Anatomy of Heart
Heart lies on the left upper part of thoracic cavity. It lies between the twolungs under sternum. It is broad above and conical below.
Histology of Heart : Heart consists of three layers.They are-
1. Pericardium - outermost layer consisting of
(a) Visceral pericardium
(b) Parietal pericardium
(2) Myocardium - Middle layer made of cardiac muscle cells and interstitial cells.
(3) Endocardium - Innermost layer.
Chambers of Heart
Heart has four chambers. Two of them are upper chambers called atria or auricles. Lower two chambers are called ventricles. The two atria are separated by interatrial septum.The two ventricles are separaed by interventricular septum. Atria are filling chambers and ventricles are pumping chambers. Compared to artia, ventricles are thicker since they are pumping chambers. Of the two ventricles, wall of left ventricle is three times thicker than that of right ventricle since left ventricle pumps oxygenated blood to all parts of body and right ventricle pumps deoxygenated blood to lungs only.
Valves of Heart
Opening between right artium and right ventricle is guarded by tricuspid valve. It prevents back entry of blood into right atrium from right ventricle at the beginning of ventricular systole. Opening between left atrium and left ventricle is guarded by bicuspid or mitral valve. It prevents back entry of blood into left
atrium at the beginning of ventricular systole - Pulmonary trunk is guarded by tricuspid semilunar valve which prevents back flow into right ventricle at the begining of ventricular diastole. Aorta has tricuspid semilunar valve which prevents
back flow of blood into left ventricle at the begining of ventricular diastole. Chordae tendinae and papillary muscles:Papillary muscles arise from ventricular walls. Chordae tendinae attach apical end of valves and papillary muscles. They prevent over distension of valves during diastole.
Blood Vessels attached to Heart
Blood vessels attached to heart are -
1. Superior and inferior venacavae - carrying deoxygenated blood from parts of body to right atrium.
2. Pulmonary artery carrying venous blood to lungs from right ventricle.
3. Pulmonary veins carrying oxygenated blood from lungs to the left atrium of heart.
4. Aorta carrying oxygenated blood to all parts of body from left ventricle of heart.
Blood vessels supplying oxygenated blood to heart :Right and left coronary arteries arising from Aorta supply oxygenated blood to heart. Blood vessels draining heart : Coronary veins bring deoxygenated blood of heart into coronary sinus, which opens directly into right atrium.
Ductus arteriosus : Ductus arteriosus is the vestigeal remnant of cord like structure which existed in foetal life between arch of aorta and pulmonary trunk. In foetal life, it bypasses pulmonary circulation. After birth, it closes, becomes obsolete and atrophies.
Septum ovale : It is crescenteric mark on interatrial setpum. It is closed foramen ovale that existed in foetus.
Foramen ovale : It is the opening in interatrial septum in foetal life. It avoids blood entry into lungs in foetal life. After birth, it closes and forms septum ovale.
Cardiac centres
1. Cardio inhibitory centre is dorsal motor nucleus of vagus in medulla.
2. Cardio accelerator centre is situated in lateral horn cells of upper thoracic segments of spinal cord.
Conducting System of Heart
System of conducting impulses of cardiac contraction consist of-
(1) Sinoatrial node (SA node) (2) Atrioventricular node (AV node)
(3) Bundle of His. (4) Right and left branches of bundle of His. (5) Purkinje fibres.
SA node : It is present at the opening of superior venacava into right atrium. It is called pacemaker of heart. It is made of modified cardiac muscle fibres. It measures about 5x20 mm.
AV node: It is present in the right atrium at the posterior part of inter atrial septum. It is close to the opening of coronary sinus. Cells of AV node are cardiac muscle fibres having a few myofibrils.It measures about 2x5 mm.
Bundle of His : Main trunk of bundle of His is continuous with AV node. It passes through interventricular septum. It is about 20 mm long.
Right and left branches of bundle of His : Bundle of His divides intoright and left branches. Right branch is longer than left branch. Left branch bifurcates into superior and inferior divisions.
Purkinje fibres : They arise from brnaches of bundles of His. They spread from interventricular septum directly to papillary muscle and ultimately end in sub endocardial network.Purkinje fibres have larger diameter than ordinary cardiac muscle fibres. Purkinje fibres have diameter of 50-70 where as cardiac
muscle fibres have diameter of about 15
Heart lies on the left upper part of thoracic cavity. It lies between the twolungs under sternum. It is broad above and conical below.
Histology of Heart : Heart consists of three layers.They are-
1. Pericardium - outermost layer consisting of
(a) Visceral pericardium
(b) Parietal pericardium
(2) Myocardium - Middle layer made of cardiac muscle cells and interstitial cells.
(3) Endocardium - Innermost layer.
Chambers of Heart
Heart has four chambers. Two of them are upper chambers called atria or auricles. Lower two chambers are called ventricles. The two atria are separated by interatrial septum.The two ventricles are separaed by interventricular septum. Atria are filling chambers and ventricles are pumping chambers. Compared to artia, ventricles are thicker since they are pumping chambers. Of the two ventricles, wall of left ventricle is three times thicker than that of right ventricle since left ventricle pumps oxygenated blood to all parts of body and right ventricle pumps deoxygenated blood to lungs only.
Valves of Heart
Opening between right artium and right ventricle is guarded by tricuspid valve. It prevents back entry of blood into right atrium from right ventricle at the beginning of ventricular systole. Opening between left atrium and left ventricle is guarded by bicuspid or mitral valve. It prevents back entry of blood into left
atrium at the beginning of ventricular systole - Pulmonary trunk is guarded by tricuspid semilunar valve which prevents back flow into right ventricle at the begining of ventricular diastole. Aorta has tricuspid semilunar valve which prevents
back flow of blood into left ventricle at the begining of ventricular diastole. Chordae tendinae and papillary muscles:Papillary muscles arise from ventricular walls. Chordae tendinae attach apical end of valves and papillary muscles. They prevent over distension of valves during diastole.
Blood Vessels attached to Heart
Blood vessels attached to heart are -
1. Superior and inferior venacavae - carrying deoxygenated blood from parts of body to right atrium.
2. Pulmonary artery carrying venous blood to lungs from right ventricle.
3. Pulmonary veins carrying oxygenated blood from lungs to the left atrium of heart.
4. Aorta carrying oxygenated blood to all parts of body from left ventricle of heart.
Blood vessels supplying oxygenated blood to heart :Right and left coronary arteries arising from Aorta supply oxygenated blood to heart. Blood vessels draining heart : Coronary veins bring deoxygenated blood of heart into coronary sinus, which opens directly into right atrium.
Ductus arteriosus : Ductus arteriosus is the vestigeal remnant of cord like structure which existed in foetal life between arch of aorta and pulmonary trunk. In foetal life, it bypasses pulmonary circulation. After birth, it closes, becomes obsolete and atrophies.
Septum ovale : It is crescenteric mark on interatrial setpum. It is closed foramen ovale that existed in foetus.
Foramen ovale : It is the opening in interatrial septum in foetal life. It avoids blood entry into lungs in foetal life. After birth, it closes and forms septum ovale.
Cardiac centres
1. Cardio inhibitory centre is dorsal motor nucleus of vagus in medulla.
2. Cardio accelerator centre is situated in lateral horn cells of upper thoracic segments of spinal cord.
Conducting System of Heart
System of conducting impulses of cardiac contraction consist of-
(1) Sinoatrial node (SA node) (2) Atrioventricular node (AV node)
(3) Bundle of His. (4) Right and left branches of bundle of His. (5) Purkinje fibres.
SA node : It is present at the opening of superior venacava into right atrium. It is called pacemaker of heart. It is made of modified cardiac muscle fibres. It measures about 5x20 mm.
AV node: It is present in the right atrium at the posterior part of inter atrial septum. It is close to the opening of coronary sinus. Cells of AV node are cardiac muscle fibres having a few myofibrils.It measures about 2x5 mm.
Bundle of His : Main trunk of bundle of His is continuous with AV node. It passes through interventricular septum. It is about 20 mm long.
Right and left branches of bundle of His : Bundle of His divides intoright and left branches. Right branch is longer than left branch. Left branch bifurcates into superior and inferior divisions.
Purkinje fibres : They arise from brnaches of bundles of His. They spread from interventricular septum directly to papillary muscle and ultimately end in sub endocardial network.Purkinje fibres have larger diameter than ordinary cardiac muscle fibres. Purkinje fibres have diameter of 50-70 where as cardiac
muscle fibres have diameter of about 15
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