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Characteristics of coronary circulation -explained

Key characteristics of  coronary circulation
  • Coronary circulation is very short , rapid, and  phasic .
  • Blood flow mainly occur during cardiac diastole
  • No efficient anastomoses between the coronary vessels.
  • It is a rich circulation (5% of the CO ,as heart wt is 300gm)
  • Regulation of coronary circulation is mainly by metabolites and not neural
  • Capillary permeability is high (the cardiac lymph is rich in protein)
  • Vessels are susceptible to degeneration and atherosclerosis.
  • Evident regional distribution of blood flow is noticed (subendocardial layer in LV receives < blood, due to compression (but normally compensated during diastoles by V.D).Hence it more prone to IHD+MI.
  • Eddy current keep the valves away from the orifices of arteries it keeps the orifices patent throughout the cardiac cycle.
  • As having highest O2 uptake achieved by a dense network of capillaries, all is perfused at rest (no capillary reserve)
The Coronary artery
  • Coronary artery represent the enlarged vasavasorum of larger vessels in the heart.
  • They are about the width of a drinking straw tht is 1/8 inch (4mm) .
  • The term Coronary comes from the latin word ”Coronarius= “Crown”. 
  • Coronary artery arises from the coronary sinuses just superior to the aortic valve behind the cusps
It has 3 cusps
  • Left coronary (LC), 
  • Right coronary (RC)
  • Posterior non-coronary(NC) cusps.  
The left coronary artery
Left coronary artery is about 10-15mm long
It arises from left coronary cusps
Left coronary artery almost immediately bifurcate into
1. left anterior descending
  • Diagonal Branch supply most of Anterior Left ventricular wall, A small part of  rightventricle
  • Septal perforating Branch supply anterior 2/3rd to interventricular septum
  • A part of the left branch of the AV bundle
  • Terminal branch supply the cardiac apex
2. Left circumflex artery.
The right coronary artery
Origin R anterior coronary sinus origin of Valsalva
It courses through the right AV groove
Branches ;
1. Conus branch
1st branch supplies the RVOT• Sinus node artery
2nd branch - SA node.(in 40% they originate from LCA)        
2.Acute marginal arteries-Arise at acute angle and runs along the margin of RV above the diaphragm. 3, Whole of the conducting system of the heart, except part of the left br of AV node
4. Posterior descending artery : Supply lower part of the ventricular septum & adjacent ventricular walls. Arises from RCA in 85% of case.
Branches of first and second segment of RCA
Branches of 1st Segment: 
  • Anterior Atrial Branch
  • Artery to SA node
  • Anterior Ventricular Brs
  • Right Marginal Artery
Branches of 2nd Segment
  • Posterior Ventricular branch
  • Posterior Interventricular branch
  • Posterior Interventricular (descending) Artery
  • Septal branch
  • AV nodal Artery
Venous drainage of heart
There are 2 systems:
There is superficial and deep venous system
Superficial system: which drains the left ventricle. It is formed of coronary sinus and anterior cardiac veins  which opens into the right atrium.
Deep system: It drains the rest of the heart. It is formed of the basian veins and arterio-sinusoidal vessels that open directly into the heart chamber.
Anastomotic channels
Between coronary arteries & extracardiac arteries there is intercoronary anastomosis
There is three common areas of anastomoses.
    1. Between branches of LAD & PIV OF RCA in iv groove
    2. Between LCX & RCA IN AV groove.
    3. Septal branches of 2 coronary arteries in the IVS
What is the Lifesaving value of collaterals in heart?
It there is occlusion in one of the larger coronary within seconds;
Dilatation n of small anastomoses( blood flow < ½)-normal or almost normal coronary (within 1 month).
Small branches of the LAD (left anterior descending/anterior interventricular) branch of the left coronary join with branches of the posterior interventricular branch of the right coronary in the interventricular groove. More superiorly, there is an anastomosis between the circumflex artery (a branch of the left coronary artery) and the right coronary artery in the atrioventricular groove. There is also an anastomosis between the septal branches of the two coronary arteries in the interventricular septum. The photograph shows area of heart supplied by the right and the left coronary arteries.