The Respiratory System

1. The Respiratory System Chapter 11

2. Respiration • Physiological process by which oxygen moves into internal environment and carbon dioxide moves out • Oxygen is needed for aerobic respiration • Carbon dioxide is produced by same

3. Respiratory System • Acts in concert with the circulatory system to deliver oxygen and remove carbon dioxide • Also helps regulate acid-base balance

4. Human Respiratory System pharynx (throat) epiglottis larynx (voice box) trachea (windpipe) pleural membrane bronchiole intercostal muscle alveoli diaphragm

5. Airways • Air enters through nose • Moves through pharynx and larynx to trachea • Trachea branches into two bronchi • Each bronchus branches into bronchioles • Bronchioles end in alveoli where gas exchange occurs

6. Speech Production • Vocal cords stretch across laryngeal opening; opening between them is glottis • Position of cords is varied to create different sounds Glottis closed Glottis open

7. Pressure Gradients • Concentration gradients for gases • Gases diffuse down their pressure gradients • Gases enter and leave the body by diffusing down pressure gradients across respiratory membranes

8. Atmospheric Pressure • Pressure exerted by the weight of the air on objects on Earth’s surface • At sea level = 760 mm Hg • Oxygen is 21% of air; its partial pressure is about 160 mm Hg

9. Fick’s Law • Describes the rate at which a substance (such as oxygen) will diffuse across a membrane (such as a respiratory surface) • Rate is proportional to the pressure gradient across the membrane and to the surface area of the membrane

10. Altitude Sickness • Humans are adapted to lower elevations where oxygen levels are relatively high • At high altitude • Hyperventilation leads to ion imbalances in cerebrospinal fluid • Increased capillary permeability can cause edema

11. Decompression Sickness • Pressure increases with water depth • While diving, pressurized air keeps lungs from collapsing • During ascent, pressure decreases • Bubbles of gaseous nitrogen can form in blood and block flow

12. Carbon Monoxide Poisoning • Colorless, odorless gas • Binds to hemoglobin 200 times more tightly than oxygen does • Even tiny amounts can tie up hemoglobin and prevent oxygen delivery

13. Bronchitis • Irritation of the ciliated epithelium that lines the bronchiole walls • Air pollutants, smoking, or allergies can be the cause • Excess mucus causes coughing, can harbor bacteria • Chronic bronchitis scars and constricts airways

14. Emphysema • An irreversible breakdown in alveolar walls • Lungs become inelastic • May be caused by a genetic defect • Most often caused by smoking

15. Asthma • Can be triggered by allergens • Smooth muscle ringing bronchi contracts • Mucus is produced by bronchial epithelium • Result is reduced air flow • Can be treated with aerosol inhalers

16. Breathing • Moves air into and out of lungs • Occurs in a cyclic pattern called the respiratory cycle • One respiratory cycle consists of inhalation and exhalation

17. Changes in Pressure 760 760 760 Atmospheric pressure: 754 Intrapleural pressure: 756 756 759 Intrapulmonary pressure: 760 761 Before inhalation During inhalation (lungs expanded) During exhalation

18. Inhalation • Diaphragm flattens • External intercostal muscles contract • Volume of thoracic cavity increases • Lungs expand • Air flows down pressure gradient into lungs

19. Normal (Passive) Exhalation • Muscles of inhalation relax • Thoracic cavity recoils • Lung volume decreases • Air flows down pressure gradient and out of lungs

20. Active Exhalation • Muscles in the abdomen and the internal intercostal muscles contract • This decreases thoracic cavity volume more than passive exhalation • A greater volume of air must flow out to equalize intrapulmonary pressure with atmospheric pressure

21. Lung Volume • Tidal volume is 500ml of air • Vital capacity is tidal volume, plus inspiratory reserve and expiratory reserve • This is still less than total lung capacity • Lungs are never fully deflated

22. Respiratory Membrane alveolar epithelium • Area between an alveolus and a pulmonary capillary • Oxygen and carbon dioxide diffuse across easily capillary endothelium fused basement membranes of both epithelial tissues

23. Oxygen Transport • Most oxygen is carried bound to hemoglobin in red blood cells • Hemoglobin has a great affinity for oxygen when it is at high partial pressure (in pulmonary capillaries) • Lower affinity for oxygen in tissues, where partial pressure is low

24. Carbon Dioxide Transport • Most carbon dioxide is transported as bicarbonate • Bicarbonate formation is enhanced by the action of carbonic anhydrase inside red blood cells • Smaller amounts are transported dissolved in blood and bound to hemoglobin

25. Bicarbonate Formation: A Two-Step Reaction • Carbon dioxide combines with water to form carbonic acid CO2 + H2O ---> H2CO3 (catalyzed by carbonic anhydrase) • Carbonic acid releases a hydrogen ion to form bicarbonate H2CO3 ---> H+ + HCO3-

26. Breathing Rhythm • Diaphragm and intercostal muscles under control of reticular formation • One cell cluster controls inspiration, the other expiration • Resulting rhythm is fine tuned by centers in the brain stem

27. Magnitude of Breathing • Receptors in medulla detect H+ • Signal increase in rate and depth of breathing • Carotid bodies and aortic bodies detect CO2, oxygen, and pH • Signal increase in rate of breathing

28. Chemical Controls • Increase in CO2 causes smooth muscle of bronchioles to dilate • Decrease in CO2 causes smooth muscle of bronchioles to constrict • Local controls also work on lung capillaries

29. Apnea • Breathing that stops and starts • Sleep apnea is common in elderly

30. Effects of Smoking • Shortened life expectancy • Increased rates of cancers • Increased rate of heart disease • Impaired immune function and healing • Detrimental to fetus