Question and Answers on the Topic Defense Mechanisms

Question and answers on the topic Defense mechanisms → Defense: Ability of the body to prevent the entry of pathogens, and to destroy those that have already entered the body. → Defense mechanisms in our body: Body coverings and secretions - skin, mucous membrane, mucous, saliva, tears, etc. → Defense mechanisms in our body: Body fluids - Blood, lymph. → Skin is the protective covering of the body. → Epidermis: A protein called keratin present here prevents the entry of germs. → Sebaceous gland: Sebum produced by the gland makes the skin oily and waterproof. → Sweat gland: Disinfectants produced by this gland are present in sweat. These disinfectants destroy germs. → The mucous membrane is another protective covering of body parts. →Body fluids follow different defense strategies. These include: – controlling the entry of germs into the body – neutralising germs and the toxic substances they produce – preventing their multiplication → White blood cells play a significant role in defense. → When a wound occurs, that part swells up. This is called an inflammatory response. → Phagocytosis is the process of engulfing and destroying germs. →The white blood cells, namely monocytes and neutrophils, are phagocytes. →Blood clotting helps to prevent bleeding. It also checks the entry of pathogens through wounds. → Healing of wound is the stage after inflammatory response and blood clotting. →Fever is a condition when the body temperature rises above the normal level. → Non-specific defense mechanism: It protects us from all pathogens without considering their characteristic features. → Specific defense: The defense mechanism that identifies the structure of each antigen and destroys it specifically. → Foreign bodies or pathogens that enter the body and stimulate the defense mechanism are called antigens. → Lymphocytes are of two types: B lymphocytes and T lymphocytes. 1. Select the correct answer. Statement 1: Sebum produced by the sebaceous gland makes the skin oily and waterproof. Statement 2: The disinfectants present in the sweat produced by sweat glands destroy germs. (A) Statement 1 and Statement 2 are correct (B) Statement 1 and Statement 2 are wrong (C) Statement 1 correct; Statement 2 wrong (D) Statement 1 wrong; Statement 2 correct. Answer : (A) Statement 1 and Statement 2 are correct 2. Complete the table. Answer (a) Ear wax (b) Mouth (c) Lysozyme in tears (d) Stomach 3. Correct the statements given below by replacing the underlined words alone, if found incorrect. (a) Lymphocyte engulfs bacteria, synthesizes chemicals that destroy bacteria. (b) Monocytes engulf and destroy germs. (c) Eosinophil dilates the blood vessels. (d) Lymphocyte identifies and destroys germs specifically. (e) Basophil synthesizes chemicals required for inflammatory responses. Answer (a) Neutrophil engulfs bacteria, synthesizes chemicals that destroy bacteria. (c) Basophil dilates the blood vessels. (e) Eosinophil synthesizes chemicals required for the inflammatory responses. 4. Find out the odd one and give the common feature of the others. 1 Score Lysozyme, Neutrophil, Eosinophil, Basophil Answer Lysozyme. Others are white blood cells. 5.The stages related to inflammatory response are given below .Arrange them in the correct order. (i) Blood capillaries dilate. (ii) Neutrophils and monocytes engulf and destroy germs. (iii) The cells that get damaged by a wound or by an infection produce certain chemical (iii) The cells that get damaged by a wound or by an infection produce certain chemical substances. (iv) Germs enter through wounds . (v) White blood cells reach the wound site through the walls of the capillaries. Answer iv, iii, i, v, ii 6. Select the correct answer. The white blood cells that engage in phagocytosis. (A) Neutrophils, Basophils (B) Monocytes, Neutrophils (C) Eosinophil, Basophils (D) Lymphocyte, Monocyte Answer (B) Monocytes, Neutrophils 7. Observe the illustration and answer the questions given below. (a) Identify the defense action. (b) Name the white blood cells participating in this defense action. (c) What is the role of the part indicated as X in this defense action? Answer (a) Phagocytosis (b) Monocytes and Neutrophils (c) Lysosome combines with membrane sac. The pathogens are degenerated and destroyed by the enzymes in the lysosome. 8. A stage in blood clotting is given below. Fibrinogen is converted to fibrin fibres in the presence of thrombin. (a) How is thrombin formed? (b) How does this stage help in blood clotting? Answer (a) In the presence of thromboplastin, calcium and vitamin K, prothrombin in plasma is converted to thrombin. (b) The red blood cells and platelets get entangled in the network of fibrin fibres to form the blood clot. 9. The stages related to fever are given below as a flowchart. Complete the flow chart. Pathogens enter the body—>......(i)……..—>(ii)…….—> (iii)……—>(iv)...... Answer (i) The presence of toxins produced by the pathogens stimulates white blood cells. (ii) The chemical substances produced by the whiteblood cells raise body temperature. (iii) The rise in body temperature reduces the rate of multiplication of the pathogens. (iv) Increases the effect of phagocytosis.