Primary Non-specific response

Primary response

Primary defences: Prevent pathogens entering the body.

NON-specific - they prevent the spread of any pathogen.

The skin

The skin is the main primary defence. It covers the body and prevents the entry of pathogens. 

How is skin made?

Most cells in the skin are called keratinocytes. They are created at the base of the epidermis via mitosis. They then migrate up to the surface and by the time they reach the surface they are dead. 

Keritinisation

As the keritinocytes migrate up to the surface of the skin, they dry out and all the cytoplasm is replaced by the protein keratin. This takes about 30 days. 

Blood clotting  and skin repair

If the skin is complete it works very well to prevent pathogen entry, however if it is broken the body is open to infection. Blood clots stop blood loss but also put up a barrier to infection. 

How are blood clots formed?

It is important that the blood does not clot inside the vessels and only when the skin needs to rebind after an abrasion. For this reason there are a series of checks and balances to ensure this does not happen at the wrong time. 

Red blood cells and platelets are trapped this is the clot.

Mucous membrane

Some areas of the body need to be thinner than others for nutrients and oxygen to enter the blood stream. These areas are easier for pathogens to pass over as they are thinner. Food and air also contain micro-organisms so the digestive system and the respiratory system are vulnerable to infection.

In order to protect these areas susceptible to attack, they have special epithelial layers woth goblet cells. These goblet cells secrete a thick  liquid called mucous. Air borne pathogens that enter through ventilation are trapped in the mucous and swept up to the mouth again where they mucous containing the pathogen is swallowed and taken down to the stomach acid which usually destroys the pathogen.

How is mucous made?

Here is a video showing how 3 non-specific primary defence mechanisms work. 

Coughing and sneezing

A reflex action that is triggered when sensitive areas detect a micro organism or a toxin a pathogen releases. Reflexes include coughing sneezing and vomiting. all of which suddenly expel air or stomach juices and take the microbe that triggered the reflex with it.




Inflammation of an area indicates there is an infection.



1. Mast cells detect microorganisms and release histamine.

2 Histamine has many effects. 
          - It makes capillary walls become more permeable to white blood cells so they can get to              the site of the infection with more ease. 
          - It causes Vasodilation meaning more blood can flow to the area. 

3. The swelling in the infected area is caused by the increased production of tissue fluid. The excess tissue fluid is drained into the Lymph vessels. Any microorganisms in the tissue fluid are drained with it and taken to the lymph node to start a specifc immune response. 

Now here's Hank to summarise.