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CHAPTER 22-THE RESPIRATORY SYSTEM
I. THE RESPIRATORY SYSTEM-functions by supplying the body with oxygen and disposing
of carbon dioxide. To accomplish this, four processes, collectively known as respiration, must
occur:
A. Pulmonary Ventilation-movement of air into and out of the lungs so that the gases there
are continuously changed and refreshed (breathing).
B. External Respiration-movement of oxygen from the lungs to the blood and of carbon
dioxide from the blood to the lungs.
C. Transport of Respiratory Gases-movement of oxygen from the lungs to the tissue cells
of the body and of carbon dioxide from the tissue cells to the lungs. This is carried out
by blood in the cardiovascular system.
D. Internal Respiration-movement of oxygen from blood to the tissue cells and of carbon
dioxide from tissue cells to blood.
1. The first two processes are carried out by the respiratory system and the last
two processes are the responsibility of the cardiovascular system. Therefore,
both the respiratory and cardiovascular systems must work together to ensure
that body cells receive their oxygen and that carbon dioxide is removed from
the body.
2. The respiratory system is also involved in smell and speech.
II. GENERAL ANATOMY OF THE RESPIRATORY SYSTEM
A. The Major Structures that make up the Respiratory System Include:
1. The Nose, and Nasal Cavity
5. Bronchi and their smaller branches
2. The Larynx
6. The Lungs with their alveoli
3. The Pharynx
7. The Paranasal sinuses
4. The Trachea
B. Overall the Respiratory System is composed of two zones:
1. The Respiratory Zone-the actual site of gas exchange, includes the bronchioles,
alveoli and the alveolar ducts.
2. The Conducting Zone-includes all other passageways that serve as areas for
air to reach exchange zones.
III. THE NOSE AND PARANASAL SINUSES
A. The nose is the only visible portion of the Respiratory System. The nose provides an
airway for respiration, moistens and warms air, filters and cleans inspired air, serves
as a resonating chamber for speech and houses the olfactory receptors.
B. The structures of the nose are divided into the external nose and the internal nasal
cavity.
C. Major External Features of the Nose Include: the root, bridge, dorsum nasi, apex,
philtrum, and the nostrils or external nares.
1. The nose is primarily cartilage in nature and it is formed by the nasal bones, the
frontal bone and the maxillary bones.
D. The Internal Nasal Cavity-in and posterior to the external nose.
1. Air enters this cavity by passing through the nostrils (external nares).
2. This cavity is divided by a midline known as the Nasal Septum, which is formed
by the vomer bone, the perpendicular plate of the ethmoid and cartilage. The
ethmoid forms the roof of the nasal cavity and the palate forms the base of the
cavity.
3. The internal nasal cavity connects to the pharynx via two posterior openings
known as the Internal Nares.
4. The Vestibule-the portion of the nasal cavity just superior to the nostrils. This is
lined with sebaceous and sweat glands and is covered by hairs known as
vibrissae. What is the function of these hairs?
5. Olfactory mucosa-lines much of the nasal cavity. This contains smell receptors.
6. Respiratory mucosa-also lines much of the nasal cavity. This mucosa is made up
of pseudostratified ciliated columnar epithelial tissue.
a. Goblet cells are also abundant in the respiratory mucosa. What do goblet
cells do?
b. Lysozyme is also secreted by this respiratory mucosa. What does it do?
c. Capillaries and thin-walled veins are abundant beneath these mucosa
layers. These vessels act to warm incoming air as it flows over the
mucosa.
1) Epistaxis-nosebleeds, often caused by an increased blood supply
to the nasal cavity.
7. Superior, Inferior, Medial Nasal Conchae-protrude from the lateral walls of the
nasal cavity. These increase mucosal surface area within the nasal cavity and
they also enhance air flow through the cavity.
8. Paranasal Sinuses-surround the nasal cavity. These lighten the skull and aid in
warming and moistening incoming air. These also produce mucus that flows into
the nasal cavity. The paranasal cavities are located in the frontal, sphenoid,
ethmoid, and maxillary bones.
9. What is rhinitis? Sinusitis? What can happen if the adenoids are enlarged?
IV. THE PHARYNX-the throat; a funnel-shaped tube that connects the nasal cavity and mouth
superiorly to the larynx and esophagus inferiorly.
A. The Pharynx is divided into three major regions:
1. The Nasopharynx-posterior to the nasal cavity, this serves only as an air
passageway.
a. During swallowing, the uvula moves to close off the nasopharynx; thus
preventing food from moving into the nasal cavity.
b. Pharyngeal tonsil (Adenoid)-located on the posterior wall of the
nasopharynx. These trap and destroy pathogens entering the nasopharynx
via air. If these become enlarged, they can block the flow of air through
the nose and into the throat. As a result, the air is not properly warmed
before it enters the lungs. The person may breathe with their mouth open.
c. 4 Openings into the Nasopharynx
1) 2 Internal Nares
2) 2 Auditory (Eustachian) Tubes-these drain the middle ear cavity
to equalize pressure in the ear with atmospheric pressure.
2. The Oropharynx-posterior to the oral cavity, opens into the mouth through the
fauces. Both swallowed food and inhaled air pass through here.
a. This portion of the pharynx is covered by a layer of protective stratified
squamous epithelial tissue.
b. This region is separated from the nasopharynx by the soft palate.
c. 2 Pairs of Tonsils are Located in the Oropharynx:
1) The Palatine Tonsils-in the lateral walls of the facues.
2) The Lingual Tonsil-covers the base of the tongue. These are the
tonsils that are most often removed during a tonsillectomy.
3. The Laryngopharynx-opens into the larynx. Is also a passageway for food and air.
a. This structure is continuous with the esophagus (tube that carries food
to the stomach).
b. This structure also has a role in allowing us to produce certain vowel sounds.
V. THE LARYNX-the voice box, lies at the upper end of the trachea, just below the pharynx.
A. This structure connects the pharynx and trachea. It is held in place by the hyoid bone.
B. 3 Functions of the Larynx:
1. Serves as an open airway
2. Routes food and air into the proper channels
3. Voice production
C. The larynx is lined by stratified squamous epithelium and pseudostratified columnar
epithelium (which is capable of producing mucus that acts to filter dust from incoming
air).
D. The larynx is composed of 9 cartilages that form a box-like structure. Most of these are
hyaline cartilage. The 9 major cartilages that make up the Larynx include:
1. The Thyroid Cartilage-large, formed by 2 attached cartilage plates, gives a triangular
shape to the anterior portion of the larynx. This structure is often referred to as the
Adam’s Apple. It tends to be slightly larger in males than females-why is this so?
2. The Cricoid Cartilage-lower cartilage, sits atop and is anchored to the trachea.
3. Arytenoid Cartilages-paired, very small.
4. Cuneiform Cartilages-paired.
5. Corniculate Cartilages-paired.
6. Epiglottis-flexible, composed of elastic cartilage and is covered by taste buds.
a. This cartilage attaches to the superior edge of the thyroid cartilage and
the epiglottis is free on its other borders
b. When air passes into the larynx, the epiglottis remains open. However, during
swallowing, the larynx pulls the epiglottis superiorly to cover the glottis (the
hollow opening between the vocal cords).
Why is this action important?
c. The cough reflex acts to expel any materials that slip pass the epiglottis.
E. The Vocal Cords
1. True Vocal Cords-folds of elastic fibers which are stretched across the opening of
the larynx. These appear white because they are avascular. These folds vibrate as air
rushes up from the lungs; thus producing sound. The glottis is the opening between
the true vocal cords.
2. False Vocal Cords-superior to the true vocal cords. These do not produce sound.
These are only involving in helping to close the glottis during swallowing.
F. Sound Production
1. As air is forced between the vocal cords, they vibrate and produce sound waves.
2. Sound waves are modified by the nose, mouth, pharynx and the sinuses (which serve
as resonating chambers).
3. In general, the tenser the vocal cords, the higher the pitch. Longer, less tense cords
produce lower pitch. In young males, the cords begin to thicken and enlarge during
puberty. It is during this period that the male’s voice “cracks”.
G. Laryngitis-inflammation of the vocal folds. This produces changes in the voice including
hoarseness. What can cause laryngitis?
VI. THE TRACHEA (Windpipe)-cylindrical tube that connects the larynx and the 2 primary bronchi.
A. It is approximately 4 inches long and 2.5 cm in diameter. The wall of the trachea consists of
3 distinct layers: the mucosa (which is lined with pseudostratified columnar epithelial tissue
that contains cilia and goblet cells), the submucosa and adventitita.
1. Smoking inhibits the activity of and often destroys cilia in the trachea; thus coughing
becomes the only means to remove mucus from the trachea.
B. The walls of the adventitia are reinforced internally by 16-20 C-shaped rings of hyaline
cartilage. This structure provides the trachea with its great flexibility which allows the
esophagus to expand during swallowing and it provides the trachea the ability to stretch
during respiration.
C. What is the Heimlich Maneuver? What is a tracheotomy?
VII. THE BRONCHI AND THE BRONCHIAL TREE-this is the area where respiratory structures are
first encountered. The bronchial tree refers to the branched airways leading from the trachea to
microscopic air sacs in the interior of the lungs.
A. The Primary Bronchi (Right and Left) are formed where the Trachea branches (near C7).
1. One primary bronchus runs into each lung. The right primary bronchus is wider,
shorter and more vertical than the left; thus, it is a more common site for objects to
become lodged.
B. Once inside the lungs, the primary bronchi branch to form Secondary Bronchi.
1. There are three of these in the right lung and two in the left lung.
2. Secondary Bronchi branch into smaller Tertiary Bronchi which branch repeatedly
into smaller and smaller bronchi. There are about 23 orders of branching in the
bronchi. This branching is often known as the Bronchial Tree.
C. Passageways smaller than 1 mm are known as Bronchioles. The smallest of these are known
as Terminal Bronchioles which terminate in tubes known as Alveolar Ducts.
1. Alveoli-air sacs at the ends of alveolar ducts. Alveoli form clusters known as
alveolar sacs. The walls of the alveoli are covered by a thin layer of simple squamous
epithelial tissue (Type I Cells).
a. Type II Cells-scattered among the squamous epithelial cells, secrete
surfactant which reduces the surface tension of the alveolar fluids and
prevents the walls of the alveoli from sticking together and collapsing.
b. Externally, the alveoli are covered by pulmonary capillaries. THE ALVEOLI
ARE THE SITES OF EXCHANGE OF GASES BETWEEN THE AIR AND
BLOOD. There area about 3 million alveoli per lung.
D. The tissue composition of the walls of the primary bronchi resembles that of the trachea, but
as the tubes become smaller, several differences are observed:
1. Cartilage rings are replaced by smaller plates of cartilage. There is no cartilage in the
smaller bronchioles.
2. The amount of smooth muscle increases in the walls of the smaller passageways.
VIII. THE LUNGS AND PLEURA-paired structures occupying much of the thoracic cavity.
A. Each cone-shaped lung occupies its own pleural cavity. The lungs are surrounded by the rib
cage externally and the diaphragm inferiorly. The right and left lungs are separated from
each other by the mediastinum.
1. Just deep to the clavicle is the apex (pointed tip) of the lung. The base of the lung sits
on the diaphragm.
2. Hilum-located on the medial surface of the lung. Pulmonary blood vessels and
primary bronchi enter the lung through this opening.
B. The left lung is slightly smaller than the right lung.
1. The Left Lung-has an upper and lower lobe that are separated by an oblique fissure.
2. The Right Lung-has 3 lobes-an upper lobe, middle lobe and lower lobe. The
horizontal fissure divides the upper and middle lobes, while the oblique fissure
divides the middle and lower lobes.
3. Each lobe of the lung contains a number of bronchopulmonary segments that are
separated from each other by connective tissue walls (septa).
a. Each segment is served by its own artery and vein.
C. Blood Supply in the Lungs
1. Pulmonary Arteries-highly branched in the lungs, these carry ______________
blood into the lungs.
2. Capillary Networks-surround the alveoli. Oxygen diffuses into the blood through
these capillaries.
3. Pulmonary Veins-carry ___________ blood out of the lungs, back to the heart.
4. Can we explain the above statements?
D. The lungs are highly innervated with nerve fibers. These include sensory fibers and
parasympathetic and sympathetic motor fibers. Parasympathetic fibers typically constrict
the air tubes and sympathetic fibers dilate them.
E. The Pleura-form a thin, protective, double layered serous membrane around each lung.
1. What is a serous membrane?
2. 2 Layers makeup the Pleural Membranes:
a. The Parietal Pleura-covers the thoracic wall and superior portion of the
diaphragm.
b. The Visceral Pleura-covers the external surfaces of the lungs.
1) The space between these two membranes is referred to as the pleural
cavity and it is filled with pleural fluid. What is the function of this
fluid?
2) What is pleurisy?
IX. BREATHING (PULMONARY VENTILATION)
A. Breathing consists of two phases: inspiration(the period when air flows into the lungs) and
expiration (the period when gases exit the lungs).
B. Pressures Associated with Breathing
1. Atmospheric Pressure(Patm)-the pressure exerted by the air (gases) surrounding the
body. At sea level, atmospheric pressure is 760 mm Hg (or 1 atm).
a. A negative respiratory pressure indicates that the pressure in that area is less
than atmospheric pressure. The opposite is also true.
2. Intrapulmonary Pressure (Ppul) is the pressure in the alveoli. It rises and falls with
the phases of breathing but it always eventually equalizes with atmospheric pressure.
3. Intrapleural Pressure (Pip)-pressure in the pleural cavity. This is always about 4 mm
Hg less than Ppul; therefore, Pip is always negative relative to Ppul.
a. How is this negative pressure established?
1) By the natural recoil of the lungs-the lungs are elastic, so they tend to
assume the smallest size possible.
2) Due to the surface tension of the alveolar fluid-alveolar fluid surface
tension draws the alveoli to their smallest size.
b. However, the above 2 forces are countered by the natural elasticity of the
chest wall which acts to pull the thorax outward and to enlarge the lungs.
c. So, which of these forces wins? In a healthy person, neither force wins
because of the strong adhesive force between the parietal pleura and visceral
pleura.
1) Pleural fluid holds the parietal pleura and visceral pleura together
tightly, thus, it is difficult to separate the pleura. The end result is a
negative Pip.
4. Transpulmonary Pressure-the difference between Ppul and Pip (Ppul-Pip). The greater
this pressure is, the larger the lungs are. This pressure directly prevents the lungs
from collapsing.
a. What is atelectasis?
b. What is a pneumothorax?
C. Pulmonary Ventilation-the process of breathing (inspiration and expiration).
1. In the lungs, volume changes lead to pressure changes and pressure changes lead to
the flow of gases to equalize the pressure.
2. Boyle’s Law-at constant temperature, the pressure of a gas varies inversely with its
volume. In other words:
P1V1=P2V2
where: P is the pressure of the gas in mm Hg
V is its volume in mm3
1 and 2 represent the initial and resulting condition
a. Gases always fill their container. Thus, in a large container, the molecules in
a given amount of gas will be far apart and the pressure will be low but if the
volume of the container is reduced, then the gas molecules will be forced
closer together and the pressure will rise. This principle can also be applied
to the thoracic cavity. When the volume of the thoracic cavity increases, then
the gas pressure in the cavity decreases; thus allowing air to rush into the
thoracic cavity from the atmosphere.
3. Inspiration-period when air flows into the lungs.
a. Quiet Inspiration-normal inspiration. Quiet Inspiration is produced by:
1) The Diaphragm-as this muscle contracts, it moves inferiorly and
flattens out. This increases the height (volume) of the thoracic cavity.
2) Action of the Intercostal Muscles
a) As the external intercostals contract, they lift the rib cage and
pull the sternum superiorly, thus increasing the volume of the
thorax.
b) These two activities increase the size of the thoracic cavity
by only a few millimeters, however, this is enough to increase
thoracic cavity volume by about 500 ml.
c) As volume increases in the thoracic cavity, the lungs are
stretched and intrapulmonary volume increases. As a result,
Ppul drops about 1mm Hg relative to atmospheric pressure.
1) When Ppul is less than Patm, then air rushes into the
lungs.
2) Inspiration ends when Ppul = Patm.
b. During Deep or Forced Inspiration that occurs during exercise and related
events, the thoracic volume is further increased by the activity of accessory
muscles (including the scalene, the sternocleidomastoid and the pectoralis).
4. Expiration-period when air flows out of the lungs.
a. This is a passive process that depends more on lung elasticity than on muscle
contraction.
b. As the inspiratory muscles relax and resume their resting state, the rib cage
descends and the lungs recoil. Thus, both the thoracic and intrapulmonary
volumes decrease. This compresses the alveoli and Ppul rises to about 1 mm
Patm. This creates a pressure gradient in which air then flows out of the lungs.
c. Forced Expiration is an active process produced by contraction of abdominal
wall muscles (primarily the oblique and transverses muscles). These
contractions depress the rib cage and force the internal organs against the
diaphragm. Controlling forced expiration is important for regulating precise
air flow out of the lungs. Can you think of an example?
X. FACTORS THAT INFLUENCE PULMONARY VENTILATION
A. Airway Resistance-this includes friction or drag encountered in the respiratory
passageways.
1. F = P/R where F is airflow, P is pressure and R is resistance.
2. On average, we move about 55 ml of air in and out of the lungs with each breath.
3. Normally, airway resistance is reasonably low because:
a. Airway diameters are large (relatively speaking).
b. Gas flow stops at the terminal bronchioles and diffusion takes over as the
force that controls gas movement
4. What is an acute asthma attack?
B. Alveolar Surface Tension-created where air meets blood. This is produced due to the
stronger attraction of liquid molecules for each other compared to the attraction between
the gas and air.
1. This leads to cohesion between the liquid molecules and it increases the surface
area of the liquid. This cohesion between water molecules can create enough
stress to collapse alveoli.
2. Surfactant-molecule composed of lipids and proteins that is produced by alveolar
cells. This compound reduces the cohesiveness of water molecules in the blood;
thus allowing expansion of the lungs.
C. Lung Compliance-refers to the “stretchability” of the lungs.
1. Know the equation for lung compliance from textbook.
2. The more a lung expands, the greater its compliance. High compliance leads to more
efficient ventilation.
3. Lung Compliance is determined by two factors:
a. Distensibility of lung tissue and of the thoracic cage around the lungs.
b. Alveolar surface tension.
4. What factors may reduce compliance?
XI. RESPIRATORY VOLUMES AND PULMONARY FUNCTION TESTS
A. There are four major respiratory volumes that influence the lungs: tidal volume,
inspiratory reserve volume, expiratory reserve volume and residual volume.
1. Tidal Volume (TV)-refers to the 500 ml. of air that moves into and out of the lungs
during normal, quiet breathing.
2. Inspiratory Reserve Volume (IRV)-the amount of air that can be inspired forcibly
beyond the tidal volume (2100 ml to 3200 ml).
3. Expiratory Reserve Volume (ERV)-the amount of air that can be evacuated from the
lungs after a tidal expiration (1000 ml to 1200 ml). Even after a strenuous expiration,
about 1200 ml of air remains in the lungs-this volume of air is referred to as the
Residual Volume (RV).
B. Respiratory Capacities-are created by two or more lung volumes. The major respiratory
capacities include:
1. Inspiratory Capacity (IC)-the total amount of air that can be inspired after a tidal
expiration. It is TV + IRV.
2. Functional Residual Capacity (FRC)-the combined RV and ERV values. This
represents the amount of air remaining in the lungs after a tidal expiration.
3. Vital Capacity (VC)-the total amount of exchangeable air. It is: TV + IRV + ERV.
VC is approximately 4800 ml.
4. Total Lung Capacity (TLC)-sum of all the lung volumes and is normally 6000 ml
in males and slightly less in women. Why are the volumes/capacities less in women?
C. Anatomical Dead Space-refers to air that fills respiratory passageways but never contributes
to gas exchange in the alveoli (usually about 150 ml).
D. Pulmonary Function Tests-breathing is measured by a spirometer. These tests are used to
identify various pulmonary related disorders (such as obstructive pulmonary disease).
1. Minute Ventilation-the total amount of gas that flows into or out of the respiratory
tract in 1 minute. This is normally 6L/min in quiet breathing.
2. Forced Vital Capacity (FVC)-measures the amount of gas expelled when a subject
takes a deep breath and then forcefully exhales as rapidly as possible.
3. Forced Expiratory Volume (FEV)-determines the amount of air expelled during
specific time intervals of the FVC Test.
E. Nonrespiratory Air Movements-table in textbook.
XII. BASIC PROPERTIES OF GASES
A. Gas exchange in the body occurs by bulk flow or diffusion of gas into tissues.
B. Dalton’s Law of Partial Pressure-the total pressure exerted by a mixture of gases is the
sum of the pressures exerted independently by each gas in the mixture. The pressure
exerted by each gas (its partial pressure) is proportional to the percentage of that gas in
the mixture.
C. Henry’s Law-when a mixture of gases is in contact with a liquid, each gas will dissolve
in the liquid in proportion to its partial pressure. In other words, the greater concentration
of a gas in the gas phase, the more and the faster that gas will move into solution in the
liquid.
1. What are hyperbaric chambers and how do they apply to Henry’s Law?
2. Oxygen toxicityXIII. COMPOSITION OF ATMOSPHERIC AND ALVEOLAR GAS-textbook.
XIV. EXTERNAL RESPIRATION-refers to the movement of oxygen from the lungs into the blood.
Three Factors Influence this Process:
A. Partial Pressure Gradients and Gas Solubilities
1. PO2 in the alveoli is approximately 104mm Hg compared to PO2 in the
blood which is about 40mm Hg. What does this mean?
2. PCO2 is about 5mm Hg in the alveoli and 40mm Hg in the blood.
This carbon dioxide is expelled from the lungs during expiration.
Again, what happens in this case?
3. Even though the gradients are different, equal amounts of oxygen and carbon
dioxide are exchanged with each other since carbon dioxide is much more
soluble in liquid than oxygen.
B. Ventilation-Perfusion Coupling-for gas exchange to work efficiently, ventilation (the
amount of gas reaching the alveoli) must be coupled with perfusion (blood flow in
pulmonary capillaries).
1. When PO2 is high in alveoli, pulmonary arterioles dilate, thus increasing blood
flow into the associated pulmonary capillaries. This is an attempt to empty the
oxygen into the blood.
a. When PO2 is low in alveoli, pulmonary arterioles constrict, reducing the
amount of blood flowing into the pulmonary capillaries. Notice that PO2
influences pulmonary arterioles.
2. Alveolar PCO2 influences the bronchioles, not arterioles.
a. When alveolar PCO2 levels are high, bronchioles dilate. This helps remove
remove carbon dioxide from tissues.
b. When PCO2 levels are low, bronchioles constrict. Why does this occur?
C. Thickness and Surface Area of the Respiratory Membranes-the respiratory membrane is
.5 to 1 micrometers thick. Gas exchange is very efficient through this thin surface.
XV. INTERNAL RESPIRATION (CAPILLARY GAS EXCHANGE)-movement of oxygen
from blood to the tissue cells and of carbon dioxide from tissue cells to blood.
A. In this case the partial pressures and diffusion gradients are reversed from the above
situation.
B. PO2 is always lower in tissues than in the surrounding systemic arterial blood; thus,
oxygen moves from the _______________ to the ______________. The case is
reversed for carbon dioxide. Its partial pressure is greater in tissues compared to the
surrounding blood supply, therefore, carbon dioxide moves from ____________ to
______________.
C. In summary, gas exchanges occur between the blood and alveoli and the blood and
tissues based on partial pressure gradients. These exchanges are the result of simple
diffusion across respiratory membranes.
XVI. TRANSPORT OF OXYGEN AND CARBON DIOXIDE BY THE BLOOD
A. Oxygen Transport
1. Oxygen is carried in the blood in 2 ways:
a. Attached to the red pigment hemoglobin within erythrocytes.
b. Dissolved in plasma. Only a small fraction of oxygen is carried in this
manner since oxygen is poorly soluble in water.
2. Hemoglobin (Hb)-review the structure of hemoglobin from chapter 17.
a. Oxyhemoglobin (HbO2)-refers to the combination of oxygen and
hemoglobin.
b. Reduced hemoglobin vs. Deoxyhemoglobin
c. Four oxygen molecules can attach to hemoglobin. Uptake of oxygen
molecules is increased dramatically after the first oxygen attaches to
the hemoglobin.
d. The influence of PO2 on Hemoglobin Saturation
1) Oxygen-hemoglobin dissociation curve
a) Arterial blood is almost completely saturated with
oxygen.
b) Hb is almost completely saturated with oxygen at
70mm Hg. Due to this, O2 delivery to tissues can
still be adequate when inspired air is well below
regular O2 levels (as might occur in high altitudes).
c) Only 25% of bound oxygen is released during one
systemic circuit, thus O2 is still available in venous
blood. Due to this, oxygen can be released from Hb
during periods of heavy exercise without any major
changes in respiratory or cardiac output.
e. Temperature, blood pH, and PCO2 can all influence hemoglobin saturation
rates. How might these factors influence O2 release? What is the Bohr
Effect?
f. Nitric Oxide (NO)-secreted by the lungs, is a well known vasodilator that
plays a role in regulating blood pressure.
1) Hb is a vasoconstrictor and acts to destroy nitric oxide. To
prevent this from leading to problems, NO attaches to Hb in a
fashion that prevents it from being destroyed.
3. What is hypoxia? What are the major types of hypoxia based on cause? What is
carbon monoxide poisoning?
B. Carbon Dioxide Transport
1. Normal body cells produce about 200 ml of CO2 every minute-exactly the amount
excreted by the lungs. Blood transports CO2 from the tissue cells to the lungs in
three forms:
a. Dissolved in plasma-about 10% of the CO2 is carried in this fashion.
b. Chemically bound to hemoglobin-about 20% of the CO2 is carried bound to
hemoglobin. This is greatly influenced by PCO2.
c. As bicarbonate ion in plasma-about 70% of the CO2 is carried in this form.
1) What is the bicarbonate reaction?
2) In erythtrocytes, the enzyme carbonic anhydrase quickly converts
water and carbon dioxide into carbonic acid.
3) Much of the bicarbonate produced in this process is stored for use as
part of the body’s bicarbonate buffer system.
2. The Haldane Effect-the lower the extent of Hb saturation with oxygen, the more
CO2 that can be carried in the blood.
XVII. CONTROL OF RESPIRATION
A. The Medulla Oblongata-clusters of neurons in this portion of the brain play a major role in
regulating respiration.
1. The Inspiratory Center-in the medulla. When neurons here fire, impulses are sent to
the phrenic and intercostal nerves which force the diaphragm and the
intercostals muscles to contract. As a result, the thorax expands and air rushes
into the lungs.
a. Next, this area becomes dormant and the muscles recoil forcing air out of
the lungs. This process is known as eupnea or normal respiration.
B. The Pons-also regulates respiration.
1. The Pneumotaxic Center (Pontine Respiratory Group)-sends impulses that inhibit
the inspiratory center of the medulla. This portion of the pons acts to regulate the
rhythm of breathing.
C. Factors influencing Breathing Rate and Depth
1. Breathing rate and depth are modified in response to changing body demands. The
respiratory centers in the medulla and pons contain excitatory and inhibitory
neurons.
2. Pulmonary Irritant Reflexes
a. The accumulation of mucus, dirt and debris in the respiratory system leads
to constriction of air passageways. This leads to a cough when the material
accumulates in the lungs and sneezing when the materials gather in the
nasal cavity.
3. Inflation Reflex-involves impulses from the brain that inhibit inspiration. This is
initiated by stretch receptors associated with the lungs.
4. Hyperventilation-occurs when the depth and rate of breathing are increased. This
occurs due to an increase in CO2 levels in the blood.
XVIII. RESPIRATORY ADJUSTMENTS
A. Exercise
B. At High Altitudes
XIX. HOMEOSTATIC IMBALANCES OF THE RESPIRATORY SYSTEM
A. Chronic obstructive pulmonary disease
B. Asthma
C. Tuberculosis
D. Lung cancer
E. Cystic fibrosis
XX. RELATED CLINICAL TERMS-at the end of the chapter