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) larynx (voice box) trachea (windpipe) pleural membrane intercostal muscle diaphragm epiglottis bronchiole alveoli

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 closedGlottis 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 760 756 760 754 759 760 756 761 Atmospheric pressure: Intrapleural pressure: Intrapulmonary pressure: 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 Area between an alveolus and a pulmonary capillary Oxygen and carbon dioxide diffuse across easily alveolar epithelium 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 CO 2 + H 2 O ---> H 2 CO 3 (catalyzed by carbonic anhydrase) Carbonic acid releases a hydrogen ion to form bicarbonate H 2 CO 3 ---> H + + HCO 3 -

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 CO 2, oxygen, and pH Signal increase in rate of breathing

28. Chemical Controls Increase in CO 2 causes smooth muscle of bronchioles to dilate Decrease in CO 2 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