INTRODUCTION OF PHYSIOLOGY OF NOSE AND RESPIRATORY PASSAGES
INTRODUCTION OF PHYSIOLOGY OF NOSE AND RESPIRATORY PASSAGES Dr Amna Tahir Assistant Professor PHYSIOLOGY DEPARTMENT KEMU Basics of the Respiratory System Respiration
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
Schematic View of Respiration External Respiration Internal Respiration Respiratory physiology.
At rest normal human breathes 12-15 times a minute.
Each breath contains 500 ml of air. Which means 50012=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. The components of the respiratory system
The upper respiratory tract. The resp epithelium of nasal cavity and conducting system Basics of the Respiratory System Functional Anatomy
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) Ventilation The relationship between minute volume (total pulmonary ventilation) and alveolar ventilation & the subsequent mixing of air
Prominent cells in the adult human alveolus. Defense mechanisms of respiratory system
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).
Defense mechanisms of Respiratory system.
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 PAMs
smokers This ciliary motility is defective leading to chronic sinusitis,recurrent lung infections.bronchiectesis and prolonged exposure to carcinogens.
Defense mechanism. 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. Humoral and cellular defense
Pulmonary alveolar macrophages are actively phagocytic and ingest small particles. IgA against antigens Surfactant protein A ---opsonization and increase phagocytosis Complement from bloodcytotoxic Interferonin response to viruses
Lysozymes.are the enzymes in the granulocytes and are bactericidal COUGH REFLEX Cough results when these receptors are stimulated Epiglottis Larynx Trachea
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 70-100 miles per hour The cough centre is present in meddulla oblongata During coughing posterior naries are closed SNEEZING
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 innervation of the bronchi and
bronchioles 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 2adrenergic receptors.
s The 2 receptors mediate bronchodilation. They increase bronchial secretion , while 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.
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