Primary And Secondary Immune Defences

Updated on March 9, 2013

Primary Defence - Skin

  • Primary defences are the initial barriers that prevent us from being harmed by pathogenic organisms entering our body.
  • There are 2 main types of primary defences and these are the skin and mucous membranes.
  • Our bodies are covered by the skin and this is the first primary defence that we have.
  • Skin cells called keratinocytes are produced in the base of the skin's epidermis and then mitose out to the surface of the skin.
  • Keratinisation is a process that takes about 30 days and is when the cytoplasm of the keratinocyte cells is replaced by keratin as the cells move to the surface.
  • When the cells have reached the surface of the skin they are no longer alive and they fall off as dead skin cells.
  • This is very useful in the protection against pathogens as it acts as a barrier to prevent them from entering our body.

Primary Defence - Mucous Membranes

  • Mucous membranes are another type of primary defence.
  • In places like the digestive system and the lungs, the barrier between our blood and the environment is reduced and this leaves us more vulnerable to infection. Pathogens can just as easily enter our blood in the same way that, for example, oxygen can.
  • Because of this, things like our lungs are protected by mucous membranes.
  • Goblet cells are cells that secrete mucus and are found in places like our trachea.
  • The mucus that the goblet cells secrete traps any pathogens that might be in the air and then cells called ciliated epithelial cells 'wave' the mucus to the back of our throat so that we can swallow it.
  • When we swallow the pathogens the acidity of our stomach acid denatures the enzymes within the pathogen and renders it harmless.

Secondary Defence - Phagocytes

  • If pathogens make it past the primary defences, in order for them to be killed the non-specific phagocytes, that are manufactured in our bone marrow, must destroy them!
  • The two different types of phagocyte are neutrophils and macrophages.
  • Macrophages are relatively large cells and travel in the blood as monocytes. They are then transported in the blood to various organs but the majority accumulate in the lymph nodes and there in the lymph nodes, they mature into macrophages.
  • When cells are infected they release chemicals, for example histamine, and this attracts surrounding neutrophils to the area.
  • Histamine will also cause capillaries to become more leaky and this is why infected areas can be red and swollen.
  • Another result of the leaky capillaries is that there is more tissue fluid going through the lymphatic system and the pathogens are transported to the lymph nodes where the macrophages can kill them.
  • Neutrophils are the most common phagocyte, they travel around in the blood but because they are relatively small they are able to fit through capillary pores and squeeze out into the tissue fluid.
  • They don't live for very long but when an infection occurs they will be made in very large numbers to try to combat it.

How do they work?

1 - When a pathogen invades the body they are detected as foreign by the antigens on their cell surface membrane.

2- Complementary antibodies attach to the antigens.

3 - The receptors (membrane -bound proteins) on phagocytes bind to the antibodies.

4 - The phagocyte then engulfs the pathogen by folding it's membrane inwards and creating a phagosome vacuole.

5- Lysosomes that are inside the phagocyte then fuse with the phagosome and release enzymes into it.

6 - These enzymes digest the bacteria into products that are harmless nutrients that can then be absorbed by the cytoplasm of the cell.

Test what you've learned!

view quiz statistics

Questions & Answers

    Comments

      0 of 8192 characters used
      Post Comment

      • profile image

        Oasis 

        6 months ago

        I learned a lot. Thank you.

      • Anthropophobia profile imageAUTHOR

        Anthropophobia 

        5 years ago

        Thank you! Your comment is much appreciated. Thanks for stopping by!

      • dilipchandra12 profile image

        Dilip Chandra 

        5 years ago from India

        Beautiful article with very good information. It was well written and well organized. Great work!

      working

      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, owlcation.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://owlcation.com/privacy-policy#gdpr

      Show Details
      Necessary
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Features
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Marketing
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Statistics
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)