Dr Amna Tahir Assistant Professor PHYSIOLOGY DEPARTMENT KEMU

 What is respiration?  Respiration = the series of exchanges that leads to the uptake of oxygen by the cells, and the removal of carbon dioxide from the body as a whole. Step 1 = ventilation  Inspiration & expiration Step 2 = exchange between alveoli (lungs) and pulmonary capillaries (blood)  Referred to as External Respiration Step 3 = transport of gases in blood Step 4 = exchange between blood and cells  Referred to as Internal Respiration  Cellular respiration = use of oxygen in ATP synthesis

External Respiration Internal Respiration Schematic View of Respiration

 At rest normal human breathes times a minute.  Each breath contains 500 ml of air.  Which means 500×12=6L of air inspired and expired each min.  On average 250 ml of Oxygen enters the body per min and 200 ml of carbon dioxide is excreted.

 What structural aspects must be considered in the process of respiration?  The conduction portion  The exchange portion  The structures involved with ventilation  Skeletal & musculature  Pleural membranes  Neural pathways  All divided into  Upper respiratory tract  Entrance to larynx  Lower respiratory tract  Larynx to alveoli (trachea to lungs)

The relationship between minute volume (total pulmonary ventilation) and alveolar ventilation & the subsequent “mixing” of air

 Physiological mechanisms  90% of particles>10 microns are removed in nose and nasopharynx.  Pollen grains are >20 micron  Particles between 5-10 impact at the tracheal bifurcation(carina).

 The removal is by mucociliary escalators.  It is actually cilia in contact with the gel like mucus (acid and polysaccharides) formin a mucus blanket.  Cilia beat at rate of 1000/min and move the inhaled bactaria and particles at 1.5 cm/min toward larynx.  Particles 1-5 microns reach the deep lungs and are removed by PAM’s

 This ciliary motility is defective leading to chronic sinusitis,recurrent lung infections.bronchiectesis and prolonged exposure to carcinogens.

 Clara cells-non ciliated cuboidal secrete defense markers and are progenitors  Epithelial cells secrete IgA,SP-A,peptides proteases,reactive oxygen and nitrogen species.They all act directly as antimicrobials.  Epthelial cells also secrete cytokines and chemokines that recruit the immune cells to the site of infection.

 Pulmonary alveolar macrophages are actively phagocytic and ingest small particles.  IgA against antigens  Surfactant protein A ---opsonization and increase phagocytosis  Complement from blood—cytotoxic  Interferon—in response to viruses  Lysozymes.—are the enzymes in the granulocytes and are bactericidal

Cough results when these receptors are stimulated Epiglottis Larynx Trachea bronchiss

Cough reflex consists of an inspiration followed by forceful expiration. The purpose is to dislodge the irritants from airways During expiration alveolar pressure becomes very high upto 100 mmHg and irritant is dislodged The velocity of expired air may be miles per hour The cough centre is present in meddulla oblongata During coughing posterior naries are closed

 It results when there is irritation in upper respiratory tract particularly in nose  Irritation may be chemical,mechanical s  Receptors involved are irritants receptors.  Events are similar to that of cough but in sneezing uvala is depressed and expired air is expelled through both nose and mouth, posterior nares are open

The walls of the bronchi and bronchioles are innervated by the autonomic nervous system. Muscarinic receptors are abundant, and cholinergic discharge causes bronchoconstriction. The bronchial epithelium and smooth muscle contain β 2-adrenergic receptors.

The β 2 receptors mediate bronchodilation. They increase bronchial secretion, while α 1 adrenergic receptors inhibit secretion. There is in addition a noncholinergic, nonadrenergic innervation of the bronchioles that produces bronchodilation, and evidence suggests that VIP is the mediator responsible for the dilation.