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Respiratory system By Dr Shamshad Begum.Loni Lecture notes.

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1 Respiratory system By Dr Shamshad Begum.Loni Lecture notes

2 15-2 15.1 The respiratory tract Overview –Inspiration- breathing in –Expiration- breathing out –Ventilation-encompasses inspiration and expiration –Functions External respiration –Exchange of gases between air and blood Internal respiration –Exchange of gases between blood and tissue fluid Transport of gases

3 The respiratory tract

4 The respiratory tract contd. The nose –Part of upper respiratory tract –Contains 2 nasal cavities Communicate with sinuses Lined by mucous membrane –Bony ridges increase surface area Functions –Warms air- heat from vessels –Cleanses air-coarse hairs and mucus –Humidifies air-wet surfaces of membrane Olfactory receptors-on cilia high up in cavities Lacrimal glands drain into nasal cavity

5 The respiratory tract contd. The pharynx –Connects nasal and oral cavities to larynx –3 divisions Nasopharynx –Nasal cavities open posterior to soft palate Oropharynx –Where oral cavity opens –Uvula projects into oropharynx Laryngopharynx –Opens into larynx –Tonsils form a protective ring –Larynx and trachea are normally open –Esophagus is normally closed

6 The path of air

7 The respiratory tract contd. The larynx –Passageway for air between pharynx and trachea –Vocal folds found here Folds of mucosa –Glottis-opening between folds Supported by elastic ligaments Vibrate during exhalation –Pitch controlled by tension »Higher tension-higher pitch –Loudness controlled by amplitude of vibration Epiglottis –Prevents food from entering during swallowing

8 Placement of the vocal chord

9 The respiratory tract contd. The trachea –Connects larynx with primary bronchi –Supported by C-shaped cartilage rings Keeps trachea patent yet flexible –Lined with pseudostratified columnar epithelium Ciliated Goblet cells-produce mucus Combined action-mucociliary apparatus –Mucus traps debris –Cilia sweeps mucus and debris upward Smoking paralyzes the mucociliary apparatus and destroys the cilia in the trachea. –Tracheostomy-artificial opening to open airway

10 The respiratory tract contd. The bronchial tree –Right and left primary bronchi Resemble trachea in structure –Branch to secondary bronchi Eventually lead to bronchioles – as airways become smaller, walls become thinner Lack cartilage rings –Each bronchiole leads into terminal (respiratory) bronchioles Respiratory bronchioles surrounded by alveoli-air sacs

11 Gas exchange in the lungs

12 The respiratory tract contd. The lungs –Divided into lobes Right lung has 3 Left lung has 2 –Each lobe is divided into lobules Lobule has a bronchiole serving many alveoli –Lungs are covered by serous pleural membrane Double-layered Visceral pleura-on lung surfaces Parietal pleura-on walls of thoracic cavity Surface tension holds the 2 pleural layers together

13 The respiratory tract contd. The alveoli, tiny air sacs of the lung –Simple squamous epithelium –Surrounded by blood capillaries –Gas exchange occurs across alveolar wall and capillary wall Oxygen diffuses into blood Carbon dioxide diffuses into alveoli –Alveoli must stay open to receive air Surface tension has tendency to make them collapse Surfactant-soapy-like lipoprotein –Produced in lungs –Lowers surface tension –Prevents collapse Infant respiratory distress syndrome-premature babies –Lack surfactant; alveoli prone to collapse

14 15.2 Mechanism of breathing Respiratory volumes –Tidal volume Amount of air normally moving in and out with each breath during relaxed breathing. Average is 500 ml –Vital capacity Maximum volume of air that can be moved in and out in deep breathing. Illness can affect vital capacity –Inspiratory reserve volume Forced inhalation, maximum amount of air forcibly inspired above tidal volume Normally about 2,900 ml

15 Mechanism of breathing contd. Respiratory volumes contd. –Expiratory reserve volume Forced expiration, maximum amount of air forcibly expired above tidal volume Normally about 1,400 ml –Residual volume Amount of air always remaining in lungs Normally about 1,000 ml Not useful for gas exchange –Oxygen depleted –The vital capacity is tidal volume + inspiratory reserve volume + expiratory reserve volume

16 Vital capacity

17 Mechanism of breathing contd. Respiratory volumes contd. –30% of inspired air never reaches alveoli Fills respiratory tree –Nasal cavities, trachea, bronchi, bronchioles Dead space air –To increase respiratory efficiency Increase depth and not rate of breathing Slow, deep breaths Maximizes air reaching alveoli

18 Mechanism of breathing contd. Inspiration and expiration –To understand ventilation it is important to remember the following Continuous column of air from pharynx to alveoli Lungs lie in the sealed-off thoracic cavity –Rib cage forms top and sides »Intercostal muscles are between ribs –Diaphragm forms the floor Lungs adhere to the thoracic wall due to surface tension between pleural membranes

19 Mechanism of breathing contd. Inspiration –ACTIVE phase –Diaphragm and external intercostal muscles contract Rib cage elevates Increases volume of thoracic cavity Lungs expand Creates partial vacuum –Intraalveolar pressure drops below atmospheric pressure –Air flow into lungs down pressure gradient

20 Inspiration versus expiration

21 Mechanism of breathing contd. Expiration –PASSIVE phase Diaphragm and external intercostal muscles relax Rib cage drops Elastic recoil of lungs and thoracic wall Decreases volume of thoracic cavity Intraalveolar pressure rises above atmospheric pressure Air rushes out –Forced breathing Abdominal muscles contract Pushes viscera upward against diaphragm Pushes air out

22 Mechanism of breathing contd. Control of ventilation –Normal rate- 12-20 breaths per minute –Controlled by respiratory center In medulla oblongata of brain Inspiration –Sends out impulses to diaphragm and external intercostals –Causes contraction Expiration –Stops sending impulses to those muscles –Muscles relax –Input to the respiratory center Influenced by chemical and neural input

23 Mechanism of breathing contd. Chemical input to respiratory center –Directly sensitive to CO 2 and H + When levels rise respiratory center increases rate and depth of breathing –Indirectly responsive to O 2 Chemoreceptors in the carotid and aortic bodies –Sensitive to oxygen levels in blood –When oxygen levels in blood decrease, impulses are sent to respiratory center »Respiratory center then increases rate and depth of breathing

24 Nervous control of breathing

25 Gas exchanges in the body External respiration –Exchange of gas between air in alveoli and blood –Gases exert pressure Partial pressure-amount of pressure each gas in a mixture exerts –Symbolized by Pco 2 and Po 2 –Blood in pulmonary capillaries has a higher Pco 2 than atmospheric air CO 2 diffuses from blood into alveoli

26 Gas exchanges in the body contd. External respiration contd. –Carbon dioxide generated in tissue is transported in blood Most transported in the form of bicarbonate ions Small amount is transported as dissolved molecular CO2 –Molecular CO2 diffuses into alveoli This drives the following reaction to the right: H + + HCO - H 2 CO 3 H 2 O + CO 2 Carbonic anhydrase is present in RBCs –Increases rate of carbonic acid breakdown CO 2 then diffuses into alveoli carbonic anhydrase

27 Gas exchanges in the body contd. External respiration contd. –Hyperventilation Pushes preceding reaction even farther to right Decreases hydrogen ions- alkalosis –increased pH Compensation-decrease respiratory rate –Allows hydrogen ions to build up and return pH to normal –Hypoventilation Hydrogen ions build up-acidosis-decreased pH Compensation-increase respiratory rate to blow off CO 2 –Helps return pH to normal along with other mechanisms

28 Gas exchanges in the body contd. External respiration contd. –Pressure gradient for oxygen is the reverse of carbon dioxide –Po 2 is low in pulmonary capillaries and high in alveoli –Oxygen diffuses into blood –Hemoglobin in RBCs picks up oxygen oxyhemoglobin

29 Gas exchanges in the body contd. Internal respiration –Exchange of gas between systemic capillaries and tissues –Oxygen Partial pressure of oxygen is greater in capillaries than tissues Oxyhemoglobin gives up oxygen –Diffuses out of blood into tissues Gradient always remains high –Oxygen is constantly used for cell respiration

30 Gas exchanges in the body contd. Internal respiration contd. –Carbon dioxide-higher in tissues than blood –Most diffuses into RBCs Increased carbon dioxide from tissues drives reaction to right CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - Bicarbonate ions diffuse out of RBCs into plasma Hydrogen ions bind to hemoglobin- buffers Small amount of carbon dioxide binds to hemoglobin –carbaminohemoglobin carbonic anhydrase

31 External and internal respiration

32 15.4 Respiration and health Upper respiratory tract infections –Nasal cavities, larynx, pharynx –Infections can spread to sinuses, middle ear –Viral infections can lead to secondary bacterial infections –strep throat Streptococcus pyogenes Sore throat, high fever, white patches –Sinusitis Nasal congestion blocks sinus openings Postnasal discharge, facial pain Spray decongestants-help drainage

33 Respiration and health contd. Upper respiratory tract infections contd. –Otitis media Middle ear infection Spreads from nasal cavity through eustachian tubes Pain is primary symptom Antibiotics, typanostomoy tubes for recurrent –Tonsillitis –Inflammation of tonsils –Tonsillectomy »Fewer done today »Importance of tonsils recognized

34 Respiration and health contd. Upper respiratory tract infections contd. –Laryngitis Infection of larynx Hoarseness Persistant hoarseness without upper respiratory infection –Could indicate cancer

35 Respiration and health contd. Lower respiratory infections –Acute bronchitis Infection of primary and secondary bronchi Usually secondary infection Deep cough Expectoration of mucus, pus –Pneumonia Infection of lungs Viral or bacterial Alveoli and bronchioles fill with fluid High fever, chills, chest pain Can be generalized or isolated to specific lobes Pneumocytis carinii pneumonia- AIDS patients

36 Respiration and health contd. Lower respiratory infections contd. –Pulmonary tuberculosis Tubercle bacillis- bacterium Infected tissue encapsulates bacteria-tubercle State of immune system determines course –If competent, infection generally walled off –If compromised, infection spreads Treated by antibiotics –Individuals are quarantined –Tine test

37 Respiration and health contd. Lower respiratory infections contd. –Restrictive pulmonary disorders Vital capacity is reduced Lungs lose elasticity Pulmonary fibrosis –Inhalation of particles »Silica, asbestos, coal dust –Lungs cannot inflate normally

38 Respiration and health contd. Obstructive pulmonary disorders –Decreased air flow –Chronic bronchitis Airways inflammed Productive cough Degenerative changes in bronchi –Loss of mucociliary apparatus Smoking, pollutants can predispose –Emphysema Alveoli distended Loss of surface area for gas exchange Air trapped in lungs due to alveoli damage Increased workload on heart Supplemental oxygen, drug therapy, exercise may help

39 Respiration and health contd. Obstructive pulmonary disorders –Asthma Lower airway sensitivity Smooth muscle constriction in bronchioles Produces musical wheezing Chemical mediators in bronchioles cause bronchospasm Inhalant medications, bronchodilators Lung cancer Progressive steps Thickening and callusing of airway cells of mucosa of bronchi Loss of cilia Cancerous changes occur producing cells with atypical nuclei Tumor Development and then finally Metastasis. Can be caused by Active smoking and/or Passive smoking.

40 Normal lung versus cancerous lung


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