The Respiratory System • Cells continually use O2 & release CO2 • Respiratory system designed for gas exchange • Cardiovascular system transports gases in blood • Failure of either system – rapid cell death from O2 starvation Human Lungs 23-2 Respiratory System Anatomy • Nose • Pharynx = throat • Larynx = voicebox • Trachea = windpipe • Bronchi = airways • Lungs • Locations of infections – upper respiratory tract is above vocal cords – lower respiratory tract is below vocal cords External Nasal Structures • Skin, nasal bones, & cartilage lined with mucous membrane • Openings called external nares or nostrils Nose -- Internal Structures • Large chamber within the skull • Roof is made up of ethmoid and floor is hard palate • Internal nares are openings to pharynx • Nasal septum is composed of bone & cartilage • Bony swelling or conchae on lateral walls Functions of the Nasal Structures • Olfactory epithelium for sense of smell • Pseudostratified ciliated columnar with goblet cells lines nasal cavity – warms air due to high vascularity – mucous moistens air & traps dust – cilia move mucous towards pharynx • Paranasal sinuses open into nasal cavity – found in ethmoid, sphenoid, frontal & maxillary – lighten skull & resonate voice Pharynx • Muscular tube (5 inch long) hanging from skull – skeletal muscle & mucous membrane • Extends from internal nares to cricoid cartilage • Functions – passageway for food and air – resonating chamber for speech production – tonsil (lymphatic tissue) in the walls protects entryway into body • Distinct regions -- nasopharynx, oropharynx and laryngopharynx Regions of Pharynx Nasopharynx: passageway for air only Oropharynx and Laryngopharnx: passageway for food & air Cartilages of the Larynx • Thyroid cartilage forms Adam’s apple • Epiglottis---leaf-shaped piece of elastic cartilage – during swallowing, larynx moves upward – epiglottis bends to cover glottis • Cricoid cartilage---ring of cartilage attached to top of trachea • Pair of arytenoid cartilages sit upon cricoid – many muscles responsible for their movement – partially buried in vocal folds (true vocal cords) Larynx Anterior Posterior • Cartilage & connective tissue tube • Anterior to C4 to C6 • Constructed of 3 single & 3 paired cartilages Vocal Cords • False vocal cords (ventricular folds) found above vocal folds (true vocal cords) • True vocal cords attach to arytenoid cartilages Trachea • Size is 5 in long & 1in diameter • Extends from larynx to T5 anterior to the esophagus and then splits into bronchi • Layers – mucosa = pseudostratified columnar with cilia & goblet – submucosa = loose connective tissue & seromucous glands – hyaline cartilage = 16 to 20 incomplete rings • open side facing esophagus contains trachealis m. (smooth) • internal ridge on last ring called carina (cough reflex) – adventitia binds it to other organs Histology of the Trachea • Ciliated pseudostratified columnar epithelium • Hyaline cartilage as C-shaped structure closed by trachealis muscle 23-13 Trachea and Bronchial Tree Airway Epithelium • Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus. Bronchi and Bronchioles • Primary bronchi supply each lung • Secondary bronchi supply each lobe of the lungs (3 right + 2 left) • Tertiary bronchi supply each bronchopulmonary segment • Repeated branchings called bronchioles form a bronchial tree Histology of Bronchial Tree • Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal, and finally to simple squamous as pass deeper into lungs • Incomplete rings of cartilage replaced by rings of smooth muscle & then connective tissue – sympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airways – asthma attack or allergic reactions constrict distal bronchiole smooth muscle Pleural Membranes & Pleural Cavity • Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragm • Pleural cavity is potential space between ribs & lungs Gross Anatomy of Lungs • Base, apex, cardiac notch • Oblique & horizontal fissure in right lung results in 3 lobes • Oblique fissure only in left lung produces 2 lobes Mediastinal Surface of Lungs • Blood vessels & airways enter lungs at hilus • Covered with pleura (parietal becomes visceral) Lobules 23-21 Structures within a Lobule of Lung • Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT • Respiratory bronchiole – simple squamous • Alveolar ducts surrounded by alveolar sacs & alveoli – sac is 2 or more alveoli sharing a common opening Histology of Lung Tissue Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts. Cells Types of the Alveoli • Type I alveolar cells – simple squamous cells where gas exchange occurs • Type II alveolar cells – free surface has microvilli – secrete alveolar fluid containing surfactant • Alveolar dust cells – wandering macrophages remove debris Alveolar-Capillary Membrane • Respiratory membrane = 1/2 micron thick • Exchange of gas from alveoli to blood • 4 Layers of membrane to cross – alveolar epithelial wall of type I cells – alveolar epithelial basement membrane – capillary basement membrane – endothelial cells of capillary • Vast surface area = handball court Details of Respiratory Membrane.