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Questions and Answers
What role do goblet cells play in the primary defenses against pathogens?
How do ciliated cells contribute to the primary defense in the respiratory tract?
Which of the following describes a primary defense in the human gut?
What is the function of the cuticle in plant defense?
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What is callose and its role in plant defense?
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Which of the following plants’ chemical defenses acts specifically against insect pests?
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In plants, how does the presence of gut flora contribute to pathogen defense?
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What happens during expulsive reflexes in the body?
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Which of the following best describes a secondary barrier to pathogen entry in plants?
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What is the primary disadvantage of the waxy cuticle for plants?
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What is the primary role of the skin in the context of primary defenses against pathogens?
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Which of the following correctly describes the process of inflammation?
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What is the purpose of blood clotting during wound repair?
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What role do skin flora play in the body's primary defenses?
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Which attribute is NOT characteristic of primary defenses?
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What happens to blood vessels during the inflammatory response?
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What is formed during blood clotting that aids in sealing a wound?
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Which type of cells are primarily responsible for laying down collagen fibers during wound repair?
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What is one way the skin acts as a chemical barrier in the primary defenses against pathogens?
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Which of the following accurately describes the effect of vasodilation during inflammation?
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What is primarily responsible for the formation of the blood clot during wound repair?
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What is the main component that strengthens the skin barrier against pathogens?
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Which process is essential for the repair of the skin barrier after injury?
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Study Notes
Primary Defences
- Defences that aim to stop pathogens entering the body
- Can be physical or chemical
- Non-specific, acts against any pathogen, not specific to one type
Primary Defences In Animals
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Skin
- Physical barrier, dead cells, strengthened by keratin
- Chemical barrier with antimicrobial fluid (sebum)
- Skin flora - harmless microorganisms that prevent colonization by harmful pathogens
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Inflammation
- Protective response to tissue damage or foreign stimuli
- Redness, heat, swelling, and pain
- Swelling occurs due to vasodilation (blood vessels widen) and increased vascular permeability (blood vessels become leaky), bringing white blood cells to fight off pathogens
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Wound Formation
- Necessary to repair skin barrier after damage
- Blood clotting - aggregation of platelets to plug wounds and prevent blood loss, creating a mesh of fibrin
- Repair of the skin barrier - fibroblasts lay down collagen fibres, providing a foundation for new skin cells to attach and close the wound
Mucous Membranes
- Chemical defence in exposed areas (oral passages, nasal passages, eyes, ears)
- Goblet cells secrete mucous that traps pathogens
- Ciliated cells sweep trapped pathogens out
- Expulsive reflexes (coughing, sneezing, vomiting) remove trapped organisms
Gut
- Chemical and flora primary defence
- Stomach's acidity (gastric acid) destroys ingested pathogens
- Colon has its own gut flora that prevents harmful pathogen proliferation
Primary Defences in Plants
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Physical
- Waxy cuticle - barrier to pathogen entry, prevents water collection
- Cell walls - secondary barrier to pathogen entry
- Callose - polysaccharide secreted during stress, accumulates in cell walls and plasmodesmata to block pathogen entry and spread
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Chemical
- Antimicrobial chemicals - kill pathogens and prevent growth e.g. saponins
- Phytoalexins - inhibit pathogen growth on plant surface
- Insect poisons - deter insects and reduce viral transmission through insects
Primary Defences
- Primary defences aim to stop pathogens entering the body.
- They can be physical or chemical.
- Primary defences are non-specific.
- They are barriers present to generally deter entry by any foreign organisms, and are not tailored responses to specific types of pathogens.
Primary Defences in Animals
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Skin: Forms a physical barrier made of dead cells, strengthened by keratin.
- Secretes antimicrobial fluid (sebum).
- Hosts skin flora: harmless microorganisms that prevent colonisation by harmful pathogens.
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Inflammation: Protective response to pathogens or tissue damage.
- Characterised by redness, heat, swelling and pain.
- Swelling occurs as damaged cells release molecules causing vasodilation (blood vessels widen) and increased vascular permeability (blood vessels become more leaky).
- This brings white blood cells and other immune components to the affected site quickly.
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Wound formation: Repairs the skin barrier.
- Blood clotting: plugs the wound, preventing excessive blood loss.
- Platelets aggregate and form a mesh of fibres with fibrin.
- Repair of the skin barrier: Fibroblasts lay down collagen fibres, providing a foundation for new skin cells to attach.
- Skin cells proliferate and migrate towards the wound edge, closing the wound.
- Blood clotting: plugs the wound, preventing excessive blood loss.
-
Mucous membranes: Chemical primary defence.
- Found in oral passages, nasal passages, eyes and ears.
- Goblet cells secrete mucus, trapping pathogens.
- Ciliated cells sweep trapped pathogens back out.
- Expulsive reflexes (coughing, sneezing, vomiting) remove trapped organisms.
-
Gut: Chemical primary defence and its own flora.
- Stomach's acidic environment destroys ingested pathogens (due to gastric acid production).
- Colon has its own microbiota (gut flora) that prevents harmful pathogen proliferation.
Primary Defences in Plants
- Physical defences:
- Waxy cuticle: Acts as a barrier to pathogen entry.
- Prevents water collection, reducing pathogen transmission between plants.
- Cell walls: A secondary barrier to pathogen entry.
- Callose: Secreted during stress (e.g. infection), blocking pathogen entry into and between cells.
- Found at plasmodesmata, preventing pathogen spread from cell to cell.
- Waxy cuticle: Acts as a barrier to pathogen entry.
- Chemical Defences:
- Antimicrobial and/or toxic chemicals: Kill pathogens or inhibit their growth.
- Saponins: Destroy fungal cell membranes.
- Phytoalexins: Inhibit pathogen growth on the plant surface.
- Insect toxins: Reduce insect feeding, decreasing viral infection spread by insect vectors.
- Antimicrobial and/or toxic chemicals: Kill pathogens or inhibit their growth.
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Description
Explore the essential primary defenses that prevent pathogens from entering the body in animals. This quiz covers important concepts like skin barriers, inflammation responses, and wound healing. Test your knowledge of how these non-specific defenses function to protect against infections.
