Chapter 7.2 Non-specific Defences Against Disease ✓ Flashcards
(50 cards)
What are specific defences and non-specific defences?
-Specific defences are directed at a particular pathogen
-Non-specific defences work against all pathogens
What are external defences that stop pathogens from entering the body?
Short answer:
-Skin
-Mucus
-Hairs
-Cilia
-Acids
-Lysozyme
-Cerumen
-Movement of fluids
Skin
-Effective barrier covering the outside of the body. -Good at stopping the entry of micro-organisms, provided it is not broken by cuts or abrasions.
-The skin has other defence mechanisms such as it has an oily secretion called sebum which is produced by oil glands in the skin. It contains substances that kill some pathogens.
-Sweat secreted onto the skin contains salts and fatty acids that prevent the growth of many micro-organisms
Mucus
-Mucous membranes lines the body cavities that open to the exterior.
-They secrete mucus which traps air particles and therefore inhibits the entry of micro-organisms.
-The digestive, urinary and reproductive tracts are all protected in this way.
Hairs
-Hairs found in nasal cavity in the nose and ears.
-In the nose, the hairs and a layer of mucus trap up to 90% of particles inhaled when breathing
Cilia
-Tiny hair-like projections from cells that are capable of a beating motion.
-The mucous membranes lining the nasal cavity, the trachea and other air passages have cilia.
-The beating of the cilia moves mucus, containing trapped particles and micro-organisms, towards the throat, where it may be coughed up or swallowed
Acids
-Stomach juices are strongly acidic. The acid kills many of the bacteria taken in with food of those contained in mucus swallowed from the nose and windpipe.
-The vagina also has acid secretions that reduce growth of micro-organsims,
-Urine and the sweat on the skin are also slightly acidic.
Lysozyme
-An enzyme that kills bacteria.
-The eyes are protected by the flushing action of tears, which contain this enzyme.
-Lysozyme is also found in saliva, sweat, secretions of the nose and tissue fluid.
Cerumen
-Or ear wax, protects the outer ear against infection by some bacteria.
-It is slightly acidic and contains lysozyme
Movement of fluid
-The flushing action of body fluids helps to keep some areas relatively free of pathogens
-Urine flowing through the urethra has a cleansing action.
-This prevents bacterial growth and helps to stop bacteria reaching the bladder and kidneys.
-Women have a shorter urethra than men and so they tend to suffer more bladder infections.
-Tears, sweat and saliva are also involved in flushing and cleansing.
On diagram
-Eyes (cleansed by tears)
-Nasal cavity (hairs and mucus trap micro-organisms)
-Mouth cavity (mucous membrane traps micro-organisms and the mouth is cleansed by saliva)
-Skin (a barrier)
-Urethra (Urine flow prevents bacterial growth)
-Anus (Mucous membrane traps micro-organisms)
-Vagina (acidic secretion inhibit growth of pathogens)
-Stomach ( acidic juices kill many micro-organisms)
-Trachea and bronchi (mucus layer traps micro-organisms)
-Ear (cerumen inhibits bacterial growth)
What is a reflex?
An automatic, involuntary response to a stimulus.
What do protective reflexes help to protect?
Help to protect the body from injury by removing foreign particles in an automatic involuntary response
What are the four reflexes that help protect the body against infection?
Simple answer
-Sneezing
-Coughing
-Vomiting
-Diarrhoea
Sneezing
-The stimulus is irritation of the walls of the nasal cavity
-The irritation may be caused by harmful fumes or dust particles, which are likely to be carrying micro-organisms.
-Forceful expulsion of air from the lungs carries mucus, foreign particles and irritating gases out through the nose and mouth.
Coughing
-The stimulation is irritation in the lower respiratory tract - the bronchi and bronchioles
-Similar to sneezing, air if forced from the lungs to try to remove the irritant
-The air drives mucus and foreign matter up the trachea towards the throat and mouth.
Vomiting
-Psychological stimuli, excessive stretching of the stomach and bacterial toxins can all induce vomiting
-Contraction of the muscles of the abdomen and the diaphragm, not the contraction of the stomach, expels the stomach contents.
Diarrhoea
-Irritation of the small and large intestine by bacteria, viruses or protozoans can cause diarrhoea
-The irritation causes increased contractions of the muscles of the wall of the intestines so that the irritant is removed as quickly as possible.
-Material does not stay in the large intestine long enough for water to be absorbed, so the faeces are very watery.
What are phagocytes?
Specialised white blood cells that engulf and digest micro-organisms and cell debris
What are leucocytes?
white blood cells
What are the different types of cells that are phagocytic?
Short answer
-Monocytes and macrophages
-Neutrophils
-Dendritic cells
Monocytes and macrophages
-When a tissue becomes infected or inflamed, monocytes leave the bloodstream and enter the tissue.
-Here they differentiate into macrophages, which are large phagocytic cells.
-Some macrophages move through the tissues looking for and destroying pathogens
-Others are fixed in one place and only deal with the pathogens that come to them
-Macrophages are particularly important in removing microbes and dying cells through phagocytosis
Neutrophils
-Described as granulated leucocytes, due to the granules visible in their cytoplasm
-They are also characterised by their lobulated (consisting of or divided into lobules) nucleus
-Most abundant leucocytes, accounting for 55-70% of all leucocytes
-During an infection, neutrophils are the first cells to move into the tissue to destroy the pathogen by phagocytosis
-They are particularly important in killing pathogens inside cells
-They have a short life span and die after a few days.
-The dead cells make up a large portion of the pus that forms after an infection.
Dendritic cells
-Characterised by projections from the cytoplasm
-Their function goes beyond just phagocytosis (compared to other leucocytes)
-These cells have the ability to detect, engulf and process foreign particles
-They then use information about the ingested particle to assist with specific immunity
What is inflammation?
The response to damage to a tissue. It involves swelling, heat, pain and redness in the affected area
Words ending in what indicates it is an inflammation?
-itis
e.g. tonsillitis
What are the purposes of an inflammation?
-To reduce the spread of any pathogens, to destroy them and to prevent the entry of additional pathogens
-To remove damaged tissue and cell debris
-To begin repair of the damaged tissue
What are the four signs of inflammation?
-Swelling in affected area
-Pain in affected area
-Heat in affected area
-Redness in affected area
What is the complement system?
A system of proteins produced by the liver that enhances the activity of antibodies and phagocytes
What are the steps of the inflammatory response?
1) Mechanical damage or local chemical changes causes specialised leucocytes called mast cells to be activated by complement proteins. This results in the release of histamine, heparin and other chemicals into the tissue fluid.
2) Histamine increases blood flow through the area due to vasodilation, making the walls of the blood capillaries more permeable. More fluid moves through the capillary wall into the tissue. The increased blood flow causes heat and redness and the escape of fluid from the blood causes swelling
3) Heparin prevents clotting, so the release of heparin from the mast cells prevents clotting in the immediate area of the injury. A clot of the fluid forms around the damaged area, which slows the spread of the pathogen into healthy tissue.
4) Complement system proteins and some chemicals released by the mast cells attract phagocytes, particularly neutrophils, which actively consume micro-organisms and debris by phagocytosis.
5) The abnormal conditions in the tissue stimulate pain receptors, and so the person feels pain in the inflamed area
6) The phagocytes filled with bacteria, debris and dead cells, begin to die. The dead phagocytes and tissue fluid form a yellow liquid called pus.
7) New cells are produced by mitosis and repair of the damaged tissue takes place
What are mast cells?
A type of cell found in loose connective tissue; involved in the inflammatory response
What do mast cells release?
Histamine and heparin
What is a fever?
An elevation of body temperature above the normal temperature 37°C
A change in the body’s temperature is controlled by what?
The hypothalamus
What are pyrogens?
A substance that results in a fever
What releases pyrogens?
Leucocytes or White blood cells
What is interleukin-1?
A pyrogen produced primarily by macrophages
Describe the body temperature during a fever (the graph pg166)
-Due to infection, the body’s thermostat becomes set at an abnormally high level
-The body fells cold and responds by shivering and vasoconstriction in the skin
-Body temperature rises
-The fever breaks, with sweating and vasodilation in the skin
-Body temperature falls to normal
What is a fever considered beneficial?
-High body temperature is believed to inhibit the growth of some bacteria and viruses.
-Heat speeds up the rate of chemical reactions, which may in turn help body cells repair themselves more quickly during a disease
-May also inhibit viral replication by allowing chemicals called interferons to operate more quickly
What are interferons?
Any of several proteins that are produced by cells as a defensive response to viral infection, preventing replication of the virus
