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Learning Objectives. By the end of this module the learners will be able to: Explain the external and internal heart anatomy Identify the layers of the heart wall Blood circulation system of the heart Understand the structure and function of heart Understand the electrical Conduction system of the heart.. 

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By the end of this module the learners will be able to: Explain the external and internal heart anatomy Identify the layers of the heart wall Blood circulation system of the heart Understand the structure and function of heart Understand the electrical Conduction system of the heart.

Table of Contents. Introduction Anatomy of the heart Layers of the heart wall Structure and Function Heart valves Blood circulation Nerve Supply Heart Conduction System. 

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Introduction Anatomy of the heart Layers of the heart wall Structure and Function Heart valves Blood circulation Nerve Supply Heart Conduction System

The human heart is a muscular organ that collects deoxygenated blood from all parts of the body and carries it to the lungs to become oxygenated and released to all parts of the body.. 

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The human heart is a muscular organ that collects deoxygenated blood from all parts of the body and carries it to the lungs to become oxygenated and released to all parts of the body.

It is situated at the centre of the chest slightly towards the left.

Heart pumps around 72,000 litres of blood everyday throughout the body.. 

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Heart pumps around 72,000 litres of blood everyday throughout the body.

A human heart is conical shaped enclosed within the pericardium. It positions posterior to the body of the sternum, one-third of it is situated on the right and two-third on the left of the mid-line.. 

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A human heart is conical shaped enclosed within the pericardium. It positions posterior to the body of the sternum, one-third of it is situated on the right and two-third on the left of the mid-line.

A male heart weighs 310g and measures 12×8.5×6 cm while, a female heart weighs 255g.

pulmmary veins
Sug*rior vena cava
Right atrium —
Right ventricle —
—Left pulmonary artery
Left pulmonary veins
—Left atrium
Left ventricle

The heart wall consists of three layers-. Epicardium- the outer layer of the wall of the heart is formed by the visceral layer of the serous pericardium.. 

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Epicardium- the outer layer of the wall of the heart is formed by the visceral layer of the serous pericardium.

Myocardium- is the middle layer of the heart wall it is muscular and consists of excitable tissue and conducting system.

Endocardium- is the third and innermost layer of the heart wall.

The heart wall further consists of a middle concentric layer and a sub-endocardial layer.

The remaining of the heart is majorly composed of a sub-epicardial and sub-endocardial layers.

The heart is sub-divided through a septa into right and left halves further each half is subdivided into two cavities, the upper cavity is atrium and lower cavity is ventricle.. 

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The heart is sub-divided through a septa into right and left halves further each half is subdivided into two cavities, the upper cavity is atrium and lower cavity is ventricle.

These four cavities (left atrium, right atrium, left ventricle and right ventricle) form the four chambers of the heart.

The oxygenated blood that returns to the body drains into right atrium through superior vena cava, inferior vena cava and coronary sinus.

Four
chamber heart anatom
right atrim
ventricle
left atrim
ventricle

Deoxygenated blood is pumped by the right ventricle via the pulmonary semilunar valve into the pulmonary trunk to get it oxygenated in the lungs.. 

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Pulmonary Veins
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Right Atriu
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Right
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monary Veins
Left Atrium
Mitral (Bicuspid)
Left Ventricle
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Septum

Deoxygenated blood is pumped by the right ventricle via the pulmonary semilunar valve into the pulmonary trunk to get it oxygenated in the lungs.

The oxygenated blood returning the lungs drains into the left atrium through the four pulmonary veins.

Blood is pumped by the left atrium via bicuspid valve into the left ventricle.

Blood is pumped by the left ventricle via aortic semilunar valve into the ascending aorta to supply oxygenated blood to all body parts.

The human heart has four valves with a single purpose to facilitate forward flow of blood and prevent blood from backward flowing.. 

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The human heart has four valves with a single purpose to facilitate forward flow of blood and prevent blood from backward flowing.

The outflow of blood in all the four chambers is monitored by the four heart valves.

Atrioventricular valves are situated between the atria and the ventricles.

Tricuspid valves is on the right side of the heart.

Bicuspid valves is on the left side of the heart.

Semilunar valves are present on the outflow tracts of the ventricles.

Aortic valve is on the left side of the heart.

Pulmonary valve is on the right side of the heart.

The left coronary artery carries 80% of the blood to the heart muscle.. 

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The left coronary artery carries 80% of the blood to the heart muscle.

The left coronary artery is short and divided into two branches.

The left anterior descending artery transfers anterior two thirds of the inter- ventricular septum and the associated part of the left ventriculo anterior wall.

Circumflex coronary artery delivers blood to the lateral and posterior parts of the left ventricle.

The branches of the right coronary artery delivers blood to the right ventricle, right atrium and left ventriculo inferior wall.

The control of the heart stays with the medulla oblongata. The cardio-acceleratory centre, or pressor centre, is present in the upper part of the medulla oblongata, and the cardio-inhibitory centre, or depressor centre, in the lower part. These two are together known as the cardioregulatory centre, as they interact to control heart rate, etc.. 

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The control of the heart stays with the medulla oblongata.  The cardio-acceleratory centre, or pressor centre, is present in the upper part of the medulla oblongata, and the cardio-inhibitory centre, or depressor centre, in the lower part.  These two are together known as the cardioregulatory centre, as they interact to control heart rate, etc.

The nervous supply is autonomic, including both sympathetic and parasympathetic parts.  The sympathetic fibers develop from the pressor centre and the parasympathetic fibers develop in the depressor centre.

The sympathetic nervous system speeds up the depolarization rate by acting up on the sinoatrial node, this leads to increased heart rate.. 

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The sympathetic nervous system speeds up the depolarization rate by acting up on the sinoatrial node, this leads to increased heart rate.

While, The parasympathetic system works to slow the heart rate down.

The heart works as a natural pacemaker as the sinoatrial node, does not need a nervous supply to function. While, a parasympathetic supply slows the heart down.

Heart Conduction System. The pumping of the heart and contraction of chambers is regulated by an electrical conduction system. The electrical system generates electrical impulses which stimulates the heart muscles to contact and pump blood. Some of the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system.. 

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The pumping of the heart and contraction of chambers is regulated by an electrical conduction system.   The electrical system generates electrical impulses which stimulates the heart muscles to contact and pump blood. Some of the major elements in the cardiac conduction system are the sinus node,  atrioventricular  node, and the autonomic nervous system.

The sinus node is considered as the heart's natural pacemaker. It is a cluster of cells situated in the upper part of the wall of the right atrium where the electrical impulses are generated there.. 

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The sinus node is  considered as the heart's natural pacemaker. It is a cluster of cells situated in the upper part of the wall of the right atrium where the electrical impulses are generated there.

The electrical signal produced by the sinus node travels from cell to cell down via the heart until it reaches the atrioventricular node (the AV node), which is a cluster of cells present at the center of the heart between the atria and ventricles.

The AV node acts as a gate to slow down the electrical current before the signal is permitted to pass down through to the ventricles. The slowing of electrical current ensures atria has a chance to completely contract before the stimulation of the ventricles. After moving through the AV node, the electrical current moves towards the ventricles  in association with special fibers implanted on the lower part of the heart walls.

The autonomic nervous system  manages firing of the sinus node that triggers the onset of the cardiac cycle. The autonomic nervous system transmits a message swiftly to the sinus node which leads to increase in the heart rate to twice within only 3 to 5 seconds. This quick response is generated during exercising to keep up with the body's increased oxygen demand.

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Anatomy of the Heart

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