The Respiratory System

1. The Respiratory System

2. Why do we need oxygen? Answer: We need it to make energy through aerobic respiration!

3. Organs of the Respiratory System • Nose • Pharynx • Larynx • Trachea • Bronchi • Lungs – alveoli

4. Functions of the Respiratory System Gas exchange between the blood and external environment Purification, warming, and humidifying of incoming air Provides olfactory sensations to the brain for sense of smell Produces sounds for communication

5. Divisions of the Respiratory Tract Conduction portion: nasal cavity  larger bronchioles (cleans and warms the air) Respiratory portion: smallest bronchioles  alveoli (permits gas exchange)

6. Upper Respiratory Tract

7. Nose • Olfactory receptors are located on the superior surface • Mucosa: lines the nasal cavity; moistens air and traps incoming foreign particles • Conchae: projections of the nasal cavity; increases air turbulence within the nasal cavity • Sinuses: cavities within bones surrounding the nasal cavity; lighten the skull, resonate sounds for speech, and produce mucus

8. Pharynx (Throat) • Muscular passage from nasal cavity to larynx • Common passageway for air and food • Contains tonsils • Auditory tubes enter here

9. Larynx (Voice Box) • Routes air and food into proper channels • Made of eight rigid cartilages and a spoon-shaped flap of elastic cartilage (epiglottis) • Epiglottis: routes food to the esophagus and air toward the trachea • Contains vocal cords (folds) that vibrate with expelled air to create sound (speech) • Glottis: opening between vocal cords

10. Trachea (Windpipe) • Connects larynx with bronchi • Lined with ciliated mucosa that: • Beat continuously in the opposite direction of incoming air • Expel mucus loaded with dust and other debris away from lungs • Walls are reinforced with C-shaped firm cartilage (open posteriorly)

12. Primary Bronchi • Trachea divides into right and left bronchi • Right bronchus is wider, shorter, and straighter than left • Bronchi then subdivide into smaller and smaller branches

13. Lungs • Occupy most of the thoracic cavity • Apex is near the clavicle (collar bone) and base rests on the diaphragm • Each lung is divided into lobes by fissures: • Left lung – two lobes • Right lung – three lobes

14. Coverings of the Lungs • Pulmonary (visceral) pleura covers the lung surface • Parietal pleura lines the walls of the thoracic cavity • Pleural fluid fills the area between layers of pleura to allow gliding

15. Lungs

16. Bronchioles • Smallest branches of the bronchi • All but the smallest branches have reinforcing cartilage • Terminal bronchioles end in alveoli

17. Alveoli • Consist of a duct, a sac, and the alveolus • Gas exchange takes place within the alveoli in the respiratory membrane • Respiratory membrane (air-blood barrier) • Thin epithelium lines alveolar walls • Pulmonary capillaries cover external surfaces of alveoli

18. Bronchioles and Alveoli

20. Gas Exchange in the Alveoli • Gas crosses the respiratory membrane by diffusion • Oxygen enters the blood • Carbon dioxide enters the alveoli • Macrophages protect against infectious microorganisms • Surfactant coats gas-exposed alveolar surfaces to keep alveoli inflated

21. Respiratory Membrane of Alveoli

22. Events of Respiration • Pulmonary ventilation: moving air in and out of the lungs • External respiration: gas exchange between pulmonary capillaries and alveoli • Internal respiration: gas exchange between blood and tissue cells in systemic capillaries

23. Mechanics of Breathing (Pulmonary Ventilation) • Two phases: • Inspiration/inhalation – flow of air into lung • Expiration/exhalation – air leaving lung

24. Inspiration/inhalation • Diaphragm contracts (flattens), external intercostals contract raising the rib cage • Volume of the thoracic cavity increases • Pressure in thoracic cavity decreases • Air is pulled into the lungs (from high to low pressure)

25. Inspiration/inhalation

26. Expiration/exhalation • Largely a passive process which depends on natural lung elasticity • Diaphragm relaxes (pushes up), external intercostals relax depressing the rib cage • Air is pushed out of the lungs • Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage further

27. Expiration/exhalation

28. Breathing Animation

29. Respiratory Volumes and Capacities • Tidal volume (TV) is normal breathing and moves about 500 mL of air with each breath • Many factors affect respiratory capacity: • A person’s size • Sex • Age • Physical condition • Residual volume (RV) of air: amount of air remaining in the lungs after normal exhalation (~1200 mL)

30. Respiratory Volumes and Capacities • Inspiratory reserve volume (IRV): amount of air that can be taken in forcibly over the tidal volume (5x TV) • Expiratory reserve volume (ERV): amount of air that can be forcibly exhaled (approx. = to RV)

31. Respiratory Volumes and Capacities • Vital capacity (VC): the total amount of exchangeable air • Vital capacity = TV + IRV + ERV • Dead space volume: air that remains in conducting zone and never reaches alveoli (150 mL) • Functional volume: air that actually reaches the respiratory zone (350 mL)

32. Respiratory Volumes and Capacities

33. Gas Transport in the Blood • Oxygen transport in the blood • Inside red blood cells attached to hemoglobin • A small amount is carried dissolved in the plasma • Carbon dioxide transport in the blood • Most is transported in the plasma as bicarbonate ion (HCO3–) • A small amount is carried inside red blood cells on hemoglobin, but at different binding sites than those of oxygen

34. Respiration

35. Neural Regulation of Respiration • Activity of respiratory muscles is transmitted to the brain by the phrenic and intercostal nerves • Phrenic nerve controls the diaphragm • Neural centers that control rate and depth are located in the medulla • The pons appears to smooth out respiratory rate • Normal respiratory rate is 12–15 respirations per minute

36. Neural Regulation of Respiration

37. Chemical Regulation of Respiration • Carbon dioxide levels • Level of carbon dioxide in the blood is the main regulatory chemical for respiration • Increased carbon dioxide increases respiration • Changes in carbon dioxide act directly on the medulla oblongata • Oxygen levels • Changes in oxygen concentration in the blood are detected by chemoreceptors in the aorta and carotid artery • Information is sent to the medulla oblongata

38. Other Factors Influencing Respiratory Rate and Depth • Physical factors: • Increased body temperature • Exercise • Talking • Coughing • Volition (conscious control) • Emotional factors

39. Effects of Aging on the Respiratory System • Elasticity of lungs decreases • Vital capacity decreases • Blood oxygen levels decrease • Respiratory rate often increases • Stimulating effects of carbon dioxide decreases • More risks of respiratory tract infection

40. Diagnostic Tests for the Respiratory System • Spirometry: measures how much and how quickly a person can move air out of the lungs • Pulse-oximetry: non-invasive measure of the oxygen saturation of the blood • Arterial blood gas: measures the amount of oxygen and carbon dioxide in a blood sample • Stress test: lung function is measured during exercise • Chest x-ray: x-ray of the thorax while holding breath