Answer
The innate defense of the body against penetration and infection includes several chemical and physical structures; some of these are the keratinized epithelium, mucus of mucous membranes, cilia, lysozymes ( and other enzymes), and acidity of environments like the stomach, and surface of the skin.
The keratinized epithelium is an important component of the body's first line of defense against biological, chemical and physical injury. It resists weak acids and bases, and keeps out pathogenic organisms and enzymes
The sebum and eccrine sweat secretions of the skin provide an additional measure of protection. They confer acidity to the epidermal surface; this acidic mantle effectively inhibits the growth of some microorganism, and kills others. Acid pH is also protective in the digestive tract. The pH of the stomach is is very low --about pH 2.0 This highly acidic environment which facilitates the action of pepisin, is destructive to many microorganisms.
Proteolytic enzymes in the stomach are also bactericidal. So is lysozyme found in lacrimal secretions( tears), saliva, and respiratory mucous secretions. Mucous membrane lines all body cavities, and covers the surfaces of all organs that are exposed to the exterior: respiratory , digestive reproductive, and lower urinary tract are lined with mucous membrane Thick mucous traps microorganisms, and foreign matter; the watery mucous of the mouth washes microorganisms down into the stomach, where they are destroyed by acid and stomach enzymes.
The nasal passages have nasal hairs that filter incoming air of dust and some organisms. More importantly, the respiratory mucosa is lined with protective mucous-covered, motile cilia. These respiratory cilia sweep microorganisms (and physical particles that have eluded nasal hairs) away from the respiratory passages and into the oral cavity to removed from the body by expectoration.
Work Step by Step
The following are some of the important factors that are part of the body's innate defense mechanism.
Skin: The keratinized epithelial cells of the skin protect agaisnt physical and chemical injury and they are also resistant to infection by microorganisms.
The surface of the skin also has an acid ph( the acid mantle) and this enhances the resistance of the skin to certain pathological organisms. The low ph of stomach secretions is also microbiocidal.
The mucosa that lines most body cavities and covers many organs, is covered with mucous secretions of different levels of viscosity. Thick mucus traps and impedes pathogenic organisms; thin mucous fluid traps microorganisms and facilitates their removal from the body
Lysozymes are enzymes found in tears, eccrine sweat, and saliva ( also in breast milk) ; these enzymes can lyse and destroy bacteria.
Cilia that line respiratory mucosa, also contributes to the innate defense of the body. These motile cilia sweep pathogen-laden thick mucus into the oral cavity --away form the laryngo-pharynx and the glottis-- to be removed by expectoration..
