Respiratory system facts : 1,500 mi of airways

1. Respiratory system facts: • 1,500 mi of airways • 300 to 500 million alveoli w/ total surface area of about one side of a tennis court • 616 miles of capillaries

2. Functions of the Respiratory System • Warm, moisten, and filter air • External, internal, and cellular respiration • Homeostasis of gases and ph • Production of sound (vocal folds)

3. Lungs • Fill thoracic cavity • Separated by mediastinum and heart • Upper part = apex • Lower part = base • Base fits snugly over diaphragm • Lung tissue porous and spongy – it floats • R lung = larger and shorter (displaced by the liver) and has 3 lobes • L lung = smaller (displaced by heart) and has 2 lobes

4. Respiratory Movements • 1 inspiration + 1 expiration = 1 respiration • Normal adult = 14 – 20 respirations / min • Age dependent - newborn = 40 – 60 / min • Increases with exercise, body temperature, certain diseases • Sleep = respirations ↓ • Emotion can ↑ or ↓

5. Pulmonary Ventilation (Breathing) • Inspiration • Intercostal muscles lift ribs outward, sternum rises and the diaphragm contracts and moves downward – this increases the volume of the lungs (creating negative pressure) and air rushes down pressure gradient into lungs • Expiration • Opposite action takes place • Exhalation is a passive process

6. Diaphragm Large dome-shaped muscle that contracts rhythmically, continually, and most of the time, involuntarily.

7. Pleura • Thin, moist slippery serous membranes surround the lungs • Each lung is enclosed in double-walled sac • Visceral pleura attached to lung; parietal attached to thoracic cavity • Space is pleural cavity – filled with pleural fluid to prevent friction

9. Nasal cavity and Sinuses • Nasal turbinates • Essential for functional breathing • Guide, heat, humidify and filter air • Ciliated pseudostratified columnar epithelia • Contain thermoreceptors • Chemoreceptors (for olfaction) in superior turbinates • Nasal sinuses • Air filled-cavities • Create vocal resonance • Heat inhaled air

10. Pharynx • The throat • Common passageway for air and food • ~5” long • Divided into: • Nasopharynx • Oropharynx • Laryngopharynx When food is swallowed, the cartilaginous epiglottis closes over the opening to the larynx, preventing food from entering the lungs.

11. Larynx • Voice box • Triangular chamber below the pharynx • Within the larynx are vocal folds (glottis) • Adam’s Apple

12. Vocal fold video

13. Trachea • Windpipe • ~4 ½” long • Walls are alternate bands of membrane and C shaped rings of hyaline (glassy) cartilage – to keep trachea open • Lined with ciliated pseudostratified columnar mucous membranes • Coughing and expectoration gets rid of dust-laden mucous

14. Bronchi and bronchioles • Lower end of trachea divides into R and L bronchus • As they enter lungs, subdivide into bronchial tubes and bronchioles • Bronchi – similar to trachea with ciliated simple columnar mucous membrane and hyaline cartilage

15. Bronchial tubes – cartilaginous plates (instead of C-shaped rings). • Bronchioles – thinner walls of smooth muscle, lined with ciliated epithelium. Hyaline cartilage changes to smooth muscle in bronchioles and simple cuboidal cells transition to simple squamous epithelial cells. • Alveolar ducts – small branches that terminate into 2 or 3 alveolar sacs. • Gas exchange occurs in both the alveolar ducts and alveolar sacs.

16. “Conducting zone” • Upper and lower respiratory passages • Ciliated pseudostratified columnar • “Respiratory zone” • Mostly simple squamous • Site of gas exchange • Respiratory bronchioles • Alveolar ducts • Alveolar sacs

17. Alveoli • Composed of a single layer of epithelial tissue • Alveoli are covered internally by a surfactant produced by simple cuboidal cells. • Inner surfaces covered with surfactant – to keep alveoli from collapsing • Each alveolus surrounded by capillaries • O2 and CO2 exchange takes place between the alveoli and capillaries (diffusion) • Oxygen and carbon dioxide must be absorbed in water to diffuse across alveolar/capillary membranes • Macrophages patrol alveolar surfaces and consumer foreign material

19. Oxygen is the MOST critical substance needed by the body for survival. • We can only live about 4-6 minutes without oxygen. • Clinical death – the moment breathing and heartbeat stop • Biological death – when brain cells die, irreversible after 6 – 10 minutes

20. Constant removal of carbon dioxide is just as important for survival – maintains homeostasis • Cellular respiration – oxygen combines with stored nutrients in cells to release energy, carbon dioxide, and water. • Respiratory system supplies oxygen and removes carbon dioxide • Carbon dioxide leaves enters blood as carbonic acid and is dissolved into plasma as bicarbonate

21. Carbonic anhydrase (in RBCs) catalyzes disassociation of hydrogen ion to form bicarbonate • Increase of hydrogen ions decreases ph (increases acidity) of blood • Carbonic anhydrase again catalyzes bicarbonate into carbon dioxide in the lungs • Carbon dioxide is then released in the lungs • Drop in blood's pH stimulates chemoreceptors in the carotid and aortic bodies in the blood system to send nerve impulses to the respiration center in the brain causing increased respiration.

22. Hyperventilation – response to accumulated CO2 in blood or panic state • Rapid clearing of CO2 • Can result in respiratory alkalosis • Paper bag rebreathing is ineffective and dangerous when confused with heart attack or asthma symptoms • Hypoventilation – (respiratory depression) inadequate ventilation • Build-up of CO2 • Can lead to respiratory acidosis • Neurons are particularly susceptible to acidic conditions • Common cause of death from many recreational drugs

23. Mammalian diving reflex • Present in all mammals but exhibited strongest in aquatic mammals • Thermoreceptors on face respond to cold water causing bradycardia, vasoconstriction, and other responses that allow extended periods of oxygen deprivation while under water. • This is the reflex that allows some individuals, especially children, to be resuscitated after hours of oxygen deprivation while submerged in cold water.

24. Yawning • CO2? • Stretching? • Alertness? • Brain temperature? • Emotions/mood/appetite? • Anxiety? • Empathy? • Territorialism?