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CHAPTER 15: RESPIRATORY SYSTEM, Cheat Sheet of Anatomy

Cavite State University (CSU)Anatomy

This is a lecture note from Anatomy and Physiology class based on the book of Seeley's Anatomy and Physiology, 11th Edition.

Typology: Cheat Sheet

2022/2023

Available from 04/17/2025

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CHAPTER 15: RESPIRATORY SYSTEM
15.1 FUNCTIONS OF THE RESPIRATORY SYSTEM
1. Regulation of blood pH
2. Voice production
3. Olfaction
4. Innate immunity
15.2 ANATOMY OF THE RESPIRATORY SYSTEM
Two divisions:
1. The upper respiratory tract – includes
the nose, the pharynx (throat), and the
larynx
2. The lower respiratory tract – includes
the trachea, the bronchi, and the lungs.
Nose
Consists of the external nose and the nasal
cavity.
External nose – the visible structure that forms
a prominent feature of the face.
Nares or nostrils – are the external openings of
the nose,
Choanae – (funnels) are the openings into the
pharynx.
Nasal cavity – extends from the nares to the
choanae.
Nasal septum – a partition dividing the nasal
cavity into right and left parts.
Deviated nasal septum – occurs when the
septum bulges to one side.
Hard palate – forms the floor of the nasal
cavity, separating the nasal cavity from the oral
cavity.
Conchae – Are three prominent bony ridges
present on the lateral walls on each side of the
nasal cavity. Increase the surface area of the
nasal cavity and cause air to churn, so that it
can be cleansed, humidified, and warmed.
Paranasal sinuses – are air-filled spaces within
bone. They include the maxillary, frontal,
ethmoidal, and sphenoidal sinuses, each
named for the bones in which they are located.
Sinusitis –is inflammation of the mucous
membrane of a sinus, especially one or more of
the paranasal sinuses.
Nasolacrimal ducts - carry tears from the eyes,
also open into the nasal cavity.
Sensory receptors for the sense of smell are in
the superior part of the nasal cavity
Nasal cavity - lined with two different types of
epithelial tissues. Just inside the nares, the
lining of the cavity is composed of stratified
squamous epithelium containing coarse hairs.
The rest of the nasal cavity is lined with
pseudostratified columnar epithelial cells
containing cilia and many mucus-producing
goblet cells.
Many processes occur in the nose and nasal
cavity including:
(1) The coarse hairs just inside the nares
and the mucus produced by the goblet
cells trap large dust particles.
(2) Cilia sweep the debrisladen mucus
toward the pharynx, where it is
swallowed. The acid in the stomach kills
any bacteria that were trapped by the
mucus.
(3) Air is warmed by the blood vessels
underlying the mucous epithelium.
Sneeze reflex
Dislodges foreign substances from the
nasal cavity.
Sensory receptors detect the foreign
substances, and action potentials are
conducted along the trigeminal nerves
to the medulla oblongata, where the
reflex is triggered.
During this, the uvula and the soft
palate are depressed, so that rapidly
flowing air from the lungs is directed
primarily through the nasal passages,
although a considerable amount passes
through the oral cavity.
17–25% of people have a photic sneeze
reflex, which is stimulated by exposure
to bright light, such as the sun.
Pupillary reflex, causes the pupils to
constrict in response to bright light
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CHAPTER 15: RESPIRATORY SYSTEM

15.1 FUNCTIONS OF THE RESPIRATORY SYSTEM

  1. Regulation of blood pH
  2. Voice production
  3. Olfaction
  4. Innate immunity 15.2 ANATOMY OF THE RESPIRATORY SYSTEMTwo divisions :
  5. The upper respiratory tract – includes the nose, the pharynx (throat), and the larynx
  6. The lower respiratory tract – includes the trachea, the bronchi, and the lungs. Nose  Consists of the external nose and the nasal cavity.  External nose – the visible structure that forms a prominent feature of the face.  Nares or nostrils – are the external openings of the nose,  Choanae – (funnels) are the openings into the pharynx.  Nasal cavity – extends from the nares to the choanae.  Nasal septum – a partition dividing the nasal cavity into right and left parts.  Deviated nasal septum – occurs when the septum bulges to one side.  Hard palate – forms the floor of the nasal cavity, separating the nasal cavity from the oral cavity.  Conchae – Are three prominent bony ridges present on the lateral walls on each side of the nasal cavity. Increase the surface area of the nasal cavity and cause air to churn, so that it can be cleansed, humidified, and warmed.  Paranasal sinuses – are air-filled spaces within bone. They include the maxillary, frontal, ethmoidal, and sphenoidal sinuses , each named for the bones in which they are located.  Sinusitis –is inflammation of the mucous membrane of a sinus, especially one or more of the paranasal sinuses.  Nasolacrimal ducts - carry tears from the eyes, also open into the nasal cavity.  Sensory receptors for the sense of smell are in the superior part of the nasal cavity  Nasal cavity - lined with two different types of epithelial tissues. Just inside the nares, the lining of the cavity is composed of stratified squamous epithelium containing coarse hairs. The rest of the nasal cavity is lined with pseudostratified columnar epithelial cells containing cilia and many mucus-producing goblet cells.  Many processes occur in the nose and nasal cavity including : (1) The coarse hairs just inside the nares and the mucus produced by the goblet cells trap large dust particles. (2) Cilia sweep the debrisladen mucus toward the pharynx, where it is swallowed. The acid in the stomach kills any bacteria that were trapped by the mucus. (3) Air is warmed by the blood vessels underlying the mucous epithelium.  Sneeze reflex  Dislodges foreign substances from the nasal cavity.  Sensory receptors detect the foreign substances, and action potentials are conducted along the trigeminal nerves to the medulla oblongata, where the reflex is triggered.  During this, the uvula and the soft palate are depressed, so that rapidly flowing air from the lungs is directed primarily through the nasal passages, although a considerable amount passes through the oral cavity.  17–25% of people have a photic sneeze reflex , which is stimulated by exposure to bright light, such as the sun.  Pupillary reflex , causes the pupils to constrict in response to bright light

Pharynx  (Throat) is the common passageway for both the respiratory and the digestive systems.  Divided into three regions : (1) the nasopharynx, (2) the oropharynx (3) the laryngopharynx  Nasopharynx

  • Superior part of the pharynx.
  • It is located posterior to the choanae and superior to the soft palate, which is an incomplete muscle and connective tissue partition separating the nasopharynx from the oropharynx.
  • Lined with pseudostratified ciliated columnar epithelium that is continuous with the nasal cavity.  Uvula - (a little grape) is the posterior extension of the soft palate.  Soft palate - forms the floor of the nasopharynx.  Pharyngeal tonsil - helps defend the body against infection  Oropharynx
  • Extends from the uvula to the epiglottis, and the oral cavity opens into the oropharynx.
  • Lined with stratified squamous epithelium , which protects against abrasion.
  • Two sets of tonsils, the palatine tonsils and the lingual tonsil , are located near the opening between the mouth and the oropharynx.
  • Palatine tonsils - located in the lateral walls near the border of the oral cavity and the oropharynx.
  • Lingual tonsil - located on the surface of the posterior part of the tongue.  Laryngopharynx
  • Passes posterior to the larynx and extends from the tip of the epiglottis to the esophagus.
  • Food and drink pass through this to the esophagus.
  • lined with stratified squamous epithelium and ciliated columnar epithelium
  • Belching – result when swallowing too much air cause excess gas in the stomach Larynx  Commonly called the voicebox  Located in the anterior throat and extends from the base of the tongue to the trachea  It has three main functions : (1) Maintains an open airway (2) Protects the airway during swallowing (3) Produces the voice. The larynx consists of nine cartilage structures: three singles and three paired.  Thyroid cartilage
  • or Adam’s apple, the first single and largest
  • Attached superiorly to the hyoid bone.  Cricoid cartilage
  • The second single and most inferior cartilage of the larynx, which forms the base of the larynx on which the other cartilages rest  The thyroid and cricoid cartilages maintain an open passageway for air movement.  Epiglottis
  • Differs from the other cartilages in that it consists of elastic cartilage rather than hyaline cartilage.
  • Its inferior margin is attached to the thyroid cartilage anteriorly , and the superior part of the epiglottis projects superiorly as a free flap toward the tongue.
  • Protects the airway during swallowing. It prevents swallowed materials from entering the larynx by covering the glottis (the opening of the larynx). As
  • Divided from lobar bronchi which lead to the bronchopulmonary segments of the lungs  The bronchi continue to branch many times, finally giving rise to bronchioles. The bronchioles also subdivide numerous times to give rise to terminal bronchioles , which then subdivide into respiratory bronchioles. Each respiratory bronchiole subdivides to form alveolar ducts, long, branching ducts with many openings into alveoli.  Alveoli - (hollow sacs) are small air-filled chambers where the air and the blood come into close contact with each other.  There are about 300 million alveoli in the lungs.  Albuterol - help counteract the effects of an asthma attack by promoting smooth muscle relaxation in the walls of terminal bronchioles, so that air can flow more freely.  Respiratory membrane - it is where gas exchange between the air and blood takes place  The Respiratory membrane individual layers :
  1. A thin layer of alveolar fluid
  2. The alveolar epithelium , composed of a single layer of cells—simple squamous epithelium
  3. The basement membrane of the alveolar epithelium
  4. A thin interstitial space
  5. The basement membrane of the capillary endothelium
  6. The capillary endothelium , also composed of a single layer of cells— simple squamous epithelium  Surfactant - reduces the tendency of alveoli to recoil Pleural CavitiesParietal pleura - lines the walls of the thorax, diaphragm, and mediastinum  Visceral pleura - covers the surface of the lungs.  Pleural fluid functions: (1) It acts as a lubricant , allowing the visceral and parietal pleurae to slide past each other as the lungs and thorax change shape during respiration (2) It helps hold the pleural membranes together.  Pleurisy - an inflammation of the pleural membranes. So painful, especially when a person takes deep breaths Lymphatic SupplyTwo lymphatic supplies :
  7. The superficial lymphatic vessels are deep to the visceral pleura. They drain lymph from the superficial lung tissue and the visceral pleura.
  8. The deep lymphatic vessels follow the bronchi. They drain lymph from the bronchi and associated connective tissues.  No lymphatic vessels are located in the walls of the alveoli.  Both the superficial and deep lymphatic vessels exit the lungs at the main bronchi. 15.3 VENTILATION AND RESPIRATORY VOLUMES Ventilation
  • Or breathing , is the process of moving air into and out of the lungs.
  • regulated by changes in thoracic volume , which produce changes in air pressure within the lungs
  • There are two phases of ventilation : (1) Inspiration , or inhalation, is the movement of air into the lungs (2) Expiration , or exhalation, is the movement of air out of the lungs. Changing Thoracic VolumeMuscles of INSPIRATION
  • Include the diaphragm and the muscles that elevate the ribs and sternum, such as the external intercostals.
  • Diaphragm - is a large dome of skeletal muscle that separates the thoracic cavity from the abdominal cavity

- Sternocleidomastoid, Scalene, Pectoralis Minor, Diaphragm, and External intercostals.Muscle of EXPIRATION

  • Forceful exhalation requires a set of muscles called the muscles of expiration. These include the internal intercostals that depress the ribs and sternum. - Internal intercostals and Abdominal walls - occurs when the thoracic cavity volume decreases  Quiet INSPIRATION - Muscles of inspiration contract to increase the volume of the thoracic cavity. - Contraction of the diaphragm causes the top of the diaphragm to move inferiorly. - Contraction of the external intercostals also elevates the ribs and sternum to increase thoracic cavity volume. - The largest change in thoracic cavity volume is due to contraction of the diaphragm.  Quiet EXPIRATION
  • The diaphragm and external intercostals relax.
  • The elastic properties of the thorax and lungs cause them to recoil into a relaxed state.  Labored breathing
  • There is a much greater increase in thoracic cavity volume. All the inspiratory muscles are active, and they contract more forcefully than quiet breathing
  • Also during labored breathing, the internal intercostals and the abdominal muscles contract forcefully. This decreases thoracic cavity volume more quickly and to a greater degree than during quiet breathing. Pressure Changes and AirflowTwo physical principles govern the flow of air into and out of the lungs :
  1. Changes in volume result in changes in pressure ( INVERSELY PROPORTIONAL )
  2. Air flows from an area of higher pressure to an area of lower pressure ( DIFUSION/OSMOSIS RULES )  At the end of expiration
  • Alveolar pressure , which is the air pressure within the alveoli, is equal to atmospheric pressure , which is the air pressure outside the body.
  • No air moves into or out of the lungs because alveolar pressure and atmospheric pressure are equal  During inspiration
  • The volume of the thoracic cavity increases when the muscles of inspiration contract. The increased thoracic volume decreases the pressure in the alveoli below atmospheric pressure. Air flows into the alveoli  At the end of inspiration
  • The thorax and alveoli stop expanding. When the alveolar pressure and atmospheric pressure become equal, airflow stops.  During expiration
  • The thoracic cavity volume decreases. Consequently, alveolar pressure increases above atmospheric pressure, and air flows out of the alveoli. Lung Recoil  Is due to the elastic properties of its tissues and because the alveolar fluid has surface tension.  Surface tension – exists because the oppositely charged ends of water molecules are attracted to each other  Two factors keep the lungs from collapsing : (1) Surfactant and (2) Pressure in the pleural cavity  Surfactant
  • Is a mixture of lipoprotein molecules produced by secretory cells of the alveolar epithelium

volumes , but total lung capacity stays relatively constant. Minute volume is the total amount of air moved into and out of the respiratory system each minute. (Tidal volume times the respiratory rate). Respiratory rate is the number of breaths taken per minute Values of respiratory capacities , the sum of two or more pulmonary volumes

  1. Functional residual capacity is the expiratory reserve volume plus the residual volume. This is the amount of air remaining in the lungs at the end of a normal expiration (about 2300 mL at rest ).
  2. Inspiratory capacity is the tidal volume plus the inspiratory reserve volume. This is the amount of air a person can inspire maximally after a normal expiration (about 3500 mL at rest ).
  3. Vital capacity is the sum of the inspiratory reserve volume, the tidal volume, and the expiratory reserve volume. It is the maximum volume of air that a person can expel from the respiratory tract after a maximum inspiration (about 4600 mL ).
  4. Total lung capacity is the sum of the inspiratory and expiratory reserves and the tidal and residual volumes (about 5800 mL ). The total lung capacity is also equal to the vital capacity plus the residual volume.  Value of vital capacity that can be reduced to values not consistent with survival ( less than 500–1000 mL )  Forced expiratory vital capacity is the rate at which lung volume changes during direct measurement of the vital capacity  Asthma , in this disease contraction of the smooth muscle in the bronchioles increases the resistance to airflow.  Emphysema , in this disease changes in the lung tissue result in the destruction of the alveolar walls, collapse of the bronchioles, and decreased elasticity of the lung tissue  Chronic bronchitis , a condition when the air passages are inflamed. The swelling, increased mucus secretion, and gradual loss of cilia result in narrowed bronchioles and increased resistance to airflow. 15.4 GAS EXCHANGEVentilation supplies atmospheric air to the alveoli.  The next step in the process of respiration is the diffusion of gases between the alveoli and the blood in the pulmonary capillaries  Gas exchange between air and blood occurs at the respiratory membrane of the lungs  Major area of gas exchange is in the alveoli , some takes place in the respiratory bronchioles and alveolar ducts.  Gas exchange between blood and air does not occur in other areas of the respiratory passageways, such as the bronchioles, bronchi, and trachea.  Anatomical dead space - The volume of the passageways where there is no gas exchange between blood and air occur.  The exchange of gases across the respiratory membrane is influenced by three factors : (1) Thickness of the membrane (2) Total surface area of the respiratory membrane (3) Partial pressure of gases across the membrane **Factors That Affect Gas Exchange Respiratory
  5. Membrane Thickness**
  • The thickness of the respiratory membrane increases during certain respiratory diseases.
  • Edema , fluid accumulates in the alveoli, and gases must diffuse through a thicker than normal layer of fluid.
  • If the thickness of the respiratory membrane is doubled or tripled, the

rate of gas exchange is markedly decreased.

  • Oxygen exchange is affected before CO2 exchange because O2 diffuses through the respiratory membrane about 20 times less easily than does CO 2. Surface Area
  • 70 square meters - The total surface area of the respiratory membrane in the normal adult, which is approximately the floor area of a 25- × 30-ft room, or roughly the size of a racquetball court (20 × 40 ft).
  • Resting conditions – under these conditions a decrease in the surface area of the respiratory membrane to one-third or one-fourth of normal can significantly restrict gas exchange.
  • Strenuous exercise – during this exercise even small decrease in the surface area of the respiratory membrane can adversely affect gas exchange.
  • Possible reasons for having a decreased surface area include the :  Surgical removal of lung tissue  Destruction of lung tissue by cancer  Degeneration of the alveolar walls by emphysema 3. Partial Pressure
  • Gas molecules move randomly from higher concentration to lower concentration until an equilibrium is achieved.
  • Partial pressure of a gas - Is the pressure exerted by a specific gas in a mixture of gases, such as air.
  • For example , if the total pressure of all the gases in a mixture of gases is 760 millimeters of mercury (mm Hg), which is the atmospheric pressure at sea level, and 21% of the mixture is made up of O2 , the partial pressure for O2 is 160 mm Hg (0.21 × 760 mm Hg = 160 mm Hg). If the composition of air is 0.04% CO2 at sea level , the partial pressure for CO2 is 0.3 mm Hg (0.0004 × 760 = 0.3 mm Hg).
  • It is traditional to designate the partial pressure of individual gases in a mixture with a capital P followed by the symbol for the gas.
  • When air is in contact with a liquid, gases in the air dissolve in the liquid. The gases dissolve until the partial pressure of each gas in the liquid is equal to the partial pressure of that gas in the air.
  • Gases in a liquid, like gases in air, diffuse from areas of higher partial pressure toward areas of lower partial pressure, until the partial pressures of the gases are equal throughout the liquid. In other words, gases diffuse down their pressure gradient : from areas of higher partial pressure to areas of lower partial pressure. Movement of Gases in the Lungs  The cells of the body use O2 and produce CO. Thus, blood returning from tissues and entering the lungs has a lower Po2 and a higher Pco compared to alveolar air.  Oxygen diffuses from the alveoli into the pulmonary capillaries because the Po2 in the alveoli is greater than that in the pulmonary capillaries.  In contrast, CO2 diffuses from the pulmonary capillaries into the alveoli because the Pco2 is greater in the pulmonary capillaries than in the alveoli  When blood enters a pulmonary capillary, the Po2 and Pco2 in the capillary are different from the Po2 and Pco2 in the alveolus. By the time blood flows through the first third of the pulmonary capillary, equilibrium is achieved , and the Po2 and Pco2 in the capillary are the

(1) About 7% is transported as CO dissolved in the plasma (2) 23% is transported bound to blood proteins, primarily hemoglobin (3) 70% is transported in the form of bicarbonate ions.  Carbon dioxide ( CO2 ) reacts with water to form carbonic acid ( H2CO3 ), which then dissociates to form H+ and bicarbonate ions ( HCO3 − ):  Carbonic anhydrase – an enzyme located inside red blood cells and on the surface of capillary epithelial cells Increases the rate at which CO reacts with water to form H+ and HCO3 − in the tissue capillaries Promotes the uptake of CO2 by red blood cells.  In the capillaries of the lungs , the process is reversed, so that the HCO3 − and H+ combine to produce H2CO3, which then forms CO2 and H2O. The CO2 diffuses into the alveoli and is expired.  Carbon dioxide - has an important effect on the pH of blood.

  • As CO2 levels increase, the blood pH decreases (becomes more acidic) because CO2 reacts with H2O to form H2CO3.
  • The H+ that results from the dissociation of H2CO3 is responsible for the decrease in pH.
  • As blood levels of CO2 decline, the blood pH increases (becomes less acidic or more basic). 15.6 RHYTHMIC BREATHING12 and 20 breaths per minute - The normal rate of breathing in adults  20 to 40 per minute - the rates of breathing in children.  Rate of breathing - determined by the number of times respiratory muscles are stimulated.  Basic rhythm of breathing - is controlled by neurons within the medulla oblongata that stimulate the muscles of respiration. Respiratory Areas in the Brainstem

 Neurons involved with respiration are located in the brainstem.  Medullary respiratory center - consists of two dorsal respiratory groups, each forming a longitudinal column of cells located bilaterally in the dorsal part of the medulla oblongata, and two ventral respiratory groups, each forming a longitudinal column of cells located bilaterally in the ventral part of the medulla oblongata  Dorsal respiratory group – primarily responsible for stimulating contraction of the diaphragm.  Ventral respiratory group – primarily responsible for stimulating the external intercostal, internal intercostal and abdominal muscles.  Pre-Bötzinger complex - part of the ventral respiratory group, is now known to establish the basic rhythm of breathing.  Pontine respiratory group – is a collection of neurons in the pons Generation of Rhythmic Breathing The medullary respiratory center generates the basic pattern of normal breathing. Although the precise mechanism is not well understood, the generation of rhythmic breathing involves the integration of stimuli that start and stop inspiration.

  1. Starting inspiration. - The neurons in the medullary respiratory center that promote inspiration are continuously active. - The medullary respiratory center constantly receives stimulation from many sources, such as receptors that monitor blood gas levels and the movements of muscles and joints. - Stimulation can come from parts of the brain concerned with voluntary respiratory movements and emotions. When the inputs from all these sources reach a threshold level, somatic nervous system neurons stimulate respiratory muscles via action potentials, and inspiration starts. 2. Increasing inspiration. - Once inspiration begins, more and more neurons are activated. - The result is progressively stronger stimulation of the respiratory muscles, which lasts for approximately 2 seconds (s). 3. Stopping inspiration. - The neurons stimulating the muscles of respiration also stimulate the neurons in the medullary respiratory center that are responsible for stopping inspiration. - The neurons responsible for stopping inspiration also receive input from the pontine respiratory neurons, stretch receptors in the lungs, and probably other sources. When the inputs to these neurons exceed a threshold level, they cause the neurons stimulating respiratory muscles to be inhibited. - Relaxation of respiratory muscles results in expiration , which lasts approximately 3 s. - The next inspiration begins with step 1. Nervous Control of Breathing  Higher brain centers can modify the activity of the respiratory center. For example , controlling air movements out of the lungs makes speech possible, and emotions can make us sob or gasp.  Sneeze and cough reflexes – reflexes that can modify breathing.  Hering-Breuer reflex – reflex that supports rhythmic respiratory movements by limiting the extent of inspiration  The Hering-Breuer reflex
  • Plays an important role in regulating the basic rhythm of breathing and in preventing over inflation of the lungs in infants - Important only when the tidal volume is large, as occurs during heavy exercise in adults

numerous collateral fibers project to the respiratory center. During exercise, action potentials in the motor pathways stimulate skeletal muscle contractions, and action potentials in the collateral fibers stimulate the respiratory center

  1. Breathing increases gradually. After the immediate increase in breathing, breathing continues to increase gradually and then levels off within 4– minutes after the onset of exercise. Factors responsible for the immediate increase in breathing may play a role in the gradual increase as well  Anaerobic threshold - The highest level of exercise that can be performed without causing a significant change in blood pH.  If the exercise intensity becomes high enough to exceed the anaerobic threshold, skeletal muscles produce lactate through the process of anaerobic respiration  Lactate - released into the blood contributes to a decrease in blood pH, which stimulates the carotid bodies, resulting in increased breathing. 15.7 RESPIRATORY ADAPTATIONS TO EXERCISERegular exercise – with this exercise vital capacity increases slightly, and residual volume decreases slightly. Tidal volume at rest and during normal activities does not change.  Maximal exercise – during this exercise the tidal volume increases.  The respiratory rate at rest or during normal activities in athletes is slightly lower. However, at maximal exercise, athletes’ respiratory rate is usually increased. 15.8 EFFECTS OF AGING ON THE RESPIRATORY SYSTEMVital capacity, maximum ventilation rates, and gas exchange – factors that decrease with age.  With age, mucus accumulates within the respiratory passageways.  The movement of mucus by cilia in the trachea is less efficient because the mucus becomes more viscous and the number of cilia and their rate of movement decrease.  As a consequence, the elderly are more susceptible to respiratory infections and bronchitis.  Vital capacity decreases with age because of reduced ability to fill the lungs (decreased inspiratory reserve volume) and to empty the lungs (decreased expiratory reserve volume).  Maximum minute ventilation rates decrease in these decreases the ability to perform intense exercise. These changes are related to the weakening of respiratory muscles and the stiffening of cartilage and ribs.  Residual volume increases with age as the alveolar ducts and many of the larger bronchioles increase in diameter. This increases the dead space, which decreases the amount of air available for gas exchange. In addition, gas exchange across the respiratory membrane declines because parts of the alveolar walls are lost, which decreases the surface area available for gas exchange, and the remaining walls thicken, which decreases the diffusion of gases.  A gradual increase in resting tidal volume with age compensates for these changes. SYSTEMS PATHOLOGY Asthma
  • (Difficult breathing) is characterized by abnormally increased constriction of the trachea and bronchi in response to various stimuli, which decrease ventilation efficiency. Symptoms include rapid and shallow breathing, wheezing, coughing, and shortness of breath.
  • Three important characteristics of the disease are: Chronic airway inflammation, airway hyperreactivity, and airflow obstruction.
  • Inflammation - can block airflow through the bronchi.
  • Airway hyperreactivity - means that the smooth muscle in the trachea and bronchi contracts greatly in response to a stimulus, thus decreasing the diameter of the airway and increasing resistance to airflow.
  • Airflow obstruction – cause by inflammation and airway hyperreactivity combine
  • Foreign substances that evoke an inappropriate immune system response include:  Inhaled pollen  Animal dander  Dust mites  Droppings  Carcasses of cockroaches.
  • However, other inhaled substances, such as chemicals in the workplace or cigarette smoke , can provoke an asthma attack without stimulating an allergic reaction.
  • Asthma attack can also be stimulated by ingested substances such as some medicines.
  • Strenuous exercise – stimuli (especially in cold weather) that can precipitate asthma attack.
  • Viral infections, emotional upset, stress, air pollution, and even reflux of stomach acid into the esophagus are known to elicit asthma attacks.
  • Treatment of asthma involves avoiding the causative stimulus and taking medications. Steroids and mast cell–stabilizing agents, which prevent the release of chemical mediators from mast cells, can reduce airway inflammation.
  • Bronchodilators are used to increase airflow