We can define it as an ecosystem consisting of different species of micro-organisms that begins to develop in the first few days of life of the new-born baby and reaches its maximum concentration in the fourth year of age, becoming stable and permanent until adulthood.
The status of equilibrium between the different strains is defined eubiosis. Conversely, if fungi or germs prevail that can cause pathologies, it is said that the intestine is in a state of dysbiosis. This is determined by various factors: age, diet, infections, the use of drugs and general intestinal regularity.
Microflora has a basic immunity role as its function is to prevent intestinal bacteria passing through the mucosa and reaching the tissues. From the intestine (Peyer's plaques) the immune cells mature and disseminate into all the other organs and tissues. At the same time the defensive action of phagocytes and lynphocytes is activated by substances produced by lactobacilli during the fermentation process.
The so-called "friend-bacteria" or probiotics [←link to the category page], above all acidophili and bifidbacteria, constitute an important barrier to the excessive proliferation of the bacterial species, performing functions necessary to maintain the health of the entire organism.