2/19/2020 Respiratory System • Major functions of respiratory system: supply body with O2 for cellular respiration and dispose of CO2, a waste product of cellular respiration • Respiratory and circulatory system are closely coupled • Also functions in olfaction and speech Respiratory System Respiration involves four processes 1. Pulmonary ventilation (breathing): movement of air into Respiratory and out of lungs system 2. External respiration: exchange of O2 and CO2 between lungs and blood 3. Transport of O2 and CO2 in blood 4. Internal respiration: exchange of Circulatory system O2 and CO2 between systemic blood vessels and tissues The Major Respiratory Organs Conducting Zone Respiratory Zone Nasal cavity Oral cavity Nostril Pharynx Larynx Trachea Left main Carina of (primary) trachea bronchus Right main Left lung (primary) bronchus Diaphragm Right lung 1 2/19/2020 Anatomical Relationships Of Organs In The Thoracic Cavity Intercostal muscle Rib Parietal pleura Lung Pleural cavity Visceral pleura Trachea Thymus Apex of lung Left Right superior lobe superior lobe Horizontal fissure Oblique fissure Right middle lobe Left inferior Oblique fissure lobe Right inferior lobe Heart (in mediastinum) Diaphragm Base of lung Cardiac notch Anterior view. The lungs flank mediastinal structures laterally. Hilum of the Lung Apex of lung Pulmonary artery Left Left main superior lobe bronchus Oblique fissure Pulmonary vein Left inferior lobe Cardiac impression Hilum of lung Oblique Aortic fissure impression Lobules Photograph of medial view of the left lung. Anatomical relationships of organs in the thoracic cavity Esophagus Posterior Vertebra (in mediastinum) Root of lung at hilum Right lung • Left main bronchus • Left pulmonary artery Parietal pleura • Left pulmonary vein Visceral pleura Left lung Pleural cavity Thoracic wall Pulmonary trunk Pericardial membranes Heart (in mediastinum) Anterior mediastinum Sternum Anterior Transverse section through the thorax, viewed from above. Lungs, pleural membranes, and major organs in the mediastinum are shown. 2 2/19/2020 Nasal Cavity Passageway: • Moistens and warms entering air Posterior Sphenoidal Cribriform • Filters and cleans nasal sinus plate of • Resonating chamber for speech aperture ethmoid bone • Location of olfactory receptors Conchae: • Increase Frontal sinus surface area Nasal cavity of mucosa • Nasal conchae (superior, middle • Increase air and inferior) turbulence • Nasal meatuses (superior, middle, and inferior) • Nasal vestibule • Nostril Uvula Soft Tongue Hard • Vibrissae palate palate • Mucus membranes • Pseudostratified ciliated epithelium • Goblet cells • Cilia – directed toward pharynx • Seromucous glands: lysozyme • Defensins act at microbe membranes Pharynx, Larynx, and Upper Trachea Air or Posterior nasal Air and food aperture Nasopharynx passageway • Pharyngeal tonsil • Opening of pharyngotympanic ‘Eustachian’ tube tube Unencapsulated Oropharynx Hard palate • Palatine tonsil Soft palate lymphoid nodules • Isthmus of the fauces Tongue Lingual tonsil Epiglottis (elastic Laryngopharynx Hyoid bone Larynx cartilage) protects • Epiglottis airway (glottis) • Vestibular fold • Thyroid cartilage from food/drink Esophagus • Vocal fold • Cricoid cartilage during swallowing Trachea Thyroid gland (b) Structures of the pharynx and larynx The Larynx Epiglottis Body of hyoid bone Thyrohyoid membrane Thyroid cartilage Laryngeal prominence (Adam’s apple) Cricothyroid ligament Cricoid cartilage • Location of vocal folds (known as the true vocal cords) Tracheal cartilages • Airway – in and out – return to pseudostratified ciliated Anterior view epithelium • Voice production 3 2/19/2020 Movements of the vocal folds. Epiglottis Vestibular fold (false vocal cord) Vocal fold (true vocal cord) Glottis Inner lining of trachea Cuneiform cartilage Corniculate cartilage Vocal folds in closed position; Vocal folds in open position; closed glottis open glottis https://youtu.be/9Tlpkdq8a8c Tissue Composition Of The Tracheal Wall Posterior Mucosa – pseudostratified ciliated epithelium Esophagus Submucosa - glandular Trachealis Lumen of Seromucous gland trachea in submucosa Hyaline cartilage Adventitia Anterior • ‘Windpipe’ • Supported by C – shaped rings of hyaline cartilage – prevents closing even when thoracic pressure changes and food in esophagus pushes • Carina Goblet cell Mucosa • Pseudostratified ciliated columnar epithelium • Lamina propria (connective tissue) Submucosa Seromucous gland in submucosa Hyaline cartilage Tissue composition of the tracheal wall Photomicrograph of the tracheal wall (320 ) 4 2/19/2020 Conducting Zone Passages Trachea Superior lobe of left lung Left main (primary) At level of bronchus T7 Superior lobe of right lung Lobar (secondary) bronchus Segmental Middle lobe (tertiary) of right lung bronchus Inferior lobe Inferior lobe of right lung of left lung • Three lobes on right; two lobes on left • Segments • Lobules • C-rings replaced by hyaline plates • Elastic tissue present - stroma • Pseudostratified ciliated eventually replaced by simple columnar then cuboidal • Smooth muscle in walls increases Respiratory Zone Structures Alveoli Alveolar duct Respiratory Alveolar duct bronchioles Terminal Alveolar bronchiole sac • Terminal bronchioles <0.5 mm in diameter • No cartilage involvement • Smooth muscle dominates • Epithelium now non-ciliated cuboidal in the smallest tubes • Mucus production limited then ends Respiratory Zone Structures Respiratory bronchiole Alveolar Alveolar duct pores Alveoli Alveolar sac Alveolar surface area = 90 m2 or 969 ft2 in healthy lungs of adult male Floor space of a small apartment 5 2/19/2020 Alveoli And The Respiratory Membrane Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries Respiratory membrane is combination of alveolar squamous cells, basal lamina, and capillary endothelial cells • 0.5 µm thick blood-air barrier Alveoli And The Respiratory Membrane Red blood cell Nucleus of type I alveolar cell Alveolar pores Capillary O2 Capillary CO2 Macrophage Alveolus Endothelial cell nucleus Alveolus Alveolar epithelium Respiratory Fused basement membranes membrane of alveolar epithelium and capillary endothelium Capillary endothelium Alveoli (gas-filled Red blood cell Type II alveolar cell Type I air spaces) in capillary (secretes surfactant) alveolar cell Detailed anatomy of the respiratory membrane • Type I alveolar cells = simple squamous supported by thin basement membrane, dominate • Type II alveolar cells = scattered surfactant-producing cuboidal cells, produce antimicrobials also. Surfactant decreases cohesiveness (surface tension) of water on surface, reducing tendency to collapse • Alveolar pores share air between adjacent alveoli • Alveolar macrophages move along surface eventually being swept out Pulmonary Ventilation • Boyle’s law: relationship between pressure and volume of a gas • Gases always fill the container they are in • If amount of gas is the same and container size is reduced, pressure will increase • So pressure (P) varies inversely with volume (V) • Mathematically: • P1V1 = P2V2 When atmospheric pressure and intrapulmonary pressure are the same, no air moves • muscles acting on the lungs change the intrapulmonary pressure 6 2/19/2020 Atmospheric pressure (Patm) 0 mm Hg (760 mm Hg at sea level) Parietal pleura Thoracic Visceral pleura wall Pleural cavity containing pleural fluid Transpulmonary pressure 4 mm Hg (the difference between 0 mm Hg and 4 mm Hg) Must be maintained or lung collapses 4 0 Intrapleural pressure (Pip) 4 mm Hg (756 mm Hg) Lung Strong adhesive forces Diaphragm Intrapulmonary between visceral and pressure (P ) pul parietal pleurae keeps Pip 0 mm Hg negative (760 mm Hg) Changes in anterior-posterior and Changes in lateral dimensions Sequence of events superior-inferior dimensions (superior view) • Normal inspirational muscle 1 Inspiratory muscles contract (diaphragm descends; rib cage contractions lead to 500 ml change in rises). volume Ribs are elevated and • Diaphragm is dominant inspirational 2 Thoracic cavity volume sternum flares increases. as external muscle intercostals contract. 3 Lungs are stretched; intrapulmonary volume increases. External intercostals Inspiration contract. 4 Intrapulmonary pressure drops (to1 mm Hg). 5 Air (gases) flows into lungs Diaphragm moves down its pressure gradient until inferiorly during intrapulmonary pressure is 0 contraction. Forced inspirations recruit the scalenes, (equal to atmospheric pressure). sternocleidomastoids, pectoralis minors, and erector spinae 1 Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Ribs and sternum are 2 Thoracic cavity volume depressed as decreases. external intercostals relax. 3 Elastic lungs recoil passively; intrapulmonary External volume decreases. intercostals Expiration relax. 4 Intrapulmonary pressure rises (to 1 mm Hg). Diaphragm 5 Air (gases) flows out of lungs moves down its pressure gradient superiorly until intrapulmonary pressure is 0. as it relaxes. Normal expiration is passive Gas Exchange: Basic Properties of Gases • Dalton’s law of partial pressures • Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas • Partial pressure • Pressure exerted by each gas in mixture • Directly proportional to its percentage in mixture Example: atmospheric pressure = 760 mmHg; O2 = 20.95% of atmospheric air at sea level 760 mmHg x 20.95% O2 = 159.2 mmHg O2, the partial pressure of oxygen in air • Henry’s law •