The Respiratory System

1. 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

2. Human Lungs

3. 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

4. External Nasal Structures • Skin, nasal bones, & cartilage lined with mucous membrane • Openings called external nares or nostrils

5. 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

6. 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

7. 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

8. Regions of Pharynx Nasopharynx: passageway for air only Oropharynx and Laryngopharnx: passageway for food & air

9. 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)

10. Larynx • Cartilage & connective tissue tube • Anterior to C4 to C6 • Constructed of 3 single & 3 paired cartilages Anterior Posterior

11. Vocal Cords • False vocal cords (ventricular folds) found above vocal folds (true vocal cords) • True vocal cords attach to arytenoid cartilages

12. 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

13. Histology of the Trachea • Ciliated pseudostratified columnar epithelium • Hyaline cartilage as C-shaped structure closed by trachealis muscle

14. Trachea and Bronchial Tree

15. Airway Epithelium • Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus.

16. 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

17. 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

18. 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

19. 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

20. Mediastinal Surface of Lungs • Blood vessels & airways enter lungs at hilus • Covered with pleura (parietal becomes visceral)

21. Lobules

22. 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

23. Histology of Lung Tissue Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts.

24. 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

25. 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

26. Details of Respiratory Membrane