Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.4 Circulation offer valuable context and analysis.
WBBSE Class 9 Science Chapter 3.4 Question Answer – Circulation
Very Short Questions and Answers : (1 mark for each question)
Which system of animal body can be treated as the system of transport?
Circulatory system of animal body can be treated as the system of transport.
Which components of human circulatory system do act as vehicle?
Blood and lymph of the human circulatory system act as vehicle of transport.
Which gases are transported through blood?
Oxygen and carbon dioxide are transported through blood.
Which type of secretory products are transported through blood.
Hormones are the main secretory products, transported through blood.
What does pulse rate indicate?
Pulse rate indicates the rate at which the heart beats.
In which type of circulation different organs bathe in blood?
In open circulatory system different organs bathe in blood.
From which body cavity blood enters into the heart of a cockroach?
Blood enters into the heart of a cockroach from the pericardial sinus.
Why does blood of earthworm appear red?
Blood plasma of earthworm contains haemoglobin, so it appears red.
Which is the largest sinus of insect body?
Visceral sinus is the largest sinus of insect body.
How many ventricles does insect heart possess?
Insect heart possesses thirteen ventricles.
Name an invertebrate animal, which possesses closed circulatory system.
Earthworm possesses closed circulatory system.
Name an animal, in which blood does not take part in the transportation of the respiratory gases.
In cockroach, blood has no role in the transportation of the respiratory gases.
Name a nutritionally important plasma protein.
Albumin is a nutritionally important plasma protein.
Name an immunologically important plasma protein.
Globulin is an immunologically important plasma protein.
Which disease is caused due to deficiency of red blood cells?
Anaemia is caused due to the deficiency of red blood cells.
Which part of human circulatory system has the highest immunological importance?
The lymph glands of human circulatory system have the highest immunological importance.
Which type / types of blood can be transfused to a person carrying ‘O’ blood group?
A person with ‘O’ blood group can receive the ‘O’ group of blood only.
Which is the largest cell in the human blood?
Monocyte is the largest cell in the human blood (Diameter. 12-18 μ m)
Which is the smallest cell in human blood?
Platelet is the smallest cells in human blood. (Diameter, 2.5 μ m)
Which blood cells of human blood prevent blood coagulation inside blood vessels?
Basophils prevent blood coagulation inside the blood vessels.
Which are the non-nucleated cells of the human blood?
Platelets and matured red blood cells are the non-nucleated cells of the human blood.
Which blood cells of human blood take part in antibody formation?
Lymphocytes take part in antibody formation.
Increase of which blood cell indicates blood cancer?
Excessive and uncontrolled increase of WBC indicates blood cancer.
Who discovered the ABO blood grouping technique?
Dr. Karl Landsteiner discovered the ABO blood grouping technique.
A baby is suffering from erythroblastosis foetalis. His father carries Rh+ blood. Which type of blood is expected in his mother?
Mother of the baby is expected to carry Rh– blood.
Which blood cell prevents allergy?
Eosinophils prevent allergy.
Which blood cells are involved in transportation of respiratory gases?
Erythrocytes (RBC) are involved in the transportation of the respiratory gases.
Which blood cell is the most abundant in human blood?
RBC is the most abundant in human blood.
Which blood coagulating factor is possessed by platelets?
Thromboplastin is the blood coagulating factor possessed by platelets.
Which element is essential for activating thromboplastin?
Calcium ion is essential for activating thromboplastin.
Which two valves are commoniy called semilunar valves?
Aortic valve and pulmonary arterial valves are commonly called semilunar valve.
How many heartbeats are generated by a healthy sinoatrial node?
Sinoatrial node generates 70-80 heartbeats per minute.
Which junctional tissue supplements the function of a defective SA node?
AV node or atrioventricular node supplements the function of a defective SA node.
Which part of special cardiac junctional tissue supply impulse to ventricular wall?
Purkinje fibres supply impulse to the ventricular wall.
Which blood vessels carry oxygenated blood towards heart?
Pulmonary veins carry oxygenated blood towards heart.
Which chamber of human heart receives deoxygenated blood?
The right atrium receives deoxygenated blood.
How long does RBC survive?
Normal life span of RBC is 120 days.
What is pericardium?
Pericardium is the membranous outer covering of the heart.
What are systole and diastole?
Contraction of the heart is called systole and relaxation of the heart is called diastole.
Which instrument is used to measure haemoglobin in blood?
Haemoglobinometer is used to measure haemoglobin in blood.
What is haemoglobin made up of?
Haemoglobin is made up of an iron part, called haem, and a protein part, called globin.
Short Questions and Answers : (2 marks for each question)
What is meant by circulation?
Circulation is the physiological process by which nutrients, respiratory gases, hormones, minerals etc. are supplied to all the tissues of the body and the metabolic waste matters, produced inside the cells are transported to the respective excretory organs through fluid medium.
What is heart?
Heart is a muscular, multi-chambered (2 in fishes, 3 in amphibians and reptiles, 4 in birds and mammals and 13 in insects) sac-like structure, which continuously pumps blood in a rhythmic manner into arteries and receives blood from the veins and in this process, helps the blood to flow through the network of vessels to every part of the human body.
What are arteries?
Arteries are thick-walled blood vessels with roundish lumen, which carry oxygenated blood (exception-pulmonary arteries) from heart to the tissues with continuous rhythmic pulsation.
What are veins?
Veins are the blood vessels with thinner wall and flattish lumen, which carry deoxygenated blood (exception-pulmonary vein) from the tissues to the heart and possess valves to maintain unidirectional blood flow.
What are capillaries?
Capillaries are the finest of blood vessels with very thin wall, present in between arteries and veins. These fine vessels reach deep in the tissues to supply nutrients, oxygen etc. to the tissue fluid through diffusion and to collect the excretory materials and hormones from the tissues and the glands respectively.
What is meant by circulatory system?
The system of organs, involved in supplying nutrients, respiratory gases, hormones to different tissues of the body and removing metabolic wastes from the body, is known as circulatory system.
What is meant by open circulation?
The type of circulation, where body fluid does not remain confined within vessels, but pumped by the heart into open body cavity (haemocoel) to come in direct contact with the tissues, is called open circulation. This type of circulation is seen in molluscs, arthropods etc.
What is meant by closed circulation?
The type of circulation, where blood flows through heart and network of blood vessels within the body and never opens in the body cavity, is called closed circulation. This type of circulation is noticed in all vertebrates and a few invertebrates like earthworm, leech etc.
What is blood?
Blood is a red coloured, thick, faintly salty and alkaline, opaque, vascular connective tissue, composed of different types of cells suspended in a liquid matrix (plasma), which is pumped by the heart to flow through vessels for the transport of nutrients, respiratory gases, hormones, excretory substances and several other materials to all the parts of body.
What is haemolymph?
Haemolymph is a colourless fluid, composed of a watery matrix and a few cells, flowing through the body cavity (haemocoel) of insects and other arthropods.
What is lymph?
Lymph is a yellowish, transparent, modified tissue fluid, involved in absorption and transportation of nutrients, dissolved gases, immunologically important materials and different secretory and excretory substances into the tissues of higher animals.
Where do you find lymph in human body?
Lymph is present in lymph vessels and lymph glands. Lymph glands are localised in certain regions of the body viz. around neck, breasts, armpits, groin etc. of a human body.
What is CSF? Where is it found?
CSF: CSF or cerebrospinal fluid is a typical fluid, present in the central nervous system (CNS) of vertebrates.
0ccurrence of CSF: CSF is present in the ventricles of brain and in the central canal of the spinal cord. This fluid is also present in the subarachnoid space (between the second and third covering layers of brain or meninges).
What is synovial fluid? What does it do?
Synovial fluid: Synovial fluid is a slightly viscous, colourless body fluid typically present in the membrane-bound synovial cavities in between movable bone joints.
Function: Synovial fluid protects bone ends against frictional damage and supplies nutrients.
What is tissue fiuid? What is its function in animal body?
Tissue fluid: Tissue fluid is the extracellular fluid present in the tissues of multicellular animals.
Function: Tissue fluid helps in the transportation of nutrients, respiratory gases, hormones and metabolic waste materials.
What is meant by cytosol?
Cytosol is a bulk of intracellular fluid present in the cytoplasm. Different types of intracellular fluids are present in different cell organelles like mitochondria, Golgi body, plastid, endoplasmic reticulum, lysosome, vacuoles etc. performing their respective functions.
How is water utilised in human body?
Water is utilised in the human body in different ways as follows-
- It acts as the main component of the protoplasm
- Helps in hydrolysis of food matters in digestion
- Acts as the medium of diffusion and osmosis for nutrients, respiratory gases, metabolic wastes and hormones.
Mention the characteristic features of matured human RBC.
Matured human RBC is a round shaped anucleated biconcave, membrane-bound cell. It contains haemoglobin within cytoplasm but devoid of mitochondria and nucleus. The cell is 7.2 μ m in diameter and 2.6 μ m in thickness. Number of RBC is 5 million / ml in male & 4.5 million / ml in female. Its average life span is 120 days.
Mention the functions of RBC.
Functions of RBC are as follows-
- RBCs transport respiratory gases.
- They maintain acid-base balance in the plasma.
- They maintain ionic equilibrium.
- They help in the formation of colour of faeces.
From where do RBCs originate in human body?
RBCs originate from-
- Vasculosa region of early embryo.
- Spleen and liver of matured foetus, about one month before birth
- Red bone marrow after birth.
Mention the structural features and function of neutrophils.
Structural features: Neutrophils are amoeboid WBC with a diameter of 10-12 μ m. Its cytoplasm is granular and the nucleus has 2-7 lobes.
Function: Neutrophils kill germs by the process of phagocytosis.
Mention the structural features and function of eosinophil.
Structural features: Eosinophils are amoeboid WBC with a diameter of 10-12 μ m. Its cytoplasm is granular and the nucleus has 2-3 lobes.
Function: Eosinophils play important role in preventing allergy.
Mention the structural features and function of basophil.
Structural features: Basophil is a granulocytic WBC with a diameter of 8-10 μ m. The nucleus of basophil is bean-shaped.
Function: Basophils secrete an anti-coagulant to prevent coagulation of blood within blood vessels.
Mention the structural features and function of monocytes.
Structural features: Monocytes are agranulocytic WBC with a diameter of 7.5-12 μ m. It contains a round or kidney-shaped nucleus and homogenous cytoplasm.
Function: Monocytes kill germs by the process of phagocytosis.
Mention the structural features and function of lymphocytes.
Structural features: Lymphocytes are agranulocytic WBC with a diameter of 14-18 μ m. It contains a horse-shoe shaped nucleus and homogenous cytoplasm.
Function: Lymphocytes prepare antibody to maintain immunity.
Mention the structural features and function of platelets or thrombocytes.
Structural features: Platelets or thrombocytes have oval or water droplet-like cell without nucleus. This blood cell is only 2.5 μ m in diameter, treated as the smallest cell in human body.
Functions: When platelets are broken, thromboplastin is released from them to initiate the reactions of blood coagulation.
What is meant by ABO blood group?
In 1901, Karl Landsteiner classified human blood into four groups, on the basis of distribution of agglutinogens (antigens) on RBC & agglutinins (antibodies) in plasma. There are two types of agglutinogens (A and B) & two types of agglutinins (α and β) found in blood. Based on this distribution human blood is classified into A, B, AB and O groups. This system of classification of blood is called ABO blood group.
Mention the distribution of agglutinins and agglutinogens in different blood groups in a tabular form.
The following table shows the distribution of agglutinins and agglutinogens in different blood groups.
|Agglutinogens in RBC
|Agglutinins in plasma
|A and B
|α and β
What is meant by universal donor of blood?
Due to absence of agglutinogen in RBC, a person having blood group ‘ O ‘ can donate blood to any group. In this case, chance of haemagglutination does not arise. Therefore, an individual having blood group ‘O’ is called universal donor.
What is meant by universal recipient of blood?
Due to absence of any agglutinin in plasma, people having blood group ‘AB’ can receive blood from any group. In this case, chance of haemagglutination does not arise. Therefore, an individual having blood group ‘AB’ is called universal recipient.
What is Rh factor?
Rh factor is an antigenic protein present in the RBC of most of the world’s population, which has close similarity with a factor present in RBC of Indian monkey Rhesus macaques. The people having this factor are treated as Rh+whereas those do not having it are regarded as Rh–
Mention the importance of Rh factor in blood transfusion.
If a person without Rh factor (Rh–) is transfused with blood from a person carrying Rh factor (Rh+), after 12 days, an antibody, called anti-Rh factor, develops in the recipient’s blood. In case the same person gets a second transfusion with Rh+blood, a reaction will take place between Rh factor (antigen) and anti-Rh factors (antibody) in his blood. This will lead to a fatal consequence due to agglutination and haemolysis of RBC.
What is erythroblastosis foetalis?
If an Rh–mother carries a Rh+foetus, the Rh antigen enters into mother’s blood from the foetus. In this situation, anti-Rh factor (antibody) develops in mother’s blood, which comes back to Rh+foetus and destroys the foetal RBC. As a result, the baby is born with serious anaemia. This is called erythroblastosis foetalis.
What is meant by blood transfusion? Mention its importance.
Blood transfusion: Blood transfusion is a technique of intravenous infusion of blood to a person who is deficient of blood or blood components.
importance: Blood is something, which cannot be prepared by any means. Therefore, a patient, suffering from severe anaemia or excessive blood loss has to be transfused with blood to replenish the need.
What is meant by blood clotting? Mention its importance.
Blood clotting: Blood clotting is a physiochemical process by which blood turns into a semisolid jelly-like mass or clot.
importance: Blood clots at the opening of a wound within a few minutes, hereby, stops bleeding and prevents excessive blood loss.
Mention different layers of the the walls of human heart.
The wall of heart has three layers. These are-
- Epicardium (outermost layer)
- Myocardium (middle layer)
- Endocardium (innermost layer)
What is mitral valve? What does mitral valve do?
Mitral valve: Mitral valve or bicuspid valve is the double cusped valve present at the left atrioventricular opening of the human heart.
Function: Mitral valve allows blood to flow from left atrium to left ventricle but prevents its backflow.
What is tricuspid valve? What does it do?
Tricuspid valve: Tricuspid valve is the triplecusped valve present at the right atrioventricular opening of the human heart.
Function: Tricuspid valve allows blood to flow from right atrium to right ventricle but prevents the backflow.
What do semilunar valves do?
In heart, the atrial semilunar valve allows the flow of oxygenated blood from the left ventricle through the aorta and prevents the backflow of blood. The pulmonary semilunar valve allows deoxygenated blood from the right ventricle to flow through the pulmonary artery and prevents the backflow.
What are papillary muscles?
The inner surface of the ventricular wall of heart gives off many inwardly directed columnar muscular projections. These projections are called papillary muscles.
What are chordae tendineae?
From the tip of the papillary muscles, inside ventricle, some strong cord-like tendons arise, these are called chordae tendineae.
Mention the role of chordae tendineae?
The chordae tendineae attach to the ventricular face of the cusps of right and left atrioventricular valves. When the ventricles contract, these strong cords prevent the valves against opening towards the atria.
Distinguish between open and closed circulation.
|1. Body cavity
|Blood opens in the body cavity
|Blood remains confined in the blood vessels
|3. Blood cells
|Very few cells are present in the matrix
|Different cells are present in liquid matrix Exception – Invertebrates
|Arthropods and molluscs
|Annelids and vertebrates
Distinguish between human blood and lymph.
|RBC, all types of WBCs and platelets
|1. Cellular components
|Does not come in direct contact with the tissue fluid
|3. Relation with tissue fluid
|Comes in direct contact with the tissue fluid
|RBC, all types of WBCs and platelets
Distinguish between plasma and serum.
|Matrix of blood
|Watery portion of clotted blood
|3. Coagulating factors
|Does not coagulate
Distinguish between haemoglobin and haemocyanin.
|1. Metallic component
|Plasma of some invertebrates and in RBC of vertebrates
|Body fluid of crustacean, arthropods and molluscs
|4. Transportation of respiratory gases
|Carries O2 and CO2
|Carries O2 only
Distinguish between universal donor and universal recipient.
|1. Blood group
|α and β
|A and B
|Can donate blood to any group but can receive the same blood group only
|Can receive blood from any group but can donate to the same group only
Distinguish between artery and vein.
|1. Origin and termination
|Originates from the heart and terminates into the capillaries
|Originates from the capillaries and terminates in the heart
|2. Walls and lumen
|Walls thick, lumen roundish
|Walls thinner, lumen flattish
|4. Pulsating movement
|Does not occur
|Carries oxygenated blood (except pulmonary artery)
|Carries deoxygenated blood (except pulmonary vein)
Distinguish between auricle and ventricle.
|Upper portion of the heart
|Lower portion of the heart
|Thinner and less muscular
|Thicker and highly muscular
|3. Inner surface
|Projects papillary muscles
|Receives blood from the veins (superior and inferior vena cava, and pulmonary vein)
|Circulates blood through the arteries (pulmonary artery, aorta)
Distinguish between systemic circulation and pulmonary circulation.
|1. Course of circulation
|From the heart to different organs (except lungs) and back
|From the lungs to heart and back
|2. Nature of blood
|3. Size of vessels
|Long and elaborate
|Short and compact
|4. Connection to lymphatic ducts
|Lymphatic ducts join to it
|Lymphatic ducts do not join to it
Distinguish between CSF and synovial fluid.
|In ventricles and lumens of the central nervous system
|In spaces of movable bone joints
|Transportation of nutrients, respiratory gases and excretory matters, and acts as a shock absorber
|Protection against frictional damage
Distinguish between tissue fluid and intercellular fluid.
|Inside the spaces within the tissues
|In the spaces between the cells
|Keeps tissue-cells alive by supplying nutrients
|Helps in the diffusion and osmosis of important materials
Long Questions and Answers : (5 marks for each question)
What is circulation? Mention the importance of circulation in living organisms. 1 + 4
Circulation is the physiological process by which nutrients, respiratory gases, hormones and metabolic waste matters are transported within a body through a fluid medium.
Importances of circulation
Circulation is important for the living organisms for the following purposes.
- Movement of nutrients and minerals: Water, essential minerals, food materials are transported to all tissues of a living body by means of circulation.
- Transport of respiratory gases: Respiratory gases, such as O2 and CO2, are transported within the body through the process of circulation.
- Removal of metabolic wastes: The unwanted matters, produced in the cells from metabolic activities are transported from the tissues to excretory organs for elimination.
- Movement of synthesized materials: Hormones, synthesized in cells, are transported to their target organs by means of circulation.
- Maintenance of heat: Circulatory fluid maintains the body heat in warm-blooded animals.
- Storage: Amino acids are stored in the circulatory fluid (blood) to form an amino acid pool. Some lipids (cholesterol) are also stored in the blood.
Give a brief account of the different components of human circulatory system.
Components of human circulatory system
Human circulatory system is composed of three major components-
- circulating fluids.
- a pumping organ (heart).
1. Circulating fluids: Blood and lymph are the circulating fluids of human circulatory system.
Blood: Blood is the red coloured fluid connective tissue, which carries different important materials through the blood vessels.
Lymph: Lymph is a special tissue fluid that flows through the lymphatic ducts and lymph glands and acts as another transporting medium.
2. Vessels: Blood flows through three types of vessels, which form an intricate network in the human body. These are-arteries, veins and capillaries.
Arteries: Arteries are thick-walled vessels with roundish lumen. They carry oxygenated blood (exceptionpulmonary arteries) from the heart to the tissues. Arteries show rhythmic pulsation.
Veins: Veins have thinner wall and flattish lumen. Veins carry deoxygenated blood (exception-pulmonary vein) from the tissues to the heart. They have valves to maintain the unidirectional blood flow.
Capillaries: These are very thin-walled blood vessels present in between the arteries and the veins. These fine vessels reach deep in the tissues.
3. Heart: It is a muscular, four-chambered sack-like structure, which pumps blood continuously into arteries and helps blood to flow through the network of vessels in the human body.
Schematically mention different types of blood corpuscles of human body.
Different types of blood corpuscles or cells of human body
Mention the functions of lymph, cerebrospinal fluid and sweat. 2 + 2 + 1
Functions of lymph
The functions of lymph are as follows-
- It supplies nutrients and oxygen deep into the tissues,
- Lymphocyte cells and antibodies present in the lymph, kill germs
- Absorbs fat from the intestine
- It collects the metabolic wastes from the tissue fluid
- Lymph maintains pressure, volume and composition of the tissue fluids.
Functions of cerebrospinal fluid
The functions of cerebrospinal fluid are mentioned below.
- Acts as a shock absorber for the brain & spinal cord
- Supplies nutrition and oxygen to the brain tissue
- Helps in the removal of metabolic wastes from the CNS.
Functions of sweat
The functions of sweat are as mentioned below.
1. It maintains the acid-base balance, water balance and the body temperature.
2. Some salts, urea and many other materials are excreted through sweat.
What is plasma? Briefly represent the composition of plasma. 1 + 4
Plasma is the yellowish, slightly alkaline, transparent watery matrix of blood.
Composition of plasma :
Plasma contains water (91-92%) and solid matters (8-9%). These solid matters include different inorganic and organic materials.
1. Inorganic matters of plasma (0.9 %) : Compounds of sodium, potassium, calcium, magnesium, phosphorus, iron, copper, chlorine, iodine etc.
2 Organic matters of plasma (7-8 %) : Organic matters of plasma are mentioned below.
- Protein-serum albumin, serum globulin, prothrombin, fibrinogen etc.
- Fat-cholesterol, lecithin, phospholipids, neutral fat molecules.
- Non-protein nitrogenous compounds-urea, uric acids, ammonia, creatinine, creatine etc.
- Pigments-bilirubin, biliverdin, β-carotene etc.
- Secreted materials-hormones, enzymes etc.
- Gases-oxygen, carbon dioxide etc.
Mention the functions of blood plasma? How is water utilised in human body? 3 + 2
Functions of blood plasma –
The functions of blood plasma are mentioned below.
- Plasma helps in transportation of nutrients, metabolic waste matters, hormones etc.
- It maintains acid-base balance of the body.
- Plasma proteins develop immunity and provide protection against many diseases.
- Plasma proteins, like prothrombin and fibrinogen, help in blood clotting.
Utility of water in human body
Water is utilised in the human body in different ways which are mentioned below.
- Water acts as the main component of the protoplasm.
- It helps in the hydrolysis of food matters in digestion.
- Water acts as the medium of diffusion and osmosis for nutrients, respiratory gases, metabolic wastes and hormones.
Briefly describe the role of blood in human body.
Functions of blood in human body
For human life, blood is an ultimate essentiality. We need blood for-
1. Iransportation of O2, CO2 and nutrients: Blood carries O2 and nutrients to different tissues and carries CO2 to lungs.
2. Removal of the metabolic wastes: Blood collect excretory matters from the tissues and carries those materials to respective excretory organs.
3. Movement of hormones from glands to target organs: Hormones, secreted from the hormone glands are transported to the tissues or other glands by blood.
4. Maintenance of body temperature: Blood carries glucose to all the tissues, which generate heat by oxidation to maintain the body temperature.
5. Resistance against infections: Neutrophils and monocytes kill germs by phagocytosis. Lymphocytes produce antibody. Thus, blood resists infection.
6. Preventing blood loss: Excessive loss of blood from wounds is restricted by its coagulating ability.
Explain the significance of blood grouping. How do you inspire somebody for blood donation? 2 + 3
Significance of blood grouping
Due to the presence of various agglutinogens and agglutinins, transfusion is not possible among all groups. If donor’s and recipient’s blood react to cause agglutination (antigen-antibody reaction i.e. coagulation of RBC), their blood groups will be treated as mismatch or incompatible. There will be no agglutination if the blood groups are compatible. In case of incompatible transfusion, agglutinogen of donor’s RBC reacts with agglutinin of recipient’s plasma to cause agglutination.
Ways to inspire somebody for blood donation
To inspire somebody for blood donation, I shall try to eliminate his on her misconceptions regarding blood donation by saying that-
- Blood donation causes no harm to the donor.
- The donated blood is replenished within a week.
- Blood donation reduces the chance of heart attack and hypertension.
- Blood can not be created artificially. So donated blood can save any needy patients life.
- It is a noble gesture of a person towards the society.
Mention the mechanism of blood coagulation in brief.
Mechanism of blood coagulation
The components involved in the main steps of blood clotting are enzyme thrombokinase or thromboplastin, calcium ion, plasma proteins like prothrombin and fibrinogen. The main steps of blood clotting are mentioned below.
1. Some blood platelets break near the wounds. From broken platelets enzyme Platelet-thromboplastin and from damaged tissue, tissuethromboplastin are secreted.
2. These two enzymes, with other proteins and Ca2+ prepare another enzyme named prothrombinase. This enzyme inactivates heparin and activates prothrombin into thrombin. This reaction is helped by calcium ions (Ca2+).
3. This thrombin then reacts with another plasma protein, fibrinogen, to produce fine thread-like fibrin molecules. In this reaction also calcium ions play a supporting role. The fibrin molecules form a dense network at the opening of the wound. The blood cells get trapped in that net. Within a few minutes blood at that point is transformed into a thick, viscous, jelly-like mass, called thrombus. This thrombus plugs the wound and stops bleeding.
Briefly describe the structure of human heart.
Structure of heart
Human heart is a hollow, muscular, blunt-ended conical sac-like structure. It is externally covered with a bilayered coating called pericardium.
If a human heart is cut longitudinally, we can see the following anatomical features in it.
1. Chambers of the heart: Human heart has four chambers. The upper two are called auricles or atria and the two, at the lower side are the ventricles.
Auricles or atria: Auricles have comparatively thinner wall. According to the relative position, these are denoted as left and right atria. The two atria are separated by inter-atrial septum.
Ventricles: These two chambers are located lower to the auricles. Ventricular walls are more thick and muscular. A thick inter-ventricular septum separates the two ventricles.
2. Valves of heart: The left and the right atria are connected to respective ventricles with two openings, called left and right atrioventricular apertures. These two apertures are fitted with two valves. The right atrioventricular valve has three cusps (flaps), so it is called tricuspid valve. The left one has two cusps, so it is called bicuspid valve or mitral valve.
The exits of aorta and pulmonary trunk are fitted with two outwardly directed valves. These are known as aortic valve and pulmonary valve respectively. These are commonly called semilunar valves because of their half moon-shaped cusps.
Describe the structure of pacemaker system of human heart.
Structure of pacemaker system of human heart
The pacemaker of human heart is made up of a few cardiac muscle cells, specialized to generate spontaneous impulse within the heart. This impulse is spread all over the heart and makes it beat continuously in a rhythm. These tissues are called the junctional tissues or pacemaker of the heart.
The main impulse generating centre of the heart is called sinoatrial node (SA node), located near the junction of superior vena cava and right auricle. It can generate 70-80 beats / min. The next centre is atrioventricular node (AV node), positioned at right atrioventricular wall. It can take over the charge from an inactive SA node and can generate 60-70 beats/ min. SA node and AV nodes are interconnected by three pairs of internodal connectors. From AV node a bundle of junctional tissues comes down through the interventricular septum. This is called bundle of His. This bundle is also capable of generating about 50 beats / min. This bundle then ramifies into several branches and spread in the ventricular wall as Purkinje fibres.
Briefly describe the course of circulation through human heart.
Course of circulation through human heart
Human heart beats spontaneously in a rhythmic fashion. Due to this contraction and expansion movement, blood is pumped through the blood vessels and circulates in the body. The contraction and expansion of the heart is called systole and diastole respectively. During systole and diastole following events occur in different chambers of the heart.
1. Diastole of auricles: In this phase the auricles expand and auriculoventricular valves close. Pressure decreases in the auricles. Soon deoxygenated blood from superior and inferior vena cava and coronary sinus enters into right auricle. At the same time oxygenated blood from pulmonary veins enters into left auricle.
2. Systole of auricles: As the auricles get completely filled, they contract. Pressure increases in the auricle. With this pressure, both tricuspid and bicuspid valves open towards right and left ventricles respectively.
3. Diastole of ventricles: Diastole of ventricles starts with the systole of auricles. With the opening of tricuspid and bicuspid valves deoxygenated blood enters into right ventricle and oxygenated blood rushes into left ventricle respectively.
4. Systole of ventricles: When the two ventricles get filled with blood, ventricular systole starts. So pressure increases inside these chambers. With this pressure tricuspid and bicuspid valves close with a jerk. With maximum ventricular pressure the pulmonary and aortic valves open at a time. Then deoxygenated blood from right ventricle and oxygenated blood from left ventricle are pumped out through pulmonary trunk and aorta respectively.
In human heart, blood flows through two separate circuits. The right portion of it carries deoxygenated blood and oxygenated blood flows through the left portion. In a normal human heart, mixing of two different types of blood never happens. Therefore, human heart acts as a perfectly double circuit heart.
Draw a line diagram of L.S. of human heart to show the course of circulation through it, with labelling.
Diagram of human heart
Following is a labelled diagram of L.S. of human heart showing course of circulation through it.
What is meant by double circulation? Show the path of double circulation with a schematic diagram. 2 + 3
In higher vertebrates like birds and mammals, heart is four chambered. Here blood flows in two separate circuits, one through systemic path and the other through pulmonary path. This type of circulation is known as double circulation. It is called a double circulatory system, since it has two loops. The one is from the heart to the lungs and the other is from the heart to the rest of the body.
Diagram of double circulation path –
The following labelled diagram shows the path of double circulation.
Comparison among human RBC, WBC and platelets.