The heart is a hollow muscular organ located in the middle mediastinum. It has four chambers - right and left atria and right and left ventricles. The heart is surrounded by membranes including the pericardium, myocardium and endocardium. Blood flows from the right atrium to right ventricle through the tricuspid valve, then to the lungs through the pulmonary semilunar valve. Oxygenated blood returns to the left atrium through pulmonary veins and flows to the left ventricle through the mitral valve and out the aortic semilunar valve to the rest of the body. The heart receives its blood supply from the left and right coronary arteries.

1. Anatomy of Heart
Dr.M.Rajeshkumar,
MD Anatomy Postgraduate,
Trichy SRM Medical College Hospital
and Research Centre,
Irungalur ,Trichy.

2. Introduction:
Heart is a Vital Organ.
It is Conical Hollow Muscular Organ situated in middle mediastinum.
It is enclosed with in the Pericardium.
It pumps blood to the various parts of the body to meet their
requirements.
It is placed obliquely behind the body of sternum and adjoining parts
of coastal cartilage.

3. Heart Wall :
Pericardium – Double walled sac around the heart composed of
1)Superficial Fibrous
2)Deep 2 layers of Serous-Parietal &Visceral
Myocardium – cardiac muscle layer forming the bulk of the heart
Endocardium – endothelial layer of the inner myocardial surface
Fibrous skeleton of the heart – crisscrossing, interlacing layer of
connective tissue

4. Pericardium:
 Pericardial cavity is lined by the
pericardium.
 Pericardium – a double-walled sac around
the heart composed of:
 A superficial Fibrous pericardium
 A deep two-layer Serous pericardium
 The parietal layer lines the internal
surface of the fibrous pericardium
 The visceral layer or epicardium
lines the surface of the heart
 They are separated by the fluid-filled
pericardial cavity.
 Pericardial fluid acts as a lubricant reducing
friction.

5. Myocardium:
It is a muscular layer of heart.
It has cardiac muscles, which are
involuntary.
Divisions of autonomic nervous system
supply cardiac muscle.
Endocardium:
It is a single layer of endothelium lining
the chambers of heart.
It also covers the valves.
It continues as endothelial lining of blood
vessel.

6. External Features of Heart:
It has 4 Chambers:
Right- Atrium and Ventricle
 Left - Atrium and Ventricle
3 Groove:
Interatrial groove
Interventricular groove
 Atrioventricular groove (Coronary sulcus)
Parts:
1)Apex(left ventricle)
2)Base(both atria,2/3 lef atrium)
3 Borders
1)Right(right atrium) 2) Left 3) Inferior
3 Surfaces
1)Sternocoastal( right atrium auricle,left auricle
both ventricle,2/3 right ventricle)
2)Diaphragmatic(both ventricle,2/3 left ventricle)
3) Left
Anterior View
Posterior view

7. WEIGHT:
Adult Male-280 to 340gms
Adult Female-230 to 280gms
Location :
Middle mediastinum behind the
body of sternum.
costal cartilages of 2 to 6 ribs .
Superior surface of diaphragm Left of the midline.
Anterior to the vertebral column-T5 to T8 in recumbent.
-T6 to T9 in standing .

8. Anatomical Position
Of Heart
Anomalous-
Anatomical position

9. Chambers of Heart :
Right Atrium

10. Right Ventricle

11. Left Atrium and Ventricle

12. Mitral Valve complex with Zones of Cusps:

13. Pathway of Blood Through the Heart and Lungs
Right atrium Pulmonary Veins
tricuspid valve Left Atrium
right ventricle Bicuspid Valve
pulmonary semilunar Left Ventricle
pulmonary arteries Aortic Semilunar Valve
Lungs Aorta
Systemic Circulation

14. Ateries Supplying of heart:
Right coronary Artery:
It arise from the Anterior aortic sinus.
Branches:
a)Larger branches:
1)Right Marginal.
2)Posterior Interventricular.
b)Smaller branches:
1)Nodal in 60% cases.
2)Right Atrial.
3)Infundibular.
4)Terminal
Area of distribution:
1)Right Atrium.
2)Ventricles: - Greater part of right ventricle except the area adjoining the anterior interventricular groove.
- A small part of left ventricle adjoining posterior interventricular groove.
- Posterior part of interventricular septum.
3)Whole of Conducting system of heart except part of left branch of AV Bundle.

15. Left coronary artery:
 It is the larger than Right coronary artery.
 It arise from the Left posterior aortic sinus.
Branches: a)Large branches:
1)Anterior interventricular.
2)Circumflex branch.
3)Large diagonal branch.
b)Small branches:
1)Left Atrial.
2)Pulmonary and terminal.
Area of Distribution :
1)Left Atrium.
2)Ventricles:
- greater part of left ventricle except the area adjoining the posterior interventricular groove.
-A small part of right ventricle adjoining the anterior interventricular groove.
3)Anterior part of interventricular septum.
4)A part of left branch of AV bundle.

16. Cardiac dominance:
• In about 10%hearts, right coronary artery is not able to give posterior
interventricular branch.
• In these case circumflex artery a continuation of left coronary artery
provides the posterior interventricular branch as well as to AV
node.such case are called as left dominant.
• Mostly right coronary artery gives posterior interventricular artery.
such hearts are right dominant.
• Thus the artery giving the posterior interventricular branch is the
dominant artery.

17. Venous drainage of heart:
a)Coronary sinus:
 It is the largest vein of the heart
 It is situated in coronary sulcus of posterior wall of
right atrium.
Tributeries:
i. Small cardiac vein.
ii. Middle cardiac vein.
iii. Great cardiac vein.
iv. Right marginal vein.
v. Left marginal vein.
vi. Oblique vein of left atrium ,all these drain in to
coronary sinus.
b)Anterior cardiac veins:
It is 3 to 4 in number small veins drain the
infundibulum of right ventricle and open directly in to
right atrium .
c)Venae cordis minimi:
These veins open in to different chambers of heart
through the foramina minimarum,foramina more
numerous in atrial septum.

18. Collateral circulation:
Cardiac Anastomosis:
Two coronary artery anastomose with each other in myocardium.
Extracardiac anastomosis:
Coronary artery anastomosis with the
i. Vasovasorum of aorta
ii. Vasovasorum of pulmonary arteries
iii. Internal thoracic arteries
iv. Bronchial Arteries
v. phrenic arteries, in slow obstruction of coronary arteries these
collateral channels dilates and maintain nutrition of the heart.
But these channels have little practical value they are not able to
provide an alternative source of blood in case blockage of branch of
coronary. Blockage of arteries leads to Myocardial infarction.

19. Nerve supply to the heart:
Sympathetic Nerves:
 sympathetic pathway to the heart originate in lower
cervical to upper thoracic segment of spinal cord.
 continues to adjacent sympathetic ganglion.
 it pass through cardiac plexus then it continues as a
cardiac nerves to heart.
 It supply SA node ,AV node,in atrial and ventricular
myocardium as well as aorta ,pulmonary trunk and
coronary arteries.
 When it stimulated increase heart rate and dilate
coronary artery to increase myocardial blood flow.
Parasympathetic nerves:
 Parasympathetic pathway begins with nuclei of vagus
nerve in the medulla oblongata.
 extend to cardiac plexus and continue to the heart by the
way of cardiac nerves.
 fibres of right vagus nerve to SA node and left vagus to AV
node
 when it get stimulated it slowdowns the heart.

20. Cardiac plexus:
Superficial cardiac plexus:
• It is located in below arch of aorta in front of right pulmonary artery .
It is formed by
 cardiac branch from superior cervical ganglion of left sympathetic chain.
Lower of two cervical cardiac branches of the left vagus nerve.
Deep cardiac plexus:
• It is situated in front of bifurcation of trachea ,above the division of the
pulmonary trunk and behind arch of aorta
It is formed by
 cardiac branch derived from all cervical ganglion upper 4 or 5 thoracic ganglion
of both side sympathetic chain except the cardiac branch arise from the superior
cervical ganglion of left sympathetic chain.
Cardiac branch of vagus and recurrent laryngeal nerves, except those forming
the superficial plexus.

21. Conduction system:

22. Histology:
 Microscopic examination of
cardiac muscles shows cross
striation.
 Muscle fibres are branching
with centrally placed nucleus
 Intercalated disc connect the
adjacent muscle fibres.
 Intercalated disc help in rapid
spread of impulse
&contraction of muscle as a
single unit.
 It has more number of
mitochondria compared to
skeletal muscles.