Week 9: Flashcards
Primary function of the pulmonary system:
Primary function of the pulmonary system is the exchange of gases between the environmental air and the blood.
Three step process for exchange of gases between environmental air and blood:
(1) ventilation
(2) diffusion
(3) perfusion,
Ventilation
The movement of air into and out of the lungs
Diffusion
The movement of gases between air spaces in the lungs and the bloodstream
Perfusion
The movement of blood into and out of the capillary beds of the lungs to the body organs and tissues.
Ventilation and Diffusion are carried out by what systems?
Pulmonary System
What parts are included in the pulmonary system?
- Two lungs
- The upper and lower airways
- The diaphragm
- The chest wall (thoracic cage)
The lungs are divided into what?
Lobes
What are the lobes of the lungs?
Three in the right lung (upper, middle, lower)
Two in the left lung (upper, lower)
Each lobe of the lungs is further divided into what?
Segments and lobules
Mediastinum
Space between the lungs
What does the mediastinum contain?
It is the space between the lungs and contains the heart, great vessels, and esophagus.
What delivers air to each section of the lung?
A set of conducting airways or bronchi
What does the lung tissue around the bronchi do?
The lung tissue that surrounds the airways supports the bronchi, preventing distortion or collapse of the airways as gas moves in and out during ventilation
Diaphragm
dome-shaped muscle that separates the thoracic and abdominal cavities and is involved in ventilation.
How are lungs protected by contaminants in inspired air?
By a series of mechanical barriers.
What is included in the upper respiratory tract (upper airways)?
- The nasopharynx
- Oropharynx
- Laryngopharynx
- Nasal Cavity
The upper airway is lined with what?
Lines with ciliated mucosa.
What does the ciliated mucosa do in the upper airways?
Warms and humidifies inspired air and removes foreign particles from it.
Larynx
Connects the upper and lower airways.
What is important about the internal larnyx?
The internal larynx muscles control vocal cord length and tension.
These muscles also contribute to voice pitch
What is important about the external larynx?
External laryngeal muscles move the larynx as a whole.
What is the trachea supported by?
U-shaped cartilage
What does the trachea connect?
The trachea connects the larynx to the bronchi
The trachea branch off into what?
The trachea branches into two bronchi
Where does the trachea branch off at?
The trachea branches into two bronchi at the carina
Where does the left and right bronchi enter the lungs?
At the hila or “roots” of the lungs
The bronchial walls have three layers:
- Epithelial lining
- Smooth muscle layer
- Connective tissue layer
The epithelial lining of the bronchi contains what?
Goblet cells and ciliated cells
Goblet cells
Produce a mucous blanket that protects the airway epithelium
Ciliated epithelial cells in the lungs- What does it do?
Ciliated epithelial cells rhythmically beat the mucous blanket (made by goblet cells) toward the trachea and pharynx, where is can be swallowed or expectorated by coughing.
Where do the conducting airways terminate?
In the:
Respiratory bronchioles
Alveolar ducts
Alveoli
The respiratory bronchioles, alveolar ducts and alveoli make up what? What do they all participate in?
These thin walled structures together are called the acinus.
All of them participate in gas exchange
What are the primary gas exchange units of the lungs?
The alveoli
What happens in the alveoli?
The alveoli are the primary gas exchange units of the lung, where oxygen enters the blood and carbon dioxide is removed.
Bronchioles subdivide to form tiny tubes called?
Alveolar ducts
Alveolar ducts end in what?
Alveolar ducts end in clusters of alveoli called alveoli sacs
What do alveolar cells do?
- Alveolar cells provide a protective interface with the environment
- Are essential for adequate gas exchange,
- Preventing entry of foreign agents, and
- maintaining mechanical stability of the alveoli.
Two major types of epithelial cells that appear in the alveolus
- Type 1
- Type 2
Type 1 Alveolar cells
Provide structure
Type 2 alveolar cells
Alveolar cells secrete surfactant
Surfactant
A lipoprotein that coats the inner surface of the alveolus and lowers alveolar surface tension at the end expiration, thereby preventing lung collapse
Where does the pulmonary artery divide and enter the lungs?
The pulmonary artery divides and enters the lung at the hila.
What occurs during pulmonary circulation?
The pulmonary circulation facilitates gas exchange, delivers nutrients to lung tissues, acts as a reservoir for the left ventricle, and serves as a filtering system that removes clots, air, and other debris from the circulation
How does pressure and resistance of pulmonary circulation compare to systemic circulation?
The pulmonary circulation has a lower pressure and resistance than the systemic circulation.
Alveolocapillary membrane
The shared alveolar and capillary walls composed the alveolocapillary membrane.
What occurs across the alveolocapillary membrane?
Gas exchange occurs across this membrane.
What does the pulmonary veins do?
Each pulmonary vein drains several pulmonary capillaries.
How are the pulmonary veins arranged in the lungs?
Pulmonary veins are dispersed randomly throughout the lung and then leave the lung at the hila and enter the left atrium.
What does bronchial circulation do?
It both moistens inspired air and supplies nutrients to the conducting airways, large pulmonary vessels, lymph nodes, and membranes (pleurae) that surround the lungs.
What does the bronchial circulation NOT do?
The bronchial circulation does not participate in gas exchange.
What happens to the pulmonary artery lumina as the smooth muscle in the arterial walls contract?
The caliber of pulmonary artery lumina decreases as smooth muscle in the arterial walls contracts.
What happens to pulmonary artery pressure when contraction of occurs?
Contraction increases pulmonary artery pressure.
What happens to caliber of pulmonary artery as muscles relax?
Caliber increases as these muscles relax, decreasing blood pressure.
Contraction (vasoconstriction) and relaxation (vasodilation) occurs in response to what?
Contraction (vasoconstriction) and relaxation (vasodilation) occurs in response to both local humoral conditions and by the autonomic nervous system (ANS)
What is the most important cause of pulmonary artery constriction?
Low alveolar partial pressure of oxygen (PAO2)
Hypoxic Pulmonary Vasoconstriction
Pulmonary artery constriction caused by low alveolar partial pressure of oxygen
What is the function of the pulmonary system? (Three things)
The pulmonary system
(1) ventilates the alveoli,
(2) diffuses gases into and out of the blood, and
(3) perfuses the lungs so that the organs and tissues of the body receive blood that is rich in O2 and deficient in CO2
Respiration
The exchange of O2 and CO2 during cellular metabolism
The “Respiratory rate” is actually what?
Ventilatory rate
Ventilatory Rate
Number of times gas is inspired and expired per minute
How is the volume of ventilation calculated?
Ventilatory rate (breaths per minute) x amount of air per breath (liters per breath or tidal volume)
Volume of ventilation is also known as?
Minute Volume or Minute ventilation
How is minute volume expressed?
Expressed in liters per minute
How to calculate effective ventilation
Ventilatory rate x tidal volume minus the dead space
Dead space ventilation (VD)
Dead-space ventilation (VD) is the volume of air per breath that does not participate in gas exchange.
Dead space ventilation is __1___without ____2___
- Ventilation
without
- Perfusion
Anatomic dead space
Volume of air in the conducting airways
Alveolar dead space
Volume of air in unperfused alveoli
What is the gaseous form of carbonic acid?
Carbon dioxide (CO2)
How is carbon dioxide produced
Carbon dioxide (CO2), the gaseous form of carbonic acid (H2CO3), is produced by cellular metabolism.
Why does CO2 need to be eliminated?
CO2 is eliminated to maintain a normal arterial CO2 pressure (PaCO 2) of 40 mm Hg and normal acid-base balance
What is needed to maintain normal PaCO2 levels?
- Adequate ventilation
- Elimination of CO2
Diseases that limit the ventilatory rate or tidal volume or both lead to?
decrease ventilation and result in CO2 retention.
How would a healthcare professional determine the adequacy of ventilation?
If a healthcare professional needs to determine the adequacy of ventilation, an arterial blood gas analysis or capnography must be performed to determine if there is CO2 retention.
What in the brainstem controls respiration?
Respiratory center
How does the respiratory center in the brainstem control respiration?
The respiratory center in the brainstem controls respiration by transmitting impulses to the respiratory muscles, causing them to contract and relax.
The respiratory center is composed of what?
Several groups of neurons
What are the several groups of neurons that makeup the respiratory center? (four groups)
The respiratory center is composed of several groups of neurons:
- The dorsal respiratory group (DRG)
- The ventral respiratory group (VRG)
- The pneumotaxic center
- The apneustic center
The basic automatic rhythm of respiration is set up by:
DRG
The dorsal respiratory group (DRG) receives input from:
Receives afferent input from peripheral chemoreceptors in the carotid and aortic bodies; from mechanical, neural, and chemical stimuli; and from receptors in the lungs.
What does the VRG contain?
The VRG contains both inspiratory and expiratory neurons
What does the VRG do during normal, quiet respiration?
It is almost inactive during normal, quiet respiration.
When does the VRG become active?
It becomes active when increased ventilatory effort is required.
Where are the pneumotaxic center and apneustic centers located?
Situated in the pons
What do the pneumotaxic center and apneustic centers do?
Act as modifiers of the rhythm established by the medullary centers.
The pattern of breathing can be influenced by
Emotion, pain and disease
What do lung receptors do- in general?
Send impulses from the lungs to the DRG:
Three types of lung receptors send impulses from the lungs to the DRG?
- Irritant receptors (C-fibers)
- Stretch receptors
- J-receptors
Where are Irritant receptors (C-fibers) found?
Irritant receptors (C fibers) are found in the epithelium of all conducting airways.
What are Irritant receptors (C fibers) sensitive to?
They are sensitive to noxious aerosols (vapors), gases, and particulate matter (e.g., inhaled dusts), which cause them to initiate the cough reflex.
When irritant receptors come across something they are sensitive to (vapors, gases dust), what happens?
They are sensitive to noxious aerosols (vapors), gases, and particulate matter (e.g., inhaled dusts), which cause them to initiate the cough reflex.
When stimulated, what do irritant receptors cause?
When stimulated, irritant receptors also cause bronchoconstriction and increased ventilatory rate.
Where are stretch receptors located?
Stretch receptors are located in the smooth muscles of airways
What are stretch receptors sensitive to?
Are sensitive to increases in the size or volume of the lungs.
What happens when Stretch receptors are stimulated?
They decrease the ventilatory rate and volume when stimulated, an occurrence sometimes referred to as the Hering-Breuer expiratory reflex.
Hering-Breuer expiratory reflex- who is it active in?
This reflex is active in newborns and assists with ventilation.
In adults when is the Hering-Breuer expiratory reflex active?
In adults, this reflex is active only at high tidal volumes (e.g., with exercise)
In adults, what does the Hering-Breuer expiratory reflex protect against?
May protect against excess lung inflation.
What mediates the cough reflex?
Bronchopulmonary C fibers and a subset of stretch-sensitive, pH-sensitive myelinated sensory nerves mediate the cough reflex.
Where are J-receptors located?
J-receptors (juxtapulmonary capillary receptors) are located near the capillaries in the alveolar septa.
What are J-receptors sensitive to?
They are sensitive to increased pulmonary capillary pressure
What happens when J-receptors are stimulated?
They are sensitive to increased pulmonary capillary pressure, which stimulates them to initiate rapid, shallow breathing; hypotension; and bradycardia.
The lung is innervated by
By the ANS
Fibers of the sympathetic division in the lung branch- —–SKIP SLIDE
Fibers of the sympathetic division in the lung branch from the upper thoracic and cervical ganglia of the spinal cord.
upper thoracic & cervical ganglia –> spinal cord
Fibers of the parasympathetic division in the lung branch
Fibers of the parasympathetic division of the ANS travel in the vagus nerve to the lung.
vagus nerve –> lung
How do the parasympathetic and sympathetic divisions control airway caliber (interior diameter of the airway lumen)
The parasympathetic and sympathetic divisions control airway caliber (interior diameter of the airway lumen) by stimulating bronchial smooth muscle to contract or relax.
What does the parasympathetic receptors on the lungs cause
The parasympathetic receptors cause smooth muscle to contract,
What does the sympathetic receptors on the lungs cause
sympathetic receptors cause smooth muscle to relax.
Chemoreceptors
Chemoreceptors monitor the pH, PaCO 2, and PaO 2 of arterial blood.
Two types of chemoreceptors
- Central chemoreceptors
- Peripheral chemireceptors
Where are central chemoreceptors located?
Central chemoreceptors are located near the respiratory center
What do central chemoreceptors monitor?
Monitor arterial blood indirectly by sensing changes in the pH of cerebrospinal fluid (CSF)
PaCO2
Partial Pressure of CO2
Prolonged increases in PaCO2 result in what?
prolonged increases in PaCO 2 result in renal compensation through bicarbonate (HCO3-) retention. This HCO3- gradually diffuses into the CSF, where it normalizes the pH and limits the effect on ventilatory drive
What are peripheral chemoreceptors sensitive to?
Are sensitive primarily to PaO2 levels.
Are only somewhat sensitive to changes in pH
As PaO 2 and pH decrease, what does the peripheral chemoreceptors do?
As the PaO 2 and pH decrease, peripheral chemoreceptors, particularly in the carotid bodies, send signals to the respiratory center to increase ventilation.
However, the PaO 2 must drop well below normal (to approximately 60 mm Hg) before the peripheral chemoreceptors have much influence on ventilation.
What do the mechanics of breathing involve?
- Major and accessory muscles of inspiration and expiration
- Elastic properties of the lungs and chest wall
- Resistance to airflow through the conducting airways
What are the major muscles of inspiration?
- Diaphragm
- External intercostal muscles (muscles between ribs)
Interaction of Forces During Inspiration and Expiration: At end of expiration
Outward recoil of the chest wall equals inward recoil of the lungs at the end of expiration.
Interaction of Forces During Inspiration and Expiration: During inspiration
During inspiration, contraction of respiratory muscles, assisted by chest wall recoil, overcomes the tendency of lungs to recoil.
Interaction of Forces During Inspiration and Expiration: At end of inspiration
At the end of inspiration, respiratory muscle contraction maintains lung expansion.
Interaction of Forces During Inspiration and Expiration: During expiration
During expiration, respiratory muscles relax, allowing elastic recoil of the lungs to deflate the lungs.
Surface tension
Surface tension refers to the tendency for liquid molecules that are exposed to air to adhere to one another.
Alveolar ventilation, or distention, is made possible by
surfactant
How does surfactant effect surface tension?
lowers surface tension by coating the air-liquid interface in the alveoli.
Surfactant
a lipoprotein (90% lipids and 10% protein) produced by type II alveolar cells
Two groups of surfactants:
One group consists of small hydrophobic molecules that have a detergent-like effect that separates the liquid molecules, thereby decreasing alveolar surface tension.
The second group of surfactant proteins consists of large hydrophilic molecules called collectins that are capable of inhibiting foreign pathogens
The decrease in surface tension caused by surfactant is responsible for:
Keeping the alveoli free of fluid
What happens if surfactant is not produced in large quantities?
If surfactant is not produced in adequate quantities, alveolar surface tension increases, causing alveolar collapse, decreased lung expansion, increased work of breathing, and severe gas-exchange abnormalities.
Elastic recoil
Elastic recoil is the tendency of the lungs to return to the resting state after inspiration.
Normal elastic recoil allows what?
Normal elastic recoil permits passive expiration, eliminating the need for major muscles of expiration.
Under normal conditions, how does the chest wall recoil?
Under normal conditions, the chest wall tends to recoil by expanding outward.
Under normal conditions, how does the lungs tend to recoil?
The lungs to recoil or inward collapse around the hila.
How to create a negative intrapleural pressure?
The opposing forces of the chest wall and lungs create the small negative intrapleural pressure.
What occurs during inspiration?
During inspiration,:
the diaphragm and intercostal muscles contract,
air flows into the lungs,
and the chest wall expands.
What occurs during expiration?
During expiration,
the muscles relax and
the elastic recoil of the lungs causes the thorax to decrease in volume until a balance between the chest wall and lung recoil forces is reached
Compliance
Compliance is the measure of lung and chest wall distensibility
What is compliance determined by?
Compliance is determined by the alveolar surface tension and the elastic recoil of the lung and chest wall.
What does increased compliance indicate?
Increased compliance indicates that the lungs or chest wall is abnormally easy to inflate and has lost some elastic recoil.
What does a decrease in compliance indicate?
A decrease in compliance indicates that the lungs or chest wall is abnormally stiff or difficult to inflate.
What determines airway resistance?
is determined by the length, radius, and cross-sectional area of the airways and by the density, viscosity, and velocity of the gas.
The work of breathing is determined by
The work of breathing is determined by the muscular effort (and therefore oxygen and energy) required for ventilation.
More muscular effort is required when
when lung compliance decreases, chest wall compliance decreases, or airways are obstructed (e.g., in asthma or chronic obstructive pulmonary disease).
Example of when lung compliance decreases
Pulmonary edema
Example of when chest wall compliance decreases
in spinal deformity or obesity
Example of when airways are obstructed
in asthma or chronic obstructive pulmonary disease
How does increase in work of breathing effect O2 consumption
An increase in the work of breathing can result in a marked increase in O2 consumption and an inability to maintain adequate tidal volume and minute ventilation.
Gas transport
Gas transport is the delivery of O2 to the cells of the body and the removal of CO2.
Four steps of gas transport:
- ventilation of the lungs,
- diffusion of O2 from the alveoli into the capillary blood
- perfusion of systemic capillaries with oxygenated blood
- diffusion of O2 from systemic capillaries into the cells
Steps in transport of CO2
- diffusion of CO2 from the cells into the systemic capillaries
- perfusion of the pulmonary capillary bed by venous blood
- diffusion of CO2 into the alveoli
- removal of CO2 from the lung by ventilation
PA O 2
The amount of O2 that is available for diffusion from the alveoli into the blood
PA O 2 is determined by:
- The barometric pressure,
- Water vapor,
- The fraction of inspired oxygen (FIO2), and
- The adequacy of ventilation.
PaCO 2
Partial pressure of carbon dioxide in arterial blood
Effective gas exchange depends on:
Depends on an approximately even distribution of gas (ventilation) and blood (perfusion) in all portions of the lungs.
Alveolar oxygen tension (PAO2)
amount of oxygen available for diffusion from alveoli into blood
Arterial oxygen tension (PaO2)
Amount of oxygen available for diffusion from the arterial blood into the tissues.
Average PaO2
80mmHg-100mmHg
How is the relationship between ventilation and perfusion expressed?
The relationship between ventilation and perfusion is expressed as a ratio called the ventilation-perfusion ratio (V̇/Q̇).
The normal V/Q is called and the average number is:
respiratory quotient and is 0.8
fraction of inspired oxygen (FIO2)
The percentage of O2 in the inspired air is equal to the PO 2 (20.9%) and is called the fraction of inspired oxygen (FIO2) in room air.
O2 is transported in the blood in two forms:
O2 is transported in the blood in two forms:
- a small amount dissolves in plasma, and
- the remainder binds to hemoglobin molecules.
Why is the alveolocapillary membrane ideal for O2 diffusion?
The alveolocapillary membrane is ideal for O2 diffusion because it has a large total surface area and is very thin.
What is oxygen saturation (SaO 2) and how can it be measured?
The oxygen saturation (SaO 2) is the percentage of the available hemoglobin that is bound to O2 and can be measured using a device called an oximeter.
WHAT forms when hemoglobin molecules bind with O2?
Oxyhemoglobin (HbO2)
WHERE does hemoglobin molecules bind to O2?
Binding occurs in the lungs.
The actual binding of O2 to hemoglobin is called?
oxyhemoglobin association or hemoglobin saturation with oxygen (SaO 2).
What is the process in which O2 is released from hemoglobin called?
Hemoglobin desaturation
Name of graph where hemoglobin saturation and desaturation are plotted
oxyhemoglobin dissociation curve
What is on the x and y axis of the oxyhemoglobin dissociation curve?
x axis: PaO2
y-axis: SaO2
oxyhemoglobin dissociation curve to shift to the right means what?
A shift to the right depicts:
- Hemoglobin’s decreased affinity for O2 or
- an increase in the ease with which oxyhemoglobin dissociates and O2 moves into the cells.
oxyhemoglobin dissociation curve to shift to the left means what?
A shift to the left depicts hemoglobin’s increased affinity for O2, which promotes association in the lungs and inhibits dissociation in the tissues.
What specifically would cause the oxyhemoglobin dissociation curve to shift to the right?
acidosis (low pH)
hypercapnia (increased PaCO 2).
Hyperthermia (increased temp) and
increased 2,3-DPG levels
shift the curve to the right so that more O2 is released into the tissues.
What specifically would cause the oxyhemoglobin dissociation curve to shift to the left?
The curve is shifted to the left by:
alkalosis (high pH) and
hypocapnia (decreased PaCO 2).
Decreased temp
Low levels of 2,3 DPG
Carboxyhemoglobin
Methemoglobin
Abnormal hemoglobin
Bohr Effect
The shift in the oxyhemoglobin dissociation curve caused by changes in the CO2 and hydrogen ion concentrations in the blood
How does CO2 solubility compare to O2 solubility?
CO2 is 20 times more soluble than O2 and diffuses quickly from the tissue cells into the blood.
Reduced hemoglobin
Hemoglobin that is dissociated from O2
ETCO2
End Tidal Carbon Dioxide
End Tidal Carbon Dioxide (ETCO2)
Amount of CO2 present in exhaled air
PaCO2 stands for
Arterial CO2 tension
Arterial CO2 tension (PaCO2)
35-45mmHg
The movement of CO2 from the blood to the alveoli is primarily determined by what?
Effectiveness of ventilation
Upper airways disorders include:
- Rhinitis
- Cough
- Colds
Allergic rhinitis
An inflammatory disorder that affects the upper airway.
Major symptoms of allergic rhinitis
sneezing,
rhinorrhea (runny nose),
pruritus (itching), and
nasal congestion (stuffiness)
What causes the symptoms of rhinitis?
Caused by dilation and increased permeability of nasal blood vessels.
Several classes of drugs used for allergic rhinitis
(1) glucocorticoids (intranasal)
(2) cromolyn
(3) antihistamines (oral and intranasal)
(4) sympathomimetics (oral and intranasal).
What are the most effective drugs for treating Allergic rhinitis?
Glucocorticoids
