PDC Test - The Lungs
You can earn 0.25 PDC by passing the exam following this article, which has been approved for publication by NCRA's Council of the Academy of Professional Reporters.
The questions are based on the material in the article but some may require additional research. Send your answer sheet to NCRA's Continuing Education Office, 8224 Old Courthouse Road, Vienna, VA 22182, and enclose a check for $40 (member) or $50 (non-member) to cover the processing fee.
Man can live for weeks without food. He can live for days without water. But he can exist without air for only a few minutes. Without air, skeletal muscles will not contract, the brain cells will fail, the heart will not beat.
Almost all forms of life require air. It would be more accurate to say life requires oxygen, one of the several gases present in air. Oxygen is needed to burn the food, or fuel, present in living cells.
Where does oxygen come from? Why isn't it all used up sooner or later? The oxygen is produced by the plant life on the land and in the sea. Scientists estimate that algae in the ocean provide almost 90 percent of the oxygen in our atmosphere; the rest is produced by plants on land. When the plant life uses sunlight energy to make carbohydrates (starches and sugars) from water and carbon dioxide, oxygen is released.
The process through which the body combines oxygen with food substances and thus produces energy is called respiration. It is one side of a cycle of life; the other side is photosynthesis. The water and carbon dioxide released by the respiration of cells are returned to nature's reservoir of raw materials to be used again by plants.
Humans, like other larger and more complicated animals, have their oxygen delivered to the body cells indirectly -- through the blood. The blood contains a chemical that is part protein and part iron pigment, called hemoglobin. The hemoglobin attracts oxygen when the blood flows through regions where oxygen is plentiful. Similarly, the carbon dioxide produced when the body cells burn their fuel is attracted by the hemoglobin as it flows through the tissues where carbon dioxide is plentiful. And it is released in the lungs where carbon dioxide is comparatively scarce.
We say comparatively scarce. Carbon dioxide is always present in the atmosphere, but the proportion of carbon dioxide in air exhaled from the lungs is 100 times greater. The proportion of water vapor in air exhaled from the lungs is about 10 times greater than that of the normal atmosphere. You have seen your ``breath'' appear as a white cloud on cold days when the low temperature of the air caused the exhaled water vapor to condense.
External respiration begins and ends with the nose. Many people think of the nose as simply a part of the body that detects odors. But it has many other duties. It filters the air entering the breathing equipment, warms it, and moistens it. The nose also influences the sound of your voice -- as you may have noticed the last time you had a head cold.
The nose has been compared to an air-conditioning unit because it controls the temperature and humidity of the air entering the lungs and filters foreign particles from the air. The interior of the nose is divided by a wall of cartilage and bone called the septum. Near the middle of the nasal cavity, and on both sides of the septum, are a series of scroll-like bones called the conchae, or turbinates. The purpose of the turbinates is to increase the amount of tissue surface within the nose so that incoming air will have a greater opportunity to be ``conditioned'' before it continues on its way to the lungs.
The surfaces of the turbinates, like the rest of the interior walls of the nose, are covered with mucous membranes. These membranes secrete a fluid called mucus. The film of mucus is produced continuously and drains slowly into the throat. The mucus gives up heat and moisture to incoming air and serves as a trap for bacteria and dust in the air. It also helps dilute any irritating substances in the air.
In cold weather, the membranes may increase the flow of mucus. If the atmosphere is unusually dry, as in an improperly heated building, the mucus may lose its moisture too rapidly and the membrane may become dry and irritated.
In addition to the mucus, the membrane is coated with cilia, or hairlike filaments, that wave back and forth a dozen times per second. The millions of cilia lining the nasal cavity help the mucus clean the incoming air. When we breathe through the mouth, we lose the protective benefits of the cilia and mucus.
A number of larger filaments extending into the nasal cavity from the base of the skull are part of the special sense organ that is associated with smell. The filaments relay information to the olfactory nerve which leads to the brain. The nasal cavity has several small openings leading into the sinuses.
There are eight sinuses, four on each side, with mucous membranes that are continuous with the lining of the nose. The sinuses help equalize the air pressure in the nasal cavity, contribute to the sound of the voice, and reduce the weight of the skull. The sinus cavities are the frontal, on each side of the forehead; the maxillary, in the cheekbones on each side; the ethmoidal, a honeycomb of bone in the walls between the nasal cavity and the eye sockets; and the sphenoidal, behind the nasal cavity.
Because they are linked to the nasal cavity, the sinuses are easily irritated by the spread of infection from the nose. Blowing the nose too hard can speed the spread of infection from the nasal cavity.
The incoming air that has been filtered, warmed, and moistened in its trip through the nasal cavity next passes into the pharynx. The pharynx is one of the more complicated parts of the body since it serves as a passageway for both food and air. We all are aware that swallowing food and breathing cannot take place at the same time -- without the danger of choking. But nature has devised a way for food and air to use the same general opening, the pharynx, with only an occasional mixup.
The incoming air travels through the nasal cavity, into the pharynx, and through the larynx, or voice box, by crossing over the path used by food on its way to the stomach.
Similarly, food crosses over the route of air. When food is swallowed, a flap of cartilage called the epiglottis folds over the opening of the larynx. The base of the tongue pushes down the epiglottis as the food is moved back into the throat during the swallowing action. At the same time, the larynx moves up to help seal the opening. This action can be observed by watching a person's ``Adam's apple'' move up at the start of swallowing. The Adam's apple is part of the larynx.
On each side of the pharynx, behind the mouth cavity, are tonsils. Tonsil tissue also is located at the base of the tongue. And it may appear at the back and sides of the pharynx as adenoids. Tonsils usually are more prominent in children than adults. Their purpose is to guard the body against infections that may enter through the mouth or nose.
The larynx, also called the voice box, is at the top of the column that finally takes the air into the lungs, the trachea. However, it is the air expelled from the lungs, rather than incoming air, that is used to make voice sounds. The larynx is a tube held open by a series of nine cartilage rings. The tube is lined with mucous membrane. Two folds of membrane, the vocal cords, are attached to the front of the larynx wall and held by a pair of tiny cartilages. The cartilages are attached to muscles that contract and relax to move the vocal cords toward or away from the center of the larynx.
During ordinary breathing, the vocal cords are held toward the walls of the larynx so that air can pass without being obstructed. When we speak, the vocal cords swing over the center of the tube and muscles contract to make the vocal cords tense. The tension on the vocal cords, in addition to their length, sets the pitch of the voice. The loudness is determined by the pressure of air expelled from the lungs, thereby causing the vocal cords to vibrate. The size and shape of the mouth, nose, and other resonating chambers in the head, neck, and chest, affect the quality of the voice sounds.
Below the larynx, the trachea, also called the windpipe, continues down the neck and into the chest. A series of C-shaped rings of cartilage hold open the trachea. Lack of rigidity of the trachea permits us to bend the neck. The path of the esophagus, which carries food to the stomach, runs immediately behind that of the trachea.
At the point behind the middle of the breastbone, where the aorta arches away from the heart, the trachea divides into two branches -- the right and left bronchi. Each bronchus divides and subdivides many times into smaller cartilageringed branches that reach deep into the right and left lungs.
The tiniest bronchi, almost too small to be seen without a microscope, have cartilage rings in their walls. However, as the tubes become still smaller, they have little or no cartilage but have, instead, muscle cells in their walls. Bronchi of this size are called bronchioles. Finally, the bronchiole ends in a tiny air sac called an alveolus. The lungs contain nearly a billion of these microscopic, balloon-like alveoli. The alveoli, with their spaces air-filled, make the lungs appear somewhat like large sponges.
Each alveolus has a thin membrane wall, one cell thick. Networks of blood capillaries surround the alveoli. When air is breathed into the lungs, the molecules of oxygen gas pass through the thin membrane wall of the alveolus and through the capillary wall to become attached to the hemoglobin of a red blood cell. The blood turns a bright red after it picks up the oxygen.
Each lung is enclosed in a doublemembrane sac called the pleural sac. The sac is airtight and contains a lubricating fluid. The pleural layers keep the lung surface from rubbing against the chest wall.
Despite all the filtering equipment in the respiratory system, much foreign material accumulates in the lungs. The lungs of a child are pink, but those of an adult who has lived many years in a city are black because of bits of carbon that are deposited in the alveoli.
How do the lungs operate? They have been compared frequently to bellows. Opening the bellows causes air to rush in and fill the expanded space. Closing the bellows forces the air out again. This is approximately what happens when we breathe.
Breathing is controlled by a series of respiratory centers in the nervous system. One center is in the medulla, the part of the brain at the top of the spinal cord. Breathing action can be triggered by the centers when there is an increase in the amount of carbon dioxide in the blood or when there is a drop in the oxygen level of the blood. Forced breathing sometimes depletes the carbon dioxide in the blood. When there is not enough carbon dioxide to trigger the respiratory center, breathing will be interrupted for a moment. That is why a person may experience a ``blackout'' from rapid, forced breathing.
The respiratory centers control our ``living bellows,'' but what actually moves the bellows? The primary moving force is the diaphragm, a domeshaped sheet of muscle fibers and tendons separating the organs in the chest from the organs in the abdomen. The diaphragm is attached to the breastbone on the front, to the spinal column at the back, and to the lower ribs on the sides. When the muscle fibers of the diaphragm contract, the sheet of tissue is drawn downward, creating a partial vacuum in the chest cavity. This causes air to flow into the trachea, the bronchi, and the alveoli. Expiration occurs when the diaphragm muscles relax, closing the ``bellows'' and forcing the air out again. The intercostal muscles between the ribs also participate in the breathing action.
The rate of respiration is about 18 per minute for young adults. The rate is much higher for babies. It also is higher for adults engaged in active work or play. And in disease -- or anything causing higher than normal temperature -- the respiration rate is always increased. A man carries two quarts of oxygen in his blood, lungs, and body tissues -- enough to last about four minutes.
This article and accompanying test were prepared by BAPR member Nancy Patterson of Los Angeles, California. The article, ``The Lungs,'' is reprinted by permission of the American Medical Association from The Human Machine, copyright 1979.
Test for "The Lungs - CEU Exam"
Now it is time for the test on what you have read. Most of the answers to the questions will be found in the article. However, for some questions it will be necessary to consult a medical dictionary.
1. Human beings have their oxygen delivered to their body cells indirectly through
A. carbon dioxide
C. the blood
2. Hemoglobin is a substance in the blood that
A. attracts oxygen
B. repels oxygen
C. is found in the leukocytes
D. is manufactured in the lymph glands
3. The right and left nostrils are divided by the
A. mediastinal septum
B. ethmoidal sinus
C. parotid gland
D. nasal septum
4. The olfactory nerve is also
A. the trigeminal nerve
B. the first cranial nerve
C. a branch of the vagus nerve
D. a branch of the nervi maxillaris
5. The flap of cartilage which folds over the opening of the larynx is
A. arytenoid cartilage
B. the epiglottis
C. nasal cartilage
D. the bronchus
6. Inflammation of the serous membrane enveloping the lung is
7. Which is not a skull bone?
8. The pomum adami is part of the
A. apical bronchus
B. greater palatine
C. thyroid cartilage
D. basal lobe
9. The turbinates are also called
10. Which of the following muscles does not assist in breathing?
A. pectoralis minor
C. external intercostals
11. The medical term for throat is
12. The part of the brain at the top of the spinal cord is the
13. The serous membrane lining the chest walls is the
A. visceral pleura
B. parietal pleura
C. pleura pulmonalis
D. pericardial pleura
14. Normal breathing is triggered by
A. increased carbon dioxide in the blood
B. increased oxygen in the blood
C. decreased carbon dioxide in the blood
D. decreased epiphyseal growth
15. The bronchiole ends in a tiny air sac called
A. a bronchus
B. a pleural sac
C. an areolar
D. an alveolus
16. The amount of air that is inspired and expired during one respiratory cycle is called the
A. expiratory reserve volume
B. residual volume
C. minute volume
D. tidal volume
17. The larynx is held open by the
A. bronchial tree
B. cartilaginous rings
C. hyoid bone
D. cavernous struts
A. are held open by cartilaginous rings
B. terminate in the trachea
C. have muscle cells in their walls
D. subdivide into bronchi
19. The phrenic nerve is also called the
20. The right lung
A. has a notch for the heart
B. is smaller than the left
C. has a medial lobe
D. has two lobes
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