Respiratory System Notes

Respiratory System The major functions of the respiratory system are to facilitate the exchange of oxygen and carbon dioxide between the air and the blood. The respiratory tract consists of: Nose, pharynx, larynx, trachea, bronchial tree and lungs. Your respiratory system helps bring oxygen into your body so you cells can undergo cellular respiration. It helps transport carbon dioxide outside of the body. We can break respiration into four different types: Breathing External Respiration Internal Respiration Cellular Respiration

the movement of air into and out of the lungs the exchange of O2 and CO2 between AIR and BLOOD. the exchange of O2 and CO2 between BLOOD and TISSUE FLUID the process which produces ATP in mitochondria --> requires O2 and releases CO2

1. General Parts of the respiratory system:

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Respiratory System Notes

2. The Act of Breathing: a. Air normally enters through the nostrils, which are lined with hairs that filter out dust and other particles, and moistens it. b. The air then passes the back of the mouth, crossing the path of food as it enters first the larynx and the trachea (note cartilaginous rings) à larynx - “voice box”, responsible for sound production à trachea - “windpipe”carries air between larynx and bronchi c. From there it passes down through the bronchus and the bronchioles, and into the alveoli of the lungs i. bronchus -one of a pair of tubes branching from the trachea into either lung ii. bronchioles -the bronchus further subdivides into progressively f inner passageways, bronchioles, culminating at the alveoli iii. alveolus - one of many (300 million with a total surface area of ~75 square metres) small, thin walled air sacs within the lungs a. lipoproteins (see earlier notes on phospholipids) A lipoprotein is a biochemical assembly that contains both proteins and lipids, bound to the proteins, which allow fats to move through the water inside and outside cells b. Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid- lower surface tension, and allow for easier movement of gases across the alveoli walls - by increasing compliance, - reduces the pressure difference needed to allow the lung to inflate

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Respiratory System Notes c. maintaining shape which prevents alveolar collapse at low lung volumes during expiration by helping the aveoli maintain their shape (as well as preventing unequal inflation/deflation of the aveoli), d. keeps the air way dry, but the membrane moist iv. cilia à in the lungs (trachea, bronchi, larynx and nasal cavity) help sweep out debris trapped by mucus (filters) à to be coughed up and expelled or swallowed v. hair àin the nose filters incoming air of dust and debris, and can warm and moistens inhaled air d. The Thoracic Cavity The human respiratory apparatus functions as a one cycle pump. i. The thoracic cavity is bounded on its sides by ribs, and on the bottom by a thin layer of muscle, the diaphragm, which separates the thoracic cavity from the abdominal cavity. ii. Each lung is covered by a smooth membrane called the pleural membrane.

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Respiratory System Notes iii. A second pleural membrane divides the thoracic cavity in two halves; each lung is supported in its own cavity supported by water, intrapleural fluid. à The fluid also acts to even out pressure on the lungs, so all parts are compressed evenly (hydrostatic pumping) à Also reduces friction (a lubricant) during inhalation 3. Respiratory Volumes The amount of air the moves in and out of the lungs during each breath is much less than the maximum amount that can be inhaled and exhaled. There is always some air left in the lungs even after you breath all the way out! Tidal Volume: Small amount of air the moves into and out of the lungs with each breath Vital Capacity: The maximum amount of air that can be moved in plus the maximum volume that can be moved out during a single breath. Inspiratory Reserve Volume: Volume of air that can be forcibly inhaled after normal inhalation Expiratory Reserve Volume: The volume of air that can be forcibly exhaled after normal exhalation Residual Volume: Amount of air remaining in the lungs even after a forced exhale.

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Respiratory System Notes

4. Your Voice Box: The air enters the larynx. It is like a triangular box with the Adam's Apple at the front corner.

Elastic ligaments called vocal cords stretch from the back to the front of the larynx just at the sides of the glottis.

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Respiratory System Notes These cords vibrate when air is expelled past them through the glottis. àThis vibrations produce sound. àThe pitch of the voice depends on the length, thickness, and degree of elasticity of the vocal cords and the tension at which they are held. àMuscles adjust the tension of the chords to produce different sounds. 5. Control of Breathing: Adults breath at 12 to 20 reps per minutes. The rhythm of this is called Respiratory Center located in the medulla oblongata of the brain. When your brain wants your to breath in it sends a signal to your diaphragm via the phrenic nerve.

chemoreceptors in the carotid bodies of the carotid arteries and in the aortic bodies in the aorta respond to low blood oxygen, and stimulate breathing as well (to a lesser extent) Hyperventilation = not enough CO2. Which is why you treat it by breathing into a paper bag. (recycling your CO2 that you breath out)

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Respiratory System Notes 6. Inhalation and Exhalation: Carbon Dioxide and hydrogen ions (h+) in the blood control the breathing rate. a. CO2 levels in the blood will increase as cells continue to produce it. The concentration of CO2 will increase until they reach a threshold level. b. Chemoreceptors in arteries detect the increased CO2 and H+ levels. c. The chemoreceptors send a signal to a breathing center in the medulla oblongata of the brain. It detects the rising levels of CO2 and H+. This center is not affected by low oxygen levels. There are also chemoreceptors in the carotid bodies, located in the carotid arteries, and in the aortic bodies, located in the aorta, that respond primarily to H+ concentration, but also to the level of carbon dioxide and oxygen in the blood. These bodies communicate with the respiratory center. d. The medulla oblongata sends a nerve impulse to the diaphragm and muscles in the rib cage. e. The diaphragm contracts and lowers, while the rib cage moves up. f. Air flows into alveoli, and the alveolar walls expand and stretch. g. Stretch Receptors in the alveoli walls detect this stretching. h. Nerves in alveoli send signal to brain to inhibit the medulla oblongata from sending its message to the diaphragm and rib muscles to contract. They therefore stop contracting. i. The diaphragm relaxes, and moves upward, resuming its original shape. The rib cage relaxes and moves downward and inward. j. Air is forced out the lungs.

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Respiratory System Notes 7. External Respiration: External Respiration is gas exchange between air (at alveoli) and blood (in pulmonary capillaries). • •

Both alveoli walls and capillary walls are one cell layer thick. This exchange of gases is by diffusion alone. (recall that law of diffusion states that material will flow from area of high concentration to area of low concentration).

capillaries Alveoli •

in blood

[O2] low high

[CO2] high low

Deoxygenated blood is high in CO2, which is carried as bicarbonate ion (HCO3-). carbonic anhydrase in RBC H+ + HCO3----------------> H2O + CO2 Hb + O2

Tissue fluid is low in O2, high in CO2, due to constant cellular respiration. CO2 therefore diffuses into the blood 9. The Fate of CO2 A small amount of CO2 is taken up by hemoglobin.

Hb + CO2

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TISSUES ----------->

H2CO3

---->

H+ + to Hb

HCO3to Plasma

⇒ Note: Hemoglobin combines with the excess H+ that this reaction produces. That way, blood pH remains constant. You could say that Hemoglobin acts like a buffer.

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Common Disorders of the Respiratory System:

a. Common Cold: Caused by viral infection. About 150 viruses known to cause colds. Mild symptoms: sore throat, watery mucus nasal discharge. No Cure -- treat symptoms. Antihistamines, decongestants, ASA, rest b. Influenza: a more severe viral infection. Symptoms include fevers, aches, cold symptoms. Vaccines have been developed, but the virus is constantly mutating into new forms. Over 20,000,000 people died in a flu epidemic in 1919-20. c.

Bronchitis: usually caused by viral infection of nasal cavities that spreads to bronchi and causes a secondary bacterial infection.

In acute bronchitis, there is heavy mucoid discharge, coughing. Chronic bronchitis is not usually due to bacterial infection, but rather to chronic irritation of bronchial lining (leads to degeneration of lining, loss of cilia). Chronic bronchitis is usually due to smoking. Treatment for acute bronchitis is antibiotics and rest • •

d. Pneumonia: caused by bacteria or viruses which infect lungs. The lobes of the lungs fill up with mucus and pus. • Many AIDS patients die of Pneumocystis carinii infection. Treatment is antibiotics (if bacterial), hospitalization

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Respiratory System Notes

e. Emphysema: most often caused by smoking. • Deteriorating bronchioles ----> alveoli cut off. This leads to ballooning of lungs due to trapped air. The trapped air causes the alveoli to rupture. • Symptoms include coughing, sluggishness, heart racing. The heart and brain starve for oxygen. May lead to a heart condition.

•

.

Hard to treat: often surgical removal of some lung tissue helps

f. Tuberculosis: caused by tubercle bacteria. Can detect with a skin test, X-Rays. • If the bacilli invade lungs, cells the invaders with capsule called tubercles (a defense mechanism). This may kill sufferer. Treatment: quarantine, antibiotics, other drugs g. Lung Cancer: Smoking is the #1 cause! (see text). • Lung cancer is a progressive disease --> early detection is important. Progress of disease: 1. Lungs exposed to carcinogenic irritants. 2. Bronchial cells thicken, callus, cilia die. 3. "Atypical" cells start appearing in thickened lining ("in situ" cancer). 4. Some of these cells break loose and penetrate other tissues (= metastasis). This is the point where true cancer begins. 5. Tumor(s) grow, tubes become blocked, lung collapses, secondary infections can occur. •

Treatment: chemotherapy, surgery, pneumonectomy (remove lung).

Smoking Risks (a partial list): • lung cancer • larynx cancer • bladder cancer • pancreas cancer

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• • • •

bronchitis/emphysema peptic ulcers reduced lifespan weak immune system

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