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. Nose -- Internal Structures • entrance – external nares • two nasal cavities with bony outgrowths = nasal conchae(superior, middle, inferior) • nasal cavities separated by nasal septum and nasal bone • superior most region of the cavity – site for olfactory epithelium - olfactory receptors for odors (smell) • lacrimal glands drain into nasal cavities • nasal cavities communicate with cranial sinuses (air-filled chambers within the skull) • nasal cavities empty into the nasopharynx - upper portion of the pharynx • connection between nasal cavity and nasopharnyx – internal nares • functions:warm, moisten, and filter incoming air • 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

3. Eustacian tube With tubal tonsil

4. Nasopharynx From internal nares to soft palate Anatomical Landmark: openings of auditory (Eustachian) tubes from middle ear cavity adenoids or pharyngeal tonsil in roof Passageway for air only The Pharynx Oropharynx Laryngopharynx • From soft palate to epiglottis • Anatomical Landmark: behind the uvula • palatine tonsils found in side walls, lingual tonsil in tongue • Common passageway for food & air • Extends from epiglottis to cricoid cartilage • Anatomical Landmark: the epiglottis • Common passageway for food & air & ends as esophagus inferiorly

5. Tortora & Grabowski 9/e 2000 JWS

6. The Larynx • triangular box = “voicebox” • top of the larynx is a hole = glottis • covered with the epiglottis • contains the vocal cords - mucosal folds supported by elastic ligaments • Epiglottis---leaf-shaped piece of elastic cartilage • during swallowing, larynx moves upward bringing the glottis up to the epiglottis • epiglottis bends slightly to cover glottis • Laryngeal cartilages: • 1. thyroid cartilage (Adam’s apple) • 2. cricoid cartilage • 3. arytenoid cartilage – for the attachment of true vocal cords and arytenoideus muscles • filters, moistens, vocal production Tortora & Grabowski 9/e 2000 JWS

7. Vocal Cords • False vocal cords (ventricular folds) found above the true vocal cords • True vocal cords attach to arytenoid cartilages • True vocal cord contains both skeletal muscle and an elastic ligament (vocal ligament) • When intrinsic muscles of the larynx contract they move the artytenoid cartilages & stretch the true vocal cords tighter • When air is pushed past the tightened vocal ligament, sound is produced

8. Larnyx and Vocal Cords • true vocal cords vibrate upon passage of air -> speech • thickness determines frequency of vibration and timber of sound • thicker the cords – slower they vibrate – lower the pitch • thinner the cords – faster they vibrate – higher the pitch • thickness also controlled by testosterone • pitch can also be controlled by tightening the vocal cords voluntarily -arytenoideus muscle and the intrinsic muscles of the true vocal cords can alter the “tightness” of the cords • tighter the cords – faster they will vibrate

9. Tortora & Grabowski 9/e 2000 JWS

10. Trachea • flexible cylindrical tube - Size is 5 in long & 1 in diameter • sits anterior (in front of) the esophagus • splits into right and left primary bronchi – enter the lungs • held open by “C” rings of hyaline cartilage = tracheal cartilage • 16 to 20 incomplete rings • open side facing esophagus contains smooth muscle = tracheal ligament • layers: • innermost layer (mucosa) = pseudostratified columnar with cilia & goblet cells • outer layer (submucosa) = loose connective tissue & mucous glands • functions:conducts air into the lungs, filtration, moistens mucosa submucosa

11. Trachea and Bronchial Tree • Primary bronchisupply each lung • Secondary bronchisupply each lobe of the lungs (3 right + 2 left) • Tertiary bronchisplits into successive sets of Intralobular bronchiolesthat supply each bronchopulmonary segment ( right = 10, left = 8) • IL bronchioles split into Terminal bronchioles-> these split into Respiratory Bronchioles • each RB splits into multiple Alveolar ducts which end in an Alveolar sac

12. Gross Anatomy of Lungs • Blood vessels & airways enter lungs at hilus • Forms root of lungs • Covered with pleura (parietal becomes visceral) • 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

13. Alveoli • Respiratory bronchioles branch into multiple Alveolar ducts • Alveolar ducts end in a grape-like cluster = alveolar sac or lobule • -each grape = alveolus Respiratory membrane = 1/2 micron thick

14. Alveoli • site of gas exchange by simple diffusion • from heart (right ventricle)-> Pulmonary artery  multiple branches ending as the Pulmonary arteriole  Capillary bed over Alveolus  Pulmonary venule multiple veins  Pulmonary vein  heart (left atrium) • deoxygenated blood flows over the alveolus & picks up O2 via diffusion because the alveolar wall is very thin

15. 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 O2 CO2 • Respiratory membrane = 1/2 micron thick

16. Bronchioles • surrounded by “ring” of bronchiolar smooth muscle that can control the diameter of the bronchiole smooth muscle

17. Pleural Membranes & Pleural Cavity • Visceral pleuracovers lungs • Parietal pleuralines ribcage & covers upper surface of diaphragm • Pleural cavityis space between the two pleura • contains a small amount of fluid

18. Mechanism of Breathing: Boyle’s Law • As the size of closed container decreases, pressure inside is increased • As the size of a closed container increases, pressure decreases

19. Mechanism of Breathing Inspiration: -at rest: pressure inside lung = pressure outside lungs (atmospheric pressure) -inhale - diaphragm contracts and drops, external intercostal muscles swing the ribcage up and out -increase in thoracic cavity volume results -due to the cohesiveness of intrapleural fluid – lung volume increases also -pressure inside the lung drops = Boyle’s Law -air rushes in to equalize -SO: muscles of inspiration do not act directly on the lungs but act to change the volume of the thoracic and pleural cavities

20. Mechanism of Breathing Expiration: occurs because of the elasticity of the lungs - PASSIVE -in addition: relaxation of diaphragm and intercostal muscles returns thoracic and pleural cavity volume to normal -pressure of air in the lungs increases over atmospheric pressure -air leaves lungs to equalize

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

22. 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

23. Respiratory Volumes and Capacities • tidal volume (TV) =amnt of air that enters or exits the lungs • 500 ml per inhalation • inspiratory reserve volume (IRV) = max. amnt of air taken in after • a normal inhalation, 3000 ml • expiratory reserve volume • (ERV) = amnt of air forcefully • exhaled, 1100 ml • residual volume (RV) =amnt of air • left in lungs after forced expiration • 1200 ml

24. O2 and CO2 transport Body tissue CO2 transport from tissues CO2 produced Interstitial fluid CO2 • most O2 is carried in the blood bound to hemoglobin of the RBC • some is dissolved in blood plasma ( O2 not very soluble in water) • CO2 is carried by the blood in 3 ways: • 90% of the CO2 enters the RBC - combines with water of the cytosol to form carbonic acid • immediately dissociates into bicarbonate and H+ ions (binds to Hb) • catalyzed by the RBC enzyme called carbonic anhydrase • 2. some CO2 dissolves in the water of the plasma as carbonic acid  H+ and bicarbonate • 3. CO2 can combine directly with hemoglobin to form carbaminohemoglobin • in the lungs – Hb releases its H+ ion – it combines with the HCO3- to reform carbonic acid • carbonic acid breaks up into H2O and CO2 • CO2 is also released by Hb • CO2 diffuses into the alveolar air and is breathed out Plasma within capillary CO2 Capillary wall CO2 H2O Hemoglobin (Hb) picks up CO2 and H+. Red blood cell H2CO3 Hb Carbonic acid H+ HCO3 Bicarbonate  HCO3 To lungs CO2 transport to lungs HCO3 H+ HCO3  Hemoglobin releases CO2 and H+. Hb H2CO3 H2O CO2 CO2 CO2 CO2 Alveolar space in lung

25. Respiration Rate: controlled by a respiratory centermade up of a Medullary rhythmicity areain the medulla and two nuclei in the pons -MRA -group of neurons with an automatic, rhythmic discharge -groups are called the dorsal and ventral respiratory groups -controls rate and depth of breathing -dorsal group is called the inspiratory center which send signals via the motor neurons of the phrenic nerve and intercostal nerves that supply the inspiratory muscles (diaphragm and external intercostals) -ventral group contains expiratory neurons – inactive during normal quiet breathing but called into play with active breathing

26. Respiratory Center • Pneumotaxic Area • constant inhibitory impulses to inspiratory area • inhibits inspiration before lungs become too expanded • Apneustic Area • stimulatory signals to inspiratory area to prolong inspiration • Respiration also controlled by neurons in pons

27. Chemical regulation • Central chemoreceptors in medulla • respond to changes in H+ or pCO2 • Peripheral chemoreceptors • respond to changes in H+ , pO2 or pCO2 • aortic body---in wall of aorta • nerves join vagus • carotid bodies--in walls of common carotid arteries • nerves join glossopharyngeal nerve Respiratory Center • Cortical Influences • voluntarily alter breathing patterns • limitations are buildup of CO2 & H+ in blood • inspiratory center is stimulated by increase in either Tortora & Grabowski 9/e 2000 JWS

28. Negative Feedback Regulation of Breathing • Negative feedback control of breathing • Increase in arterial pCO2 • Stimulates receptors • Inspiratory center • Muscles of respiration contract more frequently & forcefully • pCO2 Decreases