BLOOD SUPPLY TO THE HEART DESCRIBING HEART OXYGENATION

The heart, a muscular four-chambered organ, requires a constant supply of oxygen and nutrients. Here’s how it works:

Coronary Arteries:
The coronary arteries originate from the aorta and supply oxygenated blood to the heart muscle (myocardium).
There are two main coronary arteries:
Left Coronary Artery (LCA): It further branches into the left anterior descending (LAD) artery and the left circumflex artery.
Right Coronary Artery (RCA): It supplies the right atrium, right ventricle, and part of the interventricular septum.
These arteries ensure that the heart receives the nutrients it needs to function properly.
Coronary Veins:
After delivering oxygen and nutrients, the coronary veins collect deoxygenated blood from the myocardium.
The main drainage system includes:
Great Cardiac Vein: Drains the left ventricle.
Middle Cardiac Vein: Collects blood from the posterior part of the left ventricle.
Small Cardiac Vein: Drains the right atrium and ventricle.
Coronary Sinus: A large vein that receives blood from the cardiac veins and empties into the right atrium.

1. BLOOD SUPPLY TO THE HEART RONO .W

2. ARTERIAL SUPPLY OF THE HEART The heart is mostly supplied by the two coronary arteries , which arise from the ascending aorta immediately above the aortic valve . The coronary arteries and their branches run on the surface of heart lying within the subpericardial fibrofatty tissue

3. RIGHT CORONARY ARTERY ORIGIN The right coronary artery arises from the anterior aortic sinus of the ascending aorta, immediately above the aortic valve. COURSE After arising from the ascending aorta, the right coronary artery first runs forwards between the pulmonary trunk and the right auricle, then it descends almost vertically in the right atrioventricular groove (right anterior coronary sulcus) up to the junction of the right and the inferior borders of the heart. At the inferior border of the heart, it turns posteriorly and runs in the posterior atrioventricular groove (right posterior coronary sulcus) up to the posterior interventricular groove where it terminates by anastomosing with the left coronary artery.

4. BRANCHES AND DISTRIBUTION 1 . Right conus artery: It supplies the anterior surface of the pulmonary conus (infundibulum of the right ventricle ). 2. Atrial branches: They supply the atria. One of the atrial branches—the artery of sinuatrial node (also called sinuatrial nodal artery) supplies the SA node in 60% cases. In 40% of individuals it arises from the left coronary artery

5. CONT.. 3 . Anterior ventricular branches: They are two or three and supply the anterior surface of the right ventricle. The marginal branch is the largest and runs along the lower margin of the sternocostal surface to reach the apex . 4. Posterior ventricular branches: They are usually two and supply the diaphragmatic surface of the right ventricle .

6. CONT… 5. Posterior interventricular artery: It runs in the posterior interventricular groove up to the apex. It supplies the: (a) posterior part of the interventricular septum, (b) atrioventricular node (AV node) in 60% of the cases, and (c) right and left ventricles.

7. LEFT CORONARY ARTERY ORIGIN The left coronary artery arises from the left posterior aortic sinus of the ascending aorta, immediately above the aortic valve. COURSE After arising from ascending aorta, the left coronary artery runs forwards and to the left between the pulmonary trunk and the left auricle. It then divides into an anterior interventricular and circumflex artery

8. CONT… The anterior interventricular artery (left anterior descending/LAD) runs downwards in the anterior interventricular groove to the apex of the heart. It then passes posteriorly around the apex of the heart to enter the posterior interventricular groove to terminate by anastomosing with the posterior interventricular artery —a branch of right coronary artery . The circumflex artery winds around the left margin of the heart and continues in the left posterior coronary sulcus up to the posterior interventricular groove where it terminates by anastomosing with the right coronary artery .

9. BRANCHES AND DISTRIBUTION 1. Anterior interventricular artery/left anterior descending (LAD) artery: It supplies anterior part of interventricular septum, (b) greater part of the left ventricle and part of right ventricle, and (c) a part of left bundle branch (of His).

10. CONT…. 2. Circumflex artery: It gives a left marginal artery that supplies the left margin of the left ventricle up to the apex of the heart. 3. Diagonal artery: It may arise directly from the trunk of the left coronary artery. 4. Conus artery: It supplies the pulmonary conus . 5. Atrial branches: They supply the left atrium.

11. VENOUS DRAINAGE OF THE HEART Venous blood from the heart is drained into right atrium by the following: 1. Coronary sinus . 2. Anterior cardiac veins . 3. Venae cordis minimae ( Thebesian veins).

12. Cont … 1.Coronary sinus : It is the principal vein of the heart . Most of the venous blood from the walls of the heart is drained into the right atrium through coronary sinus. The coronary sinus is the largest vein of the heart and lies in the posterior part of the atrioventricular groove (left posterior coronary sulcus). It develops from the left horn of the sinus venosus and a part of the left common cardinal vein.

13. Tributaries 1.Great cardiac vein : It accompanies anterior interventricular and circumflex arteries to join the left end of the coronary sinus. 2. Middle cardiac vein: It accompanies the posterior interventricular artery and joins the coronary sinus near its termination.

14. Cont … 3. Small cardiac vein: It accompanies the right ventricular artery in the right posterior coronary sulcus and the right end of the coronary sinus. 4. Posterior vein of the left ventricle: It runs on the diaphragmatic surface of the left ventricle and joins the sinus to the left of the middle cardiac vein.

15. CONT… 5. Oblique vein of the left atrium (vein of Marshall:it’s a small vein which runs downwards on the posterior surface of the left atrium to enter the left end of the coronary sinus. It develops from the left common cardial vein ( duct of Cuvier ). 6. Right marginal vein: It accompanies the marginal branch of the right coronary artery and joins the small cardiac vein or drains directly into the right atrium. 7. Left marginal vein: It accompanies the marginal branch of the left coronary artery and drains into the coronary

16. CONT… 2.Anterior cardiac veins : These are series of small veins (3 or 4) which run parallel to each other across the surface of right ventricle to open into the right atrium . 3.Venae cordis minimae ( Thebesian veins): These are extremely small veins in the walls of all the four chambers of the heart. They open directly into the respective chambers . They are most numerous in the in right atrium .

17. LYMPHATIC DRAINAGE OF THE HEART The lymphatics of the heart accompany the coronary arteries, emerge from the fibrous pericardium along with the ascending aorta and pulmonary trunk in the form of two trunks . The right trunk drains into brachiocephalic nodes and left trunk drains into tracheobronchial nodes (at the bifurcation of the aorta)

18. NERVE SUPPLY OF THE HEART The heart is supplied by sympathetic and parasympathetic fibers via the superficial and deep cardiac plexuses formed by parasympathetic and sympathetic fibers. The parasympathetic fibers are derived from vagus nerves. They are cardioinhibitory ; hence their stimulation causes slowing of the heart rate and constriction of the coronary arteries . The sympathetic fibers are derived from upper 3–5 thoracic spinal segments. They are cardioacceleratory , hence their stimulation increase the heart rate and causes the dilatation of the coronary arteries. The sympathetic fibers also cause dilatation of the coronary arteries.

19. CARDIAC PLEXUSES SUPERFICIAL CARDIAC PLEXUS The superficial cardiac plexus. lies below the arch of aorta in front of the bifurcation of pulmonary trunk, just to the right of ligamentum arteriosum . The cardiac ganglion ( of Wrisberg ) lies close to the ligamentum arteriosum . It is formed by the (a ) superior cervical cardiac branch of left cervical sympathetic trunk , and (b ) inferior cervical cardiac branch of left vagus nerve. .

20. CONT.. Distribution The superficial cardiac plexus gives branches to (a) deep cardiac plexus, (b) right coronary artery, and (c) left anterior pulmonary plexus

21. DEEP CARDIAC PLEXUS The deep cardiac plexus lies in front of the bifurcation of the trachea , behind the arch of the aorta. It is formed by (a) all the cardiac branches derived from three cervical and upper 4 or 5 thoracic ganglia of the sympathetic chains except the superior cervical cardiac branch of left cervical (b)all the cardiac branches of vagus and recurrent laryngeal nerves except the inferior cervical cardiac branch of the left vagus nerve.

22. CONT… Distribution The right and left halves of the plexus distributes branches to corresponding coronary arteries and pulmonary plexus, and ( b) separate branches to the atria.

23. PAIN AND REFLEX PATHWAYS OF THE HEART PAIN PATHWAYS The sensations of pain arising due to the ischemia of the heart pass through the sympathetic fibers to reach the upper five thoracic spinal segments (T1–T5) through cervical and thoracic sympathetic ganglia and follow the usual somatosensory pathway to the central nervous system. The pain fibers pass from thoracic ganglia to the spinal nerves via white rami communicantes

24. Cont … The cell bodies of the first order sensory neurons are located in the dorsal root ganglia of T1–T5 spinal nerves. Hence cardiac pain is referred mainly in the area of distribution of these nerves, i.e. pectoral region and medial aspect of the arm and forearm.

25. PATHWAYS FOR CARDIOVASCULAR REFLEXES The afferent fibers from heart subserving the cardiovascular reflexes pass by the parasympathetic fibers of vagal nerves to the reticular formation