Circulatory system supplies the food and the gases to the different parts of the body. Blood is the carrier for circulating the food and gases throughout the body regularly. It includes the blood, lymph, heart and vessels.
Different circulatory systems are :
1. Intra-cellular circulation : It is in single cell organisms like amoeba, paramecium etc. This is called cyclosis.
2. Extra-cellular circulation : As the name indicates, the circulation takes place outside the cells. In sea animals water enters the body cavities. Blood vascular system is present in higher non-chordates. The system consists of blood vessels, blood sinuses and heart. Another type in open type of blood circulatory system and close type of blood circulatory system. In all vertebrates close blood circulatory system is present. In man the blood remains confined in blood vessels. Arteries and veins are the carrier of blood.
Arteries : They carry blood from heart to tissues. Their walls are thick, and muscular. Pressure of blood is high. When arteries are empty they do not collapse. These are deeply situated in the body. Their colour is pink or red. They carry oxygenated blood.
Veins : They carry blood from tissues to heart. Their walls are thin but elastic. The pressure of the blood is low. They get collapsed when empty. They are little deep. Colour is mainly violet. These carry deoxygenated blood.
HEART
It has the capacity to contract and expand. It pumps blood into the arteries and receives blood through veins. It is made of cardiac muscles. Man’s heart is enclosed in the memberanous pericardium. It has two parts (i) Auricle and
(ii) Ventricle.
Heart has four chambers two auricles and two ventricles.
Auricles
(1) Auricles are sac like structure, thin walled separated by septum.
(2) The oxygenated pure blood goes into left auricle. The supply is made by four pulmonary veins.
(3) The deoxygenated blood is received by right auricle.
(4) Right auricle opens into right ventricle.
(5) The left auricle opens into left venlricle.
(6) These are valves which control the movement of blood.
Ventricles
(1) As compared to Auricles, the walls of Ventricles are more thick.
(2) Oblique septum devides the cavity of ventricle into two parts.
(3) Oxygenated blood from the auricle is received by left ventricle.
(4) Deoxygenated blood from right auricle is received by right ventricle.
(5) From right ventricle the pulmonary arch arises which takes deoxygenated blood to the lungs for oxygenation.
(6) Aorta originates from the left ventricle. It supplies the oxygenated blood to all parts of the body.
(7) At the origin of aorta, three samilunar valves are present. They prevent the back flow of blood.
How does heart work
(1) Human heart in a healthy person beats 72 times/minute in a normal manner.
(2) In the heart of a man there are two centres of contraction. One in the right auricle and the other in the left ventricle. Right auricle is known as sinuauricular node (SA node) and other is atrio-venticular node (AV node).
(3) Both the nodes are modified cardiac muscles.
(4) Heart works in myogenic manner.
(5) When heart beat starts, the auricles and the ventricles are in relaxed position. This stage is known as joint diastole. In this stage blood comes in the auricle.
(6) Then comes the systolic phase. In this phase contraction of auricle takes place. This forces pumping of blood into their respective ventricle.
(7) The above action is due to the excitation of the SA node which sends the waves of contraction. These contract the right auricle first then they go towards the left auricle and contract.
(8) After the contraction of the left auricle the waves of contraction are centralised at the AV node.
(9) This causes the stimulation of AV node and this node sends the electrical stimulation to the apex of ventricle.
(10) This stimulation reaches the apex of ventricle and from its apex the contraction reaches towards the anterior side and thus blood is pumped into the aorta originating from ventricle.
(11) After the systolic phase the diastole starts.
Sound of murmur : Sound of murmur is produced by the disorder of heart valves. It may be due to valvular insufficiency and Stenosis.
Sounds of heart : The sounds are produced due to the closure of valves of heart.
First sound : It is due to the closure of atrioventricular valves.
Second sound : It is due to the sudden closure of semilunar valves.
Blood pressure : The pressure of the blood flow in the arteries is called blood pressure. It is measured by sphygmomanometer.
Normal systolic pressure = 120-130 mm Hg
Normal diastolic pressure = 70-90 mm Hg
Electrocardiogram : An electronic instrument which measures different stages of potential difference in the form of a graph is known as E.C.G. A typical E.C.G. has—
1. P-wave : Depolarization of auricle.
2. Q.R.S. complex : Depolarization of ventricle.
3. T-wave : Repolarization of ventricle.
Cardiac output : The volume of blood pumped by the heart in a minute is known as cardiac output.
C.O. = Heart rate × Stroke volume.
BLOOD COAGULATION
Conversion of fibrinogen into fibrin. Carries blood coagulation. It goes through following steps.
Steps :
Bleeding time after a given incision is about 3-6 minutes.
Clotting time : After giving a incision and coming out of blood. The clotting time is about 5-8 minutes.
LYMPHATIC SYSTEM
It includes,
1. Lymph
2. Lymph vessels
3. Lymph glands
Lymph : Lymph looks like blood without RBC. It has the property to clot when it comes in contact with air. Plasma and ABC comes out of the blood capillaries during the blood circulation. It enters into the lymph capillaries. It is known as lymph. This lymph is again sent to the blood circulation. The blood and lymph circulation goes on together.
Lymph vessels : Lymph vessels are thin vessels and the smallest vessels are capillaries which unite to form lymph vessels. These vessels are provided with valves which stop the backflow of lymph in the vessels.
Only two main lymph vessels are present in the man.
1. Thoracic duct and
2. Right thoracic duct.
Lymph glands : Spleen and lymph nodes are called the lymph glands.
Functions of lymph
1. It forms the lymphocytes.
2. The glands are centre for the formation of antibodies.
3. It absorbs the fatty acids and glycerols from the alimentary canal and transports it to the different parts of the body.
4. It transports nutrients from blood to the body tissues.
Shopping Cart
