Chapter 23 The Respiratory System

1. Chapter 23The 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. 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

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

4. Nose -- Internal Structures • Large chamber within the skull • Roof is made up of ethmoid and floor is hard palate • Internal nares (choanae) are openings to pharynx • Nasal septum is composed of bone & cartilage • Bony swelling or conchae on lateral walls

5. 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

6. Rhinoplasty • Commonly called a “nose job” • Surgical procedure done for cosmetic reasons / fracture or septal repair • Procedure • local and general anesthetic • nasal cartilage is reshaped through nostrils • bones fractured and repositioned • internal packing & splint while healing Tortora & Grabowski 9/e 2000 JWS

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. Nasopharynx From choanae to soft palate openings of auditory (Eustachian) tubes from middle ear cavity adenoids or pharyngeal tonsil in roof Passageway for air only pseudostratified ciliated columnar epithelium with goblet

9. Oropharynx From soft palate to epiglottis fauces is opening from mouth into oropharynx palatine tonsils found in side walls, lingual tonsil in tongue Common passageway for food & air stratified squamous epithelium

10. Laryngopharynx Extends from epiglottis to cricoid cartilage Common passageway for food & air & ends as esophagus inferiorly stratified squamous epithelium

11. 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)

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

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

14. The Structures of Voice Production • True vocal cord contains both skeletal muscle and an elastic ligament (vocal ligament) • When 10 intrinsic muscles of the larynx contract, move cartilages & stretch vocal cord tight • When air is pushed past tight ligament, sound is produced (the longer & thicker vocal cord in male produces a lower pitch of sound) • The tighter the ligament, the higher the pitch • To increase volume of sound, push air harder

15. Movement of Vocal Cords • Opening and closing of the vocal folds occurs during breathing and speech

16. Speech and Whispering • Speech is modified sound made by the larynx. • Speech requires pharynx, mouth, nasal cavity & sinuses to resonate that sound • Tongue & lips form words • Pitch is controlled by tension on vocal folds • pulled tight produces higher pitch • male vocal folds are thicker & longer so vibrate more slowly producing a lower pitch • Whispering is forcing air through almost closed rima glottidis -- oral cavity alone forms speech

17. 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 • adventitia binds it to other organs

18. Trachea and Bronchial Tree • Full extent of airways is visible starting at the larynx and trachea

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

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

21. Tracheostomy and Intubation • Reestablishing airflow past an airway obstruction • crushing injury to larynx or chest • swelling that closes airway • vomit or foreign object • Tracheostomy is incision in trachea below cricoid cartilage if larynx is obstructed • Intubation is passing a tube from mouth or nose through larynx and trachea Tortora & Grabowski 9/e 2000 JWS

22. 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

23. Histology of Bronchial Tree • Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal 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 • nebulization therapy = inhale mist with chemicals that relax muscle & reduce thickness of mucus

24. 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

25. Gross Anatomy of Lungs • Base, apex (cupula), costal surface, cardiac notch • Oblique & horizontal fissure in right lung results in 3 lobes • Oblique fissure only in left lung produces 2 lobes

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

27. 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

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

29. Cells Types of the Alveoli • Type I alveolar cells • simple squamous cells where gas exchange occurs • Type II alveolar cells (septal cells) • free surface has microvilli • secrete alveolar fluid containing surfactant • Alveolar dust cells • wandering macrophages remove debris

30. 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

31. Details of Respiratory Membrane • Find the 4 layers that comprise the respiratory membrane

32. Double Blood Supply to the Lungs • Deoxygenated blood arrives through pulmonary trunk from the right ventricle • Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue • Venous drainage returns all blood to heart • Less pressure in venous system • Pulmonary blood vessels constrict in response to low O2 levels so as not to pick up CO2 on there way through the lungs

33. Breathing or Pulmonary Ventilation • Air moves into lungs when pressure inside lungs is less than atmospheric pressure • How is this accomplished? • Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure • How is this accomplished? • Atmospheric pressure = 1 atm or 760mm Hg

34. Boyle’s Law • As the size of closed container decreases, pressure inside is increased • The molecules have less wall area to strike so the pressure on each inch of area increases.

35. Dimensions of the Chest Cavity • Breathing in requires muscular activity & chest size changes • Contraction of the diaphragm flattens the dome and increases the vertical dimension of the chest

36. Quiet Inspiration • Diaphragm moves 1 cm & ribs lifted by muscles • Intrathoracic pressure falls and 2-3 liters inhaled

37. Quiet Expiration • Passive process with no muscle action • Elastic recoil & surface tension in alveoli pulls inward • Alveolar pressure increases & air is pushed out

38. Labored Breathing • Forced expiration • abdominal mm force diaphragm up • internal intercostals depress ribs • Forced inspiration • sternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air

39. IntrathoracicPressures • Always subatmospheric (756 mm Hg) • As diaphragm contracts intrathoracic pressure decreases even more (754 mm Hg) • Helps keep parietal & visceral pleura stick together

40. Summary of Breathing • Alveolar pressure decreases & air rushes in • Alveolar pressure increases & air rushes out

41. Alveolar Surface Tension • Thin layer of fluid in alveoli causes inwardly directed force = surface tension • water molecules strongly attracted to each other • Causes alveoli to remain as small as possible • Detergent-like substance called surfactant produced by Type II alveolar cells • lowers alveolar surface tension • insufficient in premature babies so that alveoli collapse at end of each exhalation

42. Pneumothorax • Pleural cavities are sealed cavities not open to the outside • Injuries to the chest wall that let air enter the intrapleural space • causes a pneumothorax • collapsed lung on same side as injury • surface tension and recoil of elastic fibers causes the lung to collapse Tortora & Grabowski 9/e 2000 JWS

43. Compliance of the Lungs • Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension • Some diseases reduce compliance • tuberculosis forms scar tissue • pulmonary edema --- fluid in lungs & reduced surfactant • paralysis Tortora & Grabowski 9/e 2000 JWS

44. Airway Resistance • Resistance to airflow depends upon airway size • increase size of chest • airways increase in diameter • contract smooth muscles in airways • decreases in diameter

45. Breathing Patterns • Eupnea = normal quiet breathing • Apnea = temporary cessation of breathing • Dyspnea =difficult or labored breathing • Tachypnea = rapid breathing • Diaphragmatic breathing = descent of diaphragm causes stomach to bulge during inspiration • Costal breathing = just rib activity involved

46. Modified Respiratory Movements • Coughing • deep inspiration, closure of rima glottidis & strong expiration blasts air out to clear respiratory passages • Hiccuping • spasmodic contraction of diaphragm & quick closure of rima glottidis produce sharp inspiratory sound • Chart of others on page 794

47. Lung Volumes and Capacities • Tidal volume = amount air moved during quiet breathing • MVR= minute ventilation is amount of air moved in a minute • Reserve volumes ---- amount you can breathe either in or out above that amount of tidal volume • Residual volume = 1200 mL permanently trapped air in system • Vital capacity & total lung capacity are sums of the other volumes

48. Dalton’s Law • Each gas in a mixture of gases exerts its own pressure • as if all other gases were not present • partial pressures denoted as p • Total pressure is sum of all partial pressures • atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O • to determine partial pressure of O2-- multiply 760 by % of air that is O2 (21%) = 160 mm Hg

49. What is Composition of Air? • Air = 21% O2, 79% N2 and .04% CO2 • Alveolar air = 14% O2, 79% N2 and 5.2% CO2 • Expired air = 16% O2, 79% N2 and 4.5% CO2 • Observations • alveolar air has less O2 since absorbed by blood • mystery-----expired air has more O2 & less CO2 than alveolar air? • Anatomical dead space = 150 ml of 500 ml of tidal volume

50. Henry’s Law • Quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient • explains why you can breathe compressed air while scuba diving despite 79% Nitrogen • N2 has very low solubility unlike CO2 (soda cans) • dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis) • decompression sickness if come back to surface too fast or stay deep too long • Breathing O2 under pressure dissolves more O2 in blood