walls, necessary for pumping blood with higher pressure; round shape.

Definition:
- Provides functional blood supply to the heart muscle itself and is established primarily when the heart is relaxed.
Coronary Arteries:
- Both arise from the base of the aorta; encircle the heart in a sulcus, with variations in branching.
- Anastomoses:
- Provide alternate routes for blood flow delivery; they cannot compensate for significant occlusion.
- The heart receives about rac{1}{20} of the body's total blood supply.
Coronary Veins:
- Collect blood from the cardiac capillary beds; the coronary sinus opens into the right atrium.

Angina Pectoris:
- Thoracic pain resulting from temporary reduction in blood supply to the myocardium, causing weakness in cardiac cells.
Myocardial Infarction (Heart Attack):
- Prolonged occlusion of coronary arteries leading to areas of cell death, which are repaired with noncontractile scar tissue.