The human body has a multitude of natural barriers in place to prevent infection and disease. These barriers can be both external and internal. The external barrier is the largest organ of your body, your skin. The internal barriers are your immune system, your stomach acid, the blood-brain barrier and the placental barrier.
Skin
The human skin blocks the entrance of disease-causing microbes into the body. The skin helps regulate the body's temperature, which in turn keeps the organ systems functioning at an optimal level. The skin also plays a role in water retention; it prevents water from leaving your body, thus preventing dehydration. The average person's skin covers 1.5 to 2 square meters. Skin is comprised of three primary layers the epidermis, the dermis and the hypodermis.
Immune System
A human's immunity is comprised of a complex system of biological structures and processes. The immune system is designed to distinguish external pathogens from your own tissue and neutralize their harmful effects. The immune system includes white blood cells, non-specific defense mechanisms, and humoral and chemical barriers.
Inflammation is a response conducted by your immune system; Inflammation is a complex biological response to tissue damage. Inflammation not only destroys pathogens, but it also initiates the tissue-healing process.
Stomach Acid
Gastric acid is a substance excreted by cells in the wall of your stomach. This acid not only helps digestion but also neutralizes many microbes that are ingested with the products you eat and drink. In the absence of gastric acid during certain diseases there is almost always a multitude of infections present in your digestive tract.
Blood-Brain Barrier
The blood-brain barrier is caused by a system of endothelial cells located around the capillaries that enter the central nervous system (CNS). These cells prevent large molecules from circulating in the CNS; they also prevent the entrance of most bacteria. It is because of the blood-brain barrier that bacterial infections of the brain are extremely rare.
Placental Barrier
The placenta is an organ that connects an unborn child to its mother. The placenta weighs about 500 grams (approximately two pounds). The placenta provides the unborn child with nutrients from the mother and also denies entry to microbes that would cause infection in the unborn child.
References
- "Neuroanatomy" 4th Edition: James D. Fix ; 2008
- "Obsetrics"; R.A. Abrahamyan; 2004
- "Physiology" 5th Edtion By Berne,Levy, Koeppen and Stanton
