NON RESPIRATORY LUNG FUNCTIONS and various properties

It involves all non respiratory function such as drug consumption,defence,metabolism, clotting process

1. NON RESPIRATORY FUNCTION OF THE LUNGS PHYSIOLOGY

2. Introduction The lung is responsible for several important non-respiratory functions, vital for maintenance of normal physiology. FILTRATION The lung is ideally positioned to filter out particulate matter such as clots, fibrin clumps, and other endogenous and exogenous materials from entering the systemic circulation. This plays an important role in preventing ischaemia or even infarction to vital organs. The lungs filter systemic venous return of blood and prevent the passage of endogenous and exogenous substances to systemic circulation . The lungs prevent passage of most microemboli to the arterial system while maintaining gas exchange for moderate to small clots . Abundant

3. Cont .. 2. DEFENCE The large surface area required for gas exchange leaves the lung vulnerable to invasion by airborn substances. This is weakened by: Mucous A mucous layer protects large airways, as large (>8μm) particles impact into the mucous.
Mucous is produced by goblet cells in response to noxious stimuli including chemical irritation as well as inflammatory and neuronal stimulation
The interaction of the mucous-cilia system is enhanced by bronchoconstriction, which reduces flow velocity and causes particulate matter to settle

4. Cont... Cilia Cilia are projections from epithelium which beat rhythmically at ~12Hz to propel mucous out of the airway at a rate of ~4mm.min-1.
Ciliary function can be impaired :by pollutants, smoke, and infection
Ciliary function is stimulated by anaesthetic agents
Inhaled particles which reach the respiratory zone are not trapped by mucous, but instead phagocytosed by alveolar macrophages

5. Cont 3. ENDOCRINE FUNCTIONS . . Important endocrine functions of the lung include:
Release of inflammatory mediators such as histamine, endothelin , and eicosanoids
Release of nitric oxide to regulate smooth muscle
ACE metabolises angiotensin I to angiotensin Immunoglobulin (IgA): An antibody that can attack pathogens and mark them for phagocytosis from macrophages and neutrophils.
Protease: Secreted from lung macrophages and neutrophils during inflammatory response to damage pathogens. A fibrinolytic that can break up thrombosis (blood clots) in the lungs.
Reactive oxygen species (ROS): Free radicals, which are any substance with an unpaired electron in the valence shell, can cause oxidative stress (damage) in cells. They are used to kill pathogens after being engulfed (phagocytized) by immune cells.

6. Cont... 4. PULMONARY DRUG METABOLISM Important role of lungs may therefore be to act as a buffer by binding i.v. Drugs, preventing an acute increase in systemic concentrations. The same metabolic systems also play a role in the biotransformation and detoxification of inhaled substances The same metabolic systems also play a role in the biotransformation and detoxification of inhaled substances.

7. 5. METABOLISM IN LUNGS . Formation of chemical substances in lungs and release for local use. .A, Pulmonary surfactant – formed in Type II alveolar cells (Levitzky Fig. 10-6).
B. Release of histamine and serotonin from mast cells in response to pulmonary embolism and anaphylaxis – cause bronchoconstriction and may initiate cardiopulmonary reflexes. 2. Release into blood of substances stored in pulmonary tissues or cells: bradykinin, histamine, serotonin , PGE2, PGF2alpha, heparin and many other substances are all stored in the lung and may be released. See roles of alveolar macrophages above.

8. Cont 6. BLOOD RESERVOIR The volume of the blood passing through the pulmonary vessels is equal to the right ventricular output, of which 70–100 ml is within the pulmonary capillaries1 and takes part in gas exchange. The remaining blood volume is held within the pulmonary vasculature.

9. Cont 7. PLATELET FORMATION The abundance of megakaryocytes in the pulmonary circulation coupled with a higher platelet count within the pulmonary vein when compared with the pulmonary artery suggests that megakaryocytes undergo fragmentation within the lungs to produce platelets. interaction with the vascular endothelial cells leads to the release of a variety of factors, including platelet-derived growth factor and vascular endothelial growth factor. This causes vascular hyperplasia and proliferation of periosteal layers, resulting in clubbing .Thromboplastin is a potent procoagulant which catalyses the conversion of prothrombin to thrombin. The mammalian lung is a rich source of thromboplastin.

10. Vocalisation including speech and singing. The two bands of elastic tissue that lie across the opening of the larynx, called the vocal cords, can be stretched and positioned into different shapes by the laryngeal muscles. As air is passed over the vocal folds, they vibrate to produce characteristic patterns of sound.
Water loss and heat elimination. Inspired atmospheric air can be humidified and warmed by the respiratory airways; this is essential to prevent the alveolar membranes from drying out, which would significantly reduce diffusion of O2 and CO2. Detection of smells from airborne chemicals