Chapter Outline: Use this as your textbook reading companion35.1 Impacts, Issues: Up in Smoke

A. The body reacts to tobacco smoke.1. Immediately there is coughing, nausea, dizziness, and even headaches.2. Later, the cilia that line the respiratory tract are immobilized; white blood cells are killed;

colds and bronchitis increase; and, of course, deadly cancer is a long-term reward.

B. The “active ingredient” in this scenario is nicotine.1. It constricts the blood vessels, increasing blood pressure.2. It raises the level of “bad” LDL cholesterol and creates a decline in “good” HDL

cholesterol.3. Females who start smoking as teenagers are about 70 percent more likely to develop

breast cancer.

C. Secondhand smoke also raises the risk of disease (lung cancer, asthma, respiratory problems) for nonsmokers.

35.2 The Process of Respiration

A. Gas Exchanges1. Respiratory systems rely on the diffusion of gases down pressure gradients.

a. Gases will diffuse down a pressure gradient across a membrane (respiratory surface) if it is permeable and moist.

2. The amount of diffusion depends on the surface area of the membrane and the differences in partial pressure.

B. Factors Influencing Gas Exchange1. Animals either must have a body design that keeps internal cells close to the surface or

must have a system to move the gases inward.2. Concentrations of gases on either side of a membrane are important; the larger the

gradient, the faster the rate of diffusion.a. Most animals have to keep moving gasses across their respiratory membranes in order

to maintain steep gradients.3. Respiratory Proteins

a. The main transport protein is hemoglobin, each molecule of which binds four molecules of oxygen in the lungs (high concentration) and releases them in the tissues where oxygen is low.

b. Myoglobin is another iron-containing respiratory protein, which is a good storage molecule of oxygen because it has a higher affinity for oxygen.

35.3 Invertebrate Respiration

A. Integumentary exchange, in which gases diffuse directly across a moist body surface (for example, earthworm), is adequate for small animals with a low metabolic rate.

B. Gills, highly folded, thin-walled projections from the body, enhance exchange rates between the blood of aquatic invertebrates and their watery environment.

C. Tracheal respiration in arthropods, such as insects and spiders, utilizes fine air-conducting tubules to provide gaseous exchange at the cellular level; very little participation by the circulatory system is needed.

35.4 Vertebrate Respiration

A. Respiration in Fishes1. A gill has a moist, thin, vascularized epidermis.2. External gills project from the body surface of a few amphibians and some insects.3. The internal gills of adult fishes are positioned where water can enter the mouth and then

flow over them as it exits just behind the head.a. Water flows over the gills and blood circulates through them in opposite directions.b. This mechanism, called countercurrent flow, is highly efficient in extracting oxygen

from water, whose oxygen content is lower than air.

B. Evolution of Paired Lungs1. Lungs contain internal respiratory surfaces shaped as a cavity or sac.

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2. Lungs also participate in the production of sound, when air is exhaled past the vocal cords through the glottis opening.

3. Lungs provide a membrane for gaseous exchange with blood.a. Air moves by bulk flow into and out of the lungs.b. Gases diffuse across the inner respiratory surfaces of the lungs.c. Pulmonary circulation enhances the diffusion of dissolved gases into and out of lung

capillaries.d. In body tissues, oxygen diffuses from blood → interstitial fluid → cells; carbon dioxide

travels the route in reverse.4. Various animals use different mechanisms for respiration.

a. Frogs in the larvae stage utilize gills and skin; as adults they use paired lungs and skin for respiration.

b. Amniotes have waterproof skin and no gills; they use well developed lungs for respiration.

35.5 Human Respiratory System

A. The System’s Many Functions1. The lungs accomplish gas exchange via the alveoli.2. Exhaled air permits vocalizations.3. The system helps return venous blood to the heart and helps rid the body of excess heat

and water.4. Controls over breathing adjust the body’s acid–base balance as well as the body’s

temperature.

B. From Airways to Alveoli1. The Respiratory Passageways

a. Air enters or leaves the respiratory system through nasal cavities where hair and cilia filter dust and particles from, blood vessels warm, and mucus moistens the air.

b. Air moves via this route: pharynx → larynx (route blocked by epiglottis during swallowing) → vocal cords (space between is glottis) → trachea → bronchi → bronchioles → alveoli.

c. The vocal cords lie at the entrance to the larynx.d. When air is exhaled through the glottis, the folds of the cords vibrate to produce

sounds, which are under regulation by nerve commands to the elastic ligaments that regulate the glottal opening.

2. The Paired Lungsa. Human lungs are located in the thoracic cavity, one on each side of the heart; the rib

cage encloses and protects the lungs.b. Each lung is covered with a pleural membrane, which covers the lung’s outer surface

and lines the inside of the thoracic cavity.c. Inside the lungs, respiratory bronchioles bear outpouchings of their walls called alveoli,

which are usually clustered as alveolar sacs.d. Alveoli provide a tremendous surface area for gaseous exchange with the blood located

in the dense capillary network surrounding each alveolar sac.3. Muscles and Respiration

a. The diaphragm is a sheet of smooth muscle beneath the lungs; intercostal muscles are skeletal muscles between the ribs.

b. The diaphragm and the intercostal muscles interact and exchange the volume of the thoracic cavity during breathing.

35.6 How You Breathe

A. The Respiratory Cycle1. The respiratory cycle includes on inhalation and one exhalation.2. In inhalation, the diaphragm contracts and flattens, muscles lift the rib cage upward and

outward, the chest cavity volume increases, internal pressure decreases, and air rushes in.2. In exhalation, the actions listed above are reversed; the elastic lung tissue recoils passively.3. Pressure gradients between air inside and outside the respiratory tract change, causing air

to flow into the airways.

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4. Using the Heimlich maneuver manually increases the intra-abdominal pressure to force the diaphragm up and force food out of the trachea.

B. Respiratory Volumes1. The maximum volume the lungs can hold is the total lung volume; total lung volume is 5.7

liters in men and 4.2 liters in females.2. Vital capacity is the maximum amount of air that can be moved in and out of the lungs in

one breath.3. The tidal volume, about 0.5 liters, is the volume of air that moves into and out of the lungs

in one respiratory cycle.4. The lungs never totally deflate during breathing.

C. Control of Breathing1. Respiratory centers in the brain control the rate and depth of breathing.2. When activity levels increase, chemoreceptors sense changes in the blood pH and signal

the respiratory center to alter breathing levels.3. Reflexes, such as swallowing or coughing, and commands from the sympathetic nerves

alter breathing patterns.

35.7 Gas Exchange and Transport

A. The Respiratory Membrane1. The alveolar epithelium, the capillary epithelium, and their basement membranes form a

respiratory membrane.2. Oxygen and carbon dioxide passively diffuse across the membrane in response to partial

pressure gradients.a. Partial pressures are the amount of pressure an individual gas contributes to an overall

mix of gasses; i.e. atmosphere contains nitrogen gas, oxygen, carbon dioxide, etc.

B. Oxygen Transport and Storage1. Blood cannot carry sufficient oxygen and carbon dioxide in dissolved form to satisfy the

body’s demands; hemoglobin helps enhance its capacity.2. Oxygen diffuses down a pressure gradient into the blood plasma → red blood cells → binds

to hemoglobin (four molecules per hemoglobin to form oxyhemoglobin).3. Hemoglobin gives up its oxygen in tissues where partial pressure of oxygen is low, blood is

warmer, partial pressure of carbon dioxide is higher, and pH is lower; all four conditions occur in tissues with high metabolism.

4. Myoglobin stores oxygen in cardiac muscle and in some skeletal muscles; when blood flow cannot keep up with the body’s needs, myoglobin releases oxygen.

C. Carbon Dioxide Transport1. Because carbon dioxide is higher in the body tissues, it diffuses into the blood.2. Ten percent is dissolved in plasma, 30 percent binds with hemoglobin to form

carbaminohemoglobin, and 60 percent is in bicarbonate form.3. Bicarbonate and carbonic acid formation is enhanced by the enzyme carbonic anhydrase,

which is located in the red blood cells.

D. The Carbon Monoxide Threat1. Hemoglobin has a higher affinity for carbon monoxide than oxygen.2. Carbon monoxide prevents proper oxygen transport causing carbon monoxide poisoning.

E. Effects of Altitude1. Even though the concentration of oxygen is the same at higher altitudes, the pressure is

less.a. Less oxygen crosses the respiratory membrane.b. Less oxygen binds to hemoglobin.c. Altitude sickness can result; symptoms include shortness of breath, dizziness, and

nausea.2. Over time, acclimatization leads to the production of more red blood cells to accommodate

the change.

35.8 Common Respiratory Diseases and Disorders

A. Interrupted Breathing1. Sleep apnea and sudden infant death syndrome (SIDS) are caused by a stop in breathing.

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2. Damage to the respiratory control center and weak signals (fewer serotonin receptors) may lead to these respiratory stresses.

B. Tuberculosis1. About one-third of the human population carries the bacteria that cause tuberculosis; 10

percent of these carriers will develop the disease, which can be cured with long treatment courses of antibiotics.

2. Other viruses and bacteria can infect the lungs. Pneumonia is a general term for inflammation caused by an infectious organism.

C. Bronchitis, Asthma, and Emphysema1. Chronic irritation of the lining of the bronchioles leads to bronchitis, in which there is an

excess of mucus that may promote bacterial growth.2. In asthma, and inhaled allergen or irritant triggers inflammation and constriction of

airways. 3. In emphysema, the walls of the alveoli become fibrous and inefficient in exchanging of

gases.

D. Smoking’s Impact1. Tobacco use kills millions and in the U.S. drains over $22 billion a year from the economy.2. Secondhand smoke is a real danger to innocents who do not participate in the life-

threatening habit themselves.3. Smoking marijuana may also lead to chronic throat problems, bronchitis, and emphysema.

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