functions of skin, mucous membrane, types of immunity, phagocytosis

Unit 3, 3 of Microbiology GBSN semester 1 year 1

1. U-3, 3 OF “DEFENSE MECHANISMS OF THE BODY” By: Aftab H. Abbasi RN, DCHN, BSN, MA, LL.B Lecturer Nursing Qadri College of Health Sciences Karachi QADRI COLLEGE OF HEALTH SCIENCES, KARACHI

2. “DEFENSE MECHANISM OF THE BODY” This unit focuses on the resistance of the body which microorganism’s encounter where they enter in the human body. - This unit highlights the importance of the resistance or defense of the body which will help learners in understanding that why infection occurs sometimes and not always.

3. “DEFENSE MECHANISM OF THE BODY” At the completion of this unit learners will be able to: 1- Explain the role of good health in protection against the microbial infection. 2- Define Resistance and Susceptibility. 3- Define Nonspecific Resistance. 4- Describe the role of the skin and mucous membrane in nonspecific Resistance. 5- Explain the process of Phagocytosis. 6- Define the Specific Resistance, Innate Resistance and Immunity. 7- Explain four types of acquired Immunity.

4. “DEFENSE MECHANISM OF THE BODY” At the completion of this unit learners will be able to : 8- Differentiate between humoral and cell mediated immunity. 9- Define Antigens, happen and antibodies. 10- List the five classes of antibodies and their functions. 11- Explain the role of memory, tolerance and specificity in immunity. 12- Distinguish between primary and secondary immune response. 13- Define Hypersensitivity. 14- Differentiate between i.e. delayed and immediate Hypersensitivity.

5. 2- Resistance and Susceptibility.

6. 2- Resistance and Susceptibility. DEFINITION OF RESISTANCE : However, the host can also defend itself by limiting the damage that is caused by the  infection . Resistance  is defined as the ability to limit pathogen burden, whereas tolerance is defined as the ability to limit the health impact of a given pathogen burden.

7. 2- Resistance and Susceptibility. DEFINITON OF SUSCEPTIBILITY : Disease Susceptibility  is a condition in which the individual is at a risk of getting infected by a  disease . Some  diseases  that are thought to have an inherited or genetic component are seen to cluster in families and affect more than one generation, but without a clear pattern of inheritance as for monogenic  diseases .

8. 2- Resistance and Susceptibility. Susceptibility- the quality or state of being  susceptible  especially : lack of ability to resist some extraneous agent (such as a pathogen or drug). A Susceptible Host : Is a person who can become infected by the infectious agent. Susceptible host include: Patients Health care professional Visitor from the community.

9. 4- Role of the skin and mucous membrane in nonspecific Resistance. Skin- main barrier which prevents entry of the micro-organisms . One of the body’s most important physical barriers is the  skin barrier , which is composed of three layers of closely packed cells. The thin upper layer is called the epidermis. A second, thicker layer, called the dermis, contains hair follicles, sweat glands, nerves, and blood vessels. A layer of fatty tissue called the hypodermis lies beneath the dermis and contains blood and lymph vessels.

10. 4- Role of the skin and mucous membrane in nonspecific Resistance . The topmost layer of skin, the epidermis, consists of cells that are packed with keratin. These dead cells remain as a tightly connected, dense layer of protein-filled cell husks on the surface of the skin. The keratin makes the skin’s surface mechanically tough and resistant to degradation by bacterial enzymes. Fatty acids on the skin’s surface create a dry, salty, and acidic environment that inhibits the growth of some microbes and is highly resistant to breakdown by bacterial enzymes. In addition, the dead cells of the epidermis are frequently shed, along with any microbes that may be clinging to them. Shed skin cells are continually replaced with new cells from below, providing a new barrier that will soon be shed in the same way.

11. 4- Role of the skin and mucous membrane in nonspecific Resistance. Infections can occur when the skin barrier is compromised or broken. A wound can serve as a point of entry for opportunistic pathogens, which can infect the skin tissue surrounding the wound and possibly spread to deeper tissues . Barrier which prevents entry of microbes into the body which comes in contact with body.

12. 4- Role of the skin and mucous membrane in nonspecific Resistance. Role of Mucous Membrane in Nonspecific Resistance : Mucus coating- present at epithelium lining of the respiratory, gastrointestinal and urogenital tracts -trap microbes. Mucous membranes provide a mechanical barrier at body openings. They also line the respiratory, GI, urinary, and reproductive tracts. Mucous membranes secrete  mucus , a slimy substance that traps pathogens. The membranes also have hair-like cilia. The  cilia  sweep mucus and pathogens toward body openings where they can be removed from the body. When you sneeze or cough, pathogens are removed from the nose and throat.

13. 5- The process of Phagocytosis . Phagocytosis : Phagein = "to devour", kytos = "cell“, osis = “process” (from Ancient Greek) Phagocytosis: I s the process of engulfment and destruction of solid particles such as bacteria, dead tissue and foreign particles by the cells.

14. 5- The process of Phagocytosis. Phagocytes : The cells performing phagocytosis are called phagocytes. The cell types are: • Neutrophils • Monocytes and • Macrophages

15. 5- The process of Phagocytosis. Steps : Margination: Rolling and Adhesion — In margination, leukocytes assume marginal positions in the blood vessels. 2. Diapedesis: Resting phagocytes are activated by inflammatory mediators and produce surface receptors that increase their ability to adhere to the inner surface of capillary walls enabling them to squeeze out of the capillary and enter the tissue.

16. 5- The process of Phagocytosis. 3. Chemotaxis: I s the movement of phagocytes toward an increasing concentration of some attractant such as bacterial factors (bacterial proteins, capsules, LPS, peptidoglycan, teichoic acids, etc .) 4. Opsonization: (attachment stage) R efers to the process of coating of bacteria by the opsonins. The opsonin coated bacteria gets attached to the surface of phagocyte through the opsonin receptors.

17. 5- The process of Phagocytosis. 5. Engulfment stage 6. Secretion (degranulation) stage 7. Degradation stage

18. 7- Four types of acquired Immunity . What is acquired immunity? Acquired immunity is immunity you develop over your lifetime. It can come from: - a vaccine - exposure to an infection or disease - another person’s antibodies ( infection- fighting immune cells)

19. 7- Four types of acquired Immunity. 1- Active immunity: Active immunity is the most common type. It develops in response to an infection or vaccination. These methods expose your immune system to a type of germ or pathogen (in vaccinations, just a small amount). Immune cells called T and B cells recognize there’s an “invader” pathogen and activate the immune system to fight it. The next time the T and B immune cells encounter that specific germ, they’ll recognize it and immediately activate the rest of your immune system to prevent you from getting sick.

20. 7- Four types of acquired Immunity. 2- Passive immunity: Passive immunity develops after you receive antibodies from someone or somewhere else. This type of immunity is short-lived, because it doesn’t cause your immune system to recognize the pathogen in the future. There are two main types of passive immunity: Maternal antibodies: are antibodies that transfer from a mother to child. This usually happens across the placenta or through breast milk, especially in the first few days after birth. Immunoglobulin treatments: are antibodies that are usually used to treat people at risk for infections, like after a snakebite or a baby born to a mother with hepatitis B. These antibodies are made in a lab, or come from other people or animals.

21. 7- Four types of acquired Immunity. Both natural and artificial sources of immunity can be active or passive. 3- Natural sources: aren’t specifically given to you to boost your immunity. Instead, they’re something you acquire by natural means, like an infection or from your mother during birth . 4- Artificial sources: of immunity are given to you for a specific purpose. They include vaccinations or immunoglobulin treatments.

22. 7- Four types of acquired Immunity. https://www.healthline.com/health/acquired-immunity

23. “DEFENSE MECHANISM OF THE BODY”

24. QADRI COLLEGE OF HEALTH SCIENCES, KARACHI By: Aftab H. Abbasi RN, DCHN, BSN, MA, LL.B Lecturer Nursing Qadri College of Health Sciences Karachi