8.1 Cardio Vascular System - The heart - Part A

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Cardio-Vascular System PART A - The Heart :

Cardio-Vascular System PART A - The Heart General Training Module RK


PART - A Introduction The Heart PART - B Blood Vessels Circulatory System Contents



Cardiovascular System:

Cardiovascular System The Cardiovascular system is designed to provide mechanism for transportation of different substances in the body via circulating blood (cells and plasma). It has a pump which is the heart (Cardio-) and a system of pipes or tubes made up of Blood vessels (Vascular) that carries blood – The Circulatory System

The Circulatory system:

The Circulatory system The Circulatory System has two components The Blood circulatory System The Lymphatic System – will be dealt separately Consists of lymph vessels and lymph nodes through which a colorless fluid lymph flows The two systems (that is lymphatic and blood circulatory systems) communicates with one another and are closely associated.

The Circulatory system:

The Circulatory system The Blood circulatory System has three main vessel types therefore components: The Arterial System: takes blood to tissues The Capillary System: the site at which gas and other substance exchange take place between blood and the tissues The Venous system: brings blood from the tissues to the heart usually

The Circulatory system:

The Circulatory system The Blood Circulatory System exists as two separate systems in the body Systemic Circulation – Distribute blood all across body to different regions and organs. These regional circulations may be referred to by specific names such as cerebral circulation, renal circulation, all of which are parts of Systemic Circulation except: Pulmonary Circulation – Which runs blood that is returned to the heart from the systemic circulation across lungs for the purpose of oxygenation

Blood Circulatory System:

Blood Circulatory System Schematic diagram Showing: Pulmonary Circulation : Takes deoxygnetaed blood from the heart to lungs to be oxygenated via respiration and brings back the oxygenated blood to the heart Systemic Circulation: Pumps the oxygenated blood across the body to all the tissues for cellular respiration and brings back the deoxygenated blood from the body tissues back to the heart

The Heart:

The Heart

The Heart:

The Heart The heart is a hollow muscular organ It has four chambers The heart muscle is called the Myocardium It is a specialized muscle found only in the heart It is an involuntary type muscle – that is you can’t contract at your own conscious will. It is the size of its owner’s fist Its located in your thoracic cavity

The Heart:

The Heart The heart pumps blood to maintain a constant circulation of blood throughout the body

Position of the Heart:

Position of the Heart The heart is in the thoracic cavity in the mediastinum in between the lungs. It lies obliquely little bit more to the left than the right It is cone shaped The cavity in which it lies is called the pericardial cavity

The Heart - Chambers:

The Heart - Chambers The heart is divided into right and left sides by a septum in the middle Because of this Blood on one side of the heart does not mix with blood on the other side at all Each side is further divided into an upper (ATRIUM) and a lower chamber (VENTRICLE) Atrium and Ventricle on each side are separated by a valve - Atrio -Ventricular or AV Valve

The Heart - Chambers:

The Heart - Chambers Therefore the four chambers of the heart are: Right Atrium (RA) Right Ventricle (RV) Left atrium (LA) Left ventricle (LV)

Great Vessels:

Great Vessels Great vessels are the vessels connected to the heart chambers that take blood away from the heart and bring blood to the heart Superior Vena Cava Inferior Vena Cava Aorta Pulmonary Trunk Pulmonary Veins

Great Vesseles:

Great Vesseles Superior Vena Cava – brings venous blood from the upper part of the body to the right atrium Inferior Vena Cava – brings venous blood from the lower part of the body to the right atrium Aorta – takes blood, the left ventricle pumps to the body tissues Pulmonary Trunk – takes blood from the right ventricle to the lungs Pulmonary Veins – brings blood from the lungs to the left atrium

Blood flow through the Heart:

Blood flow through the Heart Venous blood collected from the tissues from all over the body drain to the Right atrium of the heart Therefore the right side of the heart has deoxygenated blood When Right Atrium contracts blood flows to the Right Ventricle through the Tricuspid Valve (The AV valve on the right side of the heart) Right Ventricle contraction pumps blood to the Pulmonary Circulation through the Pulmonary Artery (aka pulmonary trunk) which then divides into right and left branches before entering the lungs on their respective sides This is the only arteries in the body that carries deoxygenated blood The opening of the pulmonary artery is guarded by the pulmonary valve

Blood flow through the Heart:

Blood flow through the Heart Two pulmonary veins bring the oxygenated blood to the Left Atrium. The LA then passes this blood to Left Ventricle through the Mitral Valve Left Ventricle contracts and pumps blood to the systemic circulation through aorta – which is the first vessel of the systemic circulation Aortic Valve with 3 semi-lunar cusps guards the opening of aorta and prevents back flow of blood to the LV during its relaxation. Therefore left side of the heart has oxygenated blood

Heart Valves:

Heart Valves There are four main heart valves: Tricuspid Valve: between right atrium and right ventricle The mitral valve: between the left atrium and left ventricle The Pulmonary valve: between right ventricle and the Pulmonary trunk The Aortic Valve: between the left ventricle and the Aorta


Aortic and Pulmonary valves prevent back flow of blood to the heart from Aorta and Pulmonary Trunk respectively Top View

The structure of the Heart wall:

The structure of the Heart wall The heart is made of three tissue layers: The Pericardium The myocardium The Endocardium Blausen.com staff. " Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/ wjm /2014.010. ISSN 20018762.

The Blood Supply of the Heart:

The heart also needs a blood supply to function It receives its own supply of blood from the coronary arteries . There are two major coronary arteries branch off from the aorta near the point where the aorta and the left ventricle meet. These arteries and their branches supply all parts of the heart muscle with blood. Coronary veins drains the deoxygenated blood from the heart directly to the Right atrium through Coronary Sinus posteriorly The Blood Supply of the Heart

The Blood Supply of the Heart:

The Blood Supply of the Heart

Coronary Arteries:

Coronary Arteries Coronary arteries: Left Coronary Artery (LCA) Right Coronary artery (RCA) Left Coronary Artery further divides into: (Left) Circumflex Artery (LCX) Left Anterior Descending Artery (LAD) Sometimes you may come across references to three main arteries of the heart ( eg : Triple Vessel Disease). This simply means LCX, LAD and RCA as the LCA divides soon after it starts from the aorta leaving only a short part which is also referred to as the Left Main Trunk or Left Main Stem (LMS)

Coronary Veins:

Coronary Veins

Heart Beat and Its control:

Heart Beat and Its control Heart beats continuously at a rate about 72 beats per minute This is accomplished by several mechanisms: The intrinsic mechanism of myocardium Conduction system within the heart Involuntary control Chemical control by catecholamine

Heart Beat and its control:

Heart Beat and its control The heart muscle or the myocardium has an intrinsic system that initiates impulses without any stimulation from the brain. The intrinsic system is made up of specialized myocytes that could start electrical excitation. The conduction system of the heart muscle spread these impulses across the myocardium in a wave of conduction However this intrinsic system could either be stimulated or depressed by nerve impulses from the brain and some hormones

Conduction System of the Heart:

Conduction System of the Heart Sinuatrial Node (SA Node) Atrio -ventricular Node (AV Node) Atrio -ventricular Bundle (AV Bundle or ‘Bundle of His’), Right and Left Branch Bundles and Purkinje Fibers.

Conduction System of the Heart:

Conduction System of the Heart

Nerve Supply to the Heart:

Nerve Supply to the Heart In addition to the intrinsic stimulation of the myocardium, the heart rate and the force with which it beats are regulated by the Cardiac Center in the Medulla Oblongata acting through the Autonomic Nervous System. The final rate at which the heart beat is achieved by a fine balance between the two components of the autonomic Nervous system: the Sympathetic and the Parasympathetic systems . Parasympathetic system reduces the heart rate and the force of the heart beat. The sympathetic system increase the heart rate and the force of the beat.


Catecholamines They are a group of chemical secreted by the adrenal glands medulla Includes adrenalin and noradrenalin They have the same effect as the autonomic nervous system on the heart Noradrenalin depresses the heart rate Adrenalin stimulates the heart

The Cardiac Cycle:

The Cardiac Cycle The heart beats about 60 to 80 times a minute therefore its activity is cyclical. The collection of actions of the heart within each of these beats is called the cardiac cycle Taking 75 as an average beats per minute one cardiac cycle lasts 0.8 seconds and includes: Atrial Systole – Contraction of atria (RA & LA) (= 0.1 sec) Ventricular Systole – Contraction of RV & LV (= 0.3 secs ) Complete Cardiac Diastole – Relaxation of atria & ventricles (= 0.4 secs )

The Cardiac Cycle:

The Cardiac Cycle

Heart Sounds – Lub Dup:

Heart Sounds – Lub Dup Usually an individual is not aware of his heart beat But the sound of it beating could be heard of the chest by using a stethoscope Two sounds separated by a short pause can be heard which are usually described as “ Lub – Dup” The first sound “ Lub ” is a fairly loud and is due to the contraction of the ventricular muscle and the closure of the atrio -ventricular valves The Second sound ‘Dup’ is softer and is due to the closure of the aortic and pulmonary valves

Blood Pressure:

Blood Pressure Blood pressure is the pressure that blood exerts on the walls of the vessels it is contained in The pressure in arteries are higher than that of veins Systolic Blood Pressure refers to the pressure in aorta during the ventricular contraction or ventricular systole (=120 mm Hg) Diastolic Blood Pressure refers to the pressure in aorta during complete relaxation of the heart, that is both atria and ventricles (= 80 mm hg) Therefore Blood Pressure is expressed as a combination of these two measures 120/80 mm Hg

Factors affecting Blood Pressure:

Factors affecting Blood Pressure Cardiac Output Blood Volume Peripheral Resistance Elasticity of the Arterial walls Venous Return: Changes in the thoracic cavity during respiration Skeletal Muscle Contraction Gravity


Pulse The heart beat could be felt along walls of the arteries in the periphery, especially when an artery is held against an underlying bone. The normal pulse rate is about 60 to 80 per minutes Information about the heart rate, rhythm and volume of blood could be gathered by palpating the pulse externally. Clinicians usually use Radial Pulse for this

Electrical activity of the Heart:

Electrical activity of the Heart Muscles contract by changing electrical potential across the membranes of their muscle fibers Therefore when the heart beats there is changing electrical activity of the heart Since body fluids and tissues are good conductors of electricity this changing electrical activity of the heart could be measured by electrodes on the body surface A graphical representation of this electrical activity is known as Electrocardiogram (ECG)

Echocardiogram (ECG):

Echocardiogram (ECG)

Self Study Questions?:

Self Study Questions? What is a heart attack? Name two anatomical parts of the heart affected in a heart attack?

Unit 5 - End of Part A:

Unit 5 - End of Part A

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