Lecture 2 - Circulatory System | Animal Physiology and Functional Histology-II - MBBS PDF Download

 Page 1


Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               0 
 
 
 
 
 
 
 
Subject: Zoology  
Lesson: Circulatory system 
Course Developer : Laxmi Narula 
College, Department: SGTB Khalsa College, University of 
Delhi 
 
Page 2


Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               0 
 
 
 
 
 
 
 
Subject: Zoology  
Lesson: Circulatory system 
Course Developer : Laxmi Narula 
College, Department: SGTB Khalsa College, University of 
Delhi 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               1 
 
Table of Contents 
? Introduction  
? Structure of Heart  
? Pericardium 
? Heart Wall 
? Working Cardiac Muscle Cells structure   
? Conducting system  
 
? Origin and conduction of  impulses 
? Sinoatrial node 
? Internodal pathways 
? Atrioventricular node 
? Bundle of HIS 
? Purkinje fiber 
? Ventricular  muscle fibers 
? One way conduction of impulses 
? Excitation conduction coupling 
 
? Coronary Circulation  
 
? Cardiac Cycle     
? Mid diastole  
? Late diastole 
? Early systole 
? Late systole 
? Early diastole 
 
? Cardiac Output 
? Definition 
? Stroke volume 
? Cardiac index 
? Factors that affect cardiac output 
? Exercise  
? Surface Area 
? Age  
? Sex 
? Methods to measure cardiac output 
? The Fick principle 
Page 3


Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               0 
 
 
 
 
 
 
 
Subject: Zoology  
Lesson: Circulatory system 
Course Developer : Laxmi Narula 
College, Department: SGTB Khalsa College, University of 
Delhi 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               1 
 
Table of Contents 
? Introduction  
? Structure of Heart  
? Pericardium 
? Heart Wall 
? Working Cardiac Muscle Cells structure   
? Conducting system  
 
? Origin and conduction of  impulses 
? Sinoatrial node 
? Internodal pathways 
? Atrioventricular node 
? Bundle of HIS 
? Purkinje fiber 
? Ventricular  muscle fibers 
? One way conduction of impulses 
? Excitation conduction coupling 
 
? Coronary Circulation  
 
? Cardiac Cycle     
? Mid diastole  
? Late diastole 
? Early systole 
? Late systole 
? Early diastole 
 
? Cardiac Output 
? Definition 
? Stroke volume 
? Cardiac index 
? Factors that affect cardiac output 
? Exercise  
? Surface Area 
? Age  
? Sex 
? Methods to measure cardiac output 
? The Fick principle 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               2 
 
? Dilution method 
? Control of cardiac out put 
? Stroke volume 
? Heart rate 
? Nervous control of Heart rate 
? Autonomic control 
? Cardiac reflexes 
? Chemical control of Heart Beat 
 
? Electrocardiogram (ECG) 
? Principle of Electrocardiography 
? Recording of electrocardiogram 
? Components of ECG 
? Blood circulation  
? Blood pressure 
? Definition 
? Measurement of blood pressure 
? Auscultatory metnod 
? Oscillometric method 
? Pulse pressure  
? Regulation of Blood pressure 
? Summary 
? Exercises 
? Glossary 
? References 
 
 
 
 
 
 
 
 
Page 4


Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               0 
 
 
 
 
 
 
 
Subject: Zoology  
Lesson: Circulatory system 
Course Developer : Laxmi Narula 
College, Department: SGTB Khalsa College, University of 
Delhi 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               1 
 
Table of Contents 
? Introduction  
? Structure of Heart  
? Pericardium 
? Heart Wall 
? Working Cardiac Muscle Cells structure   
? Conducting system  
 
? Origin and conduction of  impulses 
? Sinoatrial node 
? Internodal pathways 
? Atrioventricular node 
? Bundle of HIS 
? Purkinje fiber 
? Ventricular  muscle fibers 
? One way conduction of impulses 
? Excitation conduction coupling 
 
? Coronary Circulation  
 
? Cardiac Cycle     
? Mid diastole  
? Late diastole 
? Early systole 
? Late systole 
? Early diastole 
 
? Cardiac Output 
? Definition 
? Stroke volume 
? Cardiac index 
? Factors that affect cardiac output 
? Exercise  
? Surface Area 
? Age  
? Sex 
? Methods to measure cardiac output 
? The Fick principle 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               2 
 
? Dilution method 
? Control of cardiac out put 
? Stroke volume 
? Heart rate 
? Nervous control of Heart rate 
? Autonomic control 
? Cardiac reflexes 
? Chemical control of Heart Beat 
 
? Electrocardiogram (ECG) 
? Principle of Electrocardiography 
? Recording of electrocardiogram 
? Components of ECG 
? Blood circulation  
? Blood pressure 
? Definition 
? Measurement of blood pressure 
? Auscultatory metnod 
? Oscillometric method 
? Pulse pressure  
? Regulation of Blood pressure 
? Summary 
? Exercises 
? Glossary 
? References 
 
 
 
 
 
 
 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               3 
 
 Learning objectives 
? To describe the structure of heart as a pumping organ.   
? Its structural and functional components 
? Structure of heart wall and pericardium 
? Blood supply to the heart -coronary circulation 
? Describe the events of the cardiac cycle 
? Cardiac output and the factors that affect it. 
? Frank Starling law of heart 
? Nervous and chemical control of heart rate.  
? Electro cardiogram, its recoding and components 
? Blood pressure, its measurement and regulation 
 
Introduction 
Heart is a pumping organ of the circulatory system. It is mesodermal in origin and is of the 
size of a closed fist.  As the heart beats, it pumps blood through a system of blood vessels, 
which are elastic and muscular tubes .They  carry blood to every part of the body from the 
heart and back into it. 
Heart continuously pumps oxygen and nutrient-rich blood throughout the body to sustain 
life. It beats (that is expands and contracts) nearly 100,000 times per day  and pumps five  
to  six liters of blood each minute ( about 2,000 gallons per day).  
 It is the first organ that that becomes functional in a developing embryo. It is because all 
the living cells in the embryo or the adult body require continuous supply of oxygen, 
nutrients, heat, hormones and vitamins, and remove their metabolic end products. This 
function is performed by blood. Therefore, it is essential that the blood is circulating 
continuously for which it requires a pump.  Heart serves as a pump that imparts pressure to 
the blood to flow in vessels and reach cells. 
 
Structure of Heart 
All vertebrates have myogenic heart.  It is a hollow muscular organ about 300 g (250 – 450 
g) in weight.  In warm blooded animals, heart is four chambered consisting of two auricles 
and two ventricles. It is placed in between the two lungs in the mediastinum cavity. The 
human heart is blunt cone shaped. The base of the cone is formed by the atria that lie 
slightly towards the right. Nearly two third of the heart is towards the left of the midline of 
the body consisting mainly of the ventricles. The left ventricular tip forms the apex of the 
heart. 
Its total volume is 700 ml, of which 400 ml is formed by the muscles and 300 ml is lumen 
filled with blood.  The atrioventricular septum consists of valves that prevent the back flow 
of blood. Left side auricle is separated from the ventricle by bicuspid valve (Mitral Valve) 
and right side by tricuspid valve. Since these valves have either two or three cusps (cup) 
shaped depression towards the ventricular side. The valve between the aorta (left) and the 
pulmonary trunk (right) and the two ventricles are called semilunar valves as they are 
Page 5


Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               0 
 
 
 
 
 
 
 
Subject: Zoology  
Lesson: Circulatory system 
Course Developer : Laxmi Narula 
College, Department: SGTB Khalsa College, University of 
Delhi 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               1 
 
Table of Contents 
? Introduction  
? Structure of Heart  
? Pericardium 
? Heart Wall 
? Working Cardiac Muscle Cells structure   
? Conducting system  
 
? Origin and conduction of  impulses 
? Sinoatrial node 
? Internodal pathways 
? Atrioventricular node 
? Bundle of HIS 
? Purkinje fiber 
? Ventricular  muscle fibers 
? One way conduction of impulses 
? Excitation conduction coupling 
 
? Coronary Circulation  
 
? Cardiac Cycle     
? Mid diastole  
? Late diastole 
? Early systole 
? Late systole 
? Early diastole 
 
? Cardiac Output 
? Definition 
? Stroke volume 
? Cardiac index 
? Factors that affect cardiac output 
? Exercise  
? Surface Area 
? Age  
? Sex 
? Methods to measure cardiac output 
? The Fick principle 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               2 
 
? Dilution method 
? Control of cardiac out put 
? Stroke volume 
? Heart rate 
? Nervous control of Heart rate 
? Autonomic control 
? Cardiac reflexes 
? Chemical control of Heart Beat 
 
? Electrocardiogram (ECG) 
? Principle of Electrocardiography 
? Recording of electrocardiogram 
? Components of ECG 
? Blood circulation  
? Blood pressure 
? Definition 
? Measurement of blood pressure 
? Auscultatory metnod 
? Oscillometric method 
? Pulse pressure  
? Regulation of Blood pressure 
? Summary 
? Exercises 
? Glossary 
? References 
 
 
 
 
 
 
 
 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               3 
 
 Learning objectives 
? To describe the structure of heart as a pumping organ.   
? Its structural and functional components 
? Structure of heart wall and pericardium 
? Blood supply to the heart -coronary circulation 
? Describe the events of the cardiac cycle 
? Cardiac output and the factors that affect it. 
? Frank Starling law of heart 
? Nervous and chemical control of heart rate.  
? Electro cardiogram, its recoding and components 
? Blood pressure, its measurement and regulation 
 
Introduction 
Heart is a pumping organ of the circulatory system. It is mesodermal in origin and is of the 
size of a closed fist.  As the heart beats, it pumps blood through a system of blood vessels, 
which are elastic and muscular tubes .They  carry blood to every part of the body from the 
heart and back into it. 
Heart continuously pumps oxygen and nutrient-rich blood throughout the body to sustain 
life. It beats (that is expands and contracts) nearly 100,000 times per day  and pumps five  
to  six liters of blood each minute ( about 2,000 gallons per day).  
 It is the first organ that that becomes functional in a developing embryo. It is because all 
the living cells in the embryo or the adult body require continuous supply of oxygen, 
nutrients, heat, hormones and vitamins, and remove their metabolic end products. This 
function is performed by blood. Therefore, it is essential that the blood is circulating 
continuously for which it requires a pump.  Heart serves as a pump that imparts pressure to 
the blood to flow in vessels and reach cells. 
 
Structure of Heart 
All vertebrates have myogenic heart.  It is a hollow muscular organ about 300 g (250 – 450 
g) in weight.  In warm blooded animals, heart is four chambered consisting of two auricles 
and two ventricles. It is placed in between the two lungs in the mediastinum cavity. The 
human heart is blunt cone shaped. The base of the cone is formed by the atria that lie 
slightly towards the right. Nearly two third of the heart is towards the left of the midline of 
the body consisting mainly of the ventricles. The left ventricular tip forms the apex of the 
heart. 
Its total volume is 700 ml, of which 400 ml is formed by the muscles and 300 ml is lumen 
filled with blood.  The atrioventricular septum consists of valves that prevent the back flow 
of blood. Left side auricle is separated from the ventricle by bicuspid valve (Mitral Valve) 
and right side by tricuspid valve. Since these valves have either two or three cusps (cup) 
shaped depression towards the ventricular side. The valve between the aorta (left) and the 
pulmonary trunk (right) and the two ventricles are called semilunar valves as they are 
Circulatory System 
                          Institute of Life Long Learning, University of Delhi                               4 
 
crescent shaped when closed. All the valves help in the unidirectional flow of blood with in 
the heart. 
 
Fig. Anterior view of opened heart (semidiagramatic) 
Source: http://www.sharinginhealth.ca/biology/cardiovascular.html(creative 
commons) 
 
Pericardium 
Heart and the great vessels entering and leaving it are enclosed in the    double walled sac 
called pericardium. The pericardial sac consists of two layers : 
 (i) Fibrous pericardium    
(ii) Serous pericardium.  
 
? Fibrous pericardium: It consists of very heavy fibrous connective tissue and prevents 
heart from over distension and also anchors it in the mediastinum  
 
?  Serous pericardium: It is made up of two layers, the parietal pericardium and the 
visceral pericardium. These layers are separated by a pericardial cavity that is filled with 
the pericardial fluid. The parietal pericardium is inseparably fused to the fibrous 
pericardium. The epicardium of the heart wall is made by visceral pericardium. The 
visceral layer (becoming one with the parietal layer) extends where the aorta and 
pulmonary trunk leave the heart and the superior and inferior vena cava and pulmonary 
veins enter into the heart.