Heart Anatomy | Coronary Blood supply | Heart blood supply | Cardiovascular system | Lec5 #drjamil
Channel: Dr. Jamil Lectures
Date: 12/05/2023

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In this lectutre we will discuss about Heart anatomy,external features of heart,pericardium,heart layers,structure of heart,borders of heart,surfaces of heart,Coronary blood supply,right dominant circulation and left dominant circulation.


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Heart Anatomy
★ External Features
● The heart lies obliquely within the middle mediastinum, mostly
posterior to the sternum.
● The upper left corner of the heart starts at left rib 2 and ends at the
apex of the heart at left 5th intercostal space while the upper right
corner starts at right rib 3 and ends at lower right corner at rib6.
★ Pericardium
● It is protective fluid filled double membrane sac that
surrounds the heart and great vessels (aorta and
pulmonary trunk) and helps to perform the functions
properly → It is also called pericardial sac and consists
of 3 layers (from outer to inner):
1. Fibrous pericardium
2. Parietal layer of serous pericardium
3. Visceral layer of serous pericardium (also called
epicardium)
➢ Pericardial cavity lies between the parietal and visceral layers which contains
pericardial fluid → pericardial fluid decreases the friction of pericardial layers during
contraction and relaxation of heart.
➢ Pericardium innervated by phrenic nerves.
➢ Pericarditis (inflammation of pericardium)can cause pain to the neck, arms, or one or
both shoulders (often left shoulder)
★ Structure of heart
● The walls of the heart are composed of a 3 layers
➢ Endocardium (inner layer)
➢ Myocardium (middle and thick layer)
➢ Epicardium (outer layer also called visceral
pericardium)
● The atrial portion of the heart has relatively thin walls and
is divided by the atrial (interatrial) septum into the right
and left atria.
● The ventricular portion of the heart has thick walls and is
divided by the ventricular (interventricular) septum into the
right and left ventricles → Left ventricular wall is 3 times
thicker than right ventricular wall because LV has to pump
the blood with enough power to all the way of systemic circulation.
● The lower part of the interventricular septum is thick and formed of muscle (muscular
septum) →The smaller upper part of the septum is thin (membranous septum) that is
attached to the fibrous skeleton → fibrous skeleton anchors the four valves and
membranous septum & give them attachment to the myocardium.
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★ Coronary blood supply
● During early diastole the muscle of heart relaxes and coronary arteries dilates, so
blood flow to coronary artery increases during diastole→ during systole the muscle of
heart contracts and coronary arteries constricts, so blood flow to coronary artery
decreases during systole.
● Coronary artery (CA) arises from the root of the aorta and divides into right coronary
artery(RCA) and left coronary artery (LCA).
● LCA gives further 3 branches
1. Left circumflex artery (LCX)
2. Obtuse marginal artery (OMA)
3. Left anterior descending artery (LAD).
● RCA gives further 2 branches
1. Acute marginal artery (AMA)
2. Posterior descending artery (PDA)
➢ In 85% cases PDA arises from RCA ,It is
called Right-dominant circulation.
➢ In 8% cases PDA arises from LCX artery (branch of LCA),it is called Left-dominant
circulation
➢ In 7% cases PDA arises from both RCA and LCX,it is called Codominant circulation.
● LAD and its branches supply anterior 2/3 of interventricular septum, anterolateral
papillary muscle, anterior surface of LV,apex and bundle of HIS → LAD is the most
commonly occluded artery.
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● PDA supplies AV nodes that depend upon dominance (PDA may be from RCA or
from LCA) → PDA supplies posterior 1/3 of interventricular septum, posterior 2/3
walls of right and left ventricles and posteromedial papillary muscle.
● RCA supplies SA nodes via SA nodal arteries (independent of dominance i.e always
from RCA → occlusion in RCA leads to infarction of SA node → SA node cannot
create the impulses properly that leads to bradycardia or heart block.
● AMA supplies RV.
● OMA supplies the posterior,inferior and lateral wall of LV.


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