HEART

Introduction : It is conical, hollow muscular organ situated in the medial medistinum and enclosed within the pericardium It pumps blood to various parts of the body to meet their nutritive requirements

Situation : It is placed obliquely behind the body of sternum and adjoining parts of costal cartilages, so that 1/3 rd of it lies to the right and 2/3 rd to the left of median plane. Measurements: Length : 12 cm Breadth : 9 cm Weight : 300 gm in Males 250 gm in Females

Features : Four chambered heart

External Features : Apex – It is formed by left ventricle and directed downwards, forwards and to the left. It is overlapped by the anterior border of left lung. Situation – It lies in the left fifth intercostal space 9 cms lateral to the mid-sternal line

External Features : Base – It is formed mainly by the left atrium and small part of right atrium It shows openings of four pulmonary veins and superior & inferior vena cavae It is related to the T5 to T8 thoracic vertebra

Borders of the Heart : Upper Border – Slightly oblique and is formed by two atrium Right Border – It is more or less vertical and is formed by right atrium Inferior Border – It is nearly horizontal and is formed mainly by right ventricle and small part of left ventricle near at its apex

Borders of the Heart : Left Border – It is oblique and curve and formed mainly by the left ventricle and partly by the left auricle

Surfaces of the Heart : Sternocostal Surface – It is mainly formed by right atrium, right ventricle and partly by left ventricle and left auricle. Most of the surface is covered by lungs but a part of it that lies behind the cardiac notch of the left lung is uncovered.

Surfaces of the Heart : Inferior Surface – Rest on the central tendon of the diaphragm and it is formed in it’s left 2/3 rd by the left ventricle and in it’s right 1/3 rd by the right ventricle Left Surface – Formed mostly by the left ventricle and at the upper end by the left auricle

Chambers of the Heart : Right Atrium – It is a quadrilateral chamber situated behind and to the right side of right ventricle from which it is separated externally by the right part of atrio-ventricular groove. Extent – It extends from the orifice of superior vena cava behind the third right costal cartilage to the orifice of inferior vena cava behind the sixth right costal cartilage

Chambers of the Heart : Right Atrium – External Features A hollow conical muscular projection known as right auricle arises from the antero-superior part of atrium A shallow verticle groove known as sulcus terminalis runs along the right border of the heart and extends between the orifices of superior and inferior vena cavae

Interior of Right Atrium: It consists of posterior smooth part known as sinus venarum and anterior rough part known as atrium proper. Two parts are separated by a smooth muscle ridge the crista terminalis Rough Part Smooth Part

Sinus Venarum: Foramen Venarum Minimarum Opening of Coronary Sinus Opening of Inferior Vena Cava Opening of Superior Vena Cava

Atrium Proper: Crista Terminalis Musculi Pectinati Fossa Ovalis Limbus Fossa Ovalis

Right Ventricle: Introduction: It is triangular chamber which receives blood from the right atrium and pumps it to the lungs through the pulmonary trunk and pulmonary arteries.

Right Ventricle: Features : It has two parts: 1)the inflowing part It is rough due to presence of muscular ridges called trabeculae carneae. 2) the outflowing part /infundibulum It is smooth and forms the upper conical part of the right ventricle which gives rise to pulmonary trunk

Right Ventricle: Features : Trabeculae carneae is of three types: 1) Ridges : which are fixed elevations 2) Bridges: having two fixed ends, but with a free centre. 3) Pillars/Papillary Muscles: one end attached to the ventricular wall, and the other end connected to the cusps of the tricuspid valve by chordae tendinae. Anterior Posterior Septal

Right Ventricle: Features : The interior shows 2 orifices: 1. The right atrioventricular orifice (or) tricuspid valve 2. The pulmonary orifice which is guarded by the pulmonary valve.

Left Atrium  It is quadrangular chamber, situated posteriorly and receives the oxygenated blood from lungs through pulmonary veins and pumps it into left ventricle through the left atrioventricular orifice which is guarded by bicuspid valve.

Left Atrium  Its appendage left auricle projects anteriorly to overlap the infundibulum of the right ventricle.

Left Atrium  Two pulmonary veins open into left atrium on each side of posterior wall.  Most part of the atrium is smooth walled, and musculi pectinati is present only in the auricle.. Features:

Left Ventricle  The left ventricle receives oxygenated blood from the left atrium and pumps into aorta.

Left Ventricle The interior is divisible into 2 parts: 1.the lower rough part  trabeculae cornea 2.the upper smooth part gives origin to the ascending aorta Features:

Left Ventricle The interior presents 2orifices 1. the left atrioventricular orifice/bicuspid valve/mitral valve 2. the aortic orifice guarded by the aortic valve Features:

Left Ventricle They are two papillary muscles: anterior and posterior The wall is 3 times thicker than the right ventricle. Features:

Blood Supply Arterial Supply of the Heart The heart is supplied mostly by two coronary arteries, right and left. Only the inner um of endothelial surface gets nutrition directly from the blood in the cardiac chambers.

Right Coronary Artery

Origin: It arises from the anterior aortic sinus of the ascending aorta just below the supravalvular ridge.

Right Coronary Artery Branches are divided into two groups: 1. those branches arising from first segment of artery i.e. upto inferior border 2. those branches arising from the second segment i.e. upto the crux.

Right Coronary Artery

Ventricular RamiAtrial Rami Right Conus ArterySinu-Atrial Nodal Artery Right Anterior Ventricular Rami Right Marginal Artery Branches from the first segment:

1.Right conus artery: It usually first branch of right coronary artery and supplies the infundibulum of right ventricle. 2.Right anterior ventricular rami: These are 3-4 in number arises right angles to main trunk of coronary artery and supplies sternocostal wall of the right ventricle. 3.Right marginal artery: It is longest of ventricular ramus follows the inferior border of the heart towards the apex and supplies adjoining surfaces of the right ventricle. Ventricular Rami:

Branches from the first segment: Sinu-Atrial Nodal artery: It belongs to atrial rami and supplies the SA-node Atrial Rami:

Branches from the second segment: Right posterior ventricular rami Posterior inter-ventricular branch Right posterior atrial rami

Branches from the Second Segment: 1.Right posterior ventricular rami It arises from trunk of right coronary artery in posterior ventricular groove and supplies diaphragmatic surface of the right ventricle. 2. Posterior ventricular branch: It arises from right coronary artery and anastomoses with anterior interventricular branch of left coronary artery near the apex. It supplies diaphragmatic surface of the right ventricle and left ventricles. 3. Right posterior atrial rami: It supplies posterior surface of both right and left atria

Left Coronary Artery

Origin: It arises from left posterior aortic sinus of the ascending aorta.. Left Coronary Artery

Branches are divided into two groups: 1. Anterior interventricular artery 2. Circumflex artery

Anterior Interventricular Artery Circumflex Artery Anterior Interventricular RamiAtrial and Ventricular Rami Left Conus ArteryLeft Marginal Artery Septal Rami

It is continuation of left coronary artery and descends in the anterior ventricular groove and anastomoses with the posterior interventricular branch of right coronary artery. Anterior interventricular rami: It supplies right and left ventricles. Left conus artery : It is a branch of anterior ventricular rami and supplies the infundibulum of right ventricle. Septal rami: Supplies antero-superior 2/3rd of the ventricular septum. Anterior interventricular artery: Branches:

It passes along the left part of atrioventricular groove, winds round the left border of heart and occupies the posterior part of atrioventricular groove and anastomoses with the right coronary artery Circumflex Artery: Branches: Atrial and Ventricular rami: Supplies adjoining surfaces of left atrium and left ventricle. Left marginal artery: It follows the left border of heart towards the apex

About 60% of the venous blood of the heart drains into the right atrium through coronary sinus. The remaining 40% of the blood drains into the heart through venae cordis minimi and anterior cardiac veins. Coronary sinus conveys the grater part of blood from the left coronary artery. Anterior cardiac veins drain most of the blood of the right coronary artery. Venous Drainage :

Veins which donot join the coronary sinus are: 1) Anterior cardiac vein: 3-4 in number, drains the infundibulum of the right ventricle and end directly into the right atrium through foramen minimarum.

2.Venae cordi minimi: These veins open into different chambers of heart through the foramin minimarum 3. Some times right marginal vein instead of joining the small cardiac vein, opens directly into right atrium.

Coronary Sinus: It is wide venous channel, about 2-3cms long situated in the posterior part of the atrio-ventricular groove and receives about 60% venous blood of the heart.

Tributaries : Coronary Sinus 1. Great Cardiac Vein2. Middle Cardiac Vein 3. Oblique Vein of the Left Atrium 4. Posterior Vein of the Left Ventricle 5. Small Cardiac Vein

Nerve Supply : Nerves of the heart are derived from cardiac plexus which are formed by parasympathetic fibers. Parasympathetic: By vagus These are cardio inhibitory, on stimulation they slow down the heart rate. Sympathetic: Derived from the upper 4-5 thoracic segments of the spinal cord. These are cardioacceleratory, and on stimulation increases the heart rate, and also dilate the coronary arteries.

Cardiac Plexus : It consists of two parts –  Superficial and  Deep Both parasympathetic and sympathetic nerves forms cardiac plexus.

Superficial Cardiac Plexus : Situation : It is situated below the arch of aorta and in front of pulmonary artery Formation:  By the cardiac branch from the superior cervical ganglion of the left sympathetic trunk  By the inferior cervical cardiac branches of the left vagus

Branches of the superficial cardiac plexus: - To the deep cardiac plexus - The right coronary artery - The left anterior pulmonary plexus

Deep Cardiac Plexus : Situation : In front of bifurcation of trachea above the division of pulmonary trunk and behind arch of aorta Formation:  By the cardiac branches of superior, middle and inferior cervical ganglia and upper 4 (or) 5 thoracic ganglia of both sympathetic trunks  By the cardiac branches of vagus and recurrent laryngeal nerves of both sides.  Except the braches of superficial cardiac plexus.

Branches of the Deep cardiac plexus: - To the Coronary plexus - To the Pulmonary plexus