title Body defence

19.2 Non-specific defence methods 19.3 Specific defence methods content Body defence 19.1 What is body defence? 19.2 Non-specific defence methods 19.3 Specific defence methods 19.4 Vaccination

19.1 What is body defence? a function of the mammalian body which protects it from diseases caused by pathogens 2 types of defences prevent pathogens from entering the body fight against pathogens which have already entered the body

defence methods that prevent all types of pathogens

NON-SPECIFIC defence methods defence methods that prevent all types of pathogens pathogens

defence methods more powerful ! SPECIFIC defence methods more powerful ! defence methods that defend against certain type(s) of pathogens pathogens

19.2 Non-specific defence methods digestive system all have non-specific protective methods to prevent or reduce the entry of pathogens enter our body through respiratory system pathogens first line of defence reproductive system skin

Physical barriers Skin epidermis stops entry of pathogens sebum & sweat contain antiseptics sebum

Physical barriers Ciliated epithelium of the respiratory tract pathogens trapped by mucus and cilia cilia beat to move the trapped pathogens upwards to be swallowed

Chemical barriers Gastric juice secreted by gastric glands with hydrochloric acid that can kill pathogens gastric gland

Chemical barriers Other secretions kill or stop the growth of pathogens examples sweat and oils saliva tears mucus

AFTER 1 DAY Blood clotting prevents the entry of pathogens through wounds fibres hold the edge of a wound together epidermal cells red blood cell caught in fibres to form a clot AFTER 1 DAY connective tissue tiny platelets help in making fibres from some blood proteins damaged blood vessel

AFTER 2 DAYS Blood clotting edges of the epidermis start to grow together white blood cell leaves blood vessel and moves towards the wound AFTER 2 DAYS white blood cells start to engulf bacteria and debris

AFTER A WEEK Blood clotting scab thin layer of epidermis white blood cells still in action, then gradually return to blood vessels

Blood clotting scab falls off intact epidermis repaired blood vessel new connective tissue

Phagocytosis the engulfing and digesting process of pathogens by phagocytes a kind of white blood cells during which the pathogens are killed and digested by enzymes Phagocytosis

The inflammatory response pathogens phagocytes in tissue engulf and digest pathogens skin more phagocytes come out of the blood vessel blood vessel dilates phagocyte in blood

Inflammatory response The inflammatory response Inflammation because of the dilation of blood vessels and extra tissue fluid, the infected area becomes red, swollen and painful Pus a whitish liquid from the wound contains dead white blood cells Phagocytosis Second line of defence Inflammatory response

19.3 Specific defence methods pathogens not killed by phagocytes get into blood immune response triggered specific and more powerful but takes time to begin disease may have serious effects before initiation of immune response

Antibody production antibodies are produced by lymphocytes lymphocytes a kind of white blood cells antigens lymphocytes detected by produce proteins on the surfaces of pathogens Y- shaped proteins antibodies

do not kill pathogens directly Antibodies do not kill pathogens directly act against pathogens in a number of ways: Lysis hole antibodies attached make holes in the cell walls/protein coats pathogen lysed and killed antibodies pathogen

do not kill pathogens directly Antibodies do not kill pathogens directly act against pathogens in a number of ways: Help in phagocytosis antibodies attached to bacteria and make it easier for phagocytes to engulf them a phagocyte engulfing a bacterium the bacterium is engulfed and killed by the phagocyte

do not kill pathogens directly Antibodies do not kill pathogens directly act against pathogens in a number of ways: Sticking pathogens together pathogens stuck together by antibodies and cannot reproduce or enter cells due to the large size antibodies pathogens

the breaking-down process of dead pathogens in the liver Detoxification the breaking-down process of dead pathogens in the liver Not all pathogens lead to the formation of antibodies Some pathogens lead to other kinds of immune responses

days after first infection Primary and secondary immune responses concentration of antibodies in blood days after first infection 7 14 21 28 35 When a type of pathogen enters the body for the first time, it stimulates the production of antibodies. latent period first infection Primary response

days after first infection Primary and secondary immune responses concentration of antibodies in blood days after first infection 7 14 21 28 35 After this first response, ‘memory cells’ will ‘memorize’ the pathogen. certain kinds of white blood cells latent period first infection Primary response Recovery

days after first infection Primary and secondary immune responses concentration of antibodies in blood days after first infection 7 14 21 28 35 Next time when the same pathogen enters, many more antibodies will be produced in a much shorter time. latent period shorter latent period first infection re-infection Primary response Recovery Secondary response

19.4 Vaccination Natural immunity Artificial immunity Inborn body defence Vaccination

antigens memorized by the lymphocytes 19.4 Vaccination Injection of controlled amounts of Primary response a pathogen antigens memorized by the lymphocytes an altered form of a pathogen which have been made harmless

more lymphocytes and specific antibodies produced in a shorter time 19.4 Vaccination Enhanced resistance to injected diseases if infected again Secondary response more lymphocytes and specific antibodies produced in a shorter time

Concept diagram Body defence diseases pathogens is the protection of the body from consists of diseases caused by pathogens non-specific defence methods specific defence methods have consist of include

Concept diagram non-specific defence methods physical barriers consist of physical barriers chemical barriers blood clotting phagocytosis by phagocytes include include often associated with an skin ciliated epithelium (of the respiratory tract) gastric juice other secretions e.g. tears inflammatory response the second line of defence ( kills pathogens or makes them harmless) the first line of defence (prevents entry of pathogens) natural immunity

specific defence methods Concept diagram specific defence methods have include antibody production (by lymphocytes) other methods immune response natural immunity

Concept diagram specific defence methods primary response have primary response secondary response on future re-exposure to same antigens leads to has is memory a more powerful and faster response due to production of memory cells basis of artificial immunity by vaccination