Primary Defenses in Animals

Questions and Answers

What role does keratin play in the skin's primary defense against pathogens?

It helps in blood clotting.

It attracts white blood cells to the surface.

It acts as an antimicrobial agent.

It strengthens the skin barrier. (correct)

Which of the following accurately describes the process of inflammation?

It is characterized by redness, heat, swelling, and pain. (correct)

It involves immediate tissue destruction by pathogens.

It causes decrease in blood vessel permeability.

It directly kills foreign pathogens.

What is the primary purpose of blood clotting during wound formation?

To prevent pathogens from entering the bloodstream. (correct)

To facilitate white blood cell movement.

To release antimicrobial substances.

To strengthen the skin tissue structure.

How do skin flora contribute to the primary defenses of the skin?

They occupy space, preventing colonization by harmful pathogens. Signup and view all the answers

What is the significance of vasodilation during the inflammatory response?

It increases blood vessel permeability to promote healing. Signup and view all the answers

Which component is primarily responsible for initiating blood clotting at a wound site?

Platelets Signup and view all the answers

What type of defense do primary defenses represent in the immune system?

Immediate and non-specific. Signup and view all the answers

What is a key characteristic of primary defenses that differentiates them from secondary defenses?

They include physical and chemical barriers. Signup and view all the answers

What role do fibroblasts play in wound healing?

They lay down collagen fibers to provide a foundation for new cells. Signup and view all the answers

Which of the following best describes the function of goblet cells?

They secrete mucus that traps pathogens. Signup and view all the answers

What mechanism helps remove trapped pathogens from the body?

Expulsive reflexes. Signup and view all the answers

How does the acidic environment of the stomach contribute to primary defense?

It destroys many ingested pathogens. Signup and view all the answers

What is the primary function of callose in plants during infection?

To block pathogen entry and spread. Signup and view all the answers

Which two chemicals secreted by plants are known to inhibit pathogen growth?

Phytoalexins and saponins. Signup and view all the answers

What is the role of the cuticle in plants with regards to pathogen defense?

It serves as a barrier to pathogen entry. Signup and view all the answers

Which of the following is NOT a physical defense mechanism in plants?

Production of phytoalexins. Signup and view all the answers

What effect do antimicrobial chemicals produced by plants have on insects?

They deter feeding by causing toxicity. Signup and view all the answers

What is the secondary barrier to pathogen entry in plants?

The cell wall. Signup and view all the answers

Study Notes

Primary Defences in Animals

Primary defences stop pathogen entry and are non-specific, serving as general barriers.
Skin acts as a physical barrier; it consists of dead cells strengthened by keratin and secretes antimicrobial sebum to deter pathogens.
Skin flora consists of harmless microorganisms that help prevent colonization by harmful pathogens.
Inflammation is a protective response featuring redness, heat, swelling, and pain, initiated by damaged cells releasing molecules that cause vasodilation and increased vascular permeability, facilitating rapid immune response.
Wound repair is crucial when skin is damaged:
- Blood clotting occurs through platelet aggregation, forming a mesh of fibrin to plug the wound.
- Fibroblasts deposit collagen fibres at the wound site, aiding skin cell migration and closure.
Mucous membranes in areas like oral and nasal passages offer chemical defence; goblet cells produce mucous that traps pathogens, while ciliated cells help remove them.
Expulsive reflexes such as coughing and sneezing eliminate trapped pathogens automatically.
The stomach acts as a chemical barrier with highly acidic gastric acid that destroys many ingested pathogens.
Gut flora consists of beneficial bacteria in the digestive tract that inhibit harmful pathogen growth.

Primary Defences in Plants

Plants utilize physical and chemical mechanisms against pathogens.
Waxy cuticle: A protective layer covering leaves and stems that prevents pathogen entry and reduces water collection, limiting pathogen spread.
Cell walls offer a secondary barrier against pathogens that penetrate the cuticle.
Callose is secreted during stress to block pathogen entry and spread between cells by accumulating in cell walls and around plasmodesmata.
Antimicrobial chemicals secreted by plants include:
- Saponins, which disrupt fungal cell membranes and kill pathogens.
- Phytoalexins, which inhibit pathogen growth on plant surfaces.
Plants also produce toxic chemicals to deter insect herbivores, reducing the risk of viral infections carried by insect vectors.

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Description

This quiz explores the concept of primary defenses in animals, focusing on the physical and chemical barriers that prevent pathogens from entering the body. It emphasizes the non-specific nature of these defenses and the role of the skin as a crucial barrier. Test your knowledge with questions about the mechanisms that protect against foreign organisms.