CBSE Class 11 Biology Body Fluids And Circulation Worksheet Set C

 

 Body Fluids And Circulation

 

Circulation is the transport of nutrients, oxygen, CO₂ and excretory products to the concerned tissues or organs. For circulation, simple organisms (sponges, coelenterates etc.) use water from their surroundings. Complex organisms use body fluids (blood & lymph) for circulation.

♠  CIRCULATORY PATHWAYS

Circulatory system is 2 types- Open and Closed.

• Open circulatory system: Here, the blood pumped by the heart passes through large vessels into open spaces or cavities called sinuses. E.g. Arthropods and molluscs.

• Closed circulatory system: Here, the blood pumped by the heart is always circulated through blood vessels. This system is more advantageous as the flow of fluid can be more precisely regulated. E.g. Annelids and chordates. All vertebrates have a muscular chambered heart.

• Fishes: 2-chambered heart (an atrium + a ventricle).

• Amphibians: 3-chambered heart (2 atria + a ventricle).

•  Reptiles (except crocodiles): 3-chambered heart (2 atria + a ventricle). Ventricle is incompletely partitioned.

• Crocodiles, birds & mammals: 4-chambered heart.

•  Single circulation in fish: In fishes, heart receives impure blood only (venous heart). Deoxygenated blood from heart → oxygenated by gills → supplied to body parts → deoxygenated blood → to heart.

•  Incomplete double circulation in amphibians & reptiles: Left atrium receives oxygenated blood from the gills/lungs/skin and right atrium gets the deoxygenated blood from other body parts. However, they get mixed up in the single ventricle which pumps out mixed blood.

•  Double circulation in birds & mammals: Oxygenated and deoxygenated blood received by the left and right atria respectively passes on to ventricles of the same sides. The ventricles pump it out separately without any mixing up.

BLOOD VASCULAR SYSTEM

It includes Heart, Blood vessels & Blood.

♦ BLOOD

Formed of plasma (55%) & formed elements (45%).

a. Plasma

Straw-coloured, slightly alkaline (pH 7.4) viscous fluid.

♦ Constituents of plasma

• Water (90-92%): It is a good solvent.

• Plasma proteins (6-8 %): Include

o Fibrinogen: For blood coagulation.

o Globulins: Act as antibodies (for defense of the body).

o Albumins: For osmotic balance. Regulate blood pressure.

• Glucose, amino acids, lipids & cholesterol

• Inorganic constituents: Na⁺, K⁺, Mg²⁺, Cl^-, HCO₃ ^- etc.

• Gases like CO₂, O₂, N₂ etc.

Plasma without clotting factors is known as Serum.

b. Formed elements (RBC, WBC & platelets)

• Red Blood Cells (RBC) or Erythrocytes:

- Biconcave non-nucleated cells. No mitochondria, Golgi complex etc. Red colour is due to Haemoglobin (iron containing protein). Normal Hb level is 12-16 g/ 100 ml.

- Count: 5 - 5.5 millions/ mm³.

- Formed in: Red Bone marrow.

- Average lifespan: 120 days. Worn-out RBCs are destroyed in spleen (graveyard of RBCs).

- Function: CO₂ and O2 transports.

• White Blood Cells (WBC) or Leucocytes:

- Colourless nucleated cells. Different types.

- Count: 6000-8000 /mm³.

- Formed in: Bone marrow, lymph glands, spleen.

- Average lifespan: Generally short lived (1- 15 days).

- Function: Part of immune system.

♠ Types of WBC: Granulocytes & Agranulocytes

1. Granulocytes

They are 3 types:

a. Neutrophils (Heterophils): 60-65%. Soldier of the body.

Function: Phagocytosis.

b. Eosinophils (Acidophils): 2-3%. Resist infections.Cause allergic reactions.

c. Basophils (Cyanophils): 0.5-1%. Secrete histamine,serotonin, heparin etc. Cause inflammatory reactions.

2. Agranulocytes

They are 2 types:

a. Lymphocytes (20-25%): Smallest WBC with largest nucleus. Includes B- lymphocytes & T- lymphocytes. Cause immune responses. Secrete antibodies.

b. Monocytes (6-8%): Largest WBC.

Function: Phagocytosis.

•  Platelets (Thrombocytes):

- Colourless non-nucleated cell fragments.
- Count: 1.5 - 3.5 lakhs /mm3.
- Formed in: Megakaryocytes in Bone marrow.
- Average lifespan: 7 days.
- Function: Blood clotting.

♠ BLOOD COAGULATION

It is a mechanism for haemostasis (prevention of blood loss through injuries). It involves the following events:

Clumped platelets & tissues at the site of injury release thromboplastin → It forms an enzyme, thrombokinase (Prothrombinase) → Thrombokinase hydrolyses prothrombin to thrombin in presence of Ca2+ →Thrombin converts soluble fibrinogen to insoluble fibrin → Fibrin traps dead & damaged formed elements to form clot (coagulum).

BLOOD GROUPS (ABO grouping & Rh Grouping)

Blood groups were discovered by Carl Land Steiner.

1. ABO grouping

It is based on presence or absence of 2 surface antigens (chemicals that induce immune response) on RBCs namely A & B. Similarly, plasma contains 2 antibodies (proteins produced in response to antigens) namely anti-A & anti-B.

- Antigen A reacts with anti-A. Antigen B reacts with anti-B.
- If bloods with interactive antigens & antibodies are mixed together, it causes clumping (agglutination) of RBCs.
- Persons with O Group are called Universal donors because they can donate blood to persons with any other blood group. Persons with AB group are called Universal recipients because they can accept blood from all groups.

2. Rh grouping

- Rhesus (Rh) factor is another antigen found on RBC.

- Rh+ve means the presence of Rh factor and Rh-ve means absence of Rh factor. Nearly 80% of humans are Rh+ve.
- Anti-Rh antibodies are not naturally found. So Rh-ve person can receive Rh+ve blood only once but it causes the development of anti-Rh antibodies in his blood. So a second transfusion of Rh+ve blood causes agglutination. Therefore, Rh-group should be matched before transfusion.

 ♠ Erythroblastosis foetalis

- It is an Rh incompatibility between the Rh-ve blood of a pregnant mother and Rh+ve blood of the foetus.
- Rh antigens do not get mixed with maternal blood in first pregnancy because placenta separates the two bloods.
- But during first delivery, the maternal blood may be exposed to small amount of foetal blood (Rh+ve). This induces the formation of Rh antibodies in maternal blood.
- In case of her subsequent pregnancies, the Rh antibodies from the mother leak into the foetal blood (Rh+ve) and destroy the foetal RBCs. This is fatal to the foetus or cause severe anaemia and jaundice to the baby. This condition is       called Erythroblastosis foetalis.
- It can be avoided by administering anti-Rh antibodies to the mother immediately after the first delivery

BLOOD VESSELS

Blood vessels are 3 types: Arteries, Veins & Capillaries.

•  Arteries: They carry blood from heart to other tissues. They contain oxygenated blood (except pulmonary artery). Their smaller branches are called arterioles. Arteries are 3- layered- inner tunica intima (squamous endothelium), middle tunica media (smooth muscles & elastic fibres) and outer tunica externa (fibrous connective tissue).

•  Veins: They carry blood towards heart. They contain deoxygenated blood (except pulmonary vein). Their smaller branches are called venules. Veins are also 3- layered but tunica media is comparatively thin.

•  Capillaries: In tissues, arterioles divide into thin walled and single layered vessels. They are called capillaries. They unite into venules.

STRUCTURE OF HEART

- Heart is a mesodermally derived organ located in mediastinum and protected by double-layered pericardium.

- The pericardial space (between pericardial membranes) is filled with pericardial fluid. It reduces the friction between the heart walls, and surrounding tissues.

- The heart is 4 chambered, two upper atria (auricles) and two lower ventricles. The walls (cardiac muscles) of the ventricles are much thicker than that of the atria.

- The atria are separated by an inter-atrial septum and the ventricles are separated by inter-ventricular septum.

- In between atrium and ventricle there is a thick fibrous atrio-ventricular septum with an opening.

- A tricuspid valve (3 muscular flaps or cusps) guards the opening between right atrium and right ventricle. A bicuspid (mitral) valve guards the opening between left atrium and left ventricle. These valves allow the flow of blood only in one direction, i.e. from atria to ventricles.

- The openings of right and left ventricles into pulmonary artery and aorta respectively are provided with the semilunar valves. They prevent backwards flow of blood.

CONDUCTING SYSTEM OF HEART

- Human heart is myogenic, i.e. normal activities of heart are auto regulated by nodal tissues (a specialized cardiac musculature present in heart wall). It consists of

o Sino-atrial node (SAN) in the right upper corner of the right atrium.

o Atrio-ventricular node (AVN) in the lower left corner of the right atrium close to the atrio-ventricular septum.

- From the AVN, a bundle of fibrous atrio-ventricular bundle (AV bundle) passes through atrio-ventricular septa and divides into a right & left branches. Each branch passes through the ventricular walls of its side. In the ventricular wall, it breaks up into minute fibres (Purkinje fibres). These fibres along with the bundles are known as bundle of His.

- Nodal tissues generate action potential without any external stimuli, i.e. it is autoexcitable. SAN initiates and maintains contraction of heart by generating action potentials (70-75/min). So it is called the pacemaker

 

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