Question

Physiological barriers include:

1. Acid of the stomach
2. Skin
3. Saliva
4. Mucus membranes
5. Tears

How many of the above are examples of physiological barriers?

• A. 2
• B. 5
• C. 3
• D. 6

Answer 1

The correct option is C 3

Physiological barriers include the chemicals secreted by the skin and mucous membranes which helps in disposing the pathogens from the body. pH of the body fluids and lysozymes in saliva and tears are examples of physiological barriers.

Most of the microorganisms prefer a particular pH( nearly neutral pH) and a temperature around the body temperature (32℃ - 37℃) for their multiplication and metabolic activities. Acidic (HCl in stomach - pH 1. 8, Saliva - pH 6.8) or alkaline pH ( pancreatic juice - pH 7.8) of body secretions interferes with microbial multiplication and growth.

Lysozyme acts on the peptidoglycan layer of the bacterial cell wall and destroys it, which results in the leakage of contents from the cells and leads to death.

Mucus membranes like lining of the digestive and respiratory tracts prevent the entry of microorganisms. It possesses mucin which is a polymer, helps in entrapment of microorganisms and prevents them from clumping together on a surface. So they cannot establish their colony and finally die. Skin also prevents the entry of microorganisms. The continuous removal of dead cells from the skin helps in removal of microorganisms. These two barriers are present by birth itself and they are examples of physical barriers and not physiological barriers. Hence out of 5, 3 are physiological barriers and 2 are physical barriers.