CIRCULATORY SYSTEM : CIRCULATORY SYSTEM PREPARED BY :
CCP STUDENT Presentation Outline : : Presentation Outline : Position of the heart
Motion of the blood through the heart
How are the Heart & Lungs connected?
Layers of the heart
Valves of the heart
Pulmonary vs systemic circulation
Pump action of the heart
Conduction system POSITION OF THE HEART : : POSITION OF THE HEART : The heart is in the thoracic cavity in the mediastinum between the lungs.It lies obliquely, a little more towards the left, and present a base above, and apex below.The apex is about 9cm to the left of the midline at the level of the 5th intercostal space, i.e. a little below the midline and sligthly nearer the midline.The base extends to the level of the 2nd rib. ANATOMICAL STRUCTURE OF THE HEART : ANATOMICAL STRUCTURE OF THE HEART The heart is a hollow organ divided into four chambers:
Left ventricle MOTION OF THE BLOOD THROUGH THE HEART : : MOTION OF THE BLOOD THROUGH THE HEART : It is a simple squeeze pump that force blood forward by squeezing in exactly the way that abulb syringe forces out fluid when it is compressed. The blood moves from right heart to left by the way of the lungs.
In other words, the right heart pulls the blood out of the veins and pumps into the lungs. While the left heart pulls the blood out of the lungs and pumps it into the body`s circulation. HOW ARE THE HEART AND LUNGS CONNECTED ? : HOW ARE THE HEART AND LUNGS CONNECTED ? Superior & inferior vena cava empties into the right atrium. It further opens into the right ventrictle. Then through the pulmonary artery, the blood is carried to the lungs.
After oxygenation it flows back into the left atrium through two pairs pulmonary veins. It further flows down in the left ventricle. Then through the aorta into the entire body. LAYERS OF THE HEART : LAYERS OF THE HEART The heart is surrounded by a loose protective sac called pericardium. This sac is loose enough to permit the heart to beat easily.
After the pericardium, a thin, shiny, reddish-coloured membrane from the outer surface of the heart is seen called the epicardium.
Under the epicardium is a thick layer of muscle called the myocardium. The myocardium is thickest in the left ventricle; it is thinnest in the atria.
Inside walls of the heart are lined with another smooth shiny membrane called endocardium. VALVES OF THE HEART : VALVES OF THE HEART Every opening between the chambers and into the vessels is supplied with a valve that protects backward flow of blood;
The tricuspid valve consists of three cusps is located between the right atrium and right ventricle.
The mitral valve or bicuspid valve consists of two cusps is located between the left atrium and left ventricle.
The semilunar valves are located between the right ventricle and the pulmonary artery called pulmonary valve, and between the left ventricle and the aorta called the aortic valve. PULMONARY VS SYSTEMIC CIRCULATION : PULMONARY VS SYSTEMIC CIRCULATION A COMPLETE BLOOD CIRCULATION : A COMPLETE BLOOD CIRCULATION CORONARY CIRCULATION : CORONARY CIRCULATION The coronary arteries branch off the base of the aorta and travel a considerable distance on the epicardial surface of the heart. They lie embedded in the fat that surrounds them and covers the heart. The two main arteries are the right and left coronary arteries. They supply both the heart`s electrical and mechanical structures. Right Coronary Artery : : Right Coronary Artery : After leaving the aorta, the right coronary artery passes diagonally toward the right side of the heart and descends in the groove between the right atrium and the right ventricle. Before passing around to posterior surface of the heart, it gives of its acute marginal branch, which descends along the lateral side of the heart to the apex. Left Coronary Artery : : Left Coronary Artery : After leaving the aorta, the left coronary artery passes behind the pulmonary artery and provides small branches to supply the left atrium. As it leaves the area of the pulmonary artery it branches off into two major divisions:
Left Anterior Descending.
Left Circumflex. SUPPLY TO THE HEART : SUPPLY TO THE HEART The right coronary artery supplies:
55% SA node
90% AV node
A portion of the bundle of his
Posterior-inferior division of the left bundle branch
Posterior 1/3rd of the septum
Right atrial and ventricular musculature
Inferior-posterior wall of the ventricle Slide 18: Left anterior descending artery supplies :
Anterior 2/3rd of the septum
The right bundle branch
Anterosuperior division of the left bundle branch
Anterior wall of the ventricle
Left circumflex :
45% of the SA node
Inferoposterior division of the left bundle branch
Lateral wall of the left ventricle PUMPING ACTION OF THE HEART : PUMPING ACTION OF THE HEART Blood is pumped through the chambers of the heart and out through the great vessels by a simple squeezing action of the heart chambers. This contraction of the heart is called systole.
After the contraction, the heart relaxes and allows blood to filled within the chambers. This relaxation phase of the heart is called diastole. STAGES OF A HEART BEAT : STAGES OF A HEART BEAT The whole cycle of a heartbeat goes through these stages :
Atrial systole : The atria contract, forcing the blood down into the ventricle.
Ventricular systole : The ventricles contract, forcing the blood out of the pulmonary artery & aorta.
Atrial diastole : This starts during ventricular systole as the atria begin refilling with blood from the great veins.
Ventricular diastole : This takes place during atrial systole as a blood from the atria fills the ventricles. THE ELECTRIC CIRCUIT THAT DRIVES THE HEART : THE ELECTRIC CIRCUIT THAT DRIVES THE HEART Electric impulses initiated within the heart are transmitted along a network of specialized cells called the conduction system.
When the impulses reaches and stimulates the ventricular muscle, myocardial contraction occurs. Each normal heartbeat is the result of an electrical impulse that originates in a specialized area in the wall of the right atrium called the SA node.
This bundle of tissues acts as the battery for the heart and is the designated pacemaker. Other areas of the heart also have the ability to initiate impulses,but they assume this role only under abnormal circumstances. SINOATRIAL OR SA NODE : : SINOATRIAL OR SA NODE : A specialized piece of tissues that can initiate its own impulse which has the property of automaticity. It is located in the posterior portion of the right atrium near the superior vena cava. It acts as the pacemaker of the heart. It initiates impulses at the rate of 60-100 per minute. ATRIAL-VENTRICULAR OR AV NODE : : ATRIAL-VENTRICULAR OR AV NODE : The AV node is located in the right atrium close to the septal leaflet of the tricuspid valve. The AV node is not usually the pacemaker, but it is capable of initiating impulses at the rate of 40-60 per minute if the SA node fails. The primary function of the AV node is to relay the electrical impulses from the atria into the ventricles in an orderly and timely way. The impulses travel relatively slowly through the AV node to reach the bundle of HIS. This allows the atria to contract and empty and ventricles to fill before the ventricles contract. BUNDLE OF HIS : : BUNDLE OF HIS : This bundle lies in the upper part of the interventricular septum, connecting the AV node with the two bundle branches. RIGHT & LEFT BUNDLE BRANCHES AND PURKINJEE NETWORK : The right and left bundle branches arise from the bundle of HIS, straddle the intervascular septum, and travel down either side of the septum. They`re divided into smaller and smaller branches and connect with the purkinje network. This network also has the ability to initiate impulses at a rate of 15-40 per minute.