The physical barrier is the very first component of innate immunity and can be considered as the body’s first line of defenses.
Essentially, it’s a mechanical barrier between us and everything else. And can be thought of as any part of our bodies that make direct contact with the outside world (including all internal and external surfaces).
It’s actually quite a comprehensive layer of protection
Mucous, acids, enzymes and even physical movement (sweat, tears, etc) are all used to help stop pathogens from ever making contact with our inside world.
The skin is the most visible part of our immune system’s physical barrier, covering our bodies from head to toe.
In order to prevent any unwanted cellular (viruses, bacteria, fungi) growth, the skin depends on careful regulation of surface pH levels and temperature.
Though most of the time we think of the skin as a single layer, it’s actually made of two unique physical layers:
- The Epidermis – top-most layer
- The Dermis – layer below the epidermis
And the interrelation between these two layers is of immense importance to the skins overall ability to perform its defense functions.
The skin is discussed in detail in the section chapter
Because of it’s high degree of relevance in skin disease, the skin will be thoroughly discussed in the next chapter of this book.
The Mucous Membranes
Though our skin is the most visible physical barrier, it’s actually only a small fraction of it. In reality, the skin of an average adult only covers the surface area of about 2 square meters. While, the mucous membranes can measure roughly 400 square meters.
The mucous membranes are defined as the surfaces which line all of our body cavities open to the exterior surface.
Generally, they can be thought of as the internal skin surfaces that come in contact with the outside world. More specifically, they the surfaces which line the various tracts (digestive, respiratory and urogenital) and organs (nose, eyelids, mouth, etc.) of our bodies.
Though mucous membranes have much more structure variation then our skin, all of them have two common components (similar to the skin):
- Epithelial cells – surface layer
- Connective tissue – tissue underneath
The most prominent feature of all mucous membranes is their ability to secrete mucus. Which can trap pathogens and prevent them from ever making contact with our inside world.
This section went over the basics of the physical barrier component of innate immunity. Key points include:
- The physical barrier is the mechanical barrier between our bodies and the outside world and can be considered the utmost layer of innate immunity
- Our skin is the most visible physical barrier and it primarily relies on careful regulation of pH and temperature levels to prevent infection
- Mucous membranes line the various tracts and organs of our bodies and primarily rely on mucous secretion for protection