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Biology IB HL - 6.3 Disease Defences Part 1

Biology25 CardsCreated 19 days ago

This flashcard deck covers the key concepts of the first line of defense against infectious diseases, including the roles of skin and mucous membranes, as well as the process of blood clotting.

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What is the first line of defence?

The first line of defence against infectious disease are the surface barriers that prevent the entry of pathogens into the body
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Key Terms

Term
Definition
What is the first line of defence?
The first line of defence against infectious disease are the surface barriers that prevent the entry of pathogens into the body
What are examples of the first line of defence? 2
These surface barriers include both the intact skin and mucous membranes
What does the skin protect?
Protects external structures when intact (outer body areas)
What is the physical barrier part of the skin?
Consists of a dry, thick and tough region composed predominantly of dead surface cells
What is the chemical barrier of the skin?
Contains biochemical defence agents (sebaceous glands secrete chemicals and enzymes which inhibit microbial growth on skin)
What does the skin secrete?
The skin also secretes lactic acid and fatty acids to lower the pH (skin pH is roughly ~ 5.6 – 6.4 depending on body region)
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Biology IB HL - 6.3 Disease Defences Part 1
TermDefinition
What is the first line of defence?
The first line of defence against infectious disease are the surface barriers that prevent the entry of pathogens into the body
What are examples of the first line of defence? 2
These surface barriers include both the intact skin and mucous membranes
What does the skin protect?
Protects external structures when intact (outer body areas)
What is the physical barrier part of the skin?
Consists of a dry, thick and tough region composed predominantly of dead surface cells
What is the chemical barrier of the skin?
Contains biochemical defence agents (sebaceous glands secrete chemicals and enzymes which inhibit microbial growth on skin)
What does the skin secrete?
The skin also secretes lactic acid and fatty acids to lower the pH (skin pH is roughly ~ 5.6 – 6.4 depending on body region)
What do mucous membranes protect?
Protects internal structures (i.e. externally accessible cavities and tubes – such as the trachea, oesophagus and urethra)
What is the PHYSICAL part of the mucous membranes?
Consists of a thin region of living surface cells that release fluids to wash away pathogens (mucus, saliva, tears, etc.)
What is the CHEMICAL part of the mucous membranes?
Contains biochemical defence agents (secretions contain lysozyme which can destroy cell walls and cause cell lysis)
What may mucous membranes have, to further aid pathogen removal?
Mucous membranes may be ciliated to aid in the removal of pathogens (along with physical actions such as coughing / sneezing)
What is clotting?
Clotting (haemostasis) is the mechanism by which broken blood vessels are repaired when damaged
What is the role of clotting?
Clotting functions to prevent blood loss from the body and limit pathogenic access to the bloodstream when the skin is broken
What are the two key components of a blood clot?
platelets and insoluble fibrin strands
What is the role of platelets in blood clotting?
Platelets undergo a structural change when activated to form a sticky plug at the damaged region (PRIMARY haemostasis)
What is the role of fibrin strands in blood clotting?
Fibrin strands form an insoluble mesh of fibres that trap blood cells at the site of damage (SECONDARY haemostasis)
What set of reactions are involved in blood clotting?
The process by which blood clots are formed involves a complex set of reactions collectively called the coagulation cascade
What is the coagulation cascade triggered by?
This cascade is stimulated by clotting factors released from damaged cells (extrinsic pathway) and platelets (intrinsic pathway)
Clotting - What do clotting factors stimulate, in terms of platelets?
Clotting factors cause platelets to become sticky and adhere to the damaged region to form a solid plug
Clotting - What do clotting factors stimulate, in terms of physical changes?
These factors also initiate localised vasoconstriction to reduce blood flow through the damaged region
Clotting - What do clotting factors stimulate, in terms of a conversion?
Additionally, clotting factors trigger the conversion of the inactive zymogen prothrombin into the activated enzyme thrombin
Clotting - What does thrombin catalyse?
Thrombin in turn catalyses the conversion of the soluble plasma protein fibrinogen into an insolube fibrous form called fibrin
Clotting - What do fibrin strands form?
The fibrin strands form a mesh of fibres around the platelet plug and traps blood cells to form a temporary clot
Clotting - What happens once the area has healed?
When the damaged region is completely repaired, an enzyme (plasmin) is activated to dissolve the clot
Where can the concept of clotting be applied to, i.e. another part of the syllabus?
Coronary thrombosis is the formation of a clot within the blood vessels that supply and sustain the heart tissue (coronary arteries) Occlusion of a coronary artery by a blood clot may lead to an acute myocardial infarction (heart attack)
Explain the process of atherosclerosis and coronary thrombosis
(better flashcard i.e. process broken down in 6.2. blood system flashcards) Blood clots form in coronary arteries when the vessels are damaged as a result of the deposition of cholesterol (atherosclerosis); Atheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen (stenosis); The restricted blood flow increases pressure in the artery, leading to damage to the arterial wall (from shear stress); The damaged region is repaired with fibrous tissue which significantly reduces the elasticity of the vessel wall; As the smooth lining of the artery is progressively degraded, lesions form called atherosclerotic plaques; If the plaque ruptures, blood clotting is triggered, forming a thrombus that restricts blood flow; If the thrombus is dislodged it becomes an embolus and can cause a blockage in a smaller arteriole