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RESPIRATORY SYSTEM

RESPIRATORY SYSTEM. By DR. M.B.Bhat. RESPIRATION. Definition 2-Processes of Respiration – External Respiration –definition & Internal Respiration –definition

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RESPIRATORY SYSTEM

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  1. RESPIRATORY SYSTEM By DR. M.B.Bhat.

  2. RESPIRATION • Definition • 2-Processes of Respiration – • External Respiration –definition & • Internal Respiration –definition • Respiratory system (in Physiology) deals with external respiration –i.e. Exchange of gases between atmosphere & tissues (of the body) through blood & Vice versa.

  3. Important normal values • Respiratory rate –12 to 18/min • O2 uptake per minute –250ml • CO2 expulsion per minute –200ml

  4. Major routes of respiration • Air ways –Upper & lower respiratory tracts • Gas-exchange organ –Lungs • Pump (to ventilate the lungs) –Thoracic cage –consists of Chest wall & the respiratory muscles.

  5. Air ways (passages)Respiratory tracts • Upper respiratory tracts – • consists of nose/or mouth & Pharynx • Nose (Nasal cavities) –External nares –Conchae –Internal nares –Naso-pharynx • (Mouth –oropharynx)

  6. Lower respiratory tracts • Consists of • Larynx & • Tracheo-bronchial tree (Pulmonary tree) –Consists of Trachea & its bronchial branches • Trachea dichotomously divided repeated and give rise to thousands of branches

  7. Larynx • –Voice box fitted on the trachea (–Helps in phonation also) • Made up of –Thyroid cartilages (anterior & lateral surfaces); Arytenoids cartilages (posterior) & Cricoids cartilages (inferior) • Opening of superior surface –glottis (guarded by epiglottis) –having two vocal folds (cords) originating from either of the lateral side towards center of glottis • Many muscles connect Vocal cords & cartilages with one another.

  8. Tracheo-bronchial tree(Pulmonary tree)

  9. Tracheo-Bronchial tree • Consists of • Trachea --- • Bronchi (Bronchus) • Bronchiole(s) • Respiratory Bronchiole(s) • Alveolar ducts –Atria – Alveolar sacs – (Pulmonary) Alveoli (Functional respiratory units)

  10. Numbering of Tracheo-Bronchial tree • By E.R. Weibel (1963) –Swiss Anatomist • Has got –23 generations of air ways • Trachea –as 0 generation & its first division the right & left bronchi as 1 • Up to 16 generation (up to terminal bronchioles) –Conductive zone • Rest 7 –Respiratory zoneOR Transitional (3) & Respiratory zone (last 4)

  11. Conducting zone 16 generations Respiratory zone 7 generations

  12. Conducting Zone • From trachea up to terminal bronchiole (16th generation) forms conducting zone • Mere conducting the air in & out • Including Larynx, the conducting zone is also called Lower respiratory tract • They form the dead space

  13. Functions of dead space • Purification of air –Removal of solid particles of various size from air • Air-conditioning function –air temperature of 37oC • Humidifying function –air water vapor pressure of 47 mm Hg

  14. Because of multiple divisions of the air ways – Diameter decreases from 2.5cm of trachea to 1.5cm of bronchus –to—<1mm of bronchiole –to –0.5mm of respiratory bronchiole to 200µm of alveoli Total cross-sectional area (A) increases from Trachea 2.5 cm2; --Terminal bronchioles 180cm2 & alveoli—11800cm2 Velocity of air flow falls in small air way as (V=1/A) Number of branches from 1trachea to 65000 terminal bronchioles to 3 million alveoli.

  15. Structure of air way • Trachea made up of – • (On the outer surface is) ‘C’—shaped (hyaline) cartilages (up to 20 in number) –open end posteriorly towards esophagus. A fibro-elastic ring sealed to form tube. • (Middle) Smooth muscle (layer) is very little • (Inner) mucosa made up of ciliated columnar epithelium & also contains mucus & serous glands • Diameter of 2.5cm & 10cm long; divided to form left & right bronchus

  16. In bronchus & bronchiole– (up to 1mm in dia) (outer) less extensive cartilage plates (middle) extensive smooth muscle layer (inner) ciliated columnar epithelium & also contain mucus gland In bronchiole –(<1mm diameter) No cartilage Smooth muscle layer forms the outer coat Ciliated columnar epithelium with mucus gland

  17. Respiratory bronchioles of <0.5mm diameter)—less smooth muscle & ciliated columnar epithelium Alveolar duct –cone shaped; made up of squamous epithelium Atria --smooth muscle forms a sphincter between alveolar duct & sac Alveolar sac –No smooth muscle; squamous epithelium The functional unit –alveolar duct, atria, alveolar sac & alveoli are surrounded y fibrous septa that penetrate from lung surface to lung parenchyma

  18. Alveoli (alveolus) • Polygonal or polyhedral shape; Made up of squamous epithelial cells (Pneumocytes) • Two types of cells • Type I cells (Type I pneumocytes) –flat squamous cells form main lining cells –90% • Type II cells (Type II pneumocytes or granular pneumocytes) –10% of cells; secrete surfactant • Other cells –PAMs; Lymphocytes, Plasma cells, APUD cells, Mast cells • Inner surface lined by (alveolar) fluid with thin surface film of surfactant

  19. Blood – Gas Barrier • Blood-gas barrier – • surfactant –alveolar fluid –alveolar epithelium –basal lamina –capillary endothelium (Total thickness of 0.5µm)

  20. Factors aids collapse of alveoli – Elastic recoiling of alveoli Surface tension Factors preventing collapse of alveoli – Air in the alveoli (residual volume) (Negative) intra pleural pressure Inter-dependence of alveoli Outer fibrous septa Surfactant

  21. Factors prevent collapse of air way • Cartilages • Intra pleural pressure

  22. Lungs • Consists of intra pulmonary respiratory tracts & alveoli covered by fibrous sac (pleural sac) • Weight – 500 to 700gms; (fetus 60gm) • 300million alveoli; (fetus 10million) • surface are of 70m2

  23. Pleura • Have visceral & parietal pleural layer • Space in between –pleural space • Filled with fluid –pleural fluid (2ml) • Intra pleural pressure –negative pressure of 2mm Hg (5cm H2O) –due to -- • Opposite recoil effect of lungs & chest • Lymphatic drainage

  24. Pleural effusion • Increase pleural fluid volume • Due to – • Blockage of lymphatic channels • Cardiac failure • Decrease plasma colloidal osmotic pressure • Infection & inflammation leads to breakage of pulmonary capillaries

  25. Nerve supply—Autonomic NS • Parasympathetic nerve –Broncho-constriction • Stimulus –Irritant chemicals (SO2, NO2, CO, Lead, Hydrocarbon), Cool air, Exercise, leukotrines • Normal Bronchiole tone by parasympathetic nerve –exhibits circadian rhythm –Max. constriction at 6am & max. dilation at 6pm • Sympathetic – • β2 adrenergic receptor –broncho-dilation & secretion • Αlpha adrenergic receptor –decrease secretion • VIP (receptor are also present)—broncho-dilation • Histamine –broncho-constriction

  26. Pulmonary circulation • Receive entire cardiac out put • Low resistance circulation & B. Vessels are highly distensible (hold 20% of Total B.V) • Low BP • Operate in series with systemic circulation

  27. Systolic BP –25mm Hg Diastolic BP –10mm Hg Mean BP –15mm Hg Pulmonary capillary pressure –7mm Hg Arterial end capillary pressure –15mm Hg Venous end capillary pressure –5 mm Hg Vol. of blood in pul. vessels –1L Vol. of blood in pul. Capillaries –100ml Circulation time of RBC through Pul. Capillary at rest–0.7sec & during exercise 0.3sec

  28. Thanks

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