Functional Anatomy of Cardiovascular System

Heart Chambers & Layers - Pump Foundation

• Chambers (4):
  • Right Atrium (RA): Receives deoxygenated blood (SVC, IVC, Coronary Sinus). Pectinate muscles.
  • Left Atrium (LA): Receives oxygenated blood (4 Pulmonary Veins). Smoother walls.
  • Right Ventricle (RV): Pumps to Pulmonary Artery. Thinner wall. Trabeculae carneae.
  • Left Ventricle (LV): Pumps to Aorta. Thickest wall (↑systemic pressure). Fine trabeculae.
• Layers (3):
  • Pericardium: Double-walled sac. Fibrous (outer) & Serous (inner: parietal, visceral/epicardium). Pericardial fluid: 15-50 ml.
  • Myocardium: Cardiac muscle, thickest in LV. Responsible for contraction.
  • Endocardium: Squamous epithelium lining chambers & valves. Continuous with vascular endothelium.

⭐ Crista terminalis in RA separates smooth posterior sinus venarum (embryonic Sinus Venosus) from rough anterior part with pectinate muscles (true atrium).

Valves & Great Vessels - Blood Flow Gates

• Heart Valves: Unidirectional flow; open/close by pressure gradients.
  • Atrioventricular (AV): Prevent atrial backflow (ventricular systole).
    • Tricuspid (RA-RV): 3 cusps. (📌 Right Atrium: Tricuspid)
    • Mitral/Bicuspid (LA-LV): 2 cusps. (📌 Left Atrium: Bicuspid)
    • Anchored by chordae tendineae, papillary muscles.
  • Semilunar (SL): Prevent ventricular backflow (ventricular diastole).
    • Pulmonary (RV-Pulmonary Artery): 3 cusps.
    • Aortic (LV-Aorta): 3 cusps.
• Great Vessels:
  • Inflow: SVC, IVC, Coronary Sinus (to RA); Pulmonary Veins (to LA).
  • Outflow: Pulmonary Artery (from RV); Aorta (from LV).

⭐ Rheumatic heart disease most commonly affects the Mitral valve, often causing stenosis.

Conduction System - Cardiac Spark Plugs

• Sinoatrial (SA) Node: "Pacemaker". Location: Crista terminalis (sup. cavo-atrial junction). Rate: 60-100/min. Supply: RCA (~60%).
• Internodal/Interatrial Pathways:
  • Internodal: Anterior, Middle, Posterior tracts.
  • Interatrial: Bachmann’s bundle (to LA).
• Atrioventricular (AV) Node: Location: Koch's triangle. Function: Physiological delay (~0.1s) for ventricular filling. Rate: 40-60/min. Supply: RCA (~90%).
• Bundle of His (AV Bundle): Sole electrical link: atria → ventricles. Divides: RBB & LBB. Rate: 20-40/min.
• Bundle Branches (RBB & LBB): Conduct to RV & LV. LBB: ant. & post. fascicles.
• Purkinje Fibers: Subendocardial, ventricular walls. Fastest conduction (~4 m/s). Rate: <20-40/min.
• 📌 Mnemonic (Pathway Order): SA node → AV node → Bundle of His → Bundle Branches → Purkinje fibers.

⭐ AV nodal delay (P-R interval component) allows atrial kick, optimizing ventricular filling. Primarily due to slow Ca2+ current (I_Ca-L).

Coronary Circulation & Innervation - Heart's Own Supply

• Arterial Supply
  • RCA: From Ant. aortic sinus. Supplies: RA, RV, SA node (60%), AV node (80-90%), post. 1/3 IVS. Branches: SA Nodal, Marginal, PDA (📌 SNoMP).
  • LCA: From L. post. aortic sinus. Supplies: LA, LV, ant. 2/3 IVS, His bundle. Branches: LAD (ant. IVS, apex), LCx (📌 LAD-LCX).
  • Dominance: PDA origin defines (RCA ~85%).
• Venous Drainage
  • Coronary Sinus: To RA. Tributaries: Great (LAD), Middle (PDA), Small cardiac vv.
  • Ant. cardiac vv. → RA; Thebesian vv. → all chambers.
• Innervation (Autonomic)
  • Sympathetic (T1-T5): ↑HR, ↑force, coronary VD (β2).
  • Parasympathetic (Vagus n.): ↓HR, ↓AV conduction.
  • Cardiac plexus.
  • Sensory (angina): With sympathetics (T1-T5 pain).

⭐ LAD artery: most common site of MI ("Widow Maker").

High‑Yield Points - ⚡ Biggest Takeaways

• RCA typically determines coronary dominance (supplies PDA in ~85%).
• SA node (pacemaker) supplied by RCA (60%) or LCX (40%).
• AV node (Triangle of Koch) causes crucial conduction delay.
• Mitral valve is most affected in rheumatic heart disease.
• LAD artery supplies anterior LV wall, apex, anterior 2/3 septum.
• Fetal ductus arteriosus becomes ligamentum arteriosum.
• Fetal foramen ovale becomes fossa ovalis.