The Initiation of Infection and the Causes of Disease (Part 2): The Sites of Entry

So, we’ve been able to discover the factors that can initiate infections in the last post, and we’ve identified that immunocompromisity is one of the primary causes. Let’s now take a brief look at the possible ways in which our first lines of immune defense, which are incidentally at the sites/points of entry, can be breached and compromised.

The mouth is supposed to be one of the most secured places in our body in terms of its location and ability to close. However, the things we use our mouth to do won’t let this happen. From kissing, to yawning without covering up, to oral sex, to putting anything inside our mouth in the name of eating and drinking, the mouth has become one of the most abused parts of the body. However, the immune defenses of the mouth are quite much, hence why we don’t usually get diseased. There are lysosyme enzyme, which can lyse bacteria, and antimicrobial proteins such as lactoferrin and histatins, which fights fungi like Candida albican (usually gotten from oral sex and which causes oral thrush).

Others include some immunoglobulin A (IgA) and other mechanical and anatomical barriers that make it impossible most times for our mouth to be colonised by organisms. Even, the regular flushing of the mouth by saliva, spitting or swallowing this saliva is also a defence mechanism. And if most of these organisms escape the mouth, they will encounter stringent ones in the stomach that contains acidity and numerous antimicrobial enzymes and immunoglobulins.

The eyes defence mechanism include the continuous blinking of the eyelids, the flushing effects of the tears, the saltiness of the tears and the presence of the antimicrobial proteins like lysosyme, lactoferrin and IgA, which can neutralise viruses in the tears as well. Others include the keratocytes (defensins), the epithelial cells, the corneal nerves which transmit info to the brain for release of more immune fighters and immune complements make the eyes protected. The nose, perhaps the most exposed organs after the skin, is mostly protected by the mucus secretion, the numerous epithelial cells and the hairs present inside, apart from the numerous immunoglobulins present there. The ear wax is also the primary mode of protecting the ear and its environment. Yes, that sticky, brownish substance isn’t bad at all because it gathers the dust, microbes and dirt, and prevents them from getting to the inner parts, especially the ear drums. Please, stop cleaning it every day, as this only removes the protection of the ear. Make it occasionally like four to five days.

And now, the skin. The skin is the largest organ in the body and also the largest surface presented for infection. In fact, it is the most opened, most attacked and the toughest organ in the body. It offers protection for the other organs inside the body by providing an impermeable surface that can only be breached by any form of trauma. Apart from the epithelial nature of the cells at the surface, the skin is usually replacing its outermost cells on its surface almost on daily basis because these cells usually die and dry up, providing the first step in its array of mechanical defenses. It also produces sweat that contains a high level of salt and lysosyme capable of killing numerous bacteria and fungi. The oily nature of the sebum also makes colonisation by microbes highly difficult. However, infection can be established through the breaching of the surfaces by traumatic experience like burns, cuts, bleaching, bruises and flesh wound. Of course, insect vectors or diseases have also perfected ways of breaching the surface by using their proboscis.

The three factors that mostly determine infections can render these barriers to infection ineffective and proceed to a diseased state. Other factors that can also determine diseases include genetics/hereditary, nutrition/feeding, co-infection, lifestyle and drug use/abuse/misuse. In the next post we’ll finally discuss how a organism localised in a particular organ (e.g. Staphylococcus) can cause infection in another location or organ (e.g. sex organs).

Cheers.

Updated: February 13, 2019 — 1:51 pm

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