Respiratory Physiology Flashcards
Functions of the respiratory system
- provides O2 and eliminates CO2
- protects against microbial infection
- regulates blood pH
- contributes to phonation
- contributes to olfaciton
- blood reservoir
Upper airway parts
- nasal and oral cavity - air enters
- pharynx - composed of nasopharynx and laryngopharynx
- larynx - contains vocal cords
Air passage from larynx to lungs
larynx –> trachea –> two primary bronchi –> lungs
Trachea and primary bronchi structure
- semi-cartilaginous
- C-shaped cartilage ring in front and smooth muscle in back
- provides protection for airway and gives elasticity
Bronchi
- plates of cartilage and smooth muscle
Bronchioles
- smooth muscle
Conducting zone
- trachea, primary bronchi, bronchioles, terminal bronchioles
- no alveoli and no gas exchange
- anatomical dead space
Respiratory zone
- contains the alveoli
- initially sparse but becomes very numerous with branching
- respiratory bronchiole –> alveolar ducts –> alveolar sacs
- gas exchange
Tracheobronchial tree
- each branching is called a generation
- begin at generation 0 in trachea and goes to generation 23 at alveolar sacs
- diameter and length decrease
- number of branches and total surface area increase
Alveoli
- tiny sacs with very thin wall
- highly vascularized - many capillaries
Type I alveolar cells
- flat epithelial cells
- internal surface of alveoli is lined with liquid that contains surfactant (stabilization of sac)
- do not divide
- susceptible to inhaled or aspirated toxins
Type II alveolar cells
- not found frequently
- produce surfactant
- act as progenitor cells - able to replicate and differentiate into Type I alveolar cells
Pneumocyte
- one of the cells lining the alveoli of lung
Steps of respiration
- ventilation - movement of gas from atmosphere to alveoli by bulk flow
- exchange of O2 and CO2 between alveoli and blood system by diffusion
- transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow
- exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues by diffusion
- cellular utilization of O2 and production of CO2
How is ventilation produced?
- CNS sends excitatory drive to respiratory motor neurons that innervate respiratory muscles
- respiratory muscles contract
- changes thoracic volume and pressure
- allow for gas movement
3 categories of respiration muscles
- pump muscles
- airway muscles
- accessory muscles
Pump muscles
- make changes in pressure and volume at lungs
- inspiration - diaphragm
- expiration
Airway muscles
- muscle located at airway level and keep upper airways opens
- mostly inspiratory, some in expiration
Accessory muscles
- facilitate respiration during exercising, when there is an increased metabolic drive
Diaphragm
- most important muscle for respiration
- dome-shaped structure and separates lungs and abdominal content
- when diaphragm contracts, it moves down, allowing abdominal content to be pushed down, and rib cage to be pushed outward
- increase in thoracic volume when it contracts
External intercostals
- inspiratory pump muscle
- contract and lift the rib cage
- lateral increase in thoracic volume
- bucket handle motion
Parasternal intercostals
- inspiratory pump muscle
-contract and pull sternum forward - anterior and posterior increase of rib cage
- pump handle motion
Abdominals
- inspiratory pump muscle - active all the time
- expiratory pump muscle
- does not contract at rest
- active when making an effort to breath - stress, exercise, coughing
- return lung to resting position
Internal intercostals
- expiratory pump muscle
- relaxed at rest and recruited during forced expiration
- push rib cage down to reduce amount of air and volume of thoracic cage
Inspiration at rest
- diaphragm, external intercostals, parasternal intercostals
Inspiration when active
- stronger contraction of diaphragm and recruitment of accessory muscles
- further expanding of thoracic cavity
Expiration at rest
- no muscles are recruited
Expiration when active
- abdominal muscles contract intensely
- diaphragm is moved even higher and more air is expelled
- internal intercostals muscles contract and push rib cage down
Obstructive sleep apnea
- upper airway muscle activity is depressed when asleep
- floppy muscle
- no airflow resulting in snoring, large drops of oxygen saturation in blood, daytime sleepiness, cognitive impairment, hypertension
- treatment: mechanical device to send positive airway pressure through nasal
2 cells on trachea surface - muco-ciliary escalator
- goblet cells - sparse, produce mucus, no cilia, GEL layer, very dense fluid, distributed in patches
- ciliated cells - layer of cells with cilia on apical surface, move continuously, produce SOL layer, very low density fluid
- entrap inhaled biological and inert particulates and remove from airways
- cilia move mucus through esophagus
Macrophages in alveoli
- last defense
- smallest particulates attract the macrophages which phagocytose these particulates, digesting them, and elimination infection
Silica dust and asbestos inhalation
- macrophages can recognize but cannot digest
- breaks and kills the macrophages causing it to disintegrate and release chemotactic factors
- promotes fibroblasts and collagen
- stiff lungs –> pulmonary fibrosis
Spirometry
- test that determines amount and rate of inspired and expired air
Tidal volume
- volume of air moved in or out of the respiratory tract (breathed) during each ventilatory cycle
- approximately 0.5 L
Expiratory reserve volume
- additional volume of air that can be forcibly exhaled following a normal expiration
- accessed by expiring maximally to the maximum voluntary expiration
Inspiratory reserve volume
- additional volume of air that can be forcibly inhaled following a normal expiration
- accessed by inspiring maximally, to the maximum possible inspiration
Residual volume
- volume of air remaining in lungs after maximal expiration
- cannot be expired no matter what
- cannot be measured with spirometry test
- prevents collapsing of alveoli or atelectasis
Vital capacity
- maximal volume of air that can forcibly exhaled after maximal inspiration
- VC = TV + IRV + ERV
Inspiratory capacity
- maximal volume if air that can be forcibly inhaled
- IC + TV + IRV
Functional residual capacity
- volume of air remaining in the lungs at the end of normal expiration
- FRC = RV + ERV
Total lung capacity
- volume of air in the lungs at the end of maximal inspiration
- TLC = FRC + TV + IRV
- TLC = VC + RV
Total / minute ventilation
- amount of air that is exchanged within a rate time
= tidal volume x respiratory frequency
Alveolar ventilation
- amount of air moved into alveoli per minute
- smaller than minute ventilation because of anatomical dead space, the conducting zone (approximately 0.15 L)
= (tidal volume - dead space) x respiratory frequency
Volume of anatomic dead space is always ____, ____ from how big a breath you take
- constant; independent
To increase rate of breathing, is it more effective to take a deeper breath or increase beathing rate
- increased depth of breath
- majority of minute ventilation is dedicated to or available for gas exchange
Forced expiratory volume in 1 second - spirometry test
- patient is asked to make a maximal inspiration and then make an expiratory effort to exhale as much as they can
- FEV-1 - how much of vital capacity volume that can be expelled in 1 second (healthy person can expel most)
- FVC - total amount if air is blown out in one breath after max inspiration as fast as possible
- ratio between FEV-1/FVC represents the proportion of amount of air that is blowing out in 1 second
Obstructive lung disease
- shortness of breath due to difficulty exhaling all air from their lungs
- abnormally high amount of air still lingering in lungs
- bronchial asthma, chronic obstructive pulmonary disease or cystic fibrosis
- FEV-1 is significantly reduced
- process of expiration is much slower - lower slope
- FEV-1/FVC is reduced (<0.7)
Restrictive lung disease
- patients cannot fully filly their lungs with air, lungs are restricted from expanding
- stiffness in lung, stiffness of chest wall, weak muscles, damaged nerves, asbestos, silica dust
- FVC is reduced
- FEV-1 is reduced
- ratio will be similar
Helium dilution method
- spirometer cannot measure air the remains in lungs at the end of forced expiration
- can measure functional residual capacity
- helium is an inert gas that is not taken by vascular system but is confined to lungs
- concentration C2 is measured at the end of expiratory effort
- V2 = V1 (C1-C2) / C2
Static properties of the lung
- mechanical properties that are present in lungs when no air is flowing
- necessary to maintain lung and chest wall at certain volume
- intrapleural pressure, transpulmonary pressure, static compliance, surface tension
Dynamic properties of the lung
- mechanical properties when lungs are changing volume and air is flowing in and out
- alveolar pressure
Boyle’s law
- fixed amount if gas at constant temperature, the pressure and volume are inversely proportional
- during expiratory phase, reduce in volume will generate an increase in alveolar pressure
- during inspiratory phase, increase in volume will generate a decrease in alveolar pressure
Bulk flow
- change in pressure will lead to gas movement from a region that has a high pressure to a region that has low pressure
Pleural tissue
- lung and chest wall is closely connected to a double layer of pleural tissue separated by inreapleural fluid
Visceral pleura
- lines to lungs
Parietal pleura
- inside of chest wall
Elastic recoil of lung and chest walls
- lungs - tendency to collapse
- chest wall - tendency to expand
- at equilibrium with each other not by direct attachment but through intrapleural space
Intrapleural pressure (Pip)
- pressure in the pleural cavity
- acts a relative vacuum
- always negative (subatmospheric)
Alveolar pressure (Palv)
- pressure of the air inside the alveoli
- Palv - Patm governs the gas exchange between lungs and atmosphere
- dynamic element directly producing air flow
Transpulmonary pressure (Ptp)
- responsible for keeping alveoli open, expressed as pressure gradient across alveolar wall
- Ptp = Palv - Pip
- static parameter that determines lung volume
Steps of inspiration
- CNS sends excitatory drive to muscles
- muscles contract and generate increase in thoracic volume
- intrapleural pressure becomes more negative
- transpulmonary pressure increases
- increases in lung volume
- decrease in alveoli pressure
- difference in pressure generates movement of gas from atmosphere into alveoli
Steps of expiration
- relaxation of inspiratory muscles
- chest wall recoils
- intrapleural pressure moves back
- transpulmonary pressure decreases
- decrease in lung volume
- increase in alveoli pressure
- movement of gas from alveoli to atmosphere
Forces that affect resistance to air flow
- inertia of respiratory system (minimal)
- friction forces: between different alveolar sacs, between lungs and chest wall, resistance that airflow incurs when enters the airway (80%)
Laminar airflow
- little resistance
- linear fashion
- small airways (terminal bronchioles)
Transitional airflow
- extra energy for resistance increase
- bronchial tree at ramifications or branches
Turbulent flow
- not smooth and laminar
- large airways (trachea, larynx, pharynx)
- high gas velocity
Resistance in first part of conducting zone and respiratory zone?
minimal
Are airways arranged in series or parallel
- parallel
- radius inverse of resistance kinda
- resistance is minimal in smaller airways
3 ways airways can be occluded
- contraction of surrounding smooth muscle
- edema (fluid) can reduce space for airflow
- mucus can reduce alveolar space at bronchioles
Lung compliance
- measure of elastic properties of the lung and measure of how easily the lungs can expand
- change in lung volume (y-axis) produced by a change in transpulmonary pressure (x-axis)
- compliance is slope of curve
Static compliance
- when no air is flowing through
- patient is asked to maximally inspire then expire and take pauses
Pulmonary fibrosis
- low lung compliance
- stiff lungs
- overproduction of collagen
- bigger effort to expand chest wall
- large change in transpulmonary pressure results in small change in lung volume
- smaller slope
Emphysema
- high lung compliance
- floppy lungs
- small change in transpulmonary pressure results in large change in lung volume
- bigger slope
- floppy lungs
- lost alveolar tissue leading to many spaces and reduction in surface for gas exchange
Dynamic compliance
- periods of gas flow (inspiration or expiration)
- not just elastic properties but also airway resistance
- less or equal to static compliance
- slope falls when lung stiffness or airway resistance increases