Btec Assignment
Unit 12: Diseases and Infection
Aim D: Understand how the human body responds to diseases and infections.
Introduction: The immune system is an arrangement of cells, tissues, organs, and the
substances they produce that aid the body in fighting infections and other diseases. It is
very important as it helps protect the body and identify foreign substances so that it can
release cells that will combat the pathogens.
The three basic immune system defences against pathogenic infections are as follows:
■ The first line of defence against infection is the physical and chemical barriers that
prevent pathogens from entering the body.
■ The second line of defence consists of non-specific phagocytes and additional
internal mechanisms that contain innate immunity.
■ The third line of defence includes the specific lymphocytes that produce antibodies as
part of the immune response and work to destroy damaging microbes.
The table below explains the non specific defences of chemical and physical
Non-specific defences and how they work
First line of defence Second line of defence
Skin [Physical Barrier]: Skin is a barrier that acts as Antimicrobial proteins: Antimicrobial proteins (such as
one of the body's initial lines of defence against cytokines and complement proteins) regulate immune
potentially hazardous microorganisms Skin tissue activity within the body.
contains specialised immune cells that aid in the fight
against invading invaders.
Nasal Hairs [Physical Barrier]: Nasal hair is hair that Inflammatory Response: When a pathogen stimulates
grows inside the nose. It is one of the body's first lines increased blood flow to an affected location, the blood
of defence against dangerous environmental diseases vessels in that location dilate, allowing white blood cells to
such as inhaled bacteria, fungi, and spores. The hairs spill into contaminated tissue. Phagocytes are white blood
in your nose work as a filter, preventing dust, pollen, cells that engulf and eliminate germs. During an
and allergies from entering your lungs. inflammatory reaction, the region tends to become red,
swollen, and painful.
Mucous Membrane [Chemical Barrier]: The standard Fever: Fever raises body temperatures, causing
functions of respiratory mucus are to assist in keeping heat-shock proteins to activate and repress microbial
the respiratory tract hydrated and act as a protective development and growth to prevent the spread.
barrier against the external environment by trapping
microscopic particles, including pathogens.
Stomach Acid (HCl) [Chemical Barrier]: As soon as Phagocytosis: Phagocytosis is a process in which a cell
food enters your stomach, the lining of your stomach latches to the object it wishes to ingest on the cell surface
produces enzymes that begin breaking down the and drags it inward while swallowing it. It is a process that
proteins in the meal. Your stomach lining also occurs when a cell attempts to eliminate something, such
secretes hydrochloric acid, which creates an as a virus or an infected cell, and is frequently employed
environment for protein-digesting enzymes to by immune system cells. Phagocytosis is an important
function. It destroys germs, protecting your body from component of the immune system. Several immune
any hazardous organisms that enter your body system cells, including neutrophils, macrophages, dendritic
through food. cells, and B lymphocytes, engage in phagocytosis.
Unit 12: Diseases and Infection
Aim D: Understand how the human body responds to diseases and infections.
Introduction: The immune system is an arrangement of cells, tissues, organs, and the
substances they produce that aid the body in fighting infections and other diseases. It is
very important as it helps protect the body and identify foreign substances so that it can
release cells that will combat the pathogens.
The three basic immune system defences against pathogenic infections are as follows:
■ The first line of defence against infection is the physical and chemical barriers that
prevent pathogens from entering the body.
■ The second line of defence consists of non-specific phagocytes and additional
internal mechanisms that contain innate immunity.
■ The third line of defence includes the specific lymphocytes that produce antibodies as
part of the immune response and work to destroy damaging microbes.
The table below explains the non specific defences of chemical and physical
Non-specific defences and how they work
First line of defence Second line of defence
Skin [Physical Barrier]: Skin is a barrier that acts as Antimicrobial proteins: Antimicrobial proteins (such as
one of the body's initial lines of defence against cytokines and complement proteins) regulate immune
potentially hazardous microorganisms Skin tissue activity within the body.
contains specialised immune cells that aid in the fight
against invading invaders.
Nasal Hairs [Physical Barrier]: Nasal hair is hair that Inflammatory Response: When a pathogen stimulates
grows inside the nose. It is one of the body's first lines increased blood flow to an affected location, the blood
of defence against dangerous environmental diseases vessels in that location dilate, allowing white blood cells to
such as inhaled bacteria, fungi, and spores. The hairs spill into contaminated tissue. Phagocytes are white blood
in your nose work as a filter, preventing dust, pollen, cells that engulf and eliminate germs. During an
and allergies from entering your lungs. inflammatory reaction, the region tends to become red,
swollen, and painful.
Mucous Membrane [Chemical Barrier]: The standard Fever: Fever raises body temperatures, causing
functions of respiratory mucus are to assist in keeping heat-shock proteins to activate and repress microbial
the respiratory tract hydrated and act as a protective development and growth to prevent the spread.
barrier against the external environment by trapping
microscopic particles, including pathogens.
Stomach Acid (HCl) [Chemical Barrier]: As soon as Phagocytosis: Phagocytosis is a process in which a cell
food enters your stomach, the lining of your stomach latches to the object it wishes to ingest on the cell surface
produces enzymes that begin breaking down the and drags it inward while swallowing it. It is a process that
proteins in the meal. Your stomach lining also occurs when a cell attempts to eliminate something, such
secretes hydrochloric acid, which creates an as a virus or an infected cell, and is frequently employed
environment for protein-digesting enzymes to by immune system cells. Phagocytosis is an important
function. It destroys germs, protecting your body from component of the immune system. Several immune
any hazardous organisms that enter your body system cells, including neutrophils, macrophages, dendritic
through food. cells, and B lymphocytes, engage in phagocytosis.
