22-1 The Respiratory System Principal Organs: Nose, pharynx, larynx, trachea, bronchi, lungs Nasal cavity Nostril Hard palate Larynx Trachea Right lung Posterior nasal aperture Soft palate Pharynx Epiglottis Esophagus Left lung Left main bronchus Lobar bronchus Segmental bronchus Pleural cavity Pleura (cut) Diaphragm
22-2 The Bronchioles - diameter ≤ 1 mm Pulmonary lobule: portion of lung ventilated by one bronchiole Have ciliated cuboidal epithelium Muscularis Mucosa, well-developed layer of smooth muscle contracts or relaxes constrict or dilate airway regulates airflow Divides into 50 to 80 terminal bronchioles • Final branches of conducting division • diameter ≤ 0.5 mm • No mucous glands or goblet cells • Cilia move mucus draining into them back by mucociliary escalator • Each terminal bronchiole splits into 1+ smaller respiratory bronchioles Respiratory bronchioles Have alveoli budding from their walls Mark beginning of respiratory division, because alveoli participate in gas exchange Divide into 2 -10 alveolar ducts End in alveolar sacs : clusters of alveoli arrayed around a central space called the atrium
22-3 End of Bronchial Tree Pulmonary Alveoli Each alveolus surrounded by basket of capillaries from pulmonary artery Which vessel is coming from Right Ventricle? Which vessel going to Left Atrium?
Respiratory Membrane: Squamous alveolar cell Shared basement membrane Capillary endothelial cell Air CO 2 O 2 Blood 22-4 Pulmonary Alveoli Figure 22.12b,c Squamous alveolar cell Alveolar Macrophage Respiratory membrane Fluid with surfactant Great Alveolar Cell Lymphocyte Capillary endothelial cell Respiratory Membrane - its characteristics are essential in preventing fluid from accumulating in alveoli - HOW? ... * Gases diffuse too slowly through liquid to sufficiently aerate blood * Alveoli kept dry by absorption of excess liquid by blood capillaries * Lungs have most extensive lymphatic drainage in body * Low capillary blood pressure prevents rupture of delicate respiratory membrane Air
22-5 Pulmonary Alveoli in Health and Disease (a) Normal Pneumonia Emphysema Fluid and blood cells in alveoli Alveolar walls thickened by edema Confluent alveoli Figure 22.21 Pneumonia thickening of respiratory membrane Left ventricular failure Pulmonary edema thickening of respiratory membrane Emphysema, lung cancer, and tuberculosis surface area for gas exchange
22-6 Respiratory airflow is governed by same principles of flow, pressure, and resistance as blood flow F P / R F = Flow, P = difference in pressure , R = resistance Flow of a fluid, e.g., Air, is directly proportional to pressure difference between two points and inversely proportional to resistance Atmospheric pressure drives respiration this weight of air above us 760 mm Hg at sea level, or 1 atmosphere (1 atm), but will be l ower at higher elevations
22-7 Resistance to Airflow - F 1/R Increasing resistance (R) decreases airflow ( F ) Two factors influence airway resistance: 1. Bronchiole diameter, i.e., radius (r) 2. Pulmonary compliance
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