Term
| Organs of the upper respiratory system |
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Definition
-nose (including nasal sinuses)
-pharynx |
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Term
| Organs of the lower respiratory system |
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Definition
-Larynx
-Trachea
-Bronchi
-Lungs (including the pulmonary) |
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Term
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Definition
| - As a preliminary passage that warms, moistens and coarsely filters the incoming air. With the nasal sinuses, it modulates the sound of speech. Additionally the nose houses the olfactory receptor cells. |
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Term
| Structure of the nasal cavity |
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Definition
The nasal cavity is lined with a mucous membrane. Because this membrane is quite vascular, it normally looks pink. Part of the mucous membrane contains the olfactory epithelium. The olfactory receptor cells are not epithelial cells, but neurons.
-The remainder of the mucous membrane is lined with pseudostratified ciliated columnar epithelium containing goblet cells. |
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Term
| Pharynx is divided into three parts |
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Definition
1) nasopharynx
2) oropharynx
3) laryngopharynx |
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Term
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Definition
| is the part nearest the nose. The two nostrils open into it, as do the two eustachian tubes. |
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Term
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Definition
| the middle part. It is lined with stratified squamous epithelium, and receives the opening of the mouth. It is the common passage for air, food, and drink. The palatine and lingual tonsils are found in the oropharynx. |
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Term
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Definition
| is the part nearest the larynx. It is also lined with stratified squamous epithelium and finally divides posteriorly into the esophagus and anteriorly into the larynx, or voice box |
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Term
| Nine pieces of cartilage of the larynx |
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Definition
single structures:
-thyroed (Adam’s apple)
-epiglottis (trapdoor that closes the larynx when swallowing)
-cricoid
Paired structures:
-arytenoid (influence position and tension of vocal cords)
-cuneiform
-coroniculate |
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Term
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Definition
| are formed from folds of the laryngeal mucous membrane lined with stratified squamous epithelium. Beneath the membrane are bands of elastic fibers. The vocal fords are manipulated by skeletal muscles that attach both to the cartilage of the larynx and to the vocal cords themselves. When the tension of the vocal cords is appropriately adjusted by the contraction of the skeletal muscles, the passage of air between them can cause theme to vibrate and emit sounds. These sounds are modified by the mouth cavity, the pharnx, the nasal cavities, and the nasal sinuses. |
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Term
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Definition
| is caused by inflamation of the mucous membrane of the larynx, and is particularly common in smokers. Cancer of the larynx is also caused by smoking. |
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Term
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Definition
| The trachea is a flexible tube that extends from the larynx to the point within the thoracic cavity where it divides into right and left bronchi that connect to the right and left lungs. It is lined with a mucous membrane covered with pseudostratified ciliated columnar epithelium containing goblet cells. The walls contain about 20 C-shaped rings of hyaline cartilage, the open part of the C facing the esophagus, which lies posteriorly to the trachea. These rings prevent collapse of the trachea from external pressure or when air is sucked strongly into the lungs during heavy breathing (exercising) |
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Term
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Definition
| The left and right branches of the trachea are called the primary bronchi. These airways continue to branch, and form a structure that is sometimes called the bronchial tree. Bronchiolar (Clara) cells are serous glandular cells that secrete a surfactant-like material that appears to coat and protect the bronchiolar lining. They also serve as epithelial stem cells. There is also some evedence that they detoxify noxious gases in inhaled air using cytochrome P-450 enzymes in the rough endoplasmic reticulum (RER) Bronchial secretions contain antibodies (immunoglobulin A=IgA) to help resist infections. |
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Term
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Definition
| In form the bronchial tree, the primary bronchi divide into secondary (lobar) bronchi, which subdivide into successively smaller tertiary bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts which outpouch to form the alveoli. The alveoli provide a large surface area of “respiratory membrane”through wich oxygen and carbon dioxide can diffuse, exchanging between the respired air in the alveoli and the blood in the pulmonary capillaries. |
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Term
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Definition
| Usually, groups of alveoli are clusted together in grape-like bunches that share common openings into alveolar ducts. These bunches of alveoli are called alveolar sacs. |
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Term
| Structural changes occur in the walls of the tubes as we proceed from the primary bronchi deeper into the bronchial tree. |
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Definition
1. There is a decrease in the amount of cartilage, which finally disappears in the in the bronchioles.
2. The walls of the tubes acquire a layer of smooth muscle and connective tissue that is rich in elastic fibers. The smooth muscle is innervated by parasympathetic nerves originating in the vagus (X) nerve. Cholinergic activity causes the bronchi to constrict and secrete mucus.
There is no sympathetic innervation of the bronchial smooth muscle, but circulating epinephrine causes dialtion. Histamine and certain peptides (reaction) cause constriction. |
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Term
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Definition
| The epithelium changes from pseudostraified ciliated columnar to nonciliated simple cuboidal in the terminal bronchioles. It contains goblet cells and mucus glands. The ciliated epithelium serves to sweep inhaled particles out of the respiratory tract into the pharynx. This arrangement is sometimes called the (“muco-cilliary escalator) |
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Term
Pulmonary Alveolar Macrophages
(PAM's) |
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Definition
| can also assist in the removal of particulate matter. THe PAMs, are phagocytic cells derived from monocytes that ingest bacteria and small dust particles. Unfortunately, they release lysosomal enzymes after ingesting very large numbers of silica, asbestos, or cigarette smoke particles, and this can cause serious inflammation. |
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Term
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Definition
| The apical surface of the alveolar epithelium is covered by a thin film of fluid containing a substance called pulmonary surfactant. Pulmonary surfactant is composed of proteins and phospholipids, and lowers the surface tension of the fluid wetting the interior surfaces of the alveoli. The alviolar epithelium consists of two cell types lying on a basement membrane. The major type consists of flat Type I epithelial cells. Type II alveolar epithelial cells secrete pulmonary surfactant. In the addition to these cells and PAM’s, the lung also contains mast cells. THe mast cells contain histamine and other substances that are involved in allergic reactions. |
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Term
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Definition
| The lungs are divided by fissures into lobes enclosed is a serous membrane the pleural membrane, which consists of the parietal pleura attached to the wall of the thoracic cavity, and the visceral pleura covering the surface of the lungs. Between the vesceral and parietal pleura is potential space (the pleural space) that is really a thin film of serous fluid that lubricates the movements of the lungs as they inflate and deflate during breathing. (like the heart and the pericardial cavity) |
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Term
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Definition
| Normally, the fluid in the pleural space makes the visceral and parietal pleura adhere to one another. However, air can enter this space from a rupture of the lung or a penetrating wound of the chest wall. The presence of air is called pneumothorax, and can lead to collapse of the lungs. |
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Term
| The lungs are an elastic structure because... |
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Definition
| the tissue surrounding the alveoli contains fibers of elastin and collagen, and the fluid film lining the alveoli has surface tension. Consequently, the lungs are expanded only when the pressure around them is lower than the alveolar pressure. During inspiration (breathing in), the diaphragm contracts and moves downwards and the intercostal muscles increase the diameter of the rib cage. This causes the lungs to expand. During expiration (breathing out) the lungs return passively to their “resting” position purely because of their own elasticity. |
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Term
| Blood supply to the lungs |
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Definition
| In addition to the blood in the pulmonary circuit, which originates in the right heart, the lungs have their own blood supply that fulfils their metabolic needs and warms the inspired air. This is supplied by the bronchial arteries, which arise from the intercostal arteries to supply the walls of the trachea and bronchi. The bronchial veins drain into the systemic veins. |
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Term
| The respiratory membrane and gas exchange in the lungs |
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Definition
| The esential function of the lungs is to exchange carbon dioxide between the air in the blood in the pulmonary capillaries. Fresh is brought into the alveoli by breathing (ventilation), and blood is pumped through the pulmonary capillaries and on into the systemic circulation by the heart. |
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Term
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Definition
| The air and blood are separated by what is called the “respiratory membrane.” It is actually made up of four components, through which oxygen and carbon dioxide must diffuse in their passage from the alveolar air to the blood or vice versa. |
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Term
| The four components of the respiratory membrane are: |
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Definition
1) A thin film of alveolar fluid containing pulmonary surfactant that contains proteins and phospholipids and lowers the surface tension. This surfactant is very important. Without it, inflation of the lungs is almost impossible.
2) The alveolar epithelium consisting of squamous epithelial cells on their own basement membrane.
3) A very thin interstitial space between the alveolar epithelium and the pulmonary capillary
4) The vascular endothelial cells of the capillary wall, resting on their own basement membrane, which sometimes fuses with the alveolar epithelial basement membrane. |
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Term
| Partial pressure of a gas is a measure of gas “concentration" |
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Definition
| Molecules of all substances diffuse from regions of high concentration to regions of lower concentration. This applies to gases such as oxygen and carbon dioxide as well. For gases in a mixture, we use an expression called partial pressure to define their concentrations. |
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Term
| partial pressure of a gas in a mixture = |
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Definition
| fraction of gas in mixture x total pressure of mixture |
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Term
| Composition of the air in the lungs |
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Definition
| There is a higher partial pressure of oxygen in inspired air (atmospheric air) than in alveolar aveolar air - 160 mm Hg compared with 104 mm Hg. Part of the effect is due to the humidification of the alveolar air with water vapor, which acts just like another gas. There is less water vapor in the atmosphere. This lowers the partial pressures of all the other gases in the mixture. Additionally, however, the air in the alveoli is not completely exchanged with fresh air at each breath. This is because there is a lot of dead space in the brochial tree and respiratory passages where no gas exchange can occur. |
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Term
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Definition
| is a mixture of dead space air and alveolar air. Dead air is inspired air wich has never exchanged oxygen and carbon dioxide with blood. Therefore, the expired air contains more oxygen and less carbon dioxide than alveolar air, but less oxygen and more carbon dioxide than atmospheric air The oxygen and carbon dioxide content of expired air therefore lies between that of inspired air and that of alveolar air. |
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Term
| How does the composition of alveolar air compare with composition of the blood in the pulmonary capillaries? |
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Definition
| When blood enters the pulmonary capillaries, its partial pressure of carbon dioxide is higher. In the pulmonary capillaries, the blood gains oxygen and loses carbon dioxide. By the time the blood has left the pulmonary capillary bed it has become completly equilibrated with alveolar air. Carbon dioxide can diffuse about 20 times as rapidly as oxygen, so it does not need such a large pressure difference for effective between the blood and alveolar air. The composition of alveolar air is determined by the rates of alveolar ventilation and transfer of oxygen and carbon dioxide between the alveolar air and the blood across the respiratory membrane. |
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Term
| In order to maintain adequate pulmonary function, it is important to match two variables: |
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Definition
- ventilation - (V = frequency x depth of breathing).
- pulmonary blood flow (sometimes called pulmonary perfusion, Q: remember that the flow of blood through the lungs is equal to the cardiac output |
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Term
| Ventilation-perfusion mismatch |
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Definition
| Failure to match ventilation and blood flow is called ventilation mismatch. V/Q scans compare lung ventilation V with pulmonary perfusion Q. |
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Term
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Definition
| inadequate ventilation of the lungs. Causes include morphine and barbiturates, which depress the central nervous system |
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Term
| Airway blockage and alveolar collapse (atelectasis) |
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Definition
| inadequate ventilation of the lung or parts of the lung |
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Term
| Adequate ventilation but inadequate blood flow (perfusion) |
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Definition
| causes include pulmonary embolism, which would reduce the blood flowing through part of a lung. |
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Term
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Definition
| The purpose of the bronchial circulation is to provide oxygenated blood to the supporting tissues of the lung and bronchi. |
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Term
| The bronchi arteries & The pulmonary arteries |
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Definition
| The bronchial arteris arise from the intercostal arteries to supply the walls of the trachea and bronchi. The bronchial veins from the larger airways and hilar region of the lungs drain via the systemic veins into the right atrium. The pulmonary arteries branch off from the pulmonary tunk, and supply deoxygenated blood from the right ventricle to the pulmonary arterioles and capillaries. The pulmonary capillaries tend to be flattened and sandwitched between adjacent alveoli so that sometimes the blood flow is in the from of thin sheets. Oxygenated blood from the pulmonary capillaries is collected the pulmonary veinules and veins, which drain into the left atrium. |
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Term
| Amount of blood: blood flow |
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Definition
| The amount of blood flowing through the lungs must be approximately equivalent to the output of the right heart. On average, the output of the right heart is the same as the left heart, and is equivalent to cardiac output. |
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Term
| Cardiac output calculation |
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Definition
| heart rate by the stroke volume |
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Term
| Pressure in the pulmonary vascular system |
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Definition
| The pulmonary vascular system is a low-resistance network of highly of highly distensible vessels. The pressure in it is there quite low. The walls of the pulmonary artery, its branches and the pulmonary arterioles are very thin and contain bery little elastin and smooth muscle. The veins are also thin and have little smooth muscle. Consequently, the pulmonary vessels - particularly the arterioles - do not have the ability of vasoconstrict as occurs in the rest of the (systemic) circulation. Consequently, autonomic innervation has no major function in controlling blood flow through the lungs. |
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Term
| The Pulmonary Circulation Is a Low Resistance and Low Pressure System |
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Definition
| Because in blood vessels off such low resistance to blood flow, the pulmonary circuit is a low-pressure system. The pressure in the pulmonary arteries is 25 mm Hg at systole, compared with 120 mm Hf at systole aorta. The total peripheral resistance is much higher than the pulmonary vascular resistance. Therefore, the effect of hydrostatic pressure gradients in the lungs can be an important determinant of blood flow in different region of a lung, ranging the apex to the base. |
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Term
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Definition
| Efficient gas exchange requires that the alveolar-capillary membrane and the alveoli themselves be kept free of large quantities of accumulated fluid. However, under some conditions pulmonary edema may develop. |
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Term
| Two causes of pulmonary Edema |
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Definition
1. There can be an increase in hydrostatic pressure in the pulmonary capillaries to an increase in left atrial and pulmonary venous pressure caused by left heat failure or mitral valve stenosis (narrowing of the orifice).
2. Increase in capillary permeability due to release of endotoxins by bacteria infecting the lungs or by breathing irritant gases (e.g. chlorine, used againist British troop during the WW1) |
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Term
| Effects of Pulmonary Edema |
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Definition
| Intersitial edema occurs first. This is followed by alveolar edema once the intersitial space has reached maximum capacity. Death from pulmonary edema can be very rapid, and is a serious danger in left heart failure. Occassionally, a rise of pulmonary capillary pressure to 50 mm Hg can occur in left heart failure, leading to death from pulmonary edema in less than 1/2 hour. |
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Term
| Angiotenisn-converting Enzyme |
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Definition
| The lungs contain angiotensis-converting enzyme, or ACE, which converts the inactive decapeptide angiotensin I to the active octapeptide angiotensin II. Angiotensin II is a vasoconstrictor, and also stimulates the adrenal cortex to secrete the mineralcorticoid aldosterone. ACE is located primarily on the surfaces of the vascular endothelial cells of the pulmonary capillaries, but is found in other tissues as well. |
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Term
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Definition
| Ventilation is the process of getting air to and from the alveoli. One important way of investigating this is by a process called “spirometry,” which can be used to measure a number of important volumes associated with breathing. A knowledge of these volumes can be valuable in diseases such as emphysema and pneumonia, and bronchial asthma |
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Term
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Definition
.5 liters.
Volume of air moved in or out during quiet respiration. |
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Term
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Definition
4.6 liters.
The volume of air one can breathe out after a maximal inspiration. |
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Term
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Definition
3.5 liters.
Maximum volume that can be inhaled after a normal expiration |
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Term
| Inspiratory Reserve Volume |
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Definition
3.0 liters.
Maximum volume that can be inhaled after you have completed a normal inspiration. |
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Term
| Expiratory Reserve Volume |
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Definition
1.1 liters.
Maximum volume that can be exhaled after you have completed a normal expiration. |
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Term
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Definition
1.2 liters.
volume of gas that still remains in the lung after you have breathed out as much as you possibly can |
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Term
| Functional Residual Capacity |
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Definition
2.3 liters.
Volume of gas in the lung after a normal expiration (includes the residual volume) |
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Term
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Definition
The dead space is the volume of air in the respiratory system that is not in a position exchange oxygen and carbon dioxide with blood.
To understand the meaning of dead space, you might want to think about the consquences of increasing the size of this dead space by breathing in and out of a pipe. Obviously, if the pipe is too long and represents a large dead space, you would not survive for long because you would just be rebreathing the air at your end of the pipe and you would use up all the oxygen in it. You could call your efforts wasted ventilation. This explains why you just can’t sit on the floor of the ocean and breath in and out through a long pipe to the surface, and why you are limited in the depth to which you can use a snorkel tube |
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Term
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Definition
| The anatomic dead space represents the volume of the whole respiratory system, minus the volume of the alveoli. This is because gas exchange takes place through-out the alveoli, but not in the rest of the respiratory system. Rapid shallow respiration will therefore produce much less alveolar ventilation than slow, deep respiration that moves the same amount of air in a given time (respiratory minute volume, this is sometimes called). |
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Term
| Total (physiological) dead space |
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Definition
| Patients with lung disease often have a much larger dead space because gas exchange may not take place throughout all the alveolar volume. This can occur if some alveoli are non-functional because of an impaired blood supply or because some alveoli cannot be properly ventilated because of an impaired blood supply or because some alveoli cannot be properly ventilated because of blockages caused (for example) by inflammation and pulmonary tissue edema. This extra dead space, together with anatomical dead space, constitutes the total (= physiological) dead space. A simple definition of the total dead space is that it is the volume of air that does not equilibrate with the blood. it represents wasted ventilation. In the healthy individuals under normal breathing conditions, the total dead space and the anatomic dad space are nearly the same, because all the air in the alveoli can exchange with the blood. |
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Term
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Definition
| The lungs are elastic structures, just like balloons. They expand passively when the pressure aroung them is lower that the alveolar pressure. During inspiration (breathing in), the diaphragm contacts and moves downwards and the intercostal muscles increase the diameter of the cage. This reduces the pressure around the lungs, and causes them to expand. If there were pneumothorax (air in the plueral space), the pressure around the lungs could not be made lower than the alveolar pressure. Therefore, they cannot expand, and lung remains collapsed. |
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Term
| During quiet expiration (breathing out) |
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Definition
| the lungs return passively to their expired position purely because of their own elasticity. This property is sometimes referred to as the elastic recoil of the lungs. The opposite of elastic recoil is compliance. If the lungs have a strong tendency to return to their expired position, they are said to hve a strong elastic recoil. Clearly, if this is the case, we must also use a greater force to inflate the lungs, and they are said to be less compliant. This occurs in fibrosis and in situations where surfactant is depleted or lacking. |
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Term
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Definition
| (change in volume)/(change in pressure) |
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Term
| The elasticity of the lungs is due to: |
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Definition
-elasticity of the lung tissue
-surface tension forces that are generated at the wet surface of the alveolar epithlium (the alveolar-air interface) |
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Term
| Elasticity of the lung tissue |
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Definition
| The elasicity of lung tissue results from networks of fibers made up of collagen and elastin in the tissue surrounding the alveoli. The elastic fiber networks are stretched at low and medium lung volumes, rather like pantyhose. The collagen fibers may act to prevent overdistention of the lungs during a deep inspiration. The elasticity of the lung tissues is reduced in diseases where there is accumulation of fibrous tissue. |
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Term
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Definition
| The surface of the fluid film covering the alveolar epithelium is in contact with air filling the alveoli. In consequence, it generates a forces called surface tension. Surface tension is the force that keeps small droplets of water spherical, like the beads fromed by raindrops on the surface of a freshly waxed automobile. Therefore, it acts rather like the thin rubber on the surface of a freshly waxed automobile. Therefore, it acts rather like the thin rubber sheet that balloons are make of. |
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Term
| Surface tension must not be too high |
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Definition
| If fluid covering the surface of our alveoli lacks pulmonary surfactant, the force to inflate the lungs is enormous. |
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Term
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Definition
| Lung surfactant is a foamy material made up of lipids and proteins, that covers the surfaces of the alveoli of the lungs. Without surfactant, the surface tension of the fluid wetting the interior surfaces of the alveoli would be so that it would almost impossible to inflate the lungs. |
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Term
| Composition of pulmonary surfactant |
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Definition
| lipids - made up mainly of phosphlipids, the major one being dipalmitoyl phosphatidylcoline (DPPC) Proteins - there are four unique proteins called surfactant proteins (SP): SP-A, SP-B, SP-C, and SP-D All these substances are sythensized y the type II alveolar epithelial cells (=alveolar type II pneumocytes), which then secrete them by exocytosis. |
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Term
| Functions of pulmonary surfactant |
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Definition
a) Reduces surface tension of the alveolar-air boundary (“interface”) and makes it easier to inflate the lungs during inspiration.
b) Promotes stability of the alveoli during deflation and prevents them from collapsing at low lung volumes, when the alveoli are small. Apparently, this is because the surface tension of the surfactant becomes smaller when it is compressed in a small surface area, as would happen when the alveolus shrinks during expiration of air. |
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Term
| Adult respiratory distress syndrome |
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Definition
| can be caused by circulatory shock, various infections and trauma conditions. these conditions can cause abnormalities in surfactant properties and function. The resulting elevated surface tension at the alveolar-air interface makes it difficult to inflate the lungs, and theres is also tendency to alveolar collapse at the end of expiration (astelectasis). |
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Term
| Infant respiratory distress syndrome |
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Definition
| Because its synthesis depends on the presence of cortisol, surfactant is manufactured late in fetal life. Type II alveolar cells of babies born at 28-32 weeks (usually prematurely), are often not able to manufacture adequate amounts of pulmonary surfactant. Such babis hace to make strong efforts to inflate their lungs against the large surface tension at the surface of the alveoli. The develop infant respiratory distress syndrome (RDS). The symptoms progressively worsen over the first two to days life and the babies may die unless treated. |
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Term
| Treatment of RDS in infants |
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Definition
| Surfactant replacement therapy is now an integral part of the are of neonates. Clinicians use synthetic surfactants or get them from animals such as cows and pigs. Synthetic surfactant contains dipalmitoyl phosphatidylcholine (DPPC). THe phospholipid by itself is very effective at reducing surface tension of the alveolar-air interface. However, like natural pulmonary surfactant, it needs help from proteins. |
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