M24. Fighting Disease p2 Flashcards
What are primary defences?
Defences that attempt to prevent pathogens from entering the body
What is an immune response?
The specific response to a pathogen, which involves the action of lymphocytes and the production of antibodies.
What is the main primary defence?
the skin, specifically the outer layer of the skin- the epidermis
What does the epidermis layer of skin mainly consist of
layers of cells, most of which are called keratinocytes, which are produced by mitosis at the base of the epidermis
Why are the airways, lungs and digestive a potential area for infection?
As nutrients and oxygen must enter the blood system, so they must be allowed past the primary defence systems and therefore have the potential of bringing infection into the body.
How are the lungs, airways and digestive system protected from infection?
by being covered in mucus- membranes (goblet cells) which are aided by ciliated epithelium.
Why are most pathogens killed in the digestive system?
As it has an pH of 1-2 which denatures the pathogen’s enzymes.
Give some examples of where mucous membranes are found
gut genitals anus ears nose
Name 3 other primary defences
The eyes are protected by antibodies in tear fluid
The ear canal is lined with wax, which traps pathogens
The vagina is protected by maintaining a relatively high acidic conditions
What is the role of non-specific phagocytes
to kill pathogens that have got past the primary defences before they begin to reproduce
What are the two types of phagocytes
neutrophils
macrophages
Describe a neutrophil how common how is it recognised where is it made where is it found how long does it live how is it effective
- Most common phagocyte
- Recognised by its lobed nucleus
- manufactured in bone marrow
- found in blood, tissue fluid, epithelial surfaces eg lungs
- short lived, but released in large numbers
Describe a macrophage how big where are they produced how do they travel round the body where do they develop what role do they play
- larger than neutrophil
- producsed in bone marrow
- travel in the blood as a monocyte
- monocytes develop into macrophages in the body organs, particularly the lymph nodes
- play a role in specific responses to invading pathogens
How do phagocytes work?
- pathogen attached to phagocyte by antibody and surface receptors
- pathogen is engulfed by infolding of phagocyte membrane
- lysosomes release lysins into phagosome
- harmless end product of digestion are absorbed
How are pathogens recognised?
As a foreigner by the chemical markers on its outer membrane called antigens.
What helps the process of phagocytes receptors binding to foreign antibodies
opsonins
What is the vacuole called that phagocytes engulf pathogens in?
phagosome
How does dead neutrophils removed?
they collect in the area of infection and form pus.
What role does histamine play in defence against pathogens?
It is released from infected cells and attracts neutrophils to the area, and causes a response that makes capillaries more leaky so more fluid leaves the capillaries in the area of infection
Why is it important that histamines produce a response that makes the capillaries more leaky?
So that more tissue fluid passes into the lymphatic system where macrophages are sat waiting to engulf the pathogens.
What is an immune response?
the activation of lymphocytes in the blood to help fight disease.
What is an antigen?
molecules that stimulate an immune response
What is an antibodie?
protein molecules that can identify and neutralise antigens.
What is specificity in terms of antibodies and antigens
an antibody is specific to a particular antigen because of the shape of the variable region. Each type of antibody has a differently shaped variable region
Describe what an antigen usually looks like
a larger molecule with a specific shape (almost any molecule could act as an antigen)
They are usually proteins or glycoproteins in or on the plasma membrane (cell surface membrane)
Why dont our own antigens stimulate a response?
As they are recognised by the immune system.
What are antigen molecules produced by?
the lymphocytes
What are antibodies often referred to as?
immunoglobins, large proteins
How do antibodies work?
They attach to antigens and render them harmless
Describe the structure of an antibody briefly
Y shaped molecule that have 2 distinct regions- variable and constant
Describe in detail, the structure of an antibody
- 4 polypeptide chains held together with disulphide bridges
- a constant region which is the same in all antibodies, that enables the antibody to attach to phagocytic cells and helps in the process of phagocytosis
- a variable region which has a specific shape and differentiates the different antibodies.
- hinge regions, which allows more flexibility, allowing the branches to move further apart to allow the antibody to attach to more than one antigen.
Which region of an antibody has light and heavy polypeptide chains
light; variable
heavy; constant
What is neutralisation and what is it an example of?
Where the antibody binds to the binding site of a pathogen to prevent the pathogen from binding with a host cell.
Its an example of how pathogens act defensively.
What is aggulation?
a large antibody binds many pathogens together, then the large group of pathogens is too large to enter a host cell.
When is aggulation used rather than neutralisation?
When the antibodies are larger.
What is the primary immune response?
The response of the immune system when it first meets a new invader, but this can take a few days to build up enough antibodies.
What happens once the infection has been dealt with ?
The number of antibodies decreases rapidly
What is the secondary immune response.
The time the production starts is much quicker and they are made much more quickly so the concentration of antibodies rises sooner and reaches a much higher concentration.
