The Circulatory System Class 10 ICSE Notes
ICSE Class 10 Biology Chapter 8 The Circulatory System Notes, Summary, Definition, Diagram. The Circulatory System Notes.
Need for Transport inside the body –
→ Digestive system – digests and absorbs nutrients which are needed to be transported to every cell of the body.
→ Respiratory system – for exchange of gases , air in the lungs to all parts of the body
→ Excretory system – for removing extra water, excess salts, nitrogenous waste such as urea which should be removed out of the body.
→ Endocrine system – hormones secreted by this system need to be carried throughout the body by circulating blood.
→ Circulating fluid – blood and lymph
Fluids in our body –
1) Blood – contained in heart and blood vessels (arteries, veins and capillary) of the circulatory system.
2) Tissue fluid – occupies space between cells in organs
3) Lymph – contained within lymph vessels and lymphatic organs such as spleen and tonsils.
→ Blood which circulate through vessels are closed blood circulatory system. Ex- humans
→ Blood which flows through open spaces in body are open circulatory system. Their blood flows from heart to body spaces without vessels
- Some non-circulating fluids are located in particular organs such as synovial fluids filled in the cavities of skeletal joints, vitreous humour in the eye, etc.
They do not circulate.
Properties of blood – The Blood
→ Never stationary – always in motion
→ Colour – bright/dark red
→ Volume – 5-6 litres of blood by volume in body
→ Taste – saltish , alkaline pH=7.3 to 7.45
Function of Blood –
a) Transport by blood –
i.) Transport of digested food – glucose, amino acids, vitamins, mineral salts, etc.
ii) Transport of oxygen – combined with haemoglobin in form of unstable compound oxyhaemolobin reaches to tissue
Hb + O2 ↔ Hb.O2 (oxyhaemoglobin)
iii.) Transport of CO2 – combined with haemoglobin and partly as a solution in blood plasma
Hb + CO2 ↔ Hb.CO2 (carbaminohaemoglobin)
iv.) Transport of excretory material – from tissue to liver,kidney or skin for elimination or to render harmless.
v.) Distribution of hormones – endocrine glands secreted directly into blood
vi.) Distribution of heat – blood helps in keeping temperature of body uniform by distributing heat.
b) Protection by blood –
i.) Blood forms clot which serves to prevent further blood loss and also entry of disease causing germs.
ii.) WBCs protect body from disease by engulfing bacteria
iii.) Produces antitoxins and antibodies which neutralise the poisonous substance or kill germs which enter body.
Composition of blood –
a) Plasma – fluid part (55-60% of blood)
→ Inorganic salts mainly contains – sodium chloride and sodium bicarbonate
→ Contain glucose, amino acids, fibrinogen, hormones, urea, etc
→ The plasma from which protein fibrinogen has been removed is called serum.
b) Cellular elements – RBCs, WBCs and platelets (40-45% of blood)
→ Formed or cellular elements of blood contain 3 categories –
i. Red blood cells (erythrocytes)
ii. White blood cells (leukocytes)
iii. Blood platelets (thrombocytes)
I.) Red Blood Cells (RBCs) – the oxygen carriers
→ Biconcave disc-like structures flat in centre and thick and rounded at periphery.
→ Very small – 7 micron in diameter
→ Concavities on either side provide large surface are for efficient absorption of oxygen.
→ An adult male has above 5 million RBCs per cubic mm of blood.
→ An adult female has about 4.5 million RBCs per cubic mm of blood.
Haemoglobin – RBCs have colourless spongy body which contains a respiratory pigment “haemoglobin”
In haemoglobin, iron part (haemin) and protein (globin)
It has the ability to combine with oxygen to form oxyhaemoglobin, which gives oxygen to tissue
It can carry very small amount of CO2 in the form of carbaminohaemoglobin.
It has strong affinity for CO to form carboxyhaemoglobin (HbCO).
Carbon monoxide poisoning is when HbCO cut down the capacity of blood for transporting oxygen causing death.
Spleen is the known as graveyard for RBC.
→ RBCs are produced in bone marrow.
→ In embryo, it is produced in liver and spleen.
→ Mature RBCs have no nuclei, i.e. when they were produced they had one but as they mature they become enucleated.
→ Average life span of an RBCs is 120 days
→ Old and weak RBCs destroyed in spleen, liver and bone marrow. Their iron part is retained in liver while rest is excreted as bilirubin (bile pigment)
→ RBCs have no nucleus, mitochondria and endoplasmic reticulum
→ Polycythaemia – abnormally increased number of RBCs.
→ Erythropenia – abnormally decreased number of RBCs.
II.) White Blood Cells (WBCs) –
→ Also known as leukocytes
→ Contain nucleus and doesn’t contain haemoglobin
→ 4000-8000 WBCs per cubic mm of blood
→ Most are amoeboid and can produce pseudopodia with which they can squeeze through walls of capillaries into tissue (diapedesis).
→ 90% present in lymph and 10% present in blood
→ Produced in red bone marrow, lymph nodes and sometimes even in liver and spleen.
→ Average life span is 2 weeks.
→ Neutrophills lives only for few hours, and 125 billion Neutrophills are produced in each day.
→ Old and weak WBCs are destroyed in spleen, liver and bone marrow.
→ Leukemia – a blood cancer of tissue forming abnormally increases of WBCs at cost of RBCs. Fatal disease and treatment is only blood transfusion.
→ Leukopenia – abnormal decrease in number of WBCs.
Functions of WBCs –
1) Phagocytosis – Neutrophills engulf particle like solid substances. Abnormally increase when some infection occurs in body.
2) Inflammation – occurs due to reaction of tissues to injury or invasion of germs.
Inflamed spots have redness, swelling, pain, local heat etc.
Pus is mainly composed of dead WBCs together with tissue cells destroyed by bacteria.
3) Formation of antibodies – produce antibodies which kill or neutralise the germs, or the poisons from them.
During vaccination, weakened germs or germ substance is introduce which stimulate formation of particular antibodies, later would destroy the particular disease-causing germs if they enter into body.
WBCs –
1) Granular WBCs – cytoplasm contains granules. Nucleus usually constricted into lobes.
a) Neutrophils
b) Eosinophils
c) Basophils
2) Agranular (non-granular) WBCs – cytoplasm without granules. A single large nucleus
a) Lymphocytes
b) Monocytes
Neutrophils –
→ Nucleus with 3-4 lobes
→ Granular cytoplasm
→ stain with neutral dyes
→ engulf bacteria (Phagocytosis)
→ produced in bone marrow
Eosinophils –
→ Nucleus with 2 lobes
→ Large cytoplasmic granules
→ Stain dark red with eosin (acid dye)
→ Engulf bacteria
→ Secrete antitoxins
→ Associated with allergy
→ Produced in bone marrow
Basophils-
→ Nucleus large and indistinctly lobed
→ Granules stain with basic dyes (methylene blue)
→ Release chemicals (histamine) for inflammation which dilate blood vessels
→ Produced in Bone marrow
Lymphocytes –
→ Smallest of WBCs
→ Single large nucleus
→ Produce antibodies
→ Produced in bone marrow and lymph glands (spleen, tonsil, etc)
Monocytes –
→ Largest of WBCs
→ Nucleus large, kidney-shaped
→ At site of infection, transform into macrophages
→ Ingest germs
→ Produced bone marrow
III.) Blood platelets (thrombocytes) –
→ Initiators of clotting of blood
→ Are minute oval or round structures
→ Non-nucleated, floats in blood
→ Platelets are derived from megakaryocytes in the bone marrow
→ Life span 3-5 days and destroyed in spleen
→ At the site of injury, platelets disintegrate to release a chemical substance thrombokinase which initiates the process of clotting of blood.
Functions of platelets – coagulation of blood
→ Steps of coagulation –
1) Injured tissue cells and plates which disintegrate at the site of wound release a substance thrombokinase (thromboplastin). (also called “Factor X” or stuart factor)
2) Thrombokinase acts as an enzyme and with the help of calcium ion presnt in plasma, converts prothrombin (inactive) into thrombin (active).
3) Vitamin K, a fat soluble vitamin essential for production of prothrombin.
4) Thrombin in presence of Ca2+ ion reacts with (soluble) fibrinogen and converts into (insoluble) fibrin.
5) Fibrins are sticky threads which form a network (mesh) at the wound.
6) Blood cells are trapped in the network of fibrin, hence the network shrink and squeezes out the rest of plasma which is in the form of clear liquid called serum.
7) The solid mass which is left behind is called clot (thrombus).
The fate of blood in blood clotting –
- Clotting can be caused by movement of blood over a rough surface as on cholesterol deposit on the inside of blood vessel.
- Haemophilia is genetic disorder in which blood does not clot properly due to lack of blood clotting proteins. Also when number of platelets falls to an abnormally low count, coagulation occurs very slowly and often leads haemorrhage.
- Haemorrhage occurs in viral dengue fever.
Blood transfusion and Blood group (ABO and Rh system)
→ Injecting blood into a patient’s body via surgical operation is called blood transfusion.
→ Blood transfusion can only be done if blood of healthy (donor) is compatibility or match with the type of blood of receiving person (recipient).
→ RBCs of human beings have specific proteins on their surface. These proteins are called antigen.
→ Two types of antigen are present –
a) Antigen A
b) Antigen B
→ The plasma of blood contains complementary proteins called antibodies, with respect to the antigen that is present on the surface of RBCs.
Blood group |
Antigens on RBCs |
Antibodies in plasma |
A | Antigen A | Antibody B |
B | Antigen B | Antibody B |
AB | Antigen A & B | No Antibody |
O | No antigen | Both Antibody A &B |
Blood grouping system –
1) ABO system –
→ there are 4 types of human blood – A,B,AB,O
→ blood transfusion can only done in one’s own type of blood(A to A, AB to AB)
→ O type blood group is a universal donor, i.e. can donate to any type of blood group.
→ AB type blood group is universal recipient, i.e. can receive from any type of blood group.
→ A type blood group can receive from A and O type and B type blood group can receive from B and O type only.
- Compatibility (blood group matching)
blood group of donor |
blood group of recipient |
|||
A | B | AB | O | |
A | ✔ | X | ✔ | X |
B | X | ✔ | ✔ | X |
AB | X | X | ✔ | X |
O | ✔ | ✔ | ✔ | ✔ |
2) Rh system –
→ Most people contain a substance called Rh factor.
→ When the blood of such an individual is transfused into persons lacking it, the blood of the recipient develops an antibody for Rh substance within about two weeks of transfusion.
→ Now if second transfusion be given to such Rh negative person, the antibody produced by the first transfusion causes reaction with the transfused blood, which may lead to death. Similar to development of an allergy.
- Rh factor in pregnancy –
→ Rh negative woman may become sensitive if she carries an Rh positive child in her uterus (husband is Rh positive). The first Rh-positive child will be normal, but if it sesnitizes mother, and if the second conceived soon, may cause death of foetus and abortion performed.
→ People with Rh-positive (Rh+ve) blood group have D antigens on the surface of RbCs, while Rh-ve blood group lack these antigen.
Blood circulatory system –
→ Consists of heart, blood, and blood vessels (arteries, vein and capillaries)
The Heart –
→ It is in the centre between the two lungs and above the diaphragm.
→ Narrow end of roughly triangular heart is pointed to left side and during working, contraction of the heart is most powerful at this end giving a feeling that the heart is on the left side.
→ Human adult heart is the size of our closed fist – 12cm in length and 9cm in width.
→ Protected by double walled membranous covering calling pericardium.
→ Pericardial fluid reduces friction during heartbeat and protect from mechanical injuries.
→ Heart consists of 4 chambers – 2 upper atria and 2 lower ventricles.
→ Atria (auricles) have thinner walls, their major function is to receive blood from body and pump into next ventricles.
→ Ventricles have thick muscular walls, because have to pump blood farthest points.
→ Right ventricles pumps blood up to lungs for oxygenation.
→ Left ventricles pump it up to farthest points in the body.
Blood vessels –
A.) Blood vessels entering the heart –
Right atrium receives 2 large vessels –
1) anterior vena cava –
→ also known as superior vena cava or precaval
→ brings deoxygenated blood from anterior or upper regions of body like head, chest and arms.
2) posterior vena cava –
→ also known as inferior vena cava or postcaval
→ brings blood from the posterior or lower region of body including abdomen and legs.
→ Left atrium receives 4 pulmonary veins
→ The pulmonary vein bring oxygenated blood
B.) Blood vessels leaving the heart –
→ Arising from ventricles are 2 large blood vessels.
1) Pulmonary artery – arises from right ventricle and carries deoxygenated blood to lungs for oxygenation.
2) Aorta – arises from the left ventricle and carries oxygenated blood to supply it to all parts of the body.
Coronary arteries –
→ two coronary arteries (right and left) arising from the base of aorta.
→ These supply blood to heart muscles.
→ They collect blood from heart walls and pour it into the right auricle.
→ Myocardial infraction / heart attack – blockage in any coronary artery or in any 1 or more of their branches.
→ Angina pectoris – chest pain due to insufficient supply of blood to heart muscle
Valves regulate the flow of blood in a single direction –
- 4 valves in heart –
i.) Right atrio-ventricular valve –
→ Located between right auricle and right ventricle
→ Has 3 thin triangular leaf-like flaps (cusps), hence called tricuspid valve.
→ Apices of the flaps are held in position by tendinous cords (chordate tendinae) arises from muscular projections of ventricles called papillary muscles
ii.) Left atrio-ventricular valve –
→ Located on left side of heart
→ Has 2 cusps hence bicuspid valve (mitral valve)
iii.) Pulmonary semilunar valve –
→ Located at opening of right ventricle into pulmonary artery
→ Pocket-shaped and 3 in number
iv.) Aortic semilunar valve –
→ Located at the point of origin of aorta from the left ventricle
→ 3 in number and pocket shaped
Circulation of blood in the heart –
→ Starts with the concentration of 2 atria (auricles)
Ventricles at that time are relaxing (dilating) and are empty. Therefore, the blood from the atria passes into ventricles easily.
→ Now, ventricles contract and atria relaxes.
→ Blood from ventricles under pressure tends to return to atria, but the flap of bicuspid valve gets tightened and puffed up, thus closing passage and preventing the backflow of blood.
→ Chordate tendinae hold the flaps of the valves in position and prevent their overturning into atria.
→ Now ventricular blood is to enter the pulmonary artery from the right ventricle and the aorta from the ventricle.
→ Blood leaving the ventricles presses the valves flat and gets a clear passage in between.
→ When ventricles dilate, blood from pulmonary artery and aorta tends to return, blood fills the pockets of he valves and closes the passage.
Heart beat –
→ Atria contact first then ventricles.
→ Contraction phase (systole) is followed by a relaxing expansion phase (diastole)
→ Each full human heartbeat last for about 0.85 sec
→ At the end of ventricular systole, ventricles start relaxing (ventricular diastole).
→ Atria (auricles) have also be relaxing (atrial diastole) and for short period, both atria and ventricles are in a rlaxed state (joint diastole).
→ This whole sequence of events in the heartbeat is called cardiac cycle .
→ Heart sound is LUBB-DUP
→ The first “LUBB” is produced when the atrio-ventricular (tricuspid and bicuspid) valves get closed sharply at start of ventricular systole.
→ The second sound “DUP” is produced at beginning of ventricular diastole, the semilunar valves at the roots of aorta and pulmonary artery get closed.
→ Smaller the body size, faster the heart rate as smaller size animals loses its body heat more due to higher surface volume ratio, therefore, increased heart rate distributes body heat faster.
→ Young growing stages, such as baby have higher metabolism for body growth and therefore faster heart rate.
Pacemaker –
→ Impulse or command which starts the heartbeat arises in pacemaker (sino-atrial node “SAN”) located in the walls of right auricle.
→ Pacemaker (SAN) Present near superior vena cava, while AVN (atrio-ventricular node) is found near interauricular septum near the tricuspid valve.
→ Bundle of HIS – is a bundle of muscle from AVN and extends to the interventricular septum.
Consist of branches of fibres running along the wall of ventricles called “purkinje fibres”.
→ Sometimes pacemaker becomes faulty causing heart trouble.
→ An artificial “pace-maker” maybe fixed in heart of such a person.
The blood vessels
→ Are branched tubes extending from heart to all body parts of the body.
→ They are arteries, capillaries and vein
- Artery is a vessel which carries blood away from the heart towards any organ.
Characteristics of an artery –
→ Thick muscular walls
→ Narrow lumen (central bore)
→ Blood in it flows in spurts which correspond to the ventricular contraction of heart
- Vein is a vessel which carries the blood away from an organ towards the heart.
Characteristics of vein –
→ Thin muscular walls
→ Wider lumen
→ Blood in it flows uniformly
→ Contain thin pocket shaped valves whose openings face in the direction of the heart which prevent backflow of blood.
→ Arteriole – smallest or the final branch of an artery
They are highly muscular and can change their diameter manifold
Arteriole breaksup into capillaries
- Capillary is very narrow tube (about 8 micrometres in diameter)
Characteristics of capillary –
→ Walls consist of a single layer of squamous epithelial cells (endothelium)
→ Has no muscles
→ Total number of blood capillaries present in the whole body is almost inconceivable.
→ It allow outward diffusion of oxygen into the intercellular fluid and from there into tissues
→ It allow inward diffusion of CO2 from intercellular fluid
→ It allows inward and outward diffusion of substances like glucose, amino acid, urea, hormones, etc.
→ Also allows leukocytes (WBCs) to squeeze out through the capillary walls by amoeboid movement.
→ Capillaries have the power of dilating (vasodilation) and contracting (vasoconstriction) which respectively increase and decrease the blood supply to body parts.
→ Walking in hot sun- skin turns pink (increased blood flow)
→ Walking in too cold – face turns bluish (reduced blood flow)
→ Venule – smallest united common branch, Venule join to form larger veins.
→ Compare to arterioles , the venule are larger with much weaker muscular coat
2 blood circulation – pulmonary and systemic
→ Blood flows twice in the heart before it completes one full round
1) Short pulmonary (lung ) circulation
2) Long systemic (general body) circulation
Hence human body is having double circulation.
- Double circulation
Hepatic portal system –
- The vein starts from stomach and intestine and donot directly convey the blood to posterior vena cava.
- Instead they first enter liver as combined hepatic portal vein.
- There it breaks up into capillaries and hepatic vein is formed by reunion which joins the posterior vena cava.
- Hence a portal vein is a vein which starts with capillaries and ends in capillaries.
Main blood vessels –
a) Heart
i.) Blood vessels entering the heart
→ Anterior vena cava
→ Posterior vena cava
→ Pulmonary veins
ii.) Blood vessels leaving the heart
→ Pulmonary artery
→ Aorta
b) Liver
i.) Blood vessel entering the liver
→ Hepatic artery (aorta into liver)
→ Hepatic portal vein (stomach and intestine into liver)
ii.) Blood vessel leaving the liver
→ Hepatic vein (from liver into posterior vena cava)
c) Kidney
i.) Blood vessels entering the kidney
→ Renal artery (aorta into kidney)
ii.) Blood vessel leaving the kidney
→ Renal vein (from kidney into posterior vena cava )
The pulse
- It is the alternate expansion and elastic recoil of wall of artery during ventricular systole.
- Counting of pulse is indirectly the counting of heartbeat.
Blood pressure
- It is the pressure which the blood flowing through the arteries exerts on their walls.
- Upper limit (systolic pressure) – 100-140mm, for adults
- Lower limit (diastolic pressure) – 60-80mm , for adults
- A rise in blood pressure above 140/90 is hypertension
- Low in blood pressure than 140/90 is hypotension
- Sphygmomanometer – instrument used to measure blood pressure
Tissue fluid (intercellular fluid) –
- When blood from capillaries of tissue,plasma and leukocytes” leaks out “ through their walls. This fluid is known as tissue fluid, intercellular and extracellular fluid.
- From this fluid cells absorb oxygen and other required substances, and in turn gives out carbon dioxide and waste back into it.
Lymph and lymphatic system –
- Some tissue fluid gets reabsorbed into the blood vessels, and most of it enters another set of minute channels named lymph vessels where it is called lymph.
- Lymph vessels on the way drain lymph channels arise and ultimately pour lymph into the major anterior veins close to their entry into the right auricle and again circulation.
Composition of lymph –
a) Cellular part –
→ only leukocytes (mostly lymphocytes). No RBCs and blood platelets
b) Non-cellular part –
→ Water – 94%
→ Solids (proteins, fats, carbohydrates, enzymes, antibodies, etc) – 6%
Functions of lymph –
i.) Nutritive
ii.) Drainage
iii.) Absorption
iv.) Defence
→ Lymph nodes tend to localize the infection and prevent it from spreading to the body as a whole.
→ Tonsils on the sides of the neck are also lymph glands.
The spleen
→ Is a large lymphatic organ
→ Size about clenched fist
→ Reddish brown in colour an
→ situated in the abdomen behind the stomach and above the left kidney
→ Acts as blood reservoir
→ Spleen releases stored blood into blood steam
→ Produce lymphocytes
→ Destroy worn-out RBCs
→ An embryo, spleen produce RBCs
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