Overview and Ventilation of Lungs Flashcards
External respiration
Transport of O2 and CO2 between the environment and tissues
Internal Respiration
Oxidative phosphorylation (using oxygen to generate ATP in mitochondria)
Takes place in the tissues
What are the 4 processes involved in respiration?
- Ventilation (O2 in, CO2 out)
- Diffusion @ lung (alveoli)
- Gas transport in blood
- Diffusion @ tissue level
What does diffusion in the lung involve?
Occurs in the alveoli
O2 diffuses and is taken up by BVs
What does diffusion @ tissue level involve?
CO2 taken back to lungs for ventilation
O2 utilized by tissues
Why is the respiratory system important?
One of the vital signs to be assessed in TPR
Route of entry
Route for inhalant
Involved in vocalization, defense and metabolism
Nostrils (nares)
Airways start with nares
Paired external openings
Most pliable and dilatable in horse
Most rigid in pig
Horses are ____________ breathers
Obligate nasal
Upper airways
Portion that extends fro the nares or mouth to and including the larynx
Lower airways
Extends from the subglottis (trachea) to and including the terminal bronchioles
Generations
Progressive branchings made by airways
Alveoli start to bud off respiratory bronchioles around generation 17
Species generation differences
Humans: 0-26
Horses: 43
What happens when generation number increases?
Amount of cilia, # of mucus secreting cells, submucosal glands and cartilages decrease
Cartilage in the airways
Cartilage maintained until several branching from trachea (10th gen.), then referred to as Bronchi
Prevent airways from collapsing
Bronchioles are cartilage free
Alveoli air spaces
Gas exchange takes place
Density increases with generation number
Alveolar ducts terminate as blind alveolar sacs (gen 26)
Terminal respiratory unit
Aggregation of airways arising from a terminal bronchiole along with associated blood and lymphatic vessels
Respiratory membrane makeup (out to in)
Alveolar fluid (with surfactant)
Alveolar epith.
BM of alveolar epith.
Interstitial space
BM of capillary endothelium
Capillary endothelium
Diffusion of CO2
Diffusion of O2
RBC
Respiratory membrane
Blood-air barrier
Gas diffusion compromised if this compromised
What does O2 consumption depend on?
The level activity (metabolic rate)
O2 requirements may increase up to 30x during strenuous exercise
Which species has a greater O2 demand?
Horse and dog
Basal (resting metabolism)
Smaller species consume more O2 per Kg of bodyweight than do larger species
Respiratory cycle
Consists of an inspiratory phase followed by an expiratory phase
Inspiration
Chest cavity increase and abdominal structures pushed down
Increased abdominal pressure and volume of the thoracic cavity
Decreased thoracic cavity, alveolar/pulmonary and intrapleural pressure
Expiration
Opposite of inspiration
Passive process
Relaxation of muscles, recoil of lungs, air outflow
Ventilation
Movement of air into and out of the lungs
Direction of movement is affected by relationship between intrapulmonary and atmospheric pressures
Inhalation and exhalation pressure vs. outside environment
Inhalation: P inside < P outside
Exhalation: P inside > P outside
Rest (no flow): P inside = P outside
Intrapleaural space
Sealed cavity
Pull-on lungs (inflate)
V is inversely proportional to P
Boyle’s Law
In a closed container:
V = K/P
PV= K
K=constant
What pressures are involved in ventilation?
PB= barometric (atmospheric)
PA = alveolar (pulmonary)
PIP = intrapleural (PPL)
Intrapleural pressure in always below ________
Atmospheric pressure (negative pressure)
Transpulmonary pressure (PTP)
PA- PIP = PTP
How are the pressures at rest?
End of expiration
PA= PB
Pressures during inspiration
Increase in size of chest wall:
Decreases PIP, decline in PA and subsequent airflow into the lungs
Where would PIP be highest in domestic animals
Ventral aspect of the lungs (close to sternum)
What major muscles are involved in inspiration?
Diaphragm (phrenic n.) and intercostals (internal and external)
What are the secondary muscles involved in inspiration?
Sternocleidomastroid
Neck and back muscles
Scalenes
T/F: There are no primary muscles of expiration
TRUE
passive process
What muscles are involved in forced expiration? (asthma, exercise)
Abdominal muscles and intercostals
How are volume and pressure determined?
Using Spirometry (vol) and plethysmographs (P)
Tidal volume (TV)
Volume of each breath (rest level breathing)
Inspiratory Reserve Volume (IRV)
Extra air you breathe in after inhalation
Residual volume (RV)
Volume of air left in lungs after maximum exhalation
Expiratory residual volume (ERV)`
Volume of air you can further exhale after exhalation
Vital Capacity (VC)
ERV + TV + IRV (maximum achievable TV)
Inspiratory capacity (IC)
TV + IRV
Total lung capacity (TLC)
@ maximum inhalation, max volume of air
RV + ERV + TV + IRV
Functional residual capacity (FRC)
Volume remaining in lungs after exhalation
ERV + RV
Forced expiratory volume in 1 second (FEV1)
Should be 80% of vital capacity in a healthy adult
Dead space
Where no gas exchange takes place
Anatomic + Alveolar dead space= physiologic dead space
DV= dead space air
Anatomic dead space
Conductive airways
nares to terminal bronchioles
Alveolar dead space
Poorly perfused alveoli, limited to no exchange
Respiratory frequency (f)
Number of breaths per minute
Minute ventilation
VE= TV x f = (AV + DV) x f
What happens in deadspace?
Air is cleaned, moistened and warmed
Dead space/ tidal volume ratio
DV/TV: the fraction of each breath ventilating in dead space
30% in dogs
50-75% in cattle and horse
What is tidal volume and f responsible for?
Altering the amount of air ventilating the alveoli during exercise and thermoregulation
Heat stress
Dogs (panting) small increase in TC, f and deadspace ventilation, evaporation, and heat loss
Large animals: Increase in f, DS ventilation and heat loss present
Cold stress
Increase metabolism (O2 consumption, CO2 production that needs to be eliminated)
Increased alveolar ventilation (increase TV)
Decrease in DS ventilation and f
