Lung Defense Mechanism

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Lung defense mechanisms are very important in explaining the occurrence of respiratory infections. lung has defense mechanisms to prevent bacteria from entering into the lungs. cleaning mechanism are:
1. Cleaning mechanism in the conductive airways, including:

• Reepitelisasi airway
• The flow of mucus on the surface epithelium
• Bacteria naturally or "epithelial-cell binding site analogue"
• Local humoral factors (IgG and IgA)
• Components of the local microbial
• Mucosilliar transport system
• Sneezing and coughing reflexes

Upper respiratory tract (nasopharynx and oropharynx) is a defense mechanism through the barrier against the entry of the anatomy and mechanism of pathogenic microorganisms. Cilia and mucus push microorganisms out of the way coughed or swallowed.
If there is dysfunction of cilia as in Kartagener's syndrome, the use of nasogastric tube and pipe nasotracheal long can disrupt the flow of secretions that have been contaminated with pathogenic bacteria. In these circumstances may occur nosocomial infection or "Hospital Acquired Pneumonia".

2. Cleaning mechanism in "Respiratory airway exchange", include:

• The fluid lining the alveolar surfactant include
• The system of local humoral immunity (IgG)
• Alveolar Macrophages and inflammatory mediators
• Withdrawal of neutrophils

Humoral immune system plays an important role in lung defense mechanisms (upper airway). IgA is one part of the nasal secretions (10% of the total protein nasal secretions). Patients with IgA deficiency have an increased risk for upper respiratory tract infection recurring yan. Colonization of bacteria that often hold the upper airway often removing and damaging IgA proteolytic enzymes. Gram-negative bacteria (Pseudomonas aeruginosa, E.colli, Serratia spp, Proteus spp, and Klebsiella pneumoniae) has the ability to destroy IgA. Deficiencies and damage to any component of upper airway defense led to the colonization of pathogenic bacteria as facilities for lower respiratory tract infection.

3. Cleaning mechanism in the subglottic airways

Subglottic airway defense mechanisms composed of anatomic, mechanical, humoral and cellular components. Mechanism of closure of the glottis and cough reflex is the main defense against the aspirate from the oropharynx. In case of malfunctioning of the glottis it dangerous for lower respiratory tract that are normally sterile. Nasogastric tube mounting action, tool tracheostomy facilitate the entry of bacterial pathogens directly into the lower respiratory tract. Impaired mucociliary function may facilitate the entry of pathogenic bacteria into the lower respiratory tract, even acute infection by Mycoplasma pneumoniae, Haemophilus influenzae and viruses can damage the cilia movement.

4. Cleaning mechanism in the "respiratory airway gas exchange"

Bronchioles and alveol have a defense mechanism as follows:
• The liquid that coats alveol:

a. Surfactants

A fat-rich glycoprotein, consists of several components of SP-A, SP-B, SP-C, SP-D that serves to strengthen phagocytosis and killing of bacteria by macrophages.

b. Anti-bacterial Activity (non specific) : FFA, lysozyme, iron binding protein.

• IgG (IgG1 and IgG2 subset that serves as an opsonin)
• alveolar macrophages that act as the first defense mechanism
• Serves to attract PMN leucocytes into the alveoli (there GNB infections, Pseudomonas aeruginosa)
• Mediator biology

Ability to attract PMN to the airway, including C5a, the production of alveolar macrophages, cytokines, leucotrienes

Tags : Defense Mechanism of lung, Defense Mechanisms of the Respiratory System, Pulmonary defence mechanisms