What are physiological barriers?

Hint: Invertebrates have two main immunity strategies: the innate immune system and the adaptive immune system. The innate immune system is the most common immune system response and represents an older evolutionary protection strategy.

Complete answer:
The initial line of defence against infections is provided by anatomical and physiological barriers. Intact skin, active mucociliary clearance mechanisms, low stomach pH, and bacteriolytic lysozyme in tears, saliva, and other secretions are examples of these barriers. Body temperature, pH, and different soluble secretory products of the mucosa are physiological barriers that contribute to innate immunity.
While a normal body temperature of 37 degrees Celsius inhibits the growth of some bacteria, high body temperatures, particularly fever, limit or prevent the growth of many microbes, particularly viruses. Furthermore, at higher body temperatures, the immunological response is more effective. Many viruses and bacteria are inactivated by the acidic environment of the stomach, bladder, and kidneys, as well as the bile of the intestines. Acid production creates a low pH environment that protects various human tissues.
Most pathogens are inhibited by the low pH of the female genital tract, which is around 4.4 due to the presence of lactic acid generating bacteria (normal flora). Saliva and mucus include enzymes that attack bacteria's cell wall and cell membrane. Tears include lysozyme, which causes bacterial cell wall lysis by destroying the peptidoglycan layer. The continual cleansing of the eye with lysozyme-containing tears normally prevents microbial growth in the eye.

Note:
Physical barriers (tight connections in the skin, epithelial and mucous membrane surfaces, mucus itself); anatomical barriers; epithelium and phagocytic cell enzymes (i.e., lysozyme); phagocytes (i.e., neutrophils, monocytes, macrophages); inflammation-related serum proteins (e.g., complement, C-reactive protein.