Human circulatory system most important topic for various exams because related to body parts neccessory to could be know everyone about it.what is heart , four chambers of heart, Functions of heart ,Structure of heart ,four types of blood circulation, heart sounds, ECG ,cardiac cycle Blood pressure, and Disorders of heart ,heart attack,cardiac arrest etc.
What is the human circulatory system ?
The circulatory system is also known as cardiovascular system.It consists of heart and blood vessels. It is mainly a transport system .It transport respiratory gases (O2 and CO2 ),nutrients and excretory products to various parts of the body.
What is Heart ?
It is the mesodermaly derived organ ,is situated in the thoracic cavity ,in between the two lungs ,slightly tilted to the left. It has the size of a clenched fist.It is protected by a double walled membranous bag, pericardium enclosing the pericardial fluid.
•It is about 10 cm long and weighs about 300 grams.
Structure of heart :
- Heart is surrounded by an outer covering called pericardium. It contains two layers called visceral pericardium and parietal pericardium. Pericardial fluid is present between these two layers.
- The middle layer is made up of heart muscle fibres. It is called as myocardium.
- The inner lining is called as endocardium.
Functions of heart :
The heart acts as a pump. It maintenance of constant circulation of blood throughout the body. It is a achieved as follows :
- The superior Vena cava and inferior Vena cava bring venous blood from various parts of the body to the heart. This venous blood fills the right atrium
- It is full the right Atrium contracts sending blood to the right ventricle.
- Now the right ventricle contracts. This sends blood to the lungs through pulmonary trunk ( which is divided into you right and left pulmonary arteries. )
- The blood gets oxygenated in the lungs. The oxygenated blood is carried by pulmonary veins to the left Atrium.
- Now the left Atrium contracts and sends blood to the left ventricle.
- Now the left ventricle contracts and sends blood into the aorta. This blood is circulated throughout the body.
Four chambers of the heart
Heart is made up of 4 Chambers. The two chambers on the right side are known as right Atrium and right ventricle. The Other Chambers on the left side are known as left Atrium and left ventricle.. these four Chambers are formed by 2 Septa which divide the heart. They are inter atrial septum
and interventricular septum.
Valves of the heart :
The opening between right Atrium and right ventricle is regarded by tricuspid valve. The opening between left Atrium and left ventricle is guarded by mitral valve o r bicuspid valve.
Blood vessels attached to heart :
There are four points as follows :-
• the right Atrium receives superior Vena cava and inferior Vena cava. carry venous blood to heart.
• from the right ventricle arises the Pulmonary artery. It carries venous blood to lungs for oxygenation.
• the left Atrium receives four pulmonary veins. They carry oxygenated blood to heart.
• from the left ventricle arise the aorta. It delivers pure blood to all parts of the body.
Four types of human blood circulation :
Depending on the course aap blood circulation can be classified into following type.
1. Systemic circulation :
It is the circulation involving blood supply to all parts of the body except lungs. This circulation starts from aorta( which carries oxygenated blood from the the left ventricle.) It Breaks up into smaller arteries and finally in capillaries. The capillaries unite to form venules which join up ultimately to form two large Venous trunks namely superior Vena cava and inferior Vena cava. These two Venous trunks open in the right Atrium of the heart.
2. Pulmonary circulation :
It is the part of circulation involving the purification of blood in the lungs. Impure for venous blood is pumped by the right ventricle. The Pulmonary artery carries this blood to lungs where it is is oxygenated . four pulmonary veins carry this purified blood from lungs. These veins open in the the left Atrium .
3.Coronary circulation :
The circulation involve blood supply to the heart itself. The right and left coronary arteries arise from ascending aorta. They supply blood to the heart. The venous blood is collected by the coronary sinus which opens in the right Atrium.
4. Portal circulation :
It is the circulation of blood through the liver. In this circulation :
- Portal vein carries blood (that has circulated in the stomach intestine and pancreas ) to liver.
- The portal vein divides into capillaries. These capillaries join with the capillaries of hepatic artery.
- The venous blood of liver is collected by hepatic vein which joins with inferior Vena cava .
What is cardiac cycle?
The function of the heart is to maintain a constant circulation of blood throughout the body. This is achieved by rhythmic contraction of its muscle .
Cardiac cycle is the sequence of events which occur in the heart during a single beat. The rate of heart is 72 to beats per minute. So the time taken for one beat is 0.8 second. So the sequence of events occur every 0.8 second.
Cardiac cycle occurs in two phases they are:
1. Systole - a period of contraction
2.Diastole - a period of relaxation
Heart Sounds :
Totally four sounds are produced by the heart. The first sound as LUB and second sound as DUB can be heard with stethoscope. 3rd and 4th sounds cannot be heard.
• First sound is produced by the closure of atrioventricular valves. This is loud and of long duration .
• second sound is produced by the closure of semilunar valves (arotic and pulmonary ). It is shrill and of a short duration .
What is pulse rate ?
Pulse is the throbbing sensation felt over the walls of arteries . It is defined as the pressure difference transmitted in the form of wave over the arterial walls. Pulse rate is almost the same as heart rate 60 to 80 per minute.
• The wrist is the common site here pulse is is usually felt. At this site the radial artery is very superficial. This pulse is called as radial pulse. Other arteries where pulse can be felt are carotid artery facial artery and temporal artery. In case of fever the rate of pulse is increase at the rate of 10 per every rise of 1°F .
What is ECG ?
It is the recording of electrical activity of the heart. Electrocardiograph is the instrument which is used to record the the electrical current generated in the heart. By means of this instrument the electrical current generated in the heart is conducted to to remote Parts of the body. The heart current can be recorded by connecting any two parts of the body with this instrument. The connection are called as leads .
Full name of ECG : electrocardiogram
Machine or instrument name :electrocardiograph
Cardiac output :
It is defined as the quantity of blood pumped by the heart in one minute.
Stroke volume is the amount of blood rejected for beat of the heart. It is about 70 ml. So every minute some 5040 ml ( nearly 5 litres )of blood is pumped by the heart.
Cardiac output depends on the the following factors.
• amount of blood return to the heart through veins
• force and rate contraction of the heart
• peripheral resistance offered by blood vessels.
Blood pressure (BP) :
It is defined as the lateral pressure exerted by blood on blood vessels. The blood pressure which is is normally Express is arterial blood pressure.
It has two phases :
1. Systolic blood pressure :
It is the maximum blood pressure. This occurs during the systole of the heart range 100 to 120 mm Hg.
2.Diastolic blood pressure :
It is minimum pressure it occurs during the diastole of the heart range 60 to 80 mm Hg.
• pulse pressure is the difference between systole and diastole blood pressure it is nearly 40 mm Hg.
Disorders of heart :
1.Heart failure :
Heart failure means the state of of heart it is not pumping blood effectively enough to to meet the the needs of of the body. It is sometimes called congestive heart failure because congestion of the lungs is one of the the main symptoms of this disease.
• Heart failure is not the the same as cardiac arrest when the heart stops beating .
• Heart attack when the heart muscle is suddenly damaged by an inadequate blood circulation.
2. Angina :
It is also called angina pectoris . A symptom of acute chest pain appear no enough oxygen is reaching the heart muscle. Angina can occur in men and women aap any age but it is more common among the middle aged and elderly. It occurs due to conditions that the blood flow
3.Atherosclerosis :
It is affects the the vessels that supply blood to the heart muscle. It is caused by deposits of calcium ,fat ,cholesterol and fibrous tissues which makes the lumen of arteries narrower.
4.Arteriosclerosis :
It is thickening and inelasticity of arteries.
5.Myocardial infarction :
It is the death of of an area cardiac tissue due to lack of coronary blood supply to that segment of the myocardium. It occurs due to occlusion of coronary artery.
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