Repiratory Physiology Flashcards
Two functions of respiration
1) Transport oxygen to tissues
2) Transport CO2 away from tissues
Four components of respiration
1) pulmonary ventilation
2) Diffusion of O2 and CO2 between alveoli and blood
3) Transport of O2 and CO2 in blood
4) Regulation of ventilation
Components of the upper airway
Nose/ nasopharynx
Mouth/ oropharynx
Larynx/ hypopharynx
Components of Lower airway
- trachea
- main/lobar/segmental bronchi
-conducting/ terminal/ respiratory bronchioles
-Alveolar ducts - Alveolar sacs
-Alveoli
Where does gas exchange begin?
Respiratory bronchioles
Ala nasae/ alar cartilage
forms the borders of the anterior nares
Anterior nares lead into the _________ and eventually the nasal fossae,
which are separated by the ______
Anterior nares lead into the nasal vestibules and eventually the nasal fossae,
which are separated by the nasal septum
Nasal septum consists of:
The nasal septum consists of the vomer bones and the vomeronasal
and nasal septal cartilages
Nasal conchae
three nasal conchae are scroll-shaped prominences along the lateral
walls that are involved in filtration
nasal fossae leads into the nasopharynx via the _____ and also
communicates with the _____ air sinuses
nasal fossae leads into the nasopharynx via the nasal choanae and also
communicates with the paranasal air sinuses
4 paranasal air sinuses
frontal, ethmoid, maxillary, and
sphenoid sinuses
Nasal arterial perfusion
Anterior and posterior branches of ophthalmic
arteries
* Sphenopalatine artery, derived from internal maxillary
artery
Nasal venous drainage
Ethmoid veins to superior sagittal sinus
* Nasal veins to the ophthalmic veins and the
cavernous sinus
Nasal lymphatic drainage
Deep cervical lymph nodes
Nasal innervation
Afferent – olfactory nerve (CN I), ophthalmic nerve
(CN V1), maxillary nerve (CN V2)
Nose functions
Heating
* Warmed by nasal conchae and nasal
septum
* Humidification
* Humidified to nearly 100% relative humidity
* Filtration
* Nasal hairs (large particles)
* Turbulent precipitation (small particles [>6
m])
* Olfaction
Pharynx
Muscular tube that extends from skull base to the esophagus
at vertebral level C6
three parts of the pharynx and where they are
Nasopharynx – extends from nasal choanae to soft palate
* Oropharynx – extends from soft palate to epiglottis
* Hypopharynx – extends from epiglottis to esophagus
Tonsils
- Palatine (i.e., major tonsils)
- Lingual
- Tubal
- Pharyngeal (i.e., adenoids)
Larynx
Protective structure to prevent aspiration during swallowing that
extends from vertebral level C3 to C6
Supraglottic region –
Supraglottic region – extends from epiglottis to false vocal cords (i.e.,
vestibular folds)
Vestibular folds
Vestibular folds – bands of fibrous tissue covered by mucous membranes; superolateral to true
vocal cords
Laryngeal ventricles (i.e., vestibule)
space between false vocal cords and
true vocal cords
True vocal cords
fibromembranous folds attach to thyroid cartilage and arytenoids
Infraglottic region
extends from true vocal cords to trachea
larynx composition
Composed of one bone and nine cartilages, as well as
ligaments, muscles, and membranes
* Hyoid bone
* Epiglottis, thyroid, cricoid, arytenoids, corniculates, cuneiforms
* Thyrohyoid membrane, cricothyroid membrane
Muscles: Closure of laryngeal vestibule and epiglottis
aryepiglottic muscle,
oblique arytenoid
muscles, thyroepiglottic
muscle
Abduction of vestibular
folds
posterior
cricoarytenoid muscles
Adduction of vestibular
folds
interarytenoid
muscles, lateral
cricoarytenoid muscles
Lengthening of true vocal
cords
cricothyroid
muscles
Shortening of true vocal
cords
thyroarytenoid
muscles
Cormack- Lehane Classification
Grade 1 – full view of laryngeal inlet
* Grade 2a – partial view of vocal cords
* Grade 2b – view of posterior aspect of
vocal cords or
arytenoids
* Grade 3 – view of epiglottis only
* Grade 4 – no visible laryngeal structures Grade
Larynx Arterial Perfusion
Superior thyroid artery, derived from external carotid artery
* Inferior thyroid artery, derived from the thyrocervical trunk of subclavian
artery
Larynx Innervation
Ganglion nodosum of vagus nerve (CN X)
* Superior laryngeal nerve
* External branch of the superior laryngeal nerve – inferior
constrictor muscle of pharynx, cricothyroid muscles
* Internal branch of the superior laryngeal nerve –
interarytenoid muscles, sensory innervation between inferior
aspect of epiglottis and true vocal cords
* Inferior laryngeal nerve (i.e., recurrent laryngeal nerve [RLN]) – all
intrinsic laryngeal muscles except cricothyroid muscles and part
of interarytenoid muscles, sensory innervation between true vocal
cords and trachea
External branch of the superior laryngeal nerve –
inferior
constrictor muscle of pharynx, cricothyroid muscles
Internal branch of the superior laryngeal nerve –
interarytenoid muscles, sensory innervation between inferior
aspect of epiglottis and true vocal cords
Inferior laryngeal nerve (i.e., recurrent laryngeal nerve [RLN]) –
all intrinsic laryngeal muscles except cricothyroid muscles and part
of interarytenoid muscles, sensory innervation between true vocal
cords and trachea
Trachea
Protective structure to prevent airway
collapse consisting of incomplete rings of
cartilage that extends from inferior larynx
to carina
Trachea Arterial Perfusion
Inferior thyroid artery, derived from the
thyrocervical trunk of subclavian artery
* Superior thyroid artery, bronchial artery,
internal thoracic artery
Trachea Venous drainage
Inferior thyroid veins
Trachea innervation
Vagus nerve (CN X) – nociceptive,
parasympathetic
Types of bronchi
- Mainstem bronchi (rt and left mainstem bronchi derived from trachea at corina
*Lobar bronchi (3 on right, 2 on left)
*Segmental bronchi
*subsegmental bronchi
*20-25 generations
*Terminal bronchioles
Bronchi Arterial perfusion
bronchial arteries
Bronchi venous drainage
bronchial veins
bronchial innervation
sympathetic- epi/norepi from bronchial circulation- promotes bronchodilation
parasympathetic- acetylcholine from Vagus nerve- produces bronchoconstriction
* histamine and slow reactive substance of anaphylaxis also induce bronchoconstriction
Respiratory Zone
- respiratory bronchioles
- alveolar ducts
*alveolar sacs
*alveoli
Alveoli
Area of respiratory zone which functions primarily in gas exchange
Types of pneumocytes
Type I- structural
Type 2- surfactant-producing
Type 3- alveolar macrophages
Pulmonary hilum- what’s in it?
- mainstem bronchus
*pulmonary circulation
*bronchial circulation
*lymphatics/lymph nodes
*pulmonary innervation (vagus nerve, sympathetic nerves)
Thoracic cavity
consists of left pleural cavity, mediastinum, and right pleural cavity
Mediastinum
area of thoracic cavity that contains the heart, great vessels, trachea, esophagus, and thymus
Pleural cavity
space between parietal pleura and visceral pleura that contains pleural fluid; facilitates lung movement
pleura
serous membrane that separates the lungs from the mediastinum and thoracic cage
(Parietal lines chest wall, mediastinum and diaphragm)
(Visceral lines the lungs)
Muscles of inspiration
*Diaphragm
*EXternal intercostals
*Interchondral part of INternal intercostals
Accessory: sternocleidomastoid and scalenes
Muscles of Expiration
Expiration results from passive recoil of lungs
Active breathing: INternal intercostals, abdominal muscles
Diaphragm functions
- primary muscle of inspiration
*separates thoracic cavity from abdominal cavity
Boyle’s Law
P1V1=P2V2
Inspiration:
*contraction of inspiratory muscles increases the volume of the thoracic cavity, resulting in decreased alveolar pressure.
*increased atmospheric pressure (positive pressure ventilation) can drive air into lungs
Expiration: Relaxation of diaphragm causes lungs to contract, driving air out of lungs
Pleural pressure
- continuous negative pressure favoring lung expansion
*Ppl during inspiration: -7.5 cm H2O
*Ppl during expiration: -5 cm H2O
Alveolar pressure
*fluctuates to drive movement of gas
*Palv at rest: 0 cm H2O
*Palv during inspiration: -1 cm H2O
*Palv during expiration: +1 cm H2O
Transpulmonary pressure
Transpulm= Palv- Ppl
Transpulm pressure always positive and is a measure of elastic force
Diaphragm innervation
Phrenic nerve derived from C3/C4/C5
Lung Compliance
amount of force required to cause elastic deformation (i.e. expand) lung
*Measurement of lung stiffness
Compliance determined by two elastic forces:
*Elastic forces of the lung tissue (collagen, elastin)
*Elastic forced caused by alveolar surface tension
Compliance =
Volume/Pressure
Healthy lung compliance:
200 mL/ 1 cm H2O
Surface tension caused by:
Interfaces between air and water normally
cause water molecules to contract (i.e.,
create surface tension), resulting in collapse
of the air space
Surfactant:
Surfactant, secreted by type II
pneumocytes, contains phospholipids (e.g.,
dipalmitoyl phosphatidylcholine, surfactant
apoproteins) that reduce surface tension
What are the three functions of surfactant?
Reduces surface tension (i.e.,
tendency of water molecules to
contract)
* Increases lung compliance (i.e., alveoli
remain open)
* Decreases work of breathing
Factors in resistance to breathing:
*Elastic recoil of the lung
* Frictional resistance of lung tissues
* Resistance to airflow (i.e., turbulent >
laminar)
* Turbulent > laminar
* Autonomic Nervous System
* Sympathetic stimulation (e.g., epinephrine,
norepinephrine) produces bronchodilation
* Parasympathetic stimulation (e.g., acetylcholine)
produces bronchoconstriction
Reynold’s Number:
*Indicates whether flow is laminar or turbulent
What three things determine whether flow is laminar or turbulent?
Density, velocity, and diameter
What number indicates turbulent vs laminar flow?
turbulent >2300
laminar < 2300
Poiseuille’s law
describes resistance to laminar flow
According to Poiseuille’s Law, laminar flow is:
directly proportional to the pressure gradient
Directly proportionate to the radius of the tube
Inversely proportional to the viscosity
Inversely proportional to the length of the tube
Lung elastic recoil
The forces responsible for emptying the long during exhalation
Law of Laplace w/ alveolus
The force exerted by angular surface tension is inversely proportional to the radius of the alveolus
Three factors in law of Laplace
Pressure, serface tension, radius
Tidal volume
Amount of air inspired or expired with each normal breath, 500 mL
Inspiratory reserve volume
Extra amount of air that can be inspired when the person inspires with full force, 3000 mL
Expiratory reserve volume
Extra amount of air that can be expired by forceful expiration after the end of a normal tidal expiration, 1100 mL
Residual volume
Amount of air remaining the lungs after the most forceful expiration, 1200 mL
Inspiratory capacity
Amount of air that a person can breathe in, beginning at the normal expiratory level and distending the lungs to the max amount, VT plus IRV, 3500 mL
Functional residual capacity
Amount of air that remains in the lungs at the end of normal expiration, ERV plus RV, 2300 mL
Vital capacity
Maximum amount of air, a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring them to the maximum extent, ERV plus VT plus IR V, 4600 mL
Total lung capacity
Maximum amount of air that the lungs can contain with the greatest possible effort, RV plus ERV plus VT plus RV 5800 mL
Helium dilution method
Measures FRC and RV, as well as TLC.
Indirect measurement using helium
Minute ventilation
MV equals TV times RR
Normal equals 4 to 6 L per minute
Dead space
Ventilated areas that do not receive adequate perfusion to participate in gas exchange
Anatomic dead space
2 mL per kilogram
Alveolar dead space
Alveoli that are well ventilated, but poorly perfused
Physiologic dead space
sum of anatomic and alveolar dead space
Alveolar ventilation
Total volume of air each minute that is available for gas exchange
VA=RR x (TV- VD)
Bronchial circulation
High-pressure, low flow
2% of cardiac output
Supplies oxygenated blood to the conducting zone of the respiratory system
bronchial circulation path
Thoracic aorta to bronchial arteries to… To bronchial veins to azygos to hemiazygos to posterior intercostal to pulmonary veins
Pulmonary circulation
Low pressure, high flow
Supplies deoxygenated blood to respiratory zone for gas exchange
Normal RV Pressure
25/ 0-1 mm Hg
Normal PAP
25/8 mm Hg w/ a mean of 15 mm Hg
Normal Pulmonary Capillary Pressure
Mean 7 mm Hg
Normal Pulmonary Wedge pressure
5 mm Hg
Normal Left Atrial/ Pulmonary Venous Pressure
mean 2 mm Hg
Hypoxemia, hypercarbia, and acidosis cause ______ in the systemic circulation
Vasodilation
Hypoxia, hypercarbia, and acidosis cause _________ in the pulmonary circulation
vasoconstriction (i.e. hypoxic pulmonary vasoconstriction)
Hypoxic pulmonary vasoconstriction does what…?
When the oxygen concentration decreases (<73 mm Hg), blood vessels adjacent to alveolus constrict, diverting pulmonary blood flow to alveoli w/ better ventilation
Zone 1:
PAlv> Pa> Pv
Which zone has no blood flow during all of the cardiac cycle?
zone 1
Zone 2
Pa> PAlv> Pv
Which zone has intermittent blood flow?
Zone 2
Zone 3
Pa> Pv> PAlv
Which zone has continuous blood flow?
Zone 3
which pressure is actively trying to keep fluid in the capillaries?
Plasma colloid osmotic pressure
what is the normal ventilation/perfusion ratio?
0.8
Ventilation in excess of perfusion
Dead space
Perfusion in excess of ventilation
Shunt
Dalton’s law of partial pressures
Total pressure of a gas mixture is equal to the sum of the partial pressures of each constituent gas
Normal atmospheric pressure
760 mm Hg
What components make up air?
21% oxygen
79% nitrogen
Normal alveolar oxygen concentration per alveolar gas equation:
99 mm Hg
Fick’s Law describes…
the diffusion of gases across the alveolocapillary membrane
What components are important in Fick’s Law?
Membrane surface area, diffusion constant, partial pressure gradient, membrane thickness
Which part of Fick’s Law is inversely proportional?
Membrane thickness
How is oxygen transported?
0.3% physical dissolution in plasma
99.7% bound to hemoglobin
1 g Hgb can carry:
1.36 mL of O2
What causes a rightward shift?
- increased H+
- increased CO2
- increased temperature
- increased 2,3-BPG
What causes a leftward shift?
- decreased H+
- decreased CO2
- decreased temperature
- decreased 2,3-BPG
*methemoglobin
*carbon monoxide
CO2 transport
5 to 10% physical dissolution in plasma
5 to 10% in carbamino compounds
80 to 90% as bicarbonate
What is involved in a hamburger shift?
HCO3-, Cl-, and H+
CO2 is approximately ___ more soluble than O2
20 times
Bohr Effect
CO2/H+ affect the affinity of Hgb for O2
Acidosis/hypercarbia facilitate release of O2 at the peripheral tissues
Haldane Effect
O2 affects the affinity of Hgb for CO2/H+
Haldane Effect: deoxy hemoglobin has……
An increased affinity for CO2, thus facilitating transport to the lungs
Haldane Effect: oxyhemoglobin has…..
Decreased affinity for CO2, thus facilitating offloading of CO2 at the alveoli
Function of respiration is to….
Maintain homeostatic concentrations of O2, CO2, and H+ throughout the body
the dorsal respiratory group and the ventral respiratory group are located in the_____
Medulla
Dorsal is located in the nucleus of the tractus solitarius of the medulla
Ventral is located in the nucleus ambiguous and the nucleus retro ambiguous of the medulla
The dorsal respiratory group is the
Pacemaker of normal breathing
The ventral respiratory group is…
Involved in both inspiration and expiration during periods of increased ventilation
The pneumotaxic center, and the apneustic Center are located
In the pons
The pneumotaxic center does…..
Controls respiratory rate and depth (i.e., limits inspiration)
Where are the central chemo receptors located?
The medulla
The central chemo receptors are highly responsive to changes in:
CSF pH. (i.e. H+ concentration)
The blood brain barrier…
Is not readily crossed by charged ions like H+…. Gases like CO2 readily diffuse across.
In CSF, CO2 reacts with H2O to form carbonic acid, which then dissociates into HCO3- and. H+
Peripheral chemoreceptors are located in…
The aortic bodies and carotid bodies
Peripheral chemo receptors are highly responsive to:
Changes in O2
glomus cells contain O2 sensitive, potassium channels that are inactivated by hypoxemia, causing cellular depolarization
Hypoxemia generates afferent impulses that are transmitted to the medulla via:
Aortic bodies transmit via vagus nerve
Carotid bodies transmit via herring nerve, which is a branch of the Glossopharyngeal nerve
Hering- Breuer reflex
stretch receptors in the muscular walls of the bronchi and bronchioles transmit signals via the vagus nerve to the dorsal respiratory group
What does the Hering-Breuer reflex do?
Inhibit the dorsal respiratory group (i.e. inspiration)
Prevents over distention of alveoli by inhibiting high tidal volumes
sneeze nerve
Trigeminal nerve
Cough nerve
Vagus nerve
Cough sequence of events
*stimulation of nose, trachea, and bronchi
*irritation of epithelium generate afferent impulses transmitted to medulla
*rapid inspiration of air
- closure of epiglottis and true vocal cords
- forceful contraction of abdominal muscles and other accessory muscles of ventilation
- opening of epiglottis and vocal cords with forceful expulsion of irritants
compensatory mechanisms for pH, respiratory system
Fast acting
Acidosis: hyper ventilation
Alkalosis: hypoventilation
Compensatory mechanisms for pH, kidneys
Slow acting
Acidosis: increased excretion of non-volatile acid, increased retention of HCO3-
Alkalosis: decreased excretion of H+, decreased retention of HCO3-
