6.3 Defense Flashcards
Is fibrinogen or fibrin in blood?
Fibrinogen is soluble in blood because it is a globular protein. Fibrin is a fibrous protein and no soluble.
What is a pathogen?
A pathogen is an organism or a virus/microbes that causes diseases
What is the first line of defence for the body?
The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
Skin:
- physical barrier (against damage)
- hair follicles secrete sebum (chemical) that maintains skin moist and low pH. low pH inhibits growth of bacteria and fungi
Mucous:
- thinner and softer “skin” found in nasal passages, head of penis and foreskin and vagina
- secrete a sticky solutiom of glycoproteins
- pathogens and harmful particles trapped in it (swallowed/expelled)
- also has antiseptic properties
What is the second line of defence?
When the skin is cut, it is sealed through blood clotting.
The liquid released will turn into semi-solid gel which seals up the wound and prevents further loss of blood and blood pressure.
Clotting is also important for:
- prevent entry of pathogens until new tissue has grown
How does blood clotting occur?
- cells/tissue is damaged/cut/bruised;
Temporary Plug
- damaged cells/platelets release clotting factors;
Reenforced placelets
- (clotting factors cause the) production of thrombin;
- thrombin is an enzyme
Glue
- blood plasma contains soluble fibrinogen;
- fibrinogen converted into fibrin;
- by thrombin;
- fibrin is insoluble
Other cells
- forms a net of fibres trapping more placelets and blood cells;
- forming a clot / prevents blood loss / entry of bacteria/pathogens;
- cascade of reactions/series of stages prevent accidental clotting/speed up clotting;
How is fibrin produced?
The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
Thrombin - enzume that converts soluble (globular)protein fibrinogen into the insoluble firbin (fibrous).
What are the causes and consequences of blood clot formation in coronary arteries?
- genetic – some people predisposed for high cholesterol levels / high blood pressure;
- age – older people greater risk / less elasticity in arteries;
- sex – males at great risk than females;
- smoking – constricts blood vessels / increases blood pressure/heart-rate / decreases
- oxygenation of heart muscle;
- diet – increases fat/cholesterol/LDL in blood / leads to plaque formation in arteries;
- exercise – lack of exercise increases risk;
- obesity – increase in blood pressure / leads to plaque formation in arteries; [4 max]
- Accept any other factor correctly explained e.g. diabetes, atherosclerosis
Discuss factors which affect the occurrence of coronary heart disease
- hypertension / high blood pressure;
- having parents who have experienced heart attacks indicates a genetic precondition;
- old age leads to less flexible blood vessels;
- risk in females increases post-menopause because of fall in estrogen level;
- being male (more risk than being female) because of less estrogen;
- smoking raises blood pressure because nicotine causes vasoconstriction;
- obesity strains heart;
- eating too much saturated fat and cholesterol promotes plaque formation /
- atherosclerosis;
- sedentary life style / lack of exercise;
- but excessive exercise can be dangerous;
- high salt diet / excessive amounts of alcohol / stress can also affect coronary heart
- disease;
What is a phagocyte?
pathocytes is a type of white blood cell. Ingestion of pathogens by pathocytic white blood cells gives non-specific immunity to dieseases.
- engulf pathogens by endocytosis and digest them with enzymes from lysomes
- pathocytes increase when wound becomes infected (white liquid called plus)
What is the third line of defence?
Production of antibodies by lymphocytes in repsonse to partcular pathogens gives specific immunity.
- proteins and other molecules on pathogens are recognized as foreign by body, where upon specific immunity reponse is stimulated
- The specific immune response is the production of antibodies in reponse to a particular pathogen.
- The antibodies bind to an antigen on that pathogen
What happens when pathogens overcome the first line of defence?
Pathogens start to multiply resulting in infection which relaeases histamines.
Histamines cause:
- increased blood flow to the site of infection (causes redness, swelling, pain/ throbbing, hot feeling)
- blood capillaries become leaky, which enables blood plasma and blood cells to escape from the capillaries into the site of infection
Phatocytes escape from leaking blood capillaries and travel to infection where they destroy invading pathogens (by phatocytosis)
What is a lymphocyte?
This is a type of white blood cell which gives specific immunity.
- produces antibody
- each lymphocyte produces only one type of antibody
What is an antigen?
Any chemical that stimulates an immune repsonse is referrd to as an antigen.
Examples include chemicals on the outer surface or a bacterium or virus, toxic chemicals released by a bacteria, pollen and other substances that cause an allergic reaction
Antibodies attach themselves to antigens.
How are antibodies produced?
- produced by lymphocytes
- There are intially very few lymphocytes to produce enough antibodiesto control a pathogen never infected before
- antigens on pathogen stimulate cell division of lymphocytes that produce appropriate antibody
- large clone of lymphocytes called plasma cells are produced that secrete antibodies to control pathogen (clear infection)
What are antibodies?
large proteins that have two functional regions:
- hypervariable region that binds to a specific antigen
- region that helps the body to fight the pathogen in one of a number ways:
- making a pathogen more recognizable to phagocytes so they are more readily engolfed
- preventing viruses from docking to host cells so that they cannot enter the cells
