1.4 Respiratory Structure and Function Copy.pptx

Respiratory Structure and Function Lecture Outline I. Functions of conducting airways II. Functions of the respiratory system III. Alveoli and the Alveolar-Capillary Unit 1 Respiratory Structure and Function Objectives 1.Identify the functions of the conducting airways 2.Describe the importance o...

Respiratory Structure and Function Lecture Outline I. Functions of conducting airways II. Functions of the respiratory system III. Alveoli and the Alveolar-Capillary Unit 1 Respiratory Structure and Function Objectives 1.Identify the functions of the conducting airways 2.Describe the importance of exchange as it relates to metabolism and acidbase balance 3.Describe the transport of gas through conducting and respiratory airways 4.List factors that maintain alveolar patency (oppose collapse) 5.Explain the structure of the alveolar-capillary unit 6.Explain the function of the Pores of Kohn 2 References Assigned reading from your text: Levitzky Chapter 1 3 Functions of Conducting Airways  Functions of the conducting airways include: • Transport O2/CO2 to and from gas exchange airways • Warm inhaled air • Venous plexus of nasal septum • Turbinates – especially the middle and inferior conchae • Humidify the inhaled air • Water vapor originates from a sheet of mucus mucous glands and cells • Filtration of inhaled air: • Bacteria proliferate in a warm, moist (humid) environment • Mucus is sticky and traps particles • Vibrissae filter air inhaled through the nose • Produce turbulent airflow in the nasal cavity collision of particles with mucus • Mucociliary escalator Cilia remove phlegm that could cause infection 4 Functions of Respiratory System  Respiratory system functions include: • Gas exchange- Exchange of fresh O2 for CO2 produced by cells of the body • O2 obtained from the environment to supply metabolic needs of tissues • Vocal cords are open for bulk flow respiration to • CO2 produced by cellular metabolism is removed occur • Acid-base balance • Removes CO2 (H+ ions) from body • CNS senses CO2 + H+ in arterial blood and CSF and increase ventilation • Phonation• CNS controls muscles of respiration and airflow through the vocal cords and mouth • Position of vocal cords varies while phonating- not fully opened or closed • Pulmonary defense • Each breath allows sampling of external environment • Reflex responses include coughing, sneezing, bronchoconstriction • The epiglottis closes the laryngeal inlet when eating/drinking; cords approximated • The respiratory tract has multiple lines of cellular defense including mucus and macrophages • Metabolism • Cells of the lung metabolize substrate to supply their energy • Other pneumocytes produce surfactant • Capillary endothelium produces and metabolizes vasoactive substances 5 Gas Exchange Between Tissues and the Environment  Gas exchange with the tissues involves: • CNS commands respiratory muscles • Capillaries exchange CO2 from metabolism for fresh O2 • Venous blood containing CO2 is pumped into the lungs • CO2 exhaled as fresh O2 inhaled 6 Gas Exchange Airways Contain Alveoli  Alveoli- thin-walled outpocketings that extend from the lumen of bronchioles • Each successive level of branching produces an increased number of alveoli (more gas exchange) • Alveoli- New alveoli develop until ~ 8 yo 300 million alveoli (480- larger) 7 Alveolar Structure Maintains Patency  Alveoli are subject to collapse when compressed due to some aspects of their structure: • cartilage • No Muscular layer surrounds airways  Tendency to collapse is opposed by the: • Interdependence of alveolar arrangement- Most important facto • Lung parenchyma – Septa contains interwoven elastic and connective tissue fibers capillaries • between Their septa are almost entirely composed of capillaries I • Inner surface of alveolus lined by a thin layer of surfactant Figure 1–3. Scanning electron micrograph of human lung parenchyma. A = alveolus; S = alveolar septa; D = alveolar duct; PK = pore of Kohn; PA = small branch of the pulmonary artery. (Reproduced with permission from Weibel, 1998.) g 8 Alveolar-Capillary Unit  Alveolar-capillary unit – the site of efficient gas exchange in the lung – Alveoli are ~ 70% covered by pulmonary capillary network – 500-1000 capillaries per alveolus; 280 billion pulmonary capillaries – 50-100m2 of contact between alveoli and pulmonary capillaries for diffusion – Polygonal shaped (not spherical more SA) Figure 1–5. Transmission electron micrograph of a cross section of a pulmonary capillary. An erythrocyte (EC) is seen within the capillary. C = capillary; EN = capillary endothelial cell (note its large nucleus); EP = alveolar epithelial cell; IN = interstitial space; BM = basement membrane; FB = fibroblast processes; 2,3,4 = diffusion pathway through the alveolar-capillary barrier, the plasma, and the erythrocyte, respectively. Note that the alveolar-capillary barrier 9 Openings of Alveolar Structure  Openings in alveoli allow collateral ventilation: • Communications between bronchioles and alveoli: • Interbronchiolar channels (of Martin) • Bronchiole-alveolar canals (of Lambert) • Interalveolar pores (of Kohn)  Pores of Kohn: • Present after 3-4 yo • May become enlarged in emphysema • May facilitate spread of pulmonary infection Figure 1–4. Scanning electron micrograph of the surface and cross section of an alveolar septum. Capillaries (C) are seen sectioned in the foreground, with erythrocytes (EC) within them. A = alveolus; D = (Reproduced fromAR Weibel, alveolar duct;with PK =permission pore of Kohn; = alveolar 1998.) entrance to duct; * = connective tissue fibers. The 10 Components of the Chest Wall include  Major components of the chest wall include the axial skeleton, muscles of respiration, and pleura • Pulmonary ligament is a reflection of mediastinal parietal pleura • Allows for: movement of the lung root with • Inferior inspiration • Expansion of the pulmonary vein 11 12