Anatomy and Physiology of the Respiratory System PDF

Anatomy and physiology of the respiratory system Structure of the respiratory system  The nose:  The function of the nose is to facilitate smell and respiration.  The throat:  The throat can be considered as the oral cavity, the pharynx and the larynx. The oral cavity extends from...

Anatomy and physiology of the respiratory system Structure of the respiratory system  The nose:  The function of the nose is to facilitate smell and respiration.  The throat:  The throat can be considered as the oral cavity, the pharynx and the larynx. The oral cavity extends from the lips to the tonsils. Structure of the respiratory system  The trachea, bronchi and bronchioles  Trachea is 10 – 12 cms in length  Slightly to the right of the midline and divides at the carina (under the junction of manubrium and second costal cartilage Structure of the respiratory system  The right main bronchus is more vertical than the left, hence inhaled material tends to end up in right lung.  The right main bronchus divides into: a- Upper lobe bronchus. b- intermediate bronchus which divides into :middle lobe bronchus and lower lobe bronchus The left main bronchus divides into: a- Upper lobe bronchus. b- Lower lobe bronchus. Structure of the respiratory system  Each lobar bronchus divides further into segmental and sub- segmental bronchi.  The first seven divisions are bronchi that have:  - Walls consisting of cartilage and smooth muscles.  ~ Epithelial lining with cilia and goblet cells.  - Submucosal mucus-secreting glands, Structure of the respiratory system The next 16-18 divisions are bronchioles that have: - No cartilage and muscular layer that progressively become thinner. - A single layer of ciliated cells but very few goblet cells. - Granulated Clara cells that produces a surfactant-like substance.  The bronchioles finally divide within the acinus into smaller respiratory bronchioles that have alveoli arising from the surface.  Each respiratory bronchiole supplies approximately 200 alveoli via alveolar ducts. The term "small airways" refer to bronchioles of less than 2mm diameters. The alveoli:  There are approximately 300 million alveoli in each lung with a total surface area of 40- 80m”.  They are lined mainly by type I pneumocytes with very thin cytoplasm providing only a thin barrier to gas exchange.  The pores of kohn are holes in the alveolor wall allowing communication between alveoli of adjoining lobules. Lungs  Right lung has 3 lobes; upper, middle and lower lobes.  Left lung has 2 lobes; upper and lower lobes.  The two lugs are included in the pleural sac which consists of two layers; visceral and parietal. With thin film in between two layers. Common diseases  Pleurisy: inflammation of the pleura characterized by stitching pain increase with inspiration and decrease by lying on the affected side.  Pleural effusion: presence of excess fluid in pleural space.  Pneumonia: inflammation of lung tissue  Lobar pneumonia: inflammation of one lobe  Broncopneumonia: patchy inflammation of both lungs  Suppurative lung disease: group of diseases characteried by presence of pus  Lung abscess, empyema(pus in pleura), bronchiectasis (pus in lower air spaces pneumonia Pleural effusion bronchiectasis Defense Mechanisms of the Respiratory Tract I. Physical and physiological mechanisms:  1. Humidification: This prevents dehydration of the epithelium.  2. Particle removal: Particles >10,1m are removed in nostrils and nasopharynx e.g. most pollen grains. Particles 5-10um in diameter become impacted in the carina. Defense Mechanisms of the Respiratory Tract  3. Particle expulsion: By coughing, sneezing or gagging  4. Respiratory tract secretions: - The respiratory epithelium consists of pseudostratified columnar ciliated cells down to the small airways. - Each cell bears approximately 200 cilia beating at 1000 beats per minute in an organized beat waves. - Under normal conditions the tips of the cilia are in contact with the undersurface of the gel layer and coordinate their movement to push the mucus blanket towards the mouth. Defense Mechanisms of the Respiratory Tract  Cigarette smoke, air pollution and products of bacterial and viral infection can significantly damage and reduce mucocilliary transport.  Congenital defects in mucocilliary transport leads to recurrent infections and eventually to bronchiectasis (immotile cilia syndrome and cystic fibrosis). Defense Mechanisms of the Respiratory Tract  Il. Humoral and cellular mechanisms:  a. Non-specific soluble factors:  antitryspsin is present in lung secretions and is derived from plasma.  Antioxidant defenses (e.g. superoxide dismutase and low molecular weight antioxidant molecules such as ascorbate and urate in the epithelial lining fluid).  Defense Mechanisms of the Respiratory Tract  Il. Humoral and cellular mechanisms:  a. Non-specific soluble factors:  Lysozyme in granulocytes.  Lactoferrin in epithelial cells and neutrophils.  Interferon produced by many cells in response to viral infection  Complement in secretions and is derived from plasma.  Surfactant protein A can enhance phagocytosis by macrophages.  Defensins (bactericidal peptides from neutrophils). Defense Mechanisms of the Respiratory Tract  Il. Humoral and cellular mechanisms:  b. Alveolar macrophages:  Derived from precursors in bone marrow, they help phagocytosis, cell killing, secretion of several products including cytokines and immuno-regulation.  They are the dominant cells in the airways (90% of all cells obtained by broncho- alveolar lavage (BAL).  c. Lymphoid tissue: The lung contains large numbers of lymphocytes scattered throughout the airways. Sensitized lymphocytes contribute to local immunity through differentiation into IgA secreting plasma cells. Major Manifestations Of Lung Disease 1- DYSPNEA Causes of dyspnea referring to the patho-physiologic mechanisms: (1) Dyspnea associated with increased work of breathing: accessory muscles of respiration, sternomastoids and scalene, may be seen working and working ala nasi in children.  Airway obstruction:  1. Chronic bronchitis  2. Emphysema  3. Bronchial asthma  4. Stridor Causes of dyspnea referring to the patho-physiologic mechanisms: (1) Dyspnea associated with increased work of breathing:  Decreased pulmonary compliance (stiff lungs): 1. Pulmonary edema. 2. Pulmonary fibrosis.  Restricted chest expansion: 1. Kyphoscoliosis 2. Lung resection 3. Painful lesions: e.g. fracture rib, pleural pain. 4. Pregnancy Causes of dyspnea referring to the patho-physiologic mechanisms: (2) Dyspnea associated with hyperventilation:  Massive pulmonary embolism (decreased perfusion of well aerated alveoli— increased dead space), Striking hyperventilation is an early sign, later it’s masked by signs of decreased cardiac output. Interstitial lung disease (ILD) and pneumonia: the resultant hypoxia stimulates peripheral chemoreceptors in aortic arch and carotid body— reflex stimulation stimulate of respiratory center — hyperventilation. Causes of dyspnea referring to the patho-physiologic mechanisms:  (2) Dyspnea associated with hyperventilation:  Metabolic acidosis: increased hydrogen ions stimulates respiratory center. e.g. diabetic ketoacidosis and renal failure.  Hyperventilation syndrome: if severe and prolonged— respiratory alkalosis > tetany and may precipitate an epileptic fit.  Hysterical dyspnea: with hyperventilation and sighing. Causes of dyspnea referring to the patho-physiologic mechanisms: (3) Dyspnea associated with weakness of respiratory muscles (decrease ventilation):  Spinal cord injuries above C4  Guillan Barre syndrome (acute infective polyneuropathy).  Poliomyelitis.  Myasthenia gravis. Causes of dyspnea referring to the patho-physiologic mechanisms:  (4) Dyspnea of cardiac origin (in cardiovascular system):  Heart failure whatever the etiology produces dyspnea. It’s an early symptom of left sided heart failure associated with orthopnea & PND.  Pericardial effusion.  Constrictive pericarditis.  Acute left sided heart failure(cardiac asthma) Dyspnea with normal heart and chest Differential diagnosis of dyspneic patient with normal chest and cardiac examination and with normal CXR  Anemia.  Fevers whatever the cause.  Thyrotoxicosis.  Diabetic ketoacidosis.  Renal failure.  Hysterical dyspnea (not uncommon). Causes of sudden onset dyspnea (within minutes):  Acute pulmonary edema.  Massive pulmonary embolism.  Laryngeal edema or spasm.  Foreign body inhalation.  Pneumothorax Positional dyspnea: Orthopnea: dyspnea on lying flat relieved by sitting.  Pathogenesis:  When the patient lies flat: . Increase venous return  — increase pulmonary congestion.  High position of the diaphragm.  Compression on the diaphragm by enlarged liver and ascites.  Limited chest expansion on the recumbent position. Positional dyspnea:  When the patient sits up:  Helps venous drainage of head and neck, relieving congestion of the vital centers of the brain.  Decrease venous return from the lower part of the body.  Relieves compression of the abdominal viscera on the diaphragm.  Better performance of the diaphragm and intercostals muscles.  Sitting up and holding on to the sides of the bed to fix the shoulder girdle allows better use of the accessory muscles of respiration. Positional dyspnea:  (2) Platypnea: - Breathlessness when the patient is in the upright position (with orthodeoxia) relieved by lying down.  - It is due to a marked fall in blood oxygen saturation in sitting or standing position. –  Possible causes of this syndrome are intracardiac shunt (ASD), pulmonary parenchymal ventilation/perfusion mismatch (COPD), and _ pulmonary arteriovenous shunts. Positional dyspnea:  (3) Trepopnea: Dyspnea on lying to one side of the body, occurs in unilateral chest disease when the patient lies on the healthy side. Major Manifestations Of Lung Disease 2- COUGH II. Cough  Definition: Cough is an explosive expiration which provides a means of clearing the tracheobronchial tree of secretions and foreign bodies (as defensive reflex).  It may be dry (without sputum) or productive(with expectoration of sputum) Causes of cough  II. Expectorations:  Volume: Purulent sputum and/or large amounts of sputum suggest lung abscess or bronchiectasis.  Changes: Postural ( lung abscess) or seasonal(asthma).  Color: Yellow or green common sign of infection.  Consistency: Frothy and pink-tinged sputum, pulmonary edema.  Odor (foul smelling anaerobic infection in suppurative lung disease). Major Manifestations Of Lung Disease 3- HEAMOPTYSIS III. Hemoptysis  Definition: Coughing-up blood from the lower respiratory tract. (blood coming from above the larynx — false Hemoptysis).  Types:  1. Blood tinged.  2. Blood — streaked.  3. Frank hemoptysis. Heamoptysis or heamatemesis Heamoptysis Heamatemesis Coughing of blood Vomiting of blood Bright red in color Coffee ground in color Frothy mixed with sputum Mixed with food particles No melena Associated with melena History of cardiac History of liver disease, NSAIDS, diease,pulmonary hypertension, H pylori mitral stenosis,deep vein thrombosis Causes of heamoptysis  A. Respiratory causes infections tumors vascular others Acute Bronchial Pulmonary Foreign body bronchitis adenoma infarction (embolism) Chronic Bronchial vasculitis bronchoscopy bronchitis carcinoma Pulmonary TB Tracheal tumors Lung biopsy pneumonia metastasis Chest trauma  B. Cardiac causes: 1. Mitral stenosis. 2. Cardiac asthma.  C. General: 1. Bleeding tendency. 2. Anticoagulation. Major Manifestations Of Lung Disease 4- CHEST PAIN IV. Chest pain Analysis of Chest pain:  1. Onset, course, duration, character  2. Site, radiation, character, severity.  3. Provocation, relief, frequency.  4. Special times of occurrence.  5. Associated symptoms.  IV. Chest pain  Causes cardiac Respiratory Mediastinal Chest wall Myocardial infarction Acute pleurisy Non cardiac chest pain due Localsed aching,persist at Sudden, stitching, increase to gastro-esophageal reflux rest, tenderness with inspiration, dry cough, disease or esophageal a. skin breast abscess relieved by compression spasm b. Rib and holding breath Mediastinitis fracture,osteomyelitis Mediastinal tumor c. Spine as pott’s disease d. Intercostal muscles Pulmonary embolism Pneumothorax acute severs Intercostal nerves sudden onset smoker, (herpes zoster) vesicles, asthma, trauma diabetics pericarditis Acute massive lung collapse Aortic dissection Major Manifestations Of Lung Disease OTHERS  VI. Symptoms of Toxemia - Fever, night sweat, anorexia and weight loss. (tuberculosis)  VII. Symptoms of Systemic Congestion - Dyspepsia, right hypochondrial pain, lower limb oedema (hypoxic corpulmonale: right heart failure due to chest disease)  VIII. Symptoms of Respiratory Failure - Hypoxia (fatigue, headache) – Hypercapnea (increase co2 in blood) (headache, somnolence, altered sleep rhythm, disturbed consciousness).  IX. Symptoms of Mediastinal Syndrome - The most common symptoms are chest pain, cough, hoarseness, and dyspnea, whereas, stridor, dysphagia, and Horner's syndrome (ptosis myosis anhydrosisi, enophthalmos)are less frequent. Horner syndrome Herpes zoster pneumothorax Investigations Of The Respiratory Disease I. IMAGING 1. Plain X ray chest Investigations Of The Respiratory Disease pneumothorax Pleural effusion Pancost tumor Investigations Of The Respiratory Disease 2. High resolution CT  Further examine abnormalities found on conventional chest x-rays. - Help diagnose the cause of disease the chest, such as dyspepsia, cough, shortness of breath, chest pain, or fever. - Detect and evaluate the extent of tumors that arise in the chest, or tumors that have spread there from other parts of the body. - Assess whether tumors are responding to treatment. Investigations Of The Respiratory Disease 3. CT angiogram (CTA): in pulmonary infarction. 4. MRI: - chest MRI provides detailed pictures of tissues within the chest area. - As an alternative to angiography, or to avoid repeated exposure to radiation - Clarify findings from previous x-rays or CT scans 5. Scintigraphic imaging: Ventilation perfusion lung scan to evaluate pulmonary embolism. Gallium imaging: diagnostic value in opportunistic infection in immunosuppressed patients, especially AIDS. Investigations Of The Respiratory Disease  II. Arterial blood gases 1. Measurement of the partial pressures of oxygen (PaO2) and carbon dioxide (PaCOQ2) on arterial blood, is essential in the management of cases of respiratory failure and severe asthma. Investigations Of The Respiratory Disease  II. Arterial blood gases 2. Pulse oximetry: is a simple non-invasive device that estimates functional oxyhemoglobin saturation (Not the same as PaQ2). Investigations Of The Respiratory Disease  Ill. Respiratory function testing:  Characterizes and quantifies pulmonary dysfunction.  Typical patterns of abnormality are known as obstructive or restrictive ventilatory defects.  Tidal volume: amount of air inspired or expired during normal respiration.Usually = 500 ml  Inspiratory reserve volume: amount of air breathed in forcefully above tidal volume. Normally =3000 ml Investigations Of The Respiratory Disease  Vital capacity(VC): maximum amount of air that can be expelled forcefully after maximal inspiration  VC = IRV plus tidal volume plus expiratory reserve volume 3300 plus 500 plus 1000 = 4800 ml Investigations Of The Respiratory Disease  Spirometry:  Indications  - Spirometry is used to detect and diagnose pulmonary diseases e.g COPD, asthma.  Monitor effects of therapies and the progression of the disease help in the investigations of certain respiratory symptoms ¢.g cough, dyspepsia.  - Evaluate operative risk.  - Perform surveillance for occupational-related lung disease. - Determine the base line lung function - Investigations Of The Respiratory Disease  The spirometer measures the FEV1 and the forced vital capacity (FVC).  The technique involves a maximum inspiration followed by a forced expiration (for as long as possible) into the spirometer. Investigations Of The Respiratory Disease  The FEV, expressed as a percentage of the FVC is an excellent measure of airflow  Limitation. In normal subjects it is about 75%.  Peak expiratory flow rate (PEFR): (PEFR, also known as a peak flow) test measures how fast a person can exhale after a full inspiration.  - Peak flow rate primarily reflects large airway flow depends on the voluntary effort and muscular strength of the patient Investigations Of The Respiratory Disease  Forced expiratory volume over 1 second (FEV)) is a dynamic measure of flow used in formal spirometry.  It represents a truer indication of airway obstruction than does PEFR.  - PFER usually correlates well with FEV), this correlation decreases in asthma Pulmonary function tests in obstructive and restrictive lung disease Investigations Of The Respiratory Disease  IV. Obtaining biological specimens:  1. Sputum: -  - Gram’s staining and culture: a good sample shows alveolar macrophages and inflammatory cells rather than squamous epithelial cells.  - Staining and culture for mycobacteria or fungi  - Culture for viruses.  - Immunofluorescent stain for Pneumocystic carinii in HIV patients.  - Cytologic staining for malignant cells. Investigations Of The Respiratory Disease  2. Percutaneous needle aspiration; C-T guided.  3. Thoracocentesis: sampling pleural fluid.  4. Bronchoscopy: Flexible, or (rigid in selected circumstances)  Direct visualization of the tracheo-bronchial tree.  Retrieval of foreign body Sampling bronchial cells by brushing or bronchial biopsy or when indicated broncho-alveolar lavage.  5. Thoracoscopy: Thoracotomy, mediastinoscopy, and mediastinostomy: are invasive diagnostic procedures to obtain tissue biopsy and management of pleural, parenchymal or mediastinal masses.  V. skin test  Tuberculin test  VI. Hematological examination: Total and differential white cell count may identify pyogenic infection from tuberculous or viral infection. Eosinophilia in some allergic disorders. Both leucocytosis and leucopenia imply a poorer prognosis in community acquired pneumonia.