Right and left coronary artery er course
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Coronary Arteries - Origin and Course
Two coronary arteries arise from the aortic sinuses at the root of the ascending aorta and encircle the heart in the coronary sulcus, with branches descending in the interventricular sulci toward the apex.
Right Coronary Artery (RCA)
Origin: Arises from the right aortic sinus (right coronary sinus) of the ascending aorta.
Course:
- Passes anteriorly, then descends vertically in the coronary sulcus between the right atrium and right ventricle.
- On reaching the inferior (acute) margin of the heart, it turns posteriorly and continues in the sulcus onto the diaphragmatic surface and base of the heart.
Major branches along its course:
| Branch | Course & Supply |
|---|---|
| Atrial branch | Passes in the groove between the right auricle and ascending aorta |
| Sinuatrial (SA) nodal branch | Arises early; passes posteriorly around the superior vena cava to supply the SA node |
| Right marginal branch | Given off at the inferior (acute) margin; continues toward the apex |
| AV nodal branch | Small branch to the atrioventricular node as the RCA reaches the base/diaphragmatic surface |
| Posterior interventricular branch (posterior descending artery, PDA) | Final major branch; lies in the posterior interventricular sulcus |
Territory supplied:
- Right atrium and right ventricle
- SA node and AV node (in most people)
- Interatrial septum and a portion of the left atrium
- Posteroinferior one-third of the interventricular septum
- Portion of the posterior left ventricle
Left Coronary Artery (LCA)
Origin: Arises from the left aortic sinus (left coronary sinus) of the ascending aorta.
Course:
- Passes between the pulmonary trunk and the left auricle before entering the coronary sulcus.
- Emerges from behind the pulmonary trunk and almost immediately divides into its two terminal branches.
The left main stem (LMS) is short, and clinically this short segment is called the "left main" coronary artery.
Two terminal branches:
1. Anterior Interventricular Branch (LAD - Left Anterior Descending)
- Continues around the left side of the pulmonary trunk.
- Descends obliquely toward the apex in the anterior interventricular sulcus.
- Often gives off one or two diagonal branches across the anterior surface of the left ventricle.
- Also gives off septal perforators to the anterior two-thirds of the interventricular septum.
- Usually wraps around the apex to end in the posterior interventricular sulcus.
2. Circumflex Branch (LCx)
- Courses to the left within the coronary sulcus, onto the base/diaphragmatic surface.
- Usually ends before reaching the posterior interventricular sulcus (in right-dominant hearts).
- Gives off the left marginal artery (obtuse marginal), which crosses the rounded obtuse margin of the heart.
Territory supplied:
- Most of the left atrium and left ventricle
- Most of the interventricular septum, including the AV bundle and its branches (bundle of His and bundle branches)
Dominance
The dominant artery is the one that gives rise to the posterior interventricular branch (PDA):
| Dominance | Description | Frequency |
|---|---|---|
| Right dominant | PDA arises from RCA; RCA supplies a large portion of the posterior left ventricle; circumflex is relatively small | ~85% (most common) |
| Left dominant | PDA arises from an enlarged circumflex branch; circumflex supplies most of the posterior left ventricle | ~8% |
| Co-dominant | Both RCA and LCx contribute to the PDA territory | ~7% |
Clinical Terminology Summary
| Anatomical Name | Clinical Name |
|---|---|
| Left coronary artery (proximal) | Left main stem (LMS) |
| Anterior interventricular branch | Left anterior descending (LAD) |
| Circumflex branch | LCx |
| Posterior interventricular branch | Posterior descending artery (PDA) |
| Right marginal branch | Acute marginal branch |
| Left marginal branch | Obtuse marginal branch |
Source: Gray's Anatomy for Students, Coronary Arteries section, pp. 238-241
Flow chart daw
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Here's the flowchart covering the full origin and course of both coronary arteries - from the aortic sinuses, through their respective paths, all major branches, territories, and dominance patterns. Let me know if you want any section expanded or a separate flowchart for just one artery!
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