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Respiratory System Chapter 22. Role of Respiratory System Supplies body w/ O 2 and disposes of CO 2 Four part process – Pulmonary ventilation Moving air.

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Presentation on theme: "Respiratory System Chapter 22. Role of Respiratory System Supplies body w/ O 2 and disposes of CO 2 Four part process – Pulmonary ventilation Moving air."— Presentation transcript:

1 Respiratory System Chapter 22

2 Role of Respiratory System Supplies body w/ O 2 and disposes of CO 2 Four part process – Pulmonary ventilation Moving air in and out of lungs – External respiration Exchange of gases between lungs and blood – Transport of respiratory gases Moving air to and from tissues via blood – Internal respiration Exchange of gases between blood and tissues

3 Functional Respiratory System Conducting zone: carries air – Cleanses, humidifies, and warms air – Nose  terminal bronchioles Respiratory zone: site of gas exchange – Respiratory bronchioles – Alveolar ducts – Alveoli

4 Nose and Nasal Cavity Normal air entry, why not mouth? Moistens, warms, and filters air – Superficial capillary beds – Vibrissae filter particulates – Respiratory epithelium (what is that?) Mucus traps debris and moves posterior to pharynx Defensins and lysozymes – Turbinate bones and meatuses enhance Olfaction – Olfactory epithelia through cribriform plates – Nerve endings irritated = sneezing Resonation for speech

5 Pharynx Nasopharynx – Air mov’t only Closed off by uvula w/ swallowing Giggling prevents = nose expulsion – Respiratory epithelium (why?) – Pharyngeal tonsil (adenoids) Oropharynx – Food and air mov’t – Stratified squamous (why?) – Palatine and lingual tonsils Laryngopharnx – Food and air mov’t – Stratified squamous – Branches to esophagus and larynx

6 Larynx Keep food and fluid out of lungs – Epiglottis (elastic) covers glottis Coughing/choking when fails – False vocal cords Transport air to lungs – Supported by 8 hyaline cartilages Voice production – True vocal cords (elastic) vibrate as air passes Pitch from vibration rate (more tension = faster = higher) Loudness from force of expelled air (whisper = little/no vibration) – Additional structures amplifies, enhances, and resonates – Pseudostratified ciliated columnar again (why?) Mucus up to pharynx

7 Trachea Transports air to lungs Mucosal layer – Respiratory epithelium – Mucus trapped debris to pharynx Submucosal layer – Mucus glands Adventita – Connective tissue supported by C-rings of hyaline cartilage

8 Bronchial Tree Table 2: Divisions of the Bronchial Tree. Taken from Ross et al., Histology, a text and atlas, 10 th edition, p. 589, Table 18.1.

9 The Respiratory Membrane Walls of the alveoli where actual exchange occurs – Simple squamous cells (type I cells) surrounded by capillaries Surface tension resists inflation – Cuboidal epithelia (type II cells) produce surfactant to counter Macrophages patrol – Dead/damage swept to pharynx

10 Lung Anatomy Paired air exchange organs – Right lung Superior, middle, and inferior lobes Oblique and horizontal fissures – Left lung Superior and inferior lobes Oblique fissure Cardiac notch contributes to smaller size Costal, diaphragmatic, and mediastinal surfaces Hilum where 1° bronchi and blood vessels enter

11 Pleura Serous membrane covering – Parietal pleura – Visceral pleura – Pleural fluid in cavity Reduces friction w/ breathing – Surface tension binds tightly – Expansion/recoil with thoracic cavity Creates 3 chambers to limit organ interferences

12 Pressure Relationships Relative to atmospheric pressure (P atm ) – Sea level = 760 mmHg Intrapulmonary pressure (P pul ): pressure in alveoli Intrapleural pressure (P ip ): pressure in pleural cavity – Always negative to P pul – Surface tension b/w pleura Lung wall Atmosphere P atm Intrapleural fluid Chest wall P pul P ip (Ppul – Pip) (Patm – Ppul )

13 Transpulmonary Pressure (P tp ) Difference b/w intrapulmonary and intrapleural pressure (P pul – P ip ) – Influences lung size (Greater diff. = larger lungs) – Equalization causes collapse Keeps lungs from collapsing (parietal and visceral separation) – Alveolar surface tension and recoil favor aveoli collapse – Recoil of chest wall pulls thorax out

14 Pulmonary Ventilation Inspiration and expiration change lung volume – Volume changes cause pressure changes – Gases move to equalize Boyle’s Law – P 1 V 1 = P 2 V 2 Increase volume = decrease pressure Decrease volume = increase pressure P atm – P pul R F = P pul < P atm inspiration P pul > P atm expiration

15 Breathing Cycle InspirationExpiration Thoracic cavity increases – P ip decrease  P tp increase Lung volume increases – P pul < P atm Air flows in till P pul = P atm Inspiratory muscles relax Thoracic cavity decreases – P ip increase  P tp decrease Lung volume decreases – P pul > P atm Air flows out till P pul = P atm

16 Influencing Pulmonary Ventilation Airway resistance – Flow = pressure gradient/ resistance (F =  P/R) – Diameter influences, but insignificantly Mid-sized bronchioles highest (larger = bigger, smaller = more) Diffusion moves in terminal bronchioles (removes factor) Alveolar surface tension – Increase H 2 0 cohesion and resists SA increase – Surfactants in alveoli disrupt = less E to oppose Lung compliance – ‘Stretchiness’ of the lungs – Stretchier lungs = easier to expand

17 Tidal volume (TV): air moved in or out w/ one breath Inspiratory reserve volume (IRV): forcible inhalation over TV Expiratory reserve volume (ERV):forcible exhalation over TV Residual volume: air left in lungs after forced exhalation Pulmonary Volumes

18 Respiratory Capacities Inspiratory capacity (IC) – Inspired air after tidal expiration – TV + IRV Functional residual capacity (FRC) – Air left after tidal expiration – RV + ERV Vital capacity (VC) – Total exchangeable air – TV + IRV + ERV Total lung capacity (TLC) – All lung volumes – TV + IRV + ERV + RV

19 Non-Respiratory Air Dead space – Anatomical: volume of respiratory conducting passages – Alveolar: alveoli not acting in gas exchange – Total: sum of alveolar and anatomical Reflex movements – Cough: forcible exhalation through mouth – Sneeze: forcible exhalation through nose and mouth – Crying: inspiration and short expirations – Laughing: similar to crying – Hiccups: sudden inspiration from diaphragm spasms – Yawn: deep inspiration into all alveoli

20 Properties of Gases Dalton’s Law – Pressure exerted by each gas in a mix is independent of others P N 2 ~ 78%, P O 2 ~ 21%, P CO 2 ~.04 – Partial pressure (P) for each gas is directly proportional to its concentration O 2 at sea level  760mmHg x.21 = 160mmHg 10,000 ft above  523mmHg x 0.21 = 110mmHg Henry’s Law – In contact w/ liquid, gas dissolves proportionately to partial pressure Higher partial pressure = faster diffusion Equilibrium once partial pressure is equal – Solubility and temperature can influence too (concentration)

21 External Respiration Gas exchange – Partial pressure gradients drive Alveoli w/ higher P O 2 and tissues w/ P CO 2 – P O 2 gradients always steeper that P CO 2 – P CO 2 more soluble in plasma and alveolar fluid than P O 2 – Equal amounts exchanged Respiratory membrane – Thin to allow mov’t – Moist to prevent desiccation – Large SA for diffusion amounts

22 External Respiration (cont.) Ventilation and perfusion synchronize to regulate gas exchange – P O 2 changes arteriole diameter Low  vasoconstriction  redirect blood to higher P O 2 alveoli – P CO 2 changes bronchiole diameter High  bronchiole dilation  quicker removal of CO 2

23 Oxygen Transport 98% bound to hemoglobin as oxyhemoglobin (HbO 2 ) – Review structure – Deoxyhemoglobin (HHb) once O 2 unloaded – Rest dissolved in plasma Affinity influenced by O 2 saturation – 1 st and 4 th binding enhances – Previous unloading enhances Hemoglobin reversibly binds O 2 – Influenced by P O 2, temp., blood pH, P CO 2, and [BPG] HHb + O 2 Lungs Tissues HbO 2 + H +

24 P O 2 Influences on Hemoglobin Hb near saturation at lungs (P O 2 ~ 100mmHg) and drops ~ 25% at tissues (P O 2 ~ 40mmHg) – Hb unloads more O 2 at lower P O 2 – Beneficial at high altitudes In lungs, O 2 diffuses, Hb picks up = more diffusion – Hb bound O 2 doesn’t contribute to P O 2

25 Increase in [H + ], P CO 2, and temp – Decrease Hb affinity for O 2 Enhance O 2 unloading from the blood – Areas where O 2 unloading needed Cellular respiration Bohr effect from low pH and increased P CO 2 Decreases have reverse effects Controlling O 2 Saturation

26 Carbon Dioxide Transport Small amounts (7 – 10%) dissolved in plasma As carbaminohemoglobin (~20%) – No competition with O 2 b/c of binding location – HHb binds CO 2 and buffers H + better than HbO 2, called the Haldane effect Systemically, CO 2 stimulates Bohr effect to facilitate In the lungs, O 2 binds Hb releasing H + to bind HCO 3 -

27 Carbon Dioxide Transport (cont.) Primarily (70%) as bicarbonate ions (HCO 3 - ) CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - – Hb binds H + = Bohr effect and little pH change – HCO 3 - stored as a buffer against pH shifts in blood Bind or release H + depending on [H + ] CO 2 build up (slow breathing) = H 2 CO 3 up (acidity) Faster in RBC’s b/c carbonic anhydrase Fig 22.22

28 Neural Control of Respiration Medullary respiratory centers – Dorsal respiratory group (DRG) Integrates peripheral signals Signals VRG – Ventral respiratory group (VRG) Rhythm-generating and forced inspiration/expiration Excites inspiratory muscle to contract Pontine center – Signals VRG – ‘Fine tunes’ breathing rhythm in sleep, speech, & exercise

29 Regulating Respiration Chemical factors – Increase in P CO 2 increases depth and rate Detected by central chemoreceptors (brainstem) CO 2 diffuses into CSF to release H + (no buffering) Greater when P O 2 and pH are lower – Initial decrease in P O 2 enhances P CO 2 monitoring Peripheral chemoreceptors in carotid and aortic bodies Substantial drop to increase rate b/c Hb carrying capacity – Declining arterial pH increases depth and rate Peripheral chemoreceptors increase CO 2 elimination

30 Regulating Respiration (cont.) Higher brain center influence – Hypothalamic controls Pain and strong emotion influence rate and depth Increased temps. increases rate – Cortical controls Cerebral motor cortex bypasses medulla Signals voluntary control (overridden by brainstem monitoring) Pulmonary irritant reflexes – Reflexive constriction of bronchioles – Sneeze or cough in nasal cavity or trachea/bronchi Inflation reflex – Stretch receptors activated w/inhalation – Inhibits inspiration to allow expiration

31 Homeostatic Imbalances Sinusitis: inflamed sinuses from nasal cavity infection Laryngitis: inflammation of vocal cords Pleurisy: inflammation of pleural membranes, commonly from pneumonia Atelectasis: lung collapse from clogged bronchioles Pneumothorax: air in the intrapleural spaces Dyspnea: difficult or labored breathing Pneumonia: infectious inflammation of the lungs (viral or bacterial) Emphysema: permanent enlargement of the alveoli due to destruction Chronic bronchitis: inhaled irritants causing excessive mucus production Asthma: bronchoconstriction prevents airflow into alveoli Tuberculosis: an infectious disease (Mycobacterium tuberculosis) causing fibrous masses in the lungs Cystic fibrosis: increased mucus production which clogs respiratory passages Hypoxia: inadequate O 2 delivery – Anemic (low RBC’s), ishemic (impaired blood flow), histotoxic (cells can’t use O 2 ), hypoxemic (reduced arterial P O 2 )


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