Circulatory System, Chapter Notes, Class 11, Biology PDF Download

CIRCULATORY SYSTEM

INTRODUCTION

Each and every cell of the body requires consistent supply of O2, food etc. for energy. Similarly toxicsubstances like CO2, ammonia, urea, uric acid are needed to get removed from the body. In lower organism cell is in direct contact of surrounding medium and there is direct exchange of material in between cell and the medium so, circulatory system is not needed. In higher and multicellular organism due to its complex
form a specialized system is needed to supply useful, substance to the body cell and to remove, harmful substance out of the body. This specialized, system is called circulatory system. Components involved in circulatory system originate from mesoderm of embryo. Except the inner lining of blood vessels and capillaries which are endodermal in origin.

TYPES OF CIRCULATION

Numerous types of fluid circulation are found in animals which are as follows-

1. Intracellular circulation

(i) Streaming movement of the cytoplasm which is called cyclosis is the intracellular circulation.
(ii) In all living cells and unicellular organism intracellular circulation is found.
(iii) Cyclosis helps in uniform distribution of material like O2, food within the cell.
(iv) It also plays important role in amoeboid locomotion found in certain protozoans like Amoeba and  WBC.

2. Extracellular circulation

(i) Circulation which occurs outside of the cell is called extracellular circulation.
(ii) Such type of circulation is found in multicellular organism.
It is of numerous types which are as follows-

Water circulation : Such type of circulation is found in sponges and Hydra.

Parenchymal circulation : Such type of circulation is found in flatworm.

Pseudocoelomic fluid circulation : Such type of circulation is found in roundworm.

Blood vascular system

(i) Blood vascular system is present in higher invertebrates from the Annelida to the Echinodermata and
all the Chordates.
Note :
(I) Annelida are the 1st metazoans to have a well developed circulatory system.
(II) Nereis among Annelida and Amphioxus among the Chordata have well developed circulatory system but lacks heart.
The blood vascular system may be open or closed circulatory system.

I- Open circulatory system

(i) When the circulating fluid is present in a central cavity called Haemocoel or it flows into spaces called sinuses in the tissue, it is termed as the open circulatory system.
(ii) Animals in which circulatory system is open are Arthropoda (Prawn, lobsters, crabs, insects and spiders)and Mollusca (snails, oysters).

II- Closed circulatory system

(i) When the blood remains confined to the blood vessel it is called closed circulatory system.
(ii) In invertebrate, closed circulatory system is found in some annelida like earthworm and some mollusca like, squid.
(iii) In all vertebrate animals closed circulatory system is found.
(iv) The circulation of blood in the closed circulatory system was at first discovered and demonstrated by William Harvey who is known as father of angiology. He called heart as the ''Pumping station of body''

(1) Blood circulatory system : It consist of : - Blood, Bloood vessels, Heart.
(2) Lymphatic system : It consist of lymiph, lymph capillaries, lymph vessels, lymph nodes, lymphoid tissues/ organs

The study of blood vascular system or circulatory system is called-Angiology.

PHYSIOLOGY OF BLOOD CIRCULATION

GENERAL FACTS

(i) Physiology of blood circulation was at first described by Sir William Harvey.
(ii) Study of circulatory system is called Angiology. William Harvey is called father of Angiology.
(iii) There are two types of heart circuit in vertebrates single heart circuit and double heart circuit.
(iv) Single heart circuit is found in fishes having two chambered called venous heart.
The heart of fishes is called venous because heart receives and pumps only deoxygenated blood to gills for oxygenation.
(v) Double heart circuit is found in birds and mammals due to complete division of ventricle.
(vi) Double circulation means blood passess twice through the heart to supply once to the body. Double

circulation involves two circulation which are as follow :

SYSTEMIC CIRCULATION
(i) In this type of circulation, blood completes its circulation from left ventricle to right auricle through body organs.
(ii) From the left ventricle blood is pumped into the aorta and then to various part of the body (except lungs)

Deoxygenated blood from these organs is returned to the right auricle through two large veins superior and inferior vena cava. From right auricle blood comes to right ventricle.

PULMONARY CIRCULATION

(i) In this type of circulation blood completes its circulation from right ventricle to left auricle through lungs.
(ii) From right ventricle deoxygenated blood is pumped into pulmonary arch which carries blood to the
lungs for oxygenation. From lungs oxygenated blood is carried to left auricle by four pulmonary veins.
Left auricle pumps the blood to the left ventricle.

DOUBLE CIRCULATION OF HEART
 

HEART

STURCTURE OF HEART

Position, Size and Shape

(i) Human heart is thick, muscular, contractile, reddish brown, contractile automatic pumping organ.
(ii) It is present in the mediastinal space of thoracic cavity in between the lungs.
(iii) Human heart 12 cm in length and 9 cm in breath.
(iv) Its weight varies in males from 280-340 gm and in female from 230-280 gm.
(v) Its upper part is broader called base whereas, its lower part is pointed called apex. The apex is slightly directed to left
(vi) It is covered by a two layered sac called pericardium. Outer layer is called parietal pericardium and inner layer is called visceral pericardium in between two layers pericardial cavity is present which is filled with pericardial fluid.

The pericardial fluid keeps the outer surface moist, protects the heart from mechanical injury and shock, it also allows free movement of the heart.

The heart of rabbit or man is four chambered with 2 auricles and 2 ventricles. It is pinkish in colour and conical in shape. The broad upper part of heart is called auricular part or base and lower conical part is called ventricular part (Its tip is called apex.)

In between the auricles and ventricles, a clear groove is present, which is known as coronary sulcus. This groove is more towards auricles, by the effect of this the auricular surface is smaller than ventricles.
(a) Auricles - Auricular part of heart is smaller and of dark colour. Its walls are thin. It is divided into right and left auricles by fissure called interauricular sulcus, which is shifted slighty towards left. Therefore out of these two, right auricular surface is bigger than left auricle.

(b) Ventricles - Ventricular part is broad, muscular and of light colour. Ventricles have thicker walls than auricles.
The grooves which divide the two ventricles are termed as Inter-ventricular groove or sulcus. It is obliqu or tilted towards Right. It does not reach till the tip or apex of the heart, So the right ventricle is smaller than the left ventricle.

Left ventricle is more muscular and got more thick walls as compared to right ventricle because it has to pump blood into those arteries which take blood thoughout the body while right ventricle has to pump blood only to the lungs.

Systemic heart - Left part of the heart (i.e. left auricle and left ventricle) contains the blood whichis to be pumped into the systemic circulation, therefore it is called systemic heart. The main purpose of such a circulation is to transport oxygen, as well as nutrients to the body tissues, and to removecarbondioxide and other harmful nitrogenous waste from them.

Pulmonary heart - Right part of the heart (i.e. right auricle and right ventricle) contains the blood which is to be pumped in pulmonary circulation for oxygenation, therefore it is called pulmonary heart.
The pulmonary circulation is responsible for regular oxygenation of the impure deoxygenated blood which is received by the right auricle.

Blood supply of heart (Coronary circulation)
The oxygenated blood is supplied to the heart musculature for its consumption with the help of two coronary arteries, left and right. These arteries arise from the common origin at arch of aorta. the left and right coronary arteries then further subdivide into a number of branches carrying blood to different regions of heart. The impure blood from heart wals return back via coronary veins which drain into the coronary sinus. The coronary sinus opens in the right atrium.

Ischemic heart diseases

If the lumen of any of the coronary artery gets narrowed due to obstruction or cholestrol deposition, the cardiac tissues enter a condition of more demand and less supply whenever the person performs exhertion.

Under such hypoxic conditions a pain might arise in heart muscles, this condition is called Angina Pectoris. This condition is reversible when the demand supply ratio is restabilised. (i.e. when the person stops exhertion and rests). A coronary artery by pass grafting (CABG) may be required to provide additional channel of blood suppply in such cases.
In coronary artery By pass grafting a part of internal mammary artery or a segment of patients own saphenous vein is used as the By pass channel.
Myocardial Infarction (M.I.) - This is cellular death of cardiac tissue due to anoxia.
When the blood supply to the heart completely stops due to complete block of a coronary artery, under reduced oxygen condition the heart tries to restablish the blood supply by working even harder, thus aggravating the situation even further. Due to this reason the cardiac tissue starts dying by necrosis and myocardial infarction sets in, this is an irreversible condition. It is also called as HEART ATTACK in common language.

A blockage of left anterior descending artery (LAD) can be most fatal for the heart, (widows artery)

Internal Structure of Heart

The internal structrue of heart is discussed under following headings.

1. Cut section of heart :

The wall of heart is made of three layers, from outside inwards :
(i) Epicardium - outermost layer, mesodermal in origin. Made of simple squamous epithelium.
(ii) Myocardium - middle layer, thickest, mesodermal. Made of cardiac muscles which are striated but involuntary.
(iii) Endocardium - innermost layer, endodermal in origin. Made of simple squamous epithelium.

2. Partitions of heart :

Interauricular septum – it is a partition between the left and right auricles. It is shifted slightly towards left, so the Right auricle is slightly broader than left. An oval depression (Fossa Ovalis) is present on its Posterior part. It is remainant of foramen ovale present in fetal stage which closes at birth. In fetal circulation the lungs are non functional and by-passed so the blood directly reaches the It. Atrium from rt. Artium through foramen ovale.

Interventricular septum – it is separates the two ventricles. It is shifted slightly towards right. Therefore left venrticle is larger than right ventricle.

Auriculoventricular septum – it separates the two auricles from the two ventricles. It is shifted upwards towards Auricles. Therefore auricles are samaller than ventricles.

3. Chambers
The mammalian heart has four chambers.
(i) Right Auricle or Atrium - Inlet : it receives on S.V.C., one I.V.C. and one opening of coronary sinus in man. (it receives two S.V.C(rt. & It.) in case of rabbit).
SVC = superior vena cava = anterior vena cava =precava ; IVC = inferior vena cava = posterior vena cava = post cavals.

The SVC & IVC bring impure blood from the upper and lower body parts respectively. The Coronary sinus receives impure blood from the rt. & It. Coronary veins and drains it in the right auricle
Outlets : this impure blood drains through the right AV foramen into the right ventricle

(ii) Right ventricle - Inlets : receives impure blood through right AV foramen from right auricle .

Outlets : drains the impure blood into pulmonary artery through which it reaches lungs for oxygenation.

(iii) Left Auricle - Inlets : receives oxygenated blood from lungs via pulmonary vein Outlets : this pure blood is drained into left ventricle through left AV foramen.

(iv) Left Ventricle - Inlets : receives pure blood through left AV foramen from left auricle 

Outlets : drains pure blod into the Aorta from where it is supplied to systemic organs.

4. Walls

Auricles - The inner wall surface here presents a series of transverse muscular ridges called musculi pectinati. They run forwards and downwards towards AV foramen, giving appearance of the

teeth of a comb (combed muscles).

Ventricles - The inner wall is rough due to presence of muscular ridges trabeculae carnae or columnae

carnae. These continue as papillary muscles, whose one end is attached to the ventricular wall and the other end is connected to the cusps of AV valves by chordae tendinae. These chorda tendinae are collagenous and inelastic chords one end of which is inserted in the papillary muscles and other end is connected to the flaps of AV valves. These are meant for preventing the pushing of flaps into atrium during ventricular contraction

5. Valves

Rt. Atrium - All its inlets are guarded with valves to prevent backflow of the blood. The SVC opening is said to be guarded by Haversion valve (absent in rabbit). The IVC which opens below this has its opening guarded by a valve called Eustachian valve (during embryonic life the
valve guides the inferior vena caval blood to the left auricle through foramen ovale) The opening of coronary sinus in rt. Atrium is guarded by Thebesian valve.

Lt. Atrium - At its inlet is pulmonary vein (four veins in man and two in rabbit), these have no guarding valve.

AV formen - The right AV foramen has a unidirectional valve called tricuspid valve (made of three flaps or cusps) which allows entry of Blood from

Rt. Atrium to Rt ventricle and prevents its backflow. The unidirectional valve present on left AV foramen is made of two cusps only,
hence called bicuspid valve. (also called as the Mitral valve).
Rt. Ventricle - Its outlet is in the pulmonary artery. It is guarded by a pulmonary semilunar valve
Lt. Ventricle - Its outlet is in the systemic aorta. This opening is guarded by an aortic semilunar valve.
Both these semilunar valves are made of three cusps each and are unidirectional in nature.
From the two ventricles the pulmonary artery & systemic aorta arise out in the form of arches (called as
pulmonary and systemic arches). These arches cross each other, and at the point of crossing they are
attached by ligamentum arteriosum. Ligamentum arteriosum is the remainant of ductus arteriosus.
ductus arteriosus is a small channel connecting the lumen of the two arches which gets closed at the time of birth.

CONDUCTION PATHWAY

The Conducting system of Heart

It is made of myocardium that is specialised for initiation and conduction of the cardiac impulse. Its fibres are finer than other myocardial fibres, these are completely cross striated and posses special nerve like properties (= self excitatory neuromuscular pathway).

The conducting system has the follwoing parts.

Rate of conduction is fastest in bundle of His and slowest in AV node
(1) Sinuatrial node (SA node). It is known as the ''pacemaker'' of the heart. Located in the wall of Rt.
Atrium it generates impulses at the rate of about 72 per minute. and initiates heart beat.

(2) Internodal pathway. it is the network of neuromuscular pathway that connects the SA node to the AV node.

(3) Atrioventricular node (AV Node). It is smaller than SA node and is situated in the atria near AV septum. It capable of generating impulse at rate of about 40/mt.

(4) Bundle of His (AV Bundle) . it is the connection between the atrial and ventricular musculature. It begins at the AV node and then divides into left and right branches as it descends down towards ventricles.

The left branches of the AV bundle descends on their respective side of the interventricular septum and is distributed to the ventricles after dividing into Purkinje fibres.

(5) The Purkinje fibres. These are distributed through the endocardium of the ventricles and propogate the impulse in the entire ventricle musculature.

Why SA node is called the pacemaker of the heart ?
Although impulse is produced by the entire neuromuscular pathway, the frequency of impulse generation is maximum is case of SA node in comparison to other parts of pathway. Hence it guides the rhythm of heart beat and is called the pacemaker of the heart. The AV node on the other hand just conducts the impulse forwards.

WORKING OF HEART

Heart Beat

Rhythmic contraction and expansion of heart is called heart beat. Actually, contraction and expansion occur separately in atrial and ventricle. however, ventricular movements are quite prominent and forceful. Therefore,heart beat is synonym with ventricular or apex beat. The rate of heart beat in an adult male is on the averge 72 per minute. It is higher in women, children and infants and lower in aged persons. it increases
temporarily with activity and disease. In animals heart beat is connected with size. In mammals, smaller animals have higher heart beat is only 28/min in elephant. In frog heart beat is 64/mt. It is maximum among mammals in shrew (800/mt) and minimum in Bluewhale (25 per min).
Heart beat is entirely controlled by nervous supply in arthopods and some annelids. It is called neurogenic heart beat and the heart is called neurogenic heart. In molluscs and vertebrate heart beat originates from a special muscular tissue. Such a heart beat is called myogenic heart beat and this is called myogenic heart. Human heart is myogenic.

Differences between Neurogenic and Myogenic Hearts

Each heart beat has two components, systole and diastole. Systole represents contraction while diastole
represents expansion or distension of heart chambers.
heart beats are listened with the help of an instrument called stethoscope (invented by Laennec).

REGULATION OF HEART BEAT

The rate of heart beat is regulated by two mechanism.
– Nervous regulation – Hormonal regulation

NERVOUS REGULATION

The cardiac centre lies in the upper part of ventral wall of the medulla oblongata.
Cardiac centre is composed of-
– Cardioinhibitory centre (CIC) – Cardioacceleratory centre (CAC)

Cardioinhibitory centre
(i) It decreases rate of heart beat.
(ii) The cardio-inhibitor is connected with SA node through vagus nerve or parasymphathetic nerve fibre.
(iii) It decreases the rate of heart beat (about 20 to 30 times/minute) as well as strength of heartbeat (by
20 to 30 percent).
Cardioacceleratory centre
(i) It accelerates the rate of heart beat.
(ii) Cardio acceleratory centre is associated with SA node through sympathetic nerve fibre.
(iii) It increase rate of heart beat.

HORMONAL REGULATION

(i) Heart beat is mainly regulated by adrenaline (epinephrine) and non adrenaline (nor epinephrine).
Both hormones are secreted by medulla of adrenal gland.

(ii) Nor adrenaline and adrenaline both accelerate the rate of heart beat but operate in different conditions.
Adrenalin increase the heart beat during emergency conditions, whereas non adrenaline increase the heart beat during normal conditions.

Note :

Thyroxine hormone indirectly increase the heart beat because thyroxine increases oxidative metabolism of the body cell, so body cells require more oxygen.

Neurogenic Heart Myogenic Heart

1. Impulse of heart beat comes from outside The impulse of heart develops within the heart. heart.
2. Impulse is generated by nervous system. Impulse is generated by a special muscular tissue.
3. Nerve fibres are spread over the heart to bring There are special conducting muscles fibres for about contracton and expansion. spreading the impulse.
4. Heart will stop beating if removed from the It will continue to beat for some time, if detached body heart is supplied with proper nourishment and
favourable conditions.
Tachycardia. It is the condition where heart rate exceeds 90 per minute for an average adult.

Common causes of tachycardia :

(i) Tachycardia. Rate of heart beat increases. Fever causes tachycardia because increased body temperature increases the rate of metabolism of the sinus node, whihc in turn directly increases its excitability and rhythm.

(ii) Stimulation by sympathetic nerves. Stimulation of the sympathetic nerves releases the hormone norepinephrine at the sympathetic nerve endings. Therefore this leads to increase in the heart rate.

(iii)Weak condition of the heart. Weakening of the myocardium usually increases the heart rate because the weakened heart does not pump blood into the arterial tree to a normal extent, and this
causes sympathetic reflexes to increase heart rate.
(iv) Circulatory Shock/loss of blood. When a patient looses and passes into a state of shock or semishock, reflex stimulation of heart occurs which increases the frequency of heart beat to compensate for less delivery.

(v) Exercise. Physical exhertion cause in increased consumption of oxygen by tissues. In order to meet the increased demand the heart has to work faster.
(vi)Sinus tachycardia. Increased frequency of impulse discharges from the SA node will in run increase the heart rate.

Bradycardia. It is the condition where the heart rate falls below 60 per minute in an average adult.

Common causes of bradycardia :

(i) Temperature. Fall in body temperature leads to fall in the rate of SA node metabolism, which in turn reduces its Excitability and rhythm.
(ii) Stimulation by parasympathetic Vagus. Parasympathetic stimulation of acetylcholine secreted by vagus has an inhibitory effect on the SA node. (opposite phenomenon of sympathetic stimulation occurs here).

(iii)Stronger condition of the heart. The athelete's heart is considered stronger than that of a normal person. This allows it to pump greater stroke volume output per heart beat. When the athelete is at rest, this exessive quantity of pumped blood causes a negative feed back response resulting in bradycardia when he is at rest.

(iv)Rest. When at rest or sleeping, the oxygen demand of body is lesser this gives a negative feedback resulting in fall in heart rate.
(v) Sinus bradycardia. Peduced frequency of impulse discharge from SA node will reduce the heart rate.

The ratio of heart rate to respiratory rate in an average adult under normal circumstances is

CARDIAC CYCLE

The cardiac events that occur from the begining of one heart best to begining of the next are called cardiac cycle. The action potential travels rapidly through both atria and then through the AV bundle into the all of ventricles. Because of special arrangement of the conducting system from the atria to the ventricles, there is a delay of more than 1/10th a second between passage of the cardiac impulse from the atria into
the ventricles. This allows the artia to contract ahead of the ventricles, there by pumping blood into the ventricles before the strong ventricular contraction begins.

Thus the artria are the primer pumps for the ventricles, and ventricles then provide the major source of power for moving blood through the vascular system.
Cardiac-Cycle - The process of heart-beat begins from the time of embryonal development. Once the heart beat starts, it continues throught out the life. In resting stage of man in 1 minute the heart beats around 72 times and during this 1 minute, 5 litres of blood is pumped to different parts of the body through heart through left ventricle.

The serial wise or sequential changes which takes place in the heart are called cardiac-cycle.
The contraction of the auricles is termed as Auricular systole or Atrial-systole, and their relaxation is called Atrial diastole.

Same way the contraction and relaxation of ventricles is termed as ventricular systole and ventricular Diastole.

The time of cardiac-cycle is the reverse ratio of heart beat per minute. If heart beat per minute is 72, then the time of cardiac-cycle is 60/72 = 0.8 seconds.

Joint Diastole. 8 – .4 = 4 sec. (Period during which entire heart is in Diastole)

Following events are related to the Cardiac-cycle -
Common diagram showing events of both auricle & ventricles
In a single cardiac cycle of man -
(1) Auricular systole = 0.1 sec
(2) Auricular diastole = 0.7 sec
(3) Ventricular systole = 0.3 sec
(4) Ventricular diastole = 0.5 sec

Ventricle

(1) ''Ventricular-systole'' - It is important process because during it the blood is pumped out of the heart into the arteries. It has four main parts.

(a) ''Isometric-contraction'' - Walls of the ventricles start contracting, due to which pressure is more in the ventricles. Due to the increase of this pressure the '' Cuspid valves'' close producing ''LUBB'' sound.

(b) ''Period of Ejection'' - During this cycle when pressure increases in the ventricles, then the semilunar valves of the arches open and blood rapidly enters into the arches pushing the valves on one side.

Oxygenated blood from the left-ventricle enters into the caotico-systemic arch or aorta and deoxygenated blood from the right-ventricle enter into the pulmonary-arch.

(c) ''Protodiastole'' - Due to the ejection of blood from the ventricles now the inter-ventricular pressure decreases and the rate of blood ejection from the ventricles also decreases.

(d) ''Isometric Relaxation'' - When due to blood-ejection, the pressure inside the ventricles decreases as compared to the pressure inside the arches. The blood stops moving out and the ventricles prepare for relaxation.

(2) ''Ventricular Diastole'' - Ventricular start relaxing now due to which pressure inside them falls further.
As a result of this, closure of semilunar valves occurs due to which 'DUP' sound is heard at the onset of ventricular diastole.

Ventricular-diastole has two sub-stages -

(a) ''Rapid in-flow'' - After the systole in the ventricles the systolic pressure reduces very much. This pressure becomes very less than atrial-pressure. Moreover due to relaxation in ventricles the pressure inside them falls further. So, now the cuspid-valves open up and bood flows rapidly from the auricles to the ventricles.

(b) ''Diastasis'' - After rapid in flow, the auricles transfer the blood to the ventricles at the same rate at which they receive blood from the veins. So the inflow of blood reduces considerably. At this moment pressure inside all four chambers is equal and entire heart is in diastole. Also at this moment of this time, the AV valves are open but semilunar valves are closed.

(3) ''Auricle-Systole'' - Due to contraction in the auricles the remaining blood comes into the ventricles so the Artrial pressure now becomes zero.

(4) ''Auricle-Diastole'' - Auricle start relaxing now. Due to the presence of almost zero pressure in the auricles, the auricles now start receiving further blood from the veins.
Volumes of blood related with cardiac cycle.
During diastole, filling of the ventricles normally increases the volume of each ventricle to about 120 mililitres. This volume is known as end diastolic volume. Then as the ventricles empty during systole, the volume decrease by 70 mililitres, which is called the stroke volume. (i.e. the volume of blood pumped by left ventricle in the aorta in one stroke or beat). The remaining volume in each ventricle is now about 50 mililitres and is called end systolic volume.
The fraction of the end diastolic volume which is ejected out is called the ejection fraction. (usuallyaround 60% or 7/12). EF = SV/EDV

Cardiac output it is the amount of blood pumped by the left ventricle in the aorta in a minute. Itsvalue in a normal adult is about 5 litre/minute.
Cardiac output = stroke volume x heart rate.

End diastolic volume 120 ml.
End systolic volume EDV – SV = 50 ml (approx)

Stroke Volume = EDV– ESV = 70 ml (approx)

Filling of Heart (Ventricles) :

Blood normally flows from the great veins into the atria. About 75% of the blood flows directly through the atrial into the ventricles even before the atria contracts. Then atrial contraction usually causes an additional 25% filling of the ventricles.

The period of Atrial Systole – Fills 25 % of ventricles.
The period of Atrial Diastole fills 75% of ventricles.

Distribution of blood in Body

HEART-SOUND

(1) Ist Sound – This is a contraction sound which denotes the begining of ventricle-contraction. it arises due to closing of mitral vave and the tricuspid valve. It is weak and appears in the form of ''Lubb'' (L - U - B - B )

(2) IInd Sound – This is a diastolic sound which denotes the beginning of ventricular diastole. This arises due to the closing of the semi-lunar valves of the two arches and is heard in the form of ''Dup'' . It is shriller than the Ist sound and takes less time.

These ''Lubb'' and ''Dup'' sounds of the heart can be heard with the help of an instrument called ''Stethoscope.''

The study of heart-sounds by marking them on a Graph is termed as ''Phona-Cardiography''
The measurement of the electrical-activity of the cardiac muscles at the time of heart-beat is necessary for the healthy working of the heart. The transmission of impulses in the sarcolemma of cardiac muscle fibres is in the form of electro-chemical waves.

First stage - 70% (Rapid inflow)
Diastolic filling Second stage - 5% (Diastasis)
of ventricle Last stage - 25%(due to atrial contraction)
Systemic – 84% Pulmonary – 9%
Arteries – 13%
Veins – 64% HEART – 7%
Capillaries – 7%
&
Arterioles
Distribution of Blood Flow in various organs at rest in Man
Brain – 700 ml/mt (14%) approx
Heart – 300 ml/mt (7%)
Muscles – 1200 ml/mt (20%)
Skin – 500 ml/mt (8%)
Kidney – 1100– 1300 ml/mt (20–25%)
Abdominal organs – 1400 ml/mt (20–25%)
Others – 600 ml/mt (10%)
Total 5800 ml/mt 100%

The graph which is marked by the machine due to the voltage difference is termed as the ''E.C.G.'' ''or''
Electro Cardio Gram'' and this process is termed as ''Electro Cardio Graphy''
It was first of all recorded by ''Waller''
''Einthovan'' is known as the father of Electro Cardio Graphy.

NORMAL ELECTROCARDIOGRM (E.C.G.)

An electrocardiogram records electrical activity of the heart. The impulse travelling in the neuromuscular pathway of the heart is conduced to the wall of heart musculature where it gets amplified and part of it leaks via the pericardium to the skin surface. The leaked current is picked up with help of electrode and amplified. A time voltage graph of this current is then plotted which is called the E.C.G It is taken with help of 12 leads, placed at different positions on body Components of a normal ECG Waves

''P'' wave – it represents auricular depolarisation which is follwed by auricular contraction. Its first half represents Rt. Auricle and second half represents left auricle.

''QRS complex'' – it represents ventricular depolarisation which is followed by ventricular contraction

''T'' wave – it represents ventricular repolarisation during which the ventricles relax Intervals

P-Q interval – time period between start of auricle depolarisation and ventricular depolarisation (also called

P-r interval, it lasts normally for 0.16 seconds)

S-T interval – time period between ventricular depolarisation and ventricular repolarisation.

P-P, R-R inverval : The interval between any two successive similar wave denotes time taken for one heart beat.

BLOOD PRESSURE

DEFINITION

It is the pressure exerted by flow of blood on the wall of blood vessels (arteries).

TYPES

Arterial blood pressure is of two types :

Systolic blood pressure

(i) It is the pressure which the blood exert on the wall of arteries at the time of ventricular contraction (systole).
(ii) In normal adult person at resting condition it is about 120 mm of Hg .
(iii) It is higher limit of arterial blood pressure.

Diastolic blood pressure

(i) It is the pressure which the blood exert on the wall of arteries at the time of relaxation (diastole) of ventricle.
Blood pressure in normal person is 120/80 mmHg.
Note :
The difference between systolic and diastolic pressure is called pulse pressure. Its normal value is 40 mmHg.

MEASUREMENT OF BLOOD PRESSURE

(i) Blood pressure is measured by an instrument called Sphygmomanometer.

(ii) It was discovered by Karat koff in (1905).

(iii) At first Hales measured B.P. of horse.

FACTOR INFLUENCING THE BLOOD PRESSURE

(i) Increase in Age - B.P. increase
(ii) Thickening of arteries - B.P. increase
(iii) Due to obesity - B.P. increase
(iv) Constriction of blood vessel - B.P. increase
(v) Due to fear, tension, anxiety, B.P. increase.

PULSE

(i) Pulse is the rhythmic contraction and relaxation in aorta and its main arteries.
(ii) It is wave of contraction started in the aorta and travels down to the wall of the arteries.
(iii) Pulse rate will be exactly equal to the heart beat, so the pulse rate in normal adult person is 72/minute.
(iv) Pulse rate is more rapid in children, in newly born baby in particular. It is more rapid in female in comparison to male.

Disorders related to the Circulatory System

Hypertension :

It is also called high blood pressure. Hypertension or high blood pressure is the occurrence of persistent systolic arterial pressure of more than 140 mm Hg and diastolic arterial pressure of more than 90 mm Hg. Hypertension is of two types, primary and secondary.

Secondary hypertesion is due to an underlying cause like Hormonal or obstructional. Primary hypertension is also called essential hypertension. 90% fo the hypertensive patients suffer from this type of hypertension.
It is caused by several factors like arteriosclerosis, atherosclerosis, varicose veins, obesity, increasing age etc.

Hypotension :

It is also called low blood pressure. Hypotension or low blood pressure is the occurrence of persistent systolic arterial pressure of less than 110 mm Hg and diastolic arterial pressure of less than 70 mm Hg.
It is caused by persistent vasodilation of arterioles, ventricular pumping, valvular defects, amaemia and deficient diet.

Atherosclerosis :

It is irregular thickening of arterial walls and narrowing of their lumen due to deposition of yellow plaques or atheromas in their tunica intima and inner part of tunica media.
 

Arteriosclerosis :

It is a group of degenerative diseases characterised by thickening and loss of elasticity of arterial walls.
arteriosclerosis occurs more in elderly persons.

Varicose Veins :

On prolonged standing or due to defect in the valves of the veins of the legs. These veins may become dialated,torturous and thickened (Most commonly affected is the saphenous vein). such veins become clearly visible and prominent. Treatment is surgical removal of such veins.

BLOOD VESSELS

In closed type of blood vascular system blood vessels are of 3 types (1) Arteries (2) veins (3) Capillaries.

Normally artery carries pure blood from heart to the different organs of the body.
Veins carry impure blood from body organs to the heart.

Capillaries are present in the organs, and these are the vessels through which exhange takes place.

Anatomy of arteries and veins : Normally there are three layers are found in the walls of blood vessels -

(i) Tunical externa : It is the outer most layer. It is formed of loose connective tissue in which many collagen fibres, elastin fibres and longitudinal muscles are found.

(ii) Tunica media : It is a thick laye of circular non striated muscles and a network of elastin fibres.

(iii)Tunica interna : This layer is made up of squamous epithelium, It is also known as Endothelium

One more layer is present in the wall of bigger arteries, that is known as elastic membrane. This is found in between the tunica media and tunica interna layers.
These all layers are well developed in the walls of arteries as compared to the walls of veins.
Walls of arteries are thick and more muscular and these walls are elastic and non-collapsible.
The walls of veins are thin, less muscular non elastic and collapsible.
In the walls of blood capillaries only endothelium layer is found. Its cells are flat and squamous, Their walls are perforated. These blood capillaries join the arteries with the veins.

Blood capillaries were discovered by a scientist named as Marcello Malpighi

A thin network of blood capillaries is present in the walls of blood vessels itself which supply blood and other necessary substances to the blood vessels. This blood supply is known as Vasa-vasorum.

ARTERIAL SYSTEM IN MAN

Arterial System : It is blood vascular system which carries blood away from heart in thick walled muscular blood vessels called, arteries and systemic aora from left ventricle.

1. Pulmonary artery or Arch. It develops from left upper end of right ventricle. Pulmonary arch carries deoxygenated blood. Soon after coming out of heart, it divides into two pulmonary arteries, right and left.
They carry deoxygenated blood to the lungs of their sides for oxygenation.

2. Arch of Aorta [Carotico Systemic Arch]. It arises from right upper end of left venricle. Ascending aorta has a swelling at its base known a aortic sinus. Two coronary arteries, right and left, develop from it to suppply oxygenated blood to heart walls.

Roughly 4% to 7% of the arterial blood passes into musculature of heart, though heart forms only 0.5% of the body weight. subclavians supply blood to fore limbs, chest and spinal cord. Common carotids provide oxygenated blood to brain, scalp, face, eyes, mouth, neck, etc.

The descending aotra has two components, thoracic and abdominal. thoracic descending aorta gives off intercostal arteries to intercostal muscles, bronchial to lungs, oesophageal to oesophagus and superior phrenic to superior surface of diaphragm.

Abdominal aorta gives out following branches.

(i) Inferior phrenic to the inferior surface of diaphragm.
(ii) Coeliac artery or trunk with lieno gastric branch which then divides into gastric & splenic branch, hepatic branch to liver and pancreatic to pancreas.
(iii) Superior mesenteric to small intestine.
(iv) Two supra-renals to adrenal glands
(v) Two renals to two kidneys.
(vi) Two gonadals, ovarian in case of females and testicular in case of males.
(vii) Inferior mesenetric to large intestine.
(viii)A few pairs of lumbar arteries to skin, muscles, vertebrae and other parts of lumbar region.

Adominal aorta now divides into two common iliacs, left and right, in the pelvic region. Each common iliac divides to form an external and an internal iliac. Internal iliac or hypogastric supplies blood to pelvic region External iliac passes into lower limb of its side.

Caudal artery - In Rabbit the posterior most part of dorsal aorta enters into the tail in the form a single caudal artery after the common iliac arteries have already separated.

VENOUS SYSTEM IN MAN RABBIT

Heart Receives

(1) One superior vena cava (Two in rabbit)
(2) One inferior vena cava
(3) Pulmonary veins
(4) Coronary veins through coronary sinus

[A] Superior vena Cava (Anterior) Receives

Two (Rt. & Lt.) External jugular (Both connected by transverse jugular)
Two internal jugular (Rt & Lt)
Subclavian (Rt & Lt)
Anterior intercostal (RT & Lt)
Internal mammary (Rt & Lt)
Azygous vein (RT. Side only)

Hemiazygous vein (Lt. side only) opens in Azygous vein

[B] Inferior Vena cava I.V.C. (Posterior)

Post Intercostal vein Phrenic
Hepatic portal (to liver) Renal
Gonadal ilio lumbar
Ext & Int. iliac Veins from lower leg.

Venous System :

It is system of blood vessels through which blood is received from different parts of the body to the heart. It consists of pulmonary veins, coronary sinus, superior vena cava, inferior vena cava and portal systems.

1. PulmonaryVeins. Each lung returns oxygenated blood to left atrium of heart through two pulmonary
veins. total 4 veins open in the chamber of left atrium.

2. Coronary Sinus. It collects deoxygenated blood from different parts of the heart. Coronary into right atrium. sinus opens

3. Superior Vena Cava. It drains deoxygenated blood from head, neck, upper, limbs and Superior vena cava is formed by two brachiocephalic veins. Each branchiocephalic ve pina rist ofof rthmee cdh oefs ta. jcuhgelasrt. vAe sinm farollm u nhpeaairde da nadz yngeocsk, vae isnu fbroclmav iinatne rvceoisnt afrlo amre uap jpoeinrs l ismubp earniodr ivnetenran acla tvhao braecfiocr ev eitisn ofrpoemni npga ritn otof right atrium.

4. Iannfde rpieolvri cv reengaio nC, aItv par.o Icte iesd fso rtmoweadr dthse u ppeplevric p raergt ioofn t hbey bthoed yu nreiocne iovifn tgw goe cnoitmalm voenin sil ifarocm v egionnsa fdrso,m lu lmimbbasr vheeipnast ifcr ovmei nbsa cfrko mof tlihvee rl uamndb ainr freergioior np,h rrerneanli cv eveinins sf ofrrmom k iidnnfeeryio. rS fuapcrea roefn tahle v deiianps hfrgormag mad. rIennfearl igolra vnednsa, tcharevea opens into righ atrium.

5. Ahezmygiaozyugso uvse vinei.n A isn parxeysgeonut sin vtehien leofpt esndsie i nwtho icphr eocpaevnasl i(nStVo Ca)z yjugsotu sb evheiinnd t hthroeu gahn tae rtiroarn isnvteerrcsoes ctaoln nveeicnt.io An An accessory Hami Azygous vein also drains blood for left upper part into Azygous.
sAoz ymgoaunsy asnmda hlle mbriaznygchoeuss

PORTAL SYSTEM

When the vein of any organ of the body does not open in the caval vein or heart but it divides into capillaries in any other organ and its blood is transported by vein of that other organs to the heart, then this type of system is termed as portal system.

it is of following types -

(i) Renal portal system
(ii) Hepatic portal system
(iii) Hypophysial portal system

(I) Renal portal system - Veins which collect blood from posterior parts of the body and legs combine to fwoarmstse sa frreonmal tphoisrt abl lvoeoidn.. TThhiiss vbeloino gdo iess ninotwo ktridannesyp oarntedd d itvoid tehse i nhteoa crat.p Iiltl airsi epsr.e Ksiednnte yins sfreopgarate

nitrogenous
In mammals, renal portal system is absent.
In Frog both the portal systems; renal portal system and hepatic portal system are present.

(II) Hepatic Portal System - It is a portal system which brings venous blood directly from digestive tract, spleen, pancreas and gall bladder to liver for extraction of nutrients and other metabolites by breaking up into single celled thick capillaries and sinusoids. Portal vein is about 8 cm long. It is formed by following veins.

(i) Splenic from spleen and Gastric from stomach which join to form lienogastric vein.
(ii) Superior mesenteric from small intestine, caecum, ascending and transverse parts of colon.
(iii) Inferior mesenteric from rectum, sigmoid and descending part of colon.
(iv) Cystic vein from gall bladder.
(v) Paraumbilical vein from abdominal wall. Hepatic portal vein branches.
The branches enter into different liver lobes. They divide and redivide. Ultimately branches of hepatic portal veins open into sinusoids for exchange of materials between portal blood and liver cells. Along with deoxygenatd blood of liver, portal blood is recollected by venules which form hepatic veins.

(III)Hypophysial Portal System - It is a portal system formed by a vein from hypothalamus which breaks up into capilliaries in hypophysis or pituitary gland. The vein is called hypophysial portal vein. It is formed by union of capillaries and venules in hypothalamus. The portal vein enters anterior lobe of pituitary glandor adenohypophysis where it breaks up into capillaries. Hypophysial portal system is a short circuit
arrangement. Hypothalamus produces a number or hormones for controlling endocrine activity of adenohypophysis. They are pored into blood in hypothalamus. The same is directly drained by hypophysial portal vein into adenohypophysis.

Lymphatic Circulatory System - Here a different kind of circulating fluid (lymph) transferres CO2 and waste products from the interstitial spaces to the veins through lymph vessels. This fluid is derived from filteration of blood in the capillaries. It is devoid of RBC's. The lymph vessels originte from lymph capillaries and end either in the vein or a main big lymph vessels called thoracic duct. This fluid is propelled from the interstitial space
to the veins ultimately due to pressure differences.

The Lymph : From arteriolar regions of capillaries, about 90 percent fluid is returned back into their venous regions. To drain back the remaining ten percent of the filterd out fluid, vertebrates possess an additional independent system of pipelines, called lymphatic system. This system begins in tissue fluid with lymphatic capillaries which are always terminally closed. These capillaries occur extensively in between the blood capillaries in various body parts except in skin epidermis, hair follicles, cornea of eyes, most cartilages, brain,spinal cord, spleen and bone marrow. The cavity of lymph capillaries is wider and irregular. Their wall is thinner than that of blood capillaries, but its pores are so much larger as to allow entrance of even bacteria,cell debris and proteins and other larger colloid particles. The fluid that flows into these capillaris from theinterstituium is called lymph.
Arteries divide into blood capillaries inside the tissue.

These capillaries combine to form a vein at the other end. These veins carry impure blood from tissue. Blood presssure is more at the side of arteriole side of blood capillaries. it is approximately 40 mm Hg. Colloidal osmotic pressure of blood is 28 mm Hg.Thus net filteration pressure of blood in this region remains only 12 mm Hg column. In this region blood is filtered is called tissue fluid. There are present plasma WBCs, O2 and nutrients in tissue fluid.

The systemic venous pressure is as low as 15 mm Hg, while colloid osmotic pressure here remains 28 mm Hg. Hence due to a negative pressure (– 13 mm Hg) the lymph is poured from lymphatics into the veins.

W.B.Cs. and plasma are found in lymph but R.B.Cs. and platelets are absent from lymph.
Lymph forms second dcirculatroy system in the body. Lymphatic system is also known as helping

circulatory system.

Clotting capacity is present in lymph but its clotting takes more time as compared to blood.

This duct is connected by a structure called cisterna chyli just behind the diaphragm in abdominal cavity. Left thoracic duct opens in left sub-clavian vein at its anterior side.

Lymphatic capillaries of intestinal villi are called lacteals.Their lymph is milky in colour due to the absorbed fat from the intestine. It is called chyle. This chyle drains into cisterna chyli.
Lymphoid organs and lymph nodes - lymphoid organs made up of lymph tissue are present in lymphatic system, which are relatedd to lymph capillaries and lymph vessles. Lymph nodes, spleen, thymus, patches of payer, tonsil etc. are such type of organs.

(a) Lymph node - At places many lymphatics may intersect with each other forming a knob or node like structure called the lymph node. The vessels entering the lymph node carrying lymph from the interstitial space are called afferent lymphatics. The lymphatic leaving the lymph node and draining the lymph in veins or thoracic duct is called efferent lymphatic.

The lymph node thus acts as a filter apparatus which filter the lymph coming from the interstitial space and remove cellular debris etc. from it.

Blood Lymph

Other functions of lymph nodes are as follows -

1. These form lymphocytes and pour into lymph.
2. Filter and clean the lymph.
3. Synthesize the antibodies.
4. Destroy bacteria and other harmful substance by feeding upon (phagocytize) them

Lymph nodes are present in all parts of body, but their number is comparatively more in armpits of hand legs. groins, neck and abdomen. Their number is much more in neck region.

SPLEEN

Lymph glands includes spleen and thymus.
Spleen

Structure

(i) Spleen is dark red elongated structure lying behind the human stomach.
(ii) It is covered by sheath, called capsule, capsule is composed of white fibrous connective tissue.
(iii) Capsule further remain covered by visceral peritoneum.
(iv) The capsules are inserted deep in the body of spleen in the form of strands which is called trabeculae.
(v) Red and white pulp are found in spleen these are known as splenic pulp.
(vi) In the red pulp cord of Biltroth are found, which are blood spaces forming red pulp.
(vii) The spleen also contain macrophages.

Functions

(i) Phagocytic cells macrophages are present in the spleen which engulf foreign bodies and bacteria. Moreover lymphocytes of the spleen also produce antibodies.

(ii) In embryo (foetus) it produces erythrocytes and lymphocytes.

(iii) Spleen is 1st reservior blood, so it is called blood bank.

(iv) Spleen produces lymph.

(v) Spleen also stores iron.

(vi) Spleen is filter apparatus for blood. It filter out the old, weak and disintegrating erythrocytes from the blood stream.

Due to this speciality spleen is called as the graveyard of RBC. General information related with spleen

(i) Spleen is lymphoid gland.

(ii) It is mesodermal in origin.

(iii) It is largest lymph gland.

(iv) Spleen increase in size during malaria fever due to increased number of lymphocytes and dead RBC.
Note :

Tonsil is also lymphoid tissue. Lymphoid tissue is also found in peyer’s patches and vermiform appendix.

HEART OF VERTEBRATES

Heart (Fish)
(i) In fish 2 chambered heart is found (1 auricle + 1 ventricle)
(ii) Ventricle pumps venous blood to gills purification.
(iii) Since only deoxygenated blood is present in the heart, such heart is called venous heart.

Note :
In lung fishes 3 chambered heart is found.
Heart (Amphibia)
(i) In amphibians 3 chamberd heart is found (2 auricle + 1 ventricle)
(ii) Both accessory chamber are found.
(iii) Double circulation is found.

Heart (Reptilian)
(i) In reptilian 3½ chamberd heart is found.
(ii) The ventricle is partially divided.

Note :
(i) In crocodile and alligators ventricle is completely divided.

Sinus Venosus And Conus Arterious - Sinus venousus and conus arterious are not found in rabbit but they are present in frog. In rabbit Sinus-venosus is formed in the embryo but later it becomes a partof the right-auricle. So the impure (deoxygenated) blood collect by the precavals (SVC) and postacavals (IVC) directly comes into the right auricle.

The pure blood brought by the pulmonary veins from the lungs directly comes into the left auricle.
Due to the separation of ventricle and the absence of Conus-arterius in rabbit, the pulmonary archesand the Carotico-systemic arches or aorta, arise respectively from the right and the left-ventricles.

Anatomical Landmarks :
Coronary artery – Supplies blood to HEART
Vasso-Vassorium – Blood vessels which supply blood to wall of blood vessels
Bicuspid valve – Mitral vavle (Between L.A. & L.V.)
Tricuspid valve – (Between R.A. & R.V.)
Haversian valve – [On the end of opening of precavals]
Eustachian valve – On opening of postcavals.
Semilunar valve – At opening of Aorta and ventricles
Thebesian valve – Coronayr valve = at opening of coronary sinus
Columane carnae – Finger like projection from ventricle walls
Papillary muscles – Present at tip of columnae carnae
Chorda tendiane – Arise from papillary muscles and keep the valves in proper position.

Pulmonary arch

Arches of Heart

Arches of Heart
Lacteals  Lymph capillaries of intestinal villi
Lymphatic system present in class Amphibia is of open type.
Lymph heart and lymph sinuses found in frog are absent in the lymphatic system in rabbit & man
Payer's patches are present in mucosa of intestine and tonsils are present in mucosa of pharynx.

IMPORTANT POINTS

1. Blood plasma + tissue fluid + lymph combine to form internal enviroment of the body of vertebrates, which
is termed as '' The sea within the body'' by Baird hastings;
2. First heart transplantion was done by Dr. Christian Bernard in the world.
3. In India first heart tranplantation was done by Dr. P. Venugopal on 3rd August 1994. This transplant was done on a 42 years old person named Deviram (in AIIMS).
4. [Spleen + liver + kidneys] These three are called filter apparatus of blood.
5. In coronary artery BY Pass grafting, a segment of patients own saphenous vein or a segment of internal mammary artery is used as a by pass channel.
6. cardio-pulmonary resuscitation CPR is given in the ratio of 4 : 1 of compression : ventilation.
7. In acute M.I. Streptokinase (STK) is given intravenously to dissolve the thrombus obstruction which is
causing myocardial infarction.
8. The major switch over from foetal to adult type of circulation after parturitions occurs due to nitric oxide synthesis which causes vasodialation of pulmonary artery and veins, thereby allowing much greater quantity of blood to flow through lungs.

Ventricular Asystole
9. Cardiac arrest : Heart stops functioning as a pump ; cause Ventricular Fibrillation
10. Lowest rate of heart-beat is of Blue-Whale ''Balanoptera-musculus.'' (Less than 28 per min.)
11. On an increase of basicity the rate of heart-beat decreases
12. Solid state lithium cell is used in artificial pacemaker.