Living organisms are made up of cells .
This cells need oxygen and nutrients for their growth.
These are supplied through circulatory system.
In lower organisms like sponges and hydra circulation is through water but in higher organisms it through blood and lymph.
The entire heart is made of cardiac muscles. The walls of ventricles are much thicker than that of the atria. A specialised cardiac musculature.
Blood Group
Erythroblastosis foetalis: A special case of Rh incompatibility (mismatching) has been observed between the Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus. Rh antigens of the foetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta. However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small
amounts of the Rh+ve blood from the foetus. In such cases, the mother starts preparing antibodies against Rh antigen in her blood. In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the blood of the foetus (Rh+ve) and destroy the foetal RBCs. This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis.
This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.
Heart :Originated from embryonic mesoderm.
Situated in the thoracic cavity, in between two lungs, slightly tilted towards left.
It has the size of the clenched fist.
Heart is covered by a double walled bag, pericardium.
Our heat is four chambered, two relatively smaller upper chamber called atria and two lower larger chamber called ventricles.
Two atria are separated by thin muscular wall called inter-atrial septum.
A thick walled inter-ventricular septum separates two ventricles.
Atrium and ventricle of same side is separated by a thick fibrous tissue called the atrio-ventricular septum.
Each of atrio-ventricular septa is provided with an opening through which the atrium and ventricle of same side are connected, called atrio-ventricular opening.
Right atrio-ventricular opening is guarded by tricuspid valve.
Left atrio-ventricular opening is guarded by bicuspid or mitral valve.
The right ventricle opens into systemic aorta and left ventricle opens into pulmonary aorta.
Both the aorta is guarded by semilunar valves.
The valves in the heart allow unidirectional flow of blood i.e. from atria to ventricles and from ventricles to their respective aorta
Heart and circulation in vertebrates :
Fishes: have 2 chambered hearts with one atrium and one ventricle.Amphibian and reptilian (except crocodile) has three chambered heart with two atria and one ventricle.Crocodiles, birds and mammals possesses a 4-chambered heart with two atria and two ventriclesIn fishes the two chambered heart pumped deoxygenated blood to the gills for oxygenation and then circulated to the body. (single circulation)In amphibians and reptilians the left atrium receives oxygenated blood from the lungs and right atrium receives deoxygenated blood from the body. Blood from the atria pumped into the ventricle from which the mixed blood pumped into the body. (Incomplete double circulation).In birds and mammals oxygenated and deoxygenated blood received by left and right atria respectively passed into ventricle of their side. The ventricles pump it out without any mixing up. (double circulation)
DOUBLE CIRCULATION :
Pulmonary circulation: Right ventricle (deoxygenated blood) → pulmonary artery → lungs (oxygenation) → pulmonary vein (oxygenated blood) → left atrium.
Systemic circulation: left ventricle (oxygenated blood) → systemic aorta → body (deoxygenated) →vena cava (deoxygenated blood) → right atrium.
Portal system: the deoxygenated blood collected from one organ by means of a vein (portal vein) entered into another organ before it is delivered to the systemic circulation.
Hepatic portal system: the hepatic portal vein carries deoxygenated blood from the intestine to the liver before it is delivered to the systemic circulation by means of hepatic vein.
Coronary circulation: A special blood vessel (coronary vessel) is present in our body exclusively for the circulation of blood to and from the cardiac musculature.
Conducting system of human heart :
A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN).
Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrio-ventricular septum called the atrio-ventricular node (AVN).
A bundle of nodal fibres, atrioventricular bundle (AV bundle) continues from the AVN which passes
through the atrio-ventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle. These branches give rise to minute fibres throughout the ventricular
musculature of the respective sides and are called purkinje fibres.
These fibres alongwith right and left bundles are known as bundle of His. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable.
However, the number of action potentials that could be generated in a minute vary at different parts of
the nodal system.
The SAN can generate the maximum number of action potentials, i.e., 70-75 minñ1, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats minñ1).
Cardiac cycle :
wrist and to the left ankle) that continuously monitor the heart activity.
For a detailed evaluation of the heartÃs function, multiple leads are attached to the chest region. Here,
we will talk only about a standard ECG.
Each peak in the ECG is identified with a letter from P to T that corresponds to a specific
electrical activity of the heart.
The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria.
The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole.
The T-wave represents the return of the ventricles from excited to normal state (repolarisation). The end of the T-wave marks the end of systole.
Obviously, by counting the number of QRS complexes that occur in a given time period, one can determine the heart beat rate of an individual.
Since the ECGs obtained from different individuals have roughly the same shape for a given lead configuration, any deviation from this shape indicates a possible abnormality or disease. Hence, it is of a great clinical significance.
REGUALTION OF CARDIAC ACTIVITY :
Hypertension :
This cells need oxygen and nutrients for their growth.
These are supplied through circulatory system.
In lower organisms like sponges and hydra circulation is through water but in higher organisms it through blood and lymph.
Blood: A special connective tissue that circulates in principal
vascular system of man and other vertebrates.It consists of fluid matrix, plasma and
formed elements.
Plasma :The liquid part of blood which is straw coloured, viscous fluid constituting nearly 55 per cent of total blood.
90-92 percent of plasma is water and 6-8% organic and inorganic substances mainly proteins.
Fibrinogen, globulin and albumins are the major plasma protein found in bloodplasma.
Albumin and globulin helps in regulating osmotic balance of blood.
1Fibrinogen is required in blood clotting or coagulation of blood.
Globulins involved in defense mechanism of the body.
Albumin Plasma also contains small amounts of minerals, glucose, amino acids, lipids etc.
Plasma without the clotting factors is called serum.
Formed elements :
Erythrocytes :Also known as RBC (red blood cells) is the most abundant of all the cells of blood.
5 – 5.5 million RBC found per mm-3 of the blood.
Produced from the red bone marrow in the adult.
RBCs devoid of nucleus in most of mammals.
Biconcave in shape
Red in color due presence of complex conjugated protein called haemoglobin.
12-16 gm of haemoglobin present per 100 ml of blood in a healthy adult.
RBCs have average life span of 120 days after which is destroyed in the spleen.
Spleen is commonly known as the graveyard of RBCs.
Leukocytes :Also known as white blood cells (WBC).
They are colorless due to lack of haemoglobin.
They are nucleated and relatively lesser in number which averages 6000-8000 mm-3 of blood.
We have two main category of WBC;
Granulocytes
Neutrophils
Basophils
Eosinophils
Agranulocytes.
Lymphocytes
Monocytes.
Neutrophils (60-65%) of the total WBCs are phogocytic in nature.
Basophils (0.5-1 %), secretes histamine, serotonin and heparin and also involved in inflammatory reactions.
Eosinophils (2-3 %) resist infection and also associated with allergic reaction.
Lymphocytes (T cells and B cells) constitute 20-25 percent and involved in the immune response of the body.
Monocytes (10-15%), becomes macrophages.
Thrombocytes :Also known as blood platelets.
Produced from fragmentation of megakaryocytes.
Blood normally contain 1, 500, 00 – 3, 500, 00 platelets mm-3.
Involved in releasing thromboplastin required to initiate blood coagulation.
Plasma :The liquid part of blood which is straw coloured, viscous fluid constituting nearly 55 per cent of total blood.
90-92 percent of plasma is water and 6-8% organic and inorganic substances mainly proteins.
Fibrinogen, globulin and albumins are the major plasma protein found in bloodplasma.
Albumin and globulin helps in regulating osmotic balance of blood.
1Fibrinogen is required in blood clotting or coagulation of blood.
Globulins involved in defense mechanism of the body.
Albumin Plasma also contains small amounts of minerals, glucose, amino acids, lipids etc.
Plasma without the clotting factors is called serum.
Formed elements :
Erythrocytes :Also known as RBC (red blood cells) is the most abundant of all the cells of blood.
5 – 5.5 million RBC found per mm-3 of the blood.
Produced from the red bone marrow in the adult.
RBCs devoid of nucleus in most of mammals.
Biconcave in shape
Red in color due presence of complex conjugated protein called haemoglobin.
12-16 gm of haemoglobin present per 100 ml of blood in a healthy adult.
RBCs have average life span of 120 days after which is destroyed in the spleen.
Spleen is commonly known as the graveyard of RBCs.
Leukocytes :Also known as white blood cells (WBC).
They are colorless due to lack of haemoglobin.
They are nucleated and relatively lesser in number which averages 6000-8000 mm-3 of blood.
We have two main category of WBC;
Granulocytes
Neutrophils
Basophils
Eosinophils
Agranulocytes.
Lymphocytes
Monocytes.
Neutrophils (60-65%) of the total WBCs are phogocytic in nature.
Basophils (0.5-1 %), secretes histamine, serotonin and heparin and also involved in inflammatory reactions.
Eosinophils (2-3 %) resist infection and also associated with allergic reaction.
Lymphocytes (T cells and B cells) constitute 20-25 percent and involved in the immune response of the body.
Monocytes (10-15%), becomes macrophages.
Thrombocytes :Also known as blood platelets.
Produced from fragmentation of megakaryocytes.
Blood normally contain 1, 500, 00 – 3, 500, 00 platelets mm-3.
Involved in releasing thromboplastin required to initiate blood coagulation.
Blood Group
amounts of the Rh+ve blood from the foetus. In such cases, the mother starts preparing antibodies against Rh antigen in her blood. In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the blood of the foetus (Rh+ve) and destroy the foetal RBCs. This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis.
This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.
Heart :Originated from embryonic mesoderm.
Situated in the thoracic cavity, in between two lungs, slightly tilted towards left.
It has the size of the clenched fist.
Heart is covered by a double walled bag, pericardium.
Our heat is four chambered, two relatively smaller upper chamber called atria and two lower larger chamber called ventricles.
Two atria are separated by thin muscular wall called inter-atrial septum.
A thick walled inter-ventricular septum separates two ventricles.
Atrium and ventricle of same side is separated by a thick fibrous tissue called the atrio-ventricular septum.
Each of atrio-ventricular septa is provided with an opening through which the atrium and ventricle of same side are connected, called atrio-ventricular opening.
Right atrio-ventricular opening is guarded by tricuspid valve.
Left atrio-ventricular opening is guarded by bicuspid or mitral valve.
The right ventricle opens into systemic aorta and left ventricle opens into pulmonary aorta.
Both the aorta is guarded by semilunar valves.
The valves in the heart allow unidirectional flow of blood i.e. from atria to ventricles and from ventricles to their respective aorta
Heart and circulation in vertebrates :
Fishes: have 2 chambered hearts with one atrium and one ventricle.Amphibian and reptilian (except crocodile) has three chambered heart with two atria and one ventricle.Crocodiles, birds and mammals possesses a 4-chambered heart with two atria and two ventriclesIn fishes the two chambered heart pumped deoxygenated blood to the gills for oxygenation and then circulated to the body. (single circulation)In amphibians and reptilians the left atrium receives oxygenated blood from the lungs and right atrium receives deoxygenated blood from the body. Blood from the atria pumped into the ventricle from which the mixed blood pumped into the body. (Incomplete double circulation).In birds and mammals oxygenated and deoxygenated blood received by left and right atria respectively passed into ventricle of their side. The ventricles pump it out without any mixing up. (double circulation)
DOUBLE CIRCULATION :
Pulmonary circulation: Right ventricle (deoxygenated blood) → pulmonary artery → lungs (oxygenation) → pulmonary vein (oxygenated blood) → left atrium.
Systemic circulation: left ventricle (oxygenated blood) → systemic aorta → body (deoxygenated) →vena cava (deoxygenated blood) → right atrium.
Portal system: the deoxygenated blood collected from one organ by means of a vein (portal vein) entered into another organ before it is delivered to the systemic circulation.
Hepatic portal system: the hepatic portal vein carries deoxygenated blood from the intestine to the liver before it is delivered to the systemic circulation by means of hepatic vein.
Coronary circulation: A special blood vessel (coronary vessel) is present in our body exclusively for the circulation of blood to and from the cardiac musculature.
Conducting system of human heart :
A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN).
Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrio-ventricular septum called the atrio-ventricular node (AVN).
A bundle of nodal fibres, atrioventricular bundle (AV bundle) continues from the AVN which passes
through the atrio-ventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle. These branches give rise to minute fibres throughout the ventricular
musculature of the respective sides and are called purkinje fibres.
These fibres alongwith right and left bundles are known as bundle of His. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable.
However, the number of action potentials that could be generated in a minute vary at different parts of
the nodal system.
The SAN can generate the maximum number of action potentials, i.e., 70-75 minñ1, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats minñ1).
The cyclic
events takes place in each heart beat is called one cardiac cycle.
Lets starts with all the four chambers of heart are in a relaxed state i.e. in joint diastole.
As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and right ventricles respectively through left and right atria.
Semilunar valves are closed at this stage.
SAN generates the action potential which stimulates contraction of both atria, called atrial systole.
This increases the blood flow from atria to their respective ventricles by 30 %.
The action potential from SAN passed to AVN and then to perkinji fibres through AV bundles. This initiates ventricular systole. The atria undergo relaxation (diastole).
During ventricular systole the intra-ventricular blood pressure increases that lead to closing of tricuspid and bicuspid valves leads to production of first heart sound called lub sound.
Further increase in pressure leads to opening of semilunar valves.
Oxygenated blood from the left atrium pumped into systemic aorta and deoxygenated blood from the right atrium pumped into the pulmonary aorta.
Ventricular systole followed by ventricular diastole.
Intra-ventricular blood pressure decreases leads to closing of semilunar valves causing second heart sound (dub).
As the ventricular pressure declines further there is opening of bicuspid and tricuspid valves, blood from the atria flows into the ventricles freely.
The ventricle and atria relaxed simultaneously called joint diastole.
This sequential event in the heart which cyclically repeated called cardiac cycle.
The heart beats 72 times per minutes.
Each cardiac cycle takes 0.8 sec to complete.
During a cardiac cycle the ventricles pumped 70 ml blood to the aorta called stroke volume.
Stoke volume multiplied by heart rate (heart beat per min.) gives the cardiac output.
Cardiac out put for human heart is 5000 ml.
Lets starts with all the four chambers of heart are in a relaxed state i.e. in joint diastole.
As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and right ventricles respectively through left and right atria.
Semilunar valves are closed at this stage.
SAN generates the action potential which stimulates contraction of both atria, called atrial systole.
This increases the blood flow from atria to their respective ventricles by 30 %.
The action potential from SAN passed to AVN and then to perkinji fibres through AV bundles. This initiates ventricular systole. The atria undergo relaxation (diastole).
During ventricular systole the intra-ventricular blood pressure increases that lead to closing of tricuspid and bicuspid valves leads to production of first heart sound called lub sound.
Further increase in pressure leads to opening of semilunar valves.
Oxygenated blood from the left atrium pumped into systemic aorta and deoxygenated blood from the right atrium pumped into the pulmonary aorta.
Ventricular systole followed by ventricular diastole.
Intra-ventricular blood pressure decreases leads to closing of semilunar valves causing second heart sound (dub).
As the ventricular pressure declines further there is opening of bicuspid and tricuspid valves, blood from the atria flows into the ventricles freely.
The ventricle and atria relaxed simultaneously called joint diastole.
This sequential event in the heart which cyclically repeated called cardiac cycle.
The heart beats 72 times per minutes.
Each cardiac cycle takes 0.8 sec to complete.
During a cardiac cycle the ventricles pumped 70 ml blood to the aorta called stroke volume.
Stoke volume multiplied by heart rate (heart beat per min.) gives the cardiac output.
Cardiac out put for human heart is 5000 ml.
Electro-cardiograph
It is used to obtain an electrocardiogram (ECG). ECG is a graphical representation of the electrical activity of the heart during a cardiac cycle.
To obtain a standard ECGa patient is connected to the machine with three electrical leads (one to eachwrist and to the left ankle) that continuously monitor the heart activity.
For a detailed evaluation of the heartÃs function, multiple leads are attached to the chest region. Here,
we will talk only about a standard ECG.
Each peak in the ECG is identified with a letter from P to T that corresponds to a specific
electrical activity of the heart.
The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria.
The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole.
The T-wave represents the return of the ventricles from excited to normal state (repolarisation). The end of the T-wave marks the end of systole.
Obviously, by counting the number of QRS complexes that occur in a given time period, one can determine the heart beat rate of an individual.
Since the ECGs obtained from different individuals have roughly the same shape for a given lead configuration, any deviation from this shape indicates a possible abnormality or disease. Hence, it is of a great clinical significance.
REGUALTION OF CARDIAC ACTIVITY :
- Rhythmicity of human heart is regulated by specialized (nodal tissues), hence the heart is called myogenic.
- A special neural centre in the medulla oblongata can regulate cardiac function moderately.
- Neural signal through sympathetic nerve can increase the heart rate and cardiac output.
- Neural signal through parasympathetic nerve can decrease the heart rate and cardiac output.
- Hormones of adrenal medulla (adrenaline) also increase the cardiac output.
Hypertension :
- Hypertension is the term for blood pressure that is higher than normal (120/80).
- 120 mm Hg is the systolic pressure and 80 mm Hg is the diastolic pressure.
- Sustained blood pressure of 140/90 or higher is said to be hypertension.
- Blood pressure is measured by sphygmomanometer.
- High blood pressure leads to heart disease and also affects vital organ like brain and kidney.
- Often referred as atherosclerosis, affects the blood supply to the heart muscles.
- It is caused by deposition of calcium, fat, cholesterol and fibrous tissue which makes the lumen of coronary artery narrower.
- It is also known as ‘angina pectoris’.
- Causes acute chest pain due to inadequate oxygen supply to the heart.
- It occurs due to blockade to coronary artery.
- It is the state of the heart when it is not pumping blood effectively
- Cardiac arrest: the heart stops beating.
- Heart attack: heart muscle damaged suddenly by an inadequate blood supply to the heart muscles.
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