An extended pipeline or large open space system through which blood circulates throughout the body is called circulatory system.It is mesodermal in origin except the inner living of heart and inner living of blood vessels which are endodermal in origin.
In human beings the heart is four chambered with double circuit.it means blood travels in the body two times in one beat.
Double circulation of blood was discovered by Sir Willim Harvey According to sir willam harvey the pumping station of the body. which pump blood all our the body
They are two type of circulatory system
In a closed circulatory system blood flow through a network of blood vessels.Blood pressure is more and speed of blood is more.each and every cell is not in direct contact with blood.
example : PARAM (Pisces, Amphibia, Reptilia, Aves, Mammalia)
2. Open circulatory system:
Blood is pumped by heart into large open spaces called blood sinuses. Blood flows slowly at low pressure. Each and every cell is in direct contact with blood.
Example: Arthropods some Annelids some molluscs.
In lower vertebrates , 2 accessory cells are associated with the heart.
1. Sinus venous on dorsal surface
2.conves arteriosus on ventral surface
In humans, most oxygenated blood is found in pulmonary vein and deoxygenated blood is found in the pulmonary artery.In frog is SA node and it is found in the sinus venosus. In this most oxygenated blood is pumped in pulmo-cutaneous veins.
(In mammals ,close and double circulation consist of systemic circle and pulmonary circle. In a Systemic circle blood is oxygenated and lungs to body through artery and body to right atrium through the veins. In Pulmonary circulation blood are )
Human heart at all stage
Human heart consists of 4 chambers, two upper chambers called arteries and lower chambers called ventricles. The heart is present in the thoracic cavity mesoderm . The weight of the heart is approx 250 to 300 gram.
Embryo heart:
In embryo hearts present foramen ovale and also ductus arteriosus / ductus botalli are present. The foramen ovale is the small opening between two upper chambers of the heart, the right and the left atrium. The ductus arteriosus carries blood away from the lungs and sends it directly to the body. then a newborn breathes and begins to use the lungs. After 2 dates it will degenerate.
lungs are not functional , gas exchange occurs in placenta and heart contain mixed blood.
Foetus heart:
Heart contain mixed blood in all chamber but mixing not occurs in heart.umbilical cord contain 100% foetus blood .umbilical vein contains oxygenated.umbilical artery contain deoxygenated blood.No acts as a vasodilator for pulmonary artery and pulmonary vein.Bradykinin is powerful
vasoconstrictor.
Adult heart:
In the adult heart present fossa ovalis and ligamentum arteriosum.The fossa ovalis is a depressed structure, of varying shapes, located in the inferior aspect of the right interatrial septum. The ligamentum arteriosum (or arteriosus) is the small fibrous remnant of the fetal ductus arteriosum, located between and connecting the proximal left pulmonary artery and the undersurface of the junction of the aortic arch and descending aorta, at the aortic Isthmus.lungs are functional.Gas exchange occurs in lungs and heart contain pure and impure blood.
Heart is covered by double layer sc pericardium b/w both layers , narrow pericardial cavity present in which pericardial fluid present for frictionless movement, makes the heart moist.
wall pf consist of 3 layer
1. Outer epicardium (SSE)
2. Middle myocardium (cardiac muscle layer)
3. Inner endocardium (SSE)
The thickness of the heart wall depends on myocardium . The Atria wall is thin, smooth but the ventricles wall is thick , rough. thickness wall found in left ventricles . lumen of right ventricles is wider than left ventricles lumen.In the ventricle wall, the muscle layer form small ridge ( columnas cornac) and layer ridge ( papillary muscle )
Papillary muscles of ventricles are connected to tricuspid or bicuspid valves by chordae tendineae .These are collagen cords.They can't regulate opening of the wall. They prevent backflow of blood to the atria.
Heart beat in human being and in animals
Contraction in the heart is called systole and relaxation in heart is called diastole.( systole +diastole ) is equal to 1 beat.pulse is also known as ventricular systole. Adult human heart should be between 72-75 heartbeat per minute. child heart should be between 90-110 heartbeat per minute. New born baby heart should be between 100-120 heartbeat per minute. Embryo heart should be between 140-170 heartbeat per minute. The pygmy shrew has the fastest heartbeat, 12000 heartbeat per minute. elephants have the slowest heartbeat, 30 heartbeat per minute.
On the basis of origin of beat, heart is of two types
Neurogenic -heart is originated by a group of nerve fibre which comes from nerve ganglia.
example: Invertebrate
Myogenic - heartbeat is originated from group of muscle fibres which lie inside the heart
example : vertebrate
Impulse conduction sequence
Path of impulse is sinoatrial node (SAN) > Atrioventricular node (AVN) > bundle of his > purkinje fibres.(pf). everypath of conduction pathway can generate AP(Autoexcitable) but SAN generates Maximum. so, it is responsible for initiating and maintaining rhythymic contraction activity of the heart and it is called pacemaker.Impulse conduction fastest in purkinje fibres and slowest at AVN.Impulse delay at AVN. If SAN fails , then both do not contract but ventricle contract.
What is systolic ,diastolic cardiac cycle in human being
The serial wise changes which occur in the heart in a beat is called cardiac cycle. its duration is 0.8 second. It has following stage.
Atrial diastole : 0.7 second
In this atria receive blood from pulmonary veins and vena cava.
ventricular diastolic: 0.5 second
In this pressure of ventricle decline so, semilunar valve close and atrioventricular valve open due to this 70%-75% blood passively flow into ventricle.
Atrial systole:0.1 second
Now SA node generate AP so both atria contracts simultaneously so, 25%-30% of blood is pumped into ventricle ( actively pectinate muscles )
Ventricular systole : 0.3 second
In this ventricle contract and pressure increase Due to this atrioventricular valve close and after this semilunar valve open. so blood is pumped into the aorta.when all chambers are in relaxed: joint diastole 0.4 second in this atria and ventricular both receives blood. In this atria and ventricle both receive blood.In this atria-ventricular valve open and semilunar valve close.
In a cardiac cycle, joint diastole is 0.4 second.
The Ventricles are filled with blood in 3 steps.
Rapid-70% blood passively
diastasis-5% blood
atrial systole -25% blood
Maximum amount of blood is transferred from the auricle to ventricle in the auricle diastole stage. about 70%.
In a cardiac cycle 2 prominent heart sounds are produced.
Lubb sound : First heart sound produced at the beginning of ventricular systole. due to the closing of the tricuspid and bicuspid valve. dull sound for a long period.
DUP sound: second heart sound produced at the beginning of ventricular diastole.closing of semilunar valve. sharp sound for a short period.
due to a defect in the valve of the heart. Another sound produced called murmurs.heart sound can be heard by stethoscope.The pause between second and first sound=ventricular diastole.
LUBB-----------V.S (0.3 sec)-------DUP-----------V.D (0.5 sec)---------------LUBB
(cardiac cycle)
Stroke volume : Amount of blood pumped by each ventricle in a cardiac cycle 70ml.
Cardiac output: total amount of blood pumped by each ventricular in a minute.
stroke volume x heart rate = 70 x 72 = 5 litre.
Cardiac output depends upon physiological activities.It is higher in athletes than in ordinary man. Amount of blood pumped by the right and left ventricle is the same amount of blood flow LA to LV.
Distribution of cardiac output to organ 7% to the heart (coronary artery),9% to the lungs (bronchioles artery),84% to the systemic.blood reservoir of the body is veins.blood bank of the body is spleen.after death become empty,at rest stage ,kidney receive max amount of cardiac output.For fastest distribution of material without risk.it is injected into veins
Blood pressure in human beings
Pressure of blood on the walls of artery (narrow lumen thick elastic wall).normal blood pressure is 120/80 mm/hg.120 is the systolic and 80 is the diastolic.Pulse pressure is 40mm/hg (systolic-diastolic).In old person ,blood pressure is high ,because elasticity of artery reduces.
contained or sustained high blood pressure (hypertension).High BP =140/90mm/hg or above
Regulation of cardiac activity:
Heart attack is originated by SA nodes but it is regulated by nervous and hormonal control.cardiac centres lie on medulla. a sympathetic system increases heart rate, SV (stroke volume) there by cardiac output. parasympathetic system decreases heart rate, (stroke volume) and there by (cardiac output).Adrenal medullary hormone (adrenaline,noradrenaline ) and thyroxine hormone increases heart rate.parasympathetic system,acetylcholine, vagus nerve decreases heart beat.if we cut vagus nerves then heart rate increase.
Atherosclerosis : Narrowing of artery due to the deposition of cholesterol ,lumen of artery -narrow
blood supply to the organ is reduced.
Arteriosclerosis : Hardening of artery deposition of Ca salts in the wall so the wall becomes thicks ,hard , non elastic. arteries may rupture so internal bleeding.
How are coronary circulation works
The right and left coronary artery and its branches deliver oxygenated blood to myocardium.its one branch is the left anterior descending artery (Deposition of cholesterol is more in man ).most fatal thrombosis occurs in it.
Myocardial Ischemia : lumen of artery becomes narrow ,blood supply to cardiac tissue reduces ,oxygen supply decreases .Cardiac tissue becomes weak but live.reversible condition (treated bed rest).acute chest pain occurs called argina pectoni.
Myocardial infarction : Artery gets blocked and blood supply stops. oxygen supply stops ,cardiac tissue dies i.e. cellular death occur.It is also called heart attack.
Streptokinase injections are used to dissolve clot blood. It is used in the internal mammary artery or saphenous vein.
Heart and circulatory disorder in human being
1.Hypertension : continuous high blood pressure condition
2. CAD : It is refer to arteriosclerosis
3.Angina : acute chest pain appears when there is not enough O2 supply to the heart muscle.
4. Heart attack : Suddenly damage of cardiac tissue due to inadequate blood supply.
5. Heart block : Any part of conduction pathways is damaged then impulse condition is blocked.
6. Heart failure : State of heart when it is not pumping blood effectively to fulfill the demand of the body .It is called congestive heart failure because congestion of lungs is the main cause of it .
7. Cardiac arrest : heart stop beating
Note*=(heart failure is not the same as cardiac arrest or heart attack.)
Blood vessels : Artery , Veins and Capillaries
Artery : Always carry blood heart to organ .Their wall is thick ,muscular ,elastic they have extra elastic lamina .their lumen is narrow .they have no valve .in this blood flow rapidly at high pressure.
Veins : Always carry blood from organ to heart .their wall is thin ,less muscular but lumen is wide they have valves. In this blood flow slowly at low pressure. To provide blood supply to large blood vessels ,a network of small blood vessels present called vasa vasorum (vein of vein). Due to any deflection thick and dialated called varicose vein .
Carotid artery : deliver O2 generated blood to brain ad juglar vein carry deoxygenated blood from brain.
Lymphatic system :
In mammals , blood system and lymphatic system are called close type.In amphibia lympatic system is open typr .they have lymph heart and lymps sinus .
colourless tissue fluid middlemen of body RBC and platelets present WBC present WBC more than blood .lymph = plasma + WBC. It has clotting capacity but takes more time .It has more CO2 wastage than blood. It is for the immune responses of the body.
Lymph vessels have more valves than vein lymph nodes made up of lymphatic tissue for clearing and filtration of lymph. They mix lymphocyte WBC into lymph.their number are more in neck,armpits and groins region.