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CHAPTER 12RESPIRATORY SYSTEM

• respiration – the mechanical process of breathing –the exchange of air between the lungs and the external environment

external respiration – the exchange of air at the lungs• O2 is inhaled (21% from air) into the alveoli and immediately enters the capillaries – simultaneously CO2 (cellular waste) enters the alveoli to be exhaled

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internal (cellular) respiration - an exchange of gases at the cellular level• O2 passes out of capillaries into tissue cells and CO2

passes from the cells into the capillaries

Anatomy and Physiology of Respiration

• air enters the body through the nose (nares – two openings) and passes through the nasal cavity lined with a mucous membrane (warm and moisten) and cilia(fine hair that filter foreign bodies)• paranasal sinuses (hollow, air-containing spaces) communicate with the nasal cavity – produce mucous, lighten the bones of the skull and produce sound

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• from the nasal cavity, air enters the pharynx (throat) which is divided into three sections:

• nasopharynx contains the pharyngeal tonsils (adenoids) –collections of lymphatic tissue• oropharynx contains the palatine tonsils – two rounded masses of lymphatic tissue• laryngopharynx serves as a common passageway for food / air from the mouth and air from the nose – divides into the larynx (voice box) and the esophagus

• food (mouth) and air (nose) mix in the pharynx• when swallowing, the epiglottis (flap of cartilage attached to root of tongue) closes over the larynx pushing food into the esophagus

• after the larynx, air moves into the trachea (windpipe) – kept open by 16 – 20 c-shaped rings of cartilage separated by fibrous connective tissue (stiffen)

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• the trachea braches at the mediastinum into two sides –the L/R bronchial tubes (bronchi / bronchus(s))

• composed of epithelium surrounded by cartilage rings and a muscular wall

• each bronchus leads to a lung – divides and subdivides into smaller branches called bronchioles• each terminal bronchiole narrows to alveolar ducts – end in small air sacs called alveoli / alveolus(s)

• ~ 300M alveoli in both lungs• each alveolus is lined with epithelium that is one cell thick – allows for exchange of gases between alveolus and the capillary surrounding it• blood flowing through the capillary accepts O2 from the alveolus and deposits CO2 into the alveolus• erythrocytes (RBC) in the blood carry O2 to cells in the tissues of the body and CO2 to the lungs for exhalation

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• each lung is covered by pleura (double-folded membrane) – outer layer (near ribs) = parietal pleura / inner layer (closer to the lungs) = visceral pleura• a serous (thin, watery fluid) secretion moistens the pleura and facilitates movement of the lungs within the thorax (chest)

• two lungs are not mirror images• the R lung is slightly larger and divided into 3 lobes• the L lung is smaller and divided into 2 lobes• one lobe of a lung may be removed without damage to the rest

• the uppermost part of the lung is the apex and the lower is the base• the hilum is the middle region where blood vessels, nerves, lymphatic tissue and bronchial tubes enter / exit

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• the lungs extend from the clavicle to the diaphragm(muscle that separates the thoracic and abdominal cavities) in the thoracic cavity• the diaphragm contracts and descends with inhalation – downward movement enlarges the area in the thoracic cavity, ↓ internal air pressure allowing air to flow into the lungs• when the lungs are full, the diaphragm relaxes and elevates, reducing the size of the thoracic cavity, ↑ air pressure in the chest – exhalation (expiration) occurs to equalize the pressure

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PATHOLOGYDiagnostic Terms

auscultation – listening to sounds within the body• performed with a stethoscope• helpful in diagnosing conditions lungs, pleura, heart and abdomen

percussion – tapping on a surface to determine the difference in the density of the underlying structure• solid organ – dull sound without resonance (sound of being deep, full, reverberating)• air-filled structure – resonant, hollow note(when lungs are filled with fluid – become more dense – resonance is replaced with dullness)

plueral rub (friction rub) – scratchy sound produced by pleural surfaces rubbing against each other – pleura a roughened, thickened by inflammation, scarring or neoplastic cells• can be heard on auscultation / felt by placing fingers on the chest wall

rales (crackles) – fine crackling sounds heard on auscultation (during inhalation) when there is fluid in the alveoli – usually patients with pneumonia, bronchiectasis and acute bronchitis

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rhonchi – loud rumbling sounds (resemble snoring) heard on auscultation of bronchi obstructed by sputum – indicate congestion and inflammation in the larger bronchial tubes

sputum – material expelled from the bronchi, lungs or upper respiratory tract by spitting• purulent (containing pus) is green or brown –indicative of infection• blood-tinged is suggestive of tuberculosis or malignance

S. pneumo culturure

Streptococcus pneumoniae alpha – hemolytic sensitivity of S. pneumo to penicillin

• sputum culture – culture a sample of sputum in a nutrient rich medium to detect the presence of a pathogen (bacteria)• C&S (culture and sensitivity) – identifies the pathogen and determines the effectiveness of antibiotics

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stridor – strained, high-pitched sound heard on inspiration caused by obstruction in the pharynx or larynx (throat abscess, airway injury, croup, allergic reaction, epiglottitis, laryngitis)

wheezes – continuous high-pitched whistling sound produced during breathing – air is forced through narrowed / obstructed airways (asthma)

Upper Respiratory Disorders

croup – acute viral infection (influenza or (RSV) respiratory syncytial virus) of infants and children with obstruction of the larynx, barking cough and stridor

epistaxis – nosebleed caused from irritation of the nasal mucous membranes, trauma, vitamin K deficiency, clotting abnormalities, hypertension

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diphtheria – acute infection of the throat and upper respiratory tract caused by Corynebacterium diptheria• inflammation and a leathery, opaque membrane forms in the pharynx and trachea• vaccine DTP (diptheria, pertussis, tetanus)can produce immunity against the toxins produced by the bacteria

pertussis (whooping cough) – highly contageous bacterailinfection of the pharynx, larynx and trachea caused by Bordetella pertussis• characterized by paroxysmal (violent / sudden) spasms of coughing that ends in a large “whooping” inspiration

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Bronchial Disordersasthma – chronic bronchial inflammatory disorder with airway obstruction due to bronchial edema, constriction and increased mucus production• dyspnea, wheezing and cough• etiology can involve allergy / infection• asthma attack triggers can be exercise, cold air, strong odors, stress or allergens

treatments• trigger avoidance• inhaled anti-inflammatories (glucocorticoids)• bronchodilators (albuterol)• leukotriene blockers – block inflammation (Singulair)

bronchiectasis – chronic dilation of a bronchus secondary to infection• symptoms: cough, fever and expectoration of foul-smelling, purulent sputum• caused by chronic infection with loss of elasticity of the bronchi – secretions puddle and do not drain normally• treatment is palliative (non-curative) – antibiotics, mucolytics, bronchodilators, respiratory therapy (RT) and surgical resection

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chronic bronchitis – inflammation of bronchi persisting over a long time; type of chronic obstructive pulmonary disease (COPD - also include asthma and emphysema)• infection and smoking can be etiologic factors• signs and symptoms: excessive secretion of infected mucus, productive cough

cystic fibrosis – an inherited disorder of exocrine glands resulting in thick mucous secretions in the respiratory tract that do not drain normally• exocrine glands affected are the pancreas (insufficient secretion of enzymes – poor growth), sweat glands (abN salt production), and epithelial cells of the respiratory tract• chronic airway obstruction, infection, bronchiectasis and respiratory failure are the end result• therapy includes replacement of pancreatic enzymes and treatment of pulmonary obstruction (RT) – no known cure – lung transplant can restore lung function

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Lung Disorders

atelectasis – collapsed lung; incomplete expansion of alveoli• bronchioles and alveoli resemble a collapsed balloon• causes poor inspiratory effort after surgery, blockage of the bronchial tubes (secretion), tumor, and chest wounds that permit air, fluid / blood to accumulate in the pleural cavity• treatment – removal of the underlying cause

emphysema – hyper inflation of alveoli with destruction of alveolar walls• loss of elasticity of alveoli – expiratory flow limitation• tissue destruction causes pulmonary artery pressure to increase and L heart works harder – ventricular hypertrophy and heart failure• strong association between smoking and emphysema

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lung cancer – malignant tumor of the lungs and bronchi (most common, fatal malignancy – associated with smoking)1. non-small cell lung cancer (NSCLC – 90%)

• adenocarcinoma – mucus-secreting cells• squamous cell – epithelial cells of upper airway

2. small cell lung cancer (SCLC)• small round (“oat”) cells in pulmonary epithelium• grows rapidly and spreads quickly outside of the lungs

treatment is palliative – surgery, radiation therapy and chemotherapy

pneumoconiosis – abN condition caused by dust in the lungs – chronic inflammation, infection and bronchitis• anthracosis – coal (black lung disease)• asbestosis – asbestos (shipbuilding / construction)• silicosis – silica / glass (grinder’s disease)

bilateral

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pneumonia – acute inflammation and infection of alveoli which fill with puss or products of the inflammatory reaction• etiological agents are pneumococci, staphylococci and other bacteria, fungi or viruses• infection damages alveolar membranes - exudate (fluid, blood, cells and debris) consolidates the alveoli (become “glued” together - ↓ effective air exchange• an infiltrate (fluid filled area within the lungs) is seen on x-ray / CT scan

community acquired pneumonia – results from a contagious respiratory infection caused by viruses and bacteria (Mycoplasma, Streptococcus) – treated with antibiotics

hospital acquired pneumonia – acquired during hospitalization (usually while on mechanical ventilation)

aspiration pneumonia – cased by material (food / vomit) lodging in the bronchi or lungs

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