Explain How Microorganisms Enter The Body
Biology Unit 1 – Section 3.1.1
Microorganisms as Pathogens
To be considered a pathogen it must:
Gain entry
Colonise the tissues
Resist the defences
Cause damage to the tissues
Pathogens include bacteria, viruses and fungi
How do microorganisms enter the body
Many pathogens enter through the gas exchange system (including ones that cause flu and
TB)
Food and water can carry pathogens into the stomach and intestines via the mouth and into the digestive system (including ones that cause cholera)
Preventing pathogens entering
Mucous layer that covers the exchange surfaces and forms a thick sticky barrier that is difficult to penetrate
Enzymes that break down pathogens
Stomach acid which kills pathogens …show more content…
Pulmonary Fibrosis
Caused by scars forming on the epithelium of the lungs
Thickens the lung epithelium irreversibly
© myrevisionnotes
Page 3
Diffusion of oxygen into the blood is less efficient as diffusion pathway is longer
The volume of air the lungs can contain is also reduced
Reduced elasticity so difficulty ventilating the lungs (getting air in and out)
Effects of fibrosis
Shortness of breath especially when exercising – due to less oxygen being able to diffuse into the blood
Chronic dry cough – because the fibrous tissue obstructs the airway
Pain and discomfort in the chest – due to pressure and damage from the mass of fibrous tissue
Weakness and fatigue – due to the reduced intake of oxygen into the blood so less available for respiration
Asthma
Localised allergic reaction
Caused by the release of histamine when an allergen such as pollen is detected
Histamine has the following effects:
The lining of the airways becomes inflamed
The lining cells (epithelial cells) secrete more mucus than usual
Fluid leaves the capillaries and enters the airways
The muscle surrounding the bronchioles contracts and constricts the airways
Effects of Asthma
Microorganisms as Pathogens
To be considered a pathogen it must:
Gain entry
Colonise the tissues
Resist the defences
Cause damage to the tissues
Pathogens include bacteria, viruses and fungi
How do microorganisms enter the body
Many pathogens enter through the gas exchange system (including ones that cause flu and
TB)
Food and water can carry pathogens into the stomach and intestines via the mouth and into the digestive system (including ones that cause cholera)
Preventing pathogens entering
Mucous layer that covers the exchange surfaces and forms a thick sticky barrier that is difficult to penetrate
Enzymes that break down pathogens
Stomach acid which kills pathogens …show more content…
Pulmonary Fibrosis
Caused by scars forming on the epithelium of the lungs
Thickens the lung epithelium irreversibly
© myrevisionnotes
Page 3
Diffusion of oxygen into the blood is less efficient as diffusion pathway is longer
The volume of air the lungs can contain is also reduced
Reduced elasticity so difficulty ventilating the lungs (getting air in and out)
Effects of fibrosis
Shortness of breath especially when exercising – due to less oxygen being able to diffuse into the blood
Chronic dry cough – because the fibrous tissue obstructs the airway
Pain and discomfort in the chest – due to pressure and damage from the mass of fibrous tissue
Weakness and fatigue – due to the reduced intake of oxygen into the blood so less available for respiration
Asthma
Localised allergic reaction
Caused by the release of histamine when an allergen such as pollen is detected
Histamine has the following effects:
The lining of the airways becomes inflamed
The lining cells (epithelial cells) secrete more mucus than usual
Fluid leaves the capillaries and enters the airways
The muscle surrounding the bronchioles contracts and constricts the airways
Effects of Asthma