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Chapter 23: The Respiratory System Primary sources for figures and content: Marieb, E. N. Human Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004. Martini, F. H. Fundamentals of Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004. The primary functions of the respiratory system. The Respiratory System • Cells produce energy: – for maintenance, growth, defense, and division – through mechanisms that use oxygen and produce carbon dioxide Oxygen • Is obtained from the air by diffusion across delicate exchange surfaces of lungs • Is carried to cells by the cardiovascular system which also returns carbon dioxide to the lungs 5 Functions of the Respiratory System 1. External respiration: - Provides extensive gas exchange surface area between air and circulating blood 2. Pulmonary ventilations - Moves air to and from exchange surfaces of lungs 3. Protects respiratory surfaces from outside environment - dehydration, temperature changes, invasion by pathogens 4. Produces sounds for communication 5. Provide olfactory sensation = Smell Components of the Respiratory System Figure 23–1 Organization of the Respiratory System • The respiratory system is divided into the upper respiratory system, above the larynx, and the lower respiratory system, from the larynx down Anatomy of Respiratory System 1. Upper Respiratory System – Function to warm and humidify air – Nose, nasal cavity, sinuses, pharynx 2. Lower Respiratory System A. Conduction portion - Bring air to respiratory surfaces - Larynx, trachea, bronchi, bronchioles B. Respiratory portion - Gas exchange - Alveoli Alveoli • Are air-filled pockets within the lungs – where all gas exchange takes place The Respiratory Epithelium Figure 23–2 Respiratory Mucosa = mucus membrane • Lines conducting portion of respiratory system • Epithelial layer: • pseudostratified columnar epithelium • Usually ciliated • Scattered goblet cells = mucin production • Areolar layer = lamina propria (trachea, bronchi) • Areolar connective tissue • Mucus glands = mucin • Serous glands = lysozyme • Glands produce ~1 quart mucus fluid/day • Cilia move mucus to pharynx to be swallowed – Cilia beat slow in the cold Alveolar Epithelium • Is a very delicate, simple squamous epithelium • Contains scattered and specialized cells • Lines exchange surfaces of alveoli The Respiratory Defense System • Consists of a series of filtration mechanisms • Removes particles and pathogens Components of the Respiratory Defense System 1. Mucus – From goblet cells and glands in lamina propria, traps foreign objects 2. Cilia “mucus escalator” – Move carpet of mucus with trapped debris out of the respiratory tract 3. Alveolar macrophages – Phagocytose particles that reach alveoli 4. Filtration in nasal cavity removes large particles Disorders of the Respiratory Defense System 1. Cystic fibrosis – Cause Failure of mucus escalator – Result Produce thick mucus which blocks airways and encourages bacteria growth 2. Smoking destroys cilia 3. Inhalation of irritants chronic inflammation cancer e.g. squamous cell carcinoma The upper respiratory system and their functions. The Upper Respiratory System 1. Nose 2. Nasal Cavity 3. Pharynx -Nasopharynx -Oropharynx -Laryngopharynx Figure 23–3 1. The Nose • Only external feature • Air enters the respiratory system: – through external nares – into nasal vestibule • Space in flexible part, lined with hairs to filter particles, leads to nasal cavity • Nasal hairs in nasal vestibule are the first particle filtration system 1. The Nose • Functions 1. 2. 3. 4. 5. Opening to airway for respiration Moisten and warm entering air Filter and clean inspired air Resonating chamber for speech Houses olfactory receptors 2. The Nasal Cavity • The nasal septum: – divides nasal cavity into left and right • Superior portion of nasal cavity is the olfactory epithelium provides sense of smell • Nasal conchae (superior, middle, inferior) project into cavity on both sides – Nasal conchae cause air to swirl 1. Increase likelihood of trapping foreign material in mucus 2. Provide time for smell detection 3. Provide time and contact to warm and humidify air 2. The Nasal Cavity • Hard and soft palate form floor • Internal nares open to nasopharynx • Mucosa has large superficial blood supply – Function warm, moisten air – Epistaxis = nose bleed • Paranasal sinuses in frontal, sphenoid, ethmoid, and maxillary bones – Lined with respiratory mucosa – Connected to nasal cavity – Aid in warming/moistening air 2. The Nasal Cavity • Hard palate: – forms floor of nasal cavity – separates nasal and oral cavities • Soft palate: – extends posterior to hard palate – divides superior nasopharynx from lower pharynx • Air flow Nasal cavity opens into nasopharynx through internal nares 3. The Pharynx • A chamber shared by digestive and respiratory systems • Extends from internal nares to entrances to larynx and esophagus • Three Parts: 1. Nasopharynx 2. Oropharynx 3. Laryngopharynx 3. The Pharynx 1. Nasopharynx = air only - Posterior to nasal cavity - Pseudostratified columnar epithelium – Closed off by soft palate and uvula during swallowing – Pharyngeal tonsil located on posterior wall • Inflammation can block airway – Auditory tubes open here 2. Oropharynx = food and air – Posterior to oral cavity – Stratified squamous epithelium – Palatine and lingual tonsils in mucosa 3. The Pharynx 3. Laryngopharynx = food and air - Lower portion - Stratified squamous epithelium - Continuous with esophagus Why is the vascularization of the nasal cavity important? A. B. C. D. It heats incoming air. It moisturizes incoming air. It nourishes nasal epithelial cells. All of the above. Why is the lining of the nasopharynx different from that of the oropharynx and the laryngopharynx? A. Nasopharynx lining is not subjected to food abrasion. B. Nasopharynx lining must withstand temperature extremes. C. Nasopharynx must be protected from drying out. D. All of the above. The lower respiratory system and their functions. Air Flow • From the pharynx enters the larynx: – a cartilaginous structure that surrounds the glottis 4. Larynx Figure 23–4 4. Larynx = voice box • Hyaline cartilage around glottis – Opening form laryngopharynx to trachea • Functions of larynx 1. Provide continuous airway 2. Act as switch to route food and air properly 3. Voice production • Contains epiglottis – Elastic cartilage flap covers glottis during swallowing The Glottis Figure 23–5 4. Larynx = voice box • Folds of epithelium over ligaments of elastic fibers create focal folds/cords • Vocal cords project into glottis • Air passing through glottis vibrates folds producing sound • Pitch Controlled by tensing/relaxing of the cords • Tense + narrow = high pitch • Volume Controlled by the amount of air • Sound Production phonation 4. Larynx = voice box • Speech – Formation of sound using mouth and tongue with resonance in pharynx, mouth, sinuses and nose • Laryngitis – Inflammation of vocal folds – Cause infection or overuse that can inhibit phonation When the tension in your vocal folds increases, what happens to the pitch of your voice? A. B. C. D. It rises. It falls. Nothing happens. It squeaks and cracks. 5. Trachea Figure 23–6 The Trachea • Attached inferior to larynx • Walls composed of three layers 1. Mucosa • Pseudostratified columnar epithelium, goblet cells, lamina propria, smooth muscle and glands 2. Submucosa • CT with additional mucus glands 3. Adventitia • CT with hyaline cartilage rings (15-20) keep airway open, C-shaped • Opening toward the esophagus to allow expansion, ends connected by trachealis muscle 6. Primary Bronchi • Trachea branches into the Right and left primary bronchi • Similar structure as trachea – No trachealis muscle • Right = steeper angle • Enter lungs at groove (hilus) – Along with blood and lymphatic Hilus • Where pulmonary nerves, blood vessels, and lymphatics enter lung • Anchored in meshwork of connective tissue Gross Anatomy of the Lungs Right = 3 lobes Left = 2 lobes Figure 23–7 6. Primary Bronchi • Lungs have lobes separated by deep fissures • Inside lungs bronchi branch, get smaller in diameter – Branch ~23 times creating the bronchial tree • As bronchi get smaller, structure changes 1. Less cartilage in adventitia 2. More smooth muscle in lamina propria 3. Epithelium is thinner, less cilia, less mucus Bronchitis • Inflammation of bronchial walls: – causes constriction and breathing difficulty Relationship between Lungs and Heart Figure 23–8 7. Terminal bronchiole Smallest bronchi of Respiratory Tree Figure 23–9 7. Terminal bronchiole • • • • Smallest Bronchi No cartilage Last part of conduction portion Trachea, Bronchi and Bronchioles innervated by ANS to control airflow to the lungs – ANS Regulates smooth muscle: • controls diameter of bronchioles • controls airflow and resistance in lungs – Sympathetic bronchodilation – Parasympathetic bronchocontriction • histamine release (allergic reactions) Asthma • Excessive stimulation and bronchoconstriction • Activated by inflammatory chemicals (histamine) • Stimulation severely restricts airflow • Epinephrine inhaler mimics sympathetic ANS bronchodilation 7. Terminal bronchiole • Each terminal bronchiole delivers air to one pulmonary lobule, separated by CT • Inside lobule, terminal bronchiole branches into respiratory bronchioles – No cilia or mucus • Each respiratory bronchiole connects to alveolar sac made up of many alveoli The Bronchioles Figure 23–10 8. Alveoli Figure 23–11 8. Alveoli • Wrapped in capillaries • Held in place by elastic fibers • Three cell types 1. Type 1 cells = gas exchange • Simple squamous epithelium, lines inside 2. Type II cells = surfactant • Cuboidal epithelial cells produce surfactant – Phospholipids + proteins – Prevent alveolar collapse, reduces surface tension 3. Alveolar macrophages = Phagocytosis • Phagocytosis of particles 8. Alveoli • Alveoli connected to neighbors by alveolar pores – Equalize pressure • Gas exchange occurs across the respiratory membrane (0.5µm thick) • 3 Parts of the Respiratory Membrane 1. Squamous epithelial lining of alveolus 2. Endothelial cells lining an adjacent capillary 3. Fused basal laminae between alveolar and endothelial cells Respiratory Distress • Difficult respiration: – due to alveolar collapse – caused when septal cells do not produce enough surfactant Disorders of the Alveoli 1. Pneumonia: – Inflammation of lungs from infection or injury – causes fluid to leak into alveoli – compromises function of respiratory membrane prevents gas exchange 2. Pulmonary embolism – Block in branch of pulmonary artery – Reduce blood flow – Causes alveolar collapse Gross Anatomy of Lungs Figure 23–8 Gross Anatomy of Lungs • • • • Concave base, rest on diaphragm Right = 3 lobes Left = 2 lobes (accommodates heart) Housed in pleural cavity – Cavity lined with parietal pleura – Lungs covered by visceral pleura • Both pleura produce serous pleural fluid to reduce friction during expansion • Pleurisy – Inflammation of pleura – Restrict movement of lungs breathing difficulty Why are the cartilages that reinforce the trachea C-shaped? A. To prevent tracheal crushing. B. To conform to thoracic cavity shape. C. To allow room for esophageal expansion. D. To allow normal cardiac functioning. What would happen to the alveoli if surfactant were not produced? A. B. C. D. The alveoli would contract. The alveoli would collapse. The alveoli would expand. The alveoli would pop. What path does air take in flowing from the glottis to the respiratory membrane? A. larynx, trachea, bronchi, alveolar duct, alveolar sac, respiratory membrane B. larynx, trachea, alveolar duct, bronchioles, respiratory membrane C. trachea, bronchi, larynx, bronchioles, alveolar duct, alveolar sac, D. larynx, trachea, bronchioles, alveolar duct, bronchi, alveolar sac, respiratory membrane List the functions of the pleura. What does it secrete? A. prevents cardiac friction; secretes mucus B. prevents respiratory friction; secretes pleural fluid C. protects lungs from drying out; secretes mucus D. protects heart and thoracic cavity; secretes enzymes Respiratory Physiology Respiration • External Respiration – Includes all processes involved in exchanging O2 and CO2 with the environment • Internal Respiration – Also called cellular respiration – Involves the uptake of O2 and production of CO2 within individual cells External Respiratory Physiology • 3 steps of respiration 1. Pulmonary ventilation = breathing 2. Gas Diffusion/Exchange, across membranes and capillaries 3. Gas Transport to/from tissues – between alveolar capillaries – between capillary beds in other tissues 1. Pulmonary Ventilation • Movement of air into/out of alveoli • Visceral pleura adheres to parietal pleura via surface tension – Altering size of pleural cavity will alter size of lungs • Pneumothorax – Injury of thoracic cavity – Air breaks surface tension lung recoil = atelectasis, or collapsed lung 1. Pulmonary Ventilation • Mechanics of breathing – Boyle’s law: gas pressure is inversely proportional to volume • Defines the relationship between gas pressure and volume: P = 1/V – Air flows from area of high pressure to low pressure Gas Pressure and Volume Figure 23–13 Mechanisms of Pulmonary Ventilation Figure 23–14 Mechanisms of Pulmonary Ventilation Diaphragm • Contraction of diaphragm pulls it toward abdomen – Lung volume INCREASE – Air pressure DECREASE – Air flow ins • Relaxation causes diaphragm to rise in dome shape – Lung volume DECREASE – Air pressure INCREASE – Air flows out Rib cage movements can contribute – Superior = bigger, air in – Inferior = smaller, air out Common Methods of Reporting Gas Pressure Table 23–1 Pressure and Volume Changes with Inhalation and Exhalation Figure 23–15 Factors influencing pulmonary ventilation 1. Airway resistance – Diameter of bronchi – Obstructions 2. Alveolar surface tension – Surfactant (Type II cells) reduces alveoli surface tension • Allow inflation – Respiratory distress syndrome • Too little surfactant requires great force to open alveoli to inhale Factors influencing pulmonary ventilation 3. Compliance – Effort required to expand lungs and chest – High compliance = expand easily, normal – Low compliance = resist expansion – Compliance affected by 1. CT structure 2. Alveolar Expandability 3. Mobility of thoracic cage Factors influencing pulmonary ventilation 3. Compliance affected by 1. CT structure - Loss of elastin/replacement by fibrous tissue = Decrease compliance - Emphysema - respiratory surface replaced by scars - Decrease elasticity = Decrease compliance - Loss of surface for gas exchange 2. Alveolar Expandability - Increase surface tension (decr. Surfactant) = decrease compliance - Fluid (edema) = decrease compliance Factors influencing pulmonary ventilation 3. Compliance affected by 3. Mobility of thoracic cage - less mobility = decrease compliance Inspiration • Inhalation involves contraction of muscles to increase thoracic volume 1. Quite breathing = eupnea – Diaphragm: moves 75% of air – External intercostals: elevate ribs, 25%more 2. Forced breathing = hyperpnea – Maximum rib elevation increases respiratory volume 6x • Serratus anterior, pectoralis minor, scalenes, sternocleidomastoid The Respiratory Muscles Figure 23–16a, b Expiration 1. Eupnea – Passive, muscles relax, thoracic volume decrease 2. Hyperpnea – Abdominal muscles (obliques, transversus, rectus) contract forcing diaphragm up, thoracic volume further decrease The Respiratory Muscles Figure 23–16c, d Respiratory Volumes and Capacities Figure 23–17