Respiratory overview and ventilation of the lungs Flashcards
External Respiration
Respiration involves the transport of O2 and CO2 between the environment and tissues
Internal Respiration
Is often used to refer to oxidative phosphorylation (Mitochondria)
The 4 processes of Ventilation
- Ventilation
- Diffusion @ lung
- Gas transport in blood
- Diffusion @ tissue level
Diffusion
Gases occur in the alveoli
Importance of Respiratory System
One of the Vital signs assessed in TPR (respiratory rate)
Route of entry for certain infections/agents
Route for inhalant anesthetic agent/ drug administration
Involved in vocalization, defense, metabolism etc
How do the airways start
With nostrils (nares), which are paired external openings
Nostrils are most pliable and dilatable in the horse and most rigid in the pig
Obligate nasal breathing
Horses breathing prefered in the nose because of the long epiglottis which hinders their ability to mouth breath.
What are the upper airways
Portionthatextendsfromthenaresormouthtoandincludingthelarynx.
What are the lower airways
Extendsfromthesubglottis (trachea)toandincludingtheterminalbronchioles
Generations
Airways make progressive branchings
humans have 0 to 26 generations
What happens at approximately generation 17
Alveoli start to bud off at respiratory bronchioles
What’s th 0 generation
The trachea
What’s the 1st generation
Right and left main stem bronchi
What happens as the generation number increases
As generation number increases, amount of cilia, and # of mucus secreting cells, submucosal glands and cartilages decrease
The transition from trachea to bronchi
Airways maintain cartilage until several branching from trachea (~10th generation) up to which point they are referred to as bronchi
Importance of Cartilages
Cartilages prevent airways from collapsing
Do bronchioles lack cartilage
Bronchioles are cartilage-free airways
What is the main epithelium for the upper respiratory tract ( neres to tracheobronchial tree)
pseudostratified columnar epithelium, ciliated, goblet cells secreting mucus
Epithelium for bronchioles
Cuboidal epithelium
Epithelium of type I Alveoli
The most abundant Type I pneumocytes are squamous
Epithelium of type II Alveoli
Type II (Surfactant producing) pneumocytes are cuboidal.
What are Alveolar air spaces
Are sites of gas exchange
Start to bud off at respiratory bronchioles, which also take part in gas exchange
What happens to the density of alveoli with the increase of generation number
Density of alveoli increases with generation number, and alveolar ducts finally terminate as blind alveolar sacs (generation 26)
What is the terminal respiratory unit
The aggregation of airways arising from a terminal bronchiole (resp. bronchioles, alveolar ducts and sacs) along with associated blood and lymphatic vessels
Respiratory Membrane consists of
Alveolar (alv)Epithelium with surfactant,
Alv. basement membrane,
Interstitial space,
Capillary endothelial basement membrane, and
Capillary endothelium
What does oxygen consumption depend on
Oxygen consumption depends on the level of activity (metabolic rate)
More aerobic species (horse,dog) compared to less aerobic species
More aerobic species (horse, dog) have greater oxygen demand than less aerobic sp. (cow, goat) of similar body weight; related to more mitochondrial density in sk. muscle.
More aerobic species (horse,dog) compared to less aerobic species
More aerobic species (horse, dog) have greater oxygen demand than less aerobic sp. (cow, goat) of similar body weight; related to more mitochondrial density in sk. muscle.
Training increases VO2 max
In normal animals, the need for oxygen is met with only small increase in energy cost
What does respiratory disease do to the energy cost of breathing
Resp. disease can increase the energy cost of breathing
- Hence, energy available for other needs (growth, reproduction, exercise) is affected
What is VO2 max
VO2 max is the maximal rate of oxygen consumption that can be consumed by an animal
Human adult male vomax is ~45 ml/min/kg;
Basal ( resting) metabolism
Metabolic body weight (M0.75)
smaller species consume more O2 per Kg of b.wt than do larger species
Basal ( resting) metabolism
Metabolic body weight (M0.75)
smaller species consume more O2 per Kg of b.wt than do larger species
Basal ( resting) metabolism
Metabolic body weight (M0.75)
smaller species consume more O2 per Kg of b.wt than do larger species
Respiratory cycle/ Ventilation consists of
A resp. cycle consists of an inspiratory phase followed by an expiratory phase.
Inspiration
Involves an enlargement of the thorax and lungs, with an accompanying airflow
- Due to contraction of diaphragm and intercostal muscles
Expiration
Is a passive process- relaxation of muscles, recoil of the lungs, air outflow
What is ventilation
Is the movement of air into & out of lungs
Direction of movement is affected by relationship between intrapulmonary and atmospheric pressures
Inhalation
When P inside < P outside
Exhalation
When P inside > P outside
No flow ( Rest)
When P inside= P outside
Describe Boyle’s Law
Intrapleural pressure maintains a pull-on lungs (pleural cavity is a closed space)
In a closed container, V is inversely proportional to P, Boyle’s Law:
V = K/P; PV = K
Pressures (P) involved in ventilation
PB = Barometric (atmospheric) P.
PA = Alveolar (pulmonary) P.
PIP = Intrapleural P (also PPL); that b/n parietal and visceral pleural membranes; normally a negative pressure
PTP = Transpulmonary P. = PA – PIP
Transpulmonary P. formula
PTP = Transpulmonary P. = PA – PIP
At rest (end of expiration) what happens to P
PA = PB
What happens to P during inspiration
During inspiration, increase in the size of chest wall decreases PIP which then leads to a decline in PA and subsequent air flow into lungs
What happens to P during expiration
During expiration, PIP increases that leads to a rise in PA and subsequent air flow out of lungs
Pressure changes during ventilation
Primary muscles used during inspiration
- primary muscles are the diaphragm (phrenic n.) and Intercostals (ext/int)
- Apex of dome moves caudally, enlarging thoracic cavity (reduces and cavity); decrease PIP
In forced inhalation, additional muscles (secondary):
Scalenes, sternocleidomastoid, neck and back muscles,
Primary muscles of Expiration
There is no primary muscle of expiration
mostly passive; relaxation of insp. muscles, & elastic recoil of lungs & thorax
Expiration muscles during forced expiration
Accessory muscles become active in forced expiration (exercise, asthma etc)
Abdominal muscles, intercostals
Ventilation vs Gait
In running (cursorial) animals, ventilation is synchronized with gait in canter and gallop but not in trot or walk: i.e. 1:1 ratio between the number of breaths and strides
A horse in gallop, “expels air as the front legs strike the ground and breathes in as it pushes off with the rear limbs”
Lung Capacity
Consist of two or more volumes
Spirometry
Is used to determined volume
Plethysmographs
Used to measure pressure differences
Please know the volumes/capacities in the chart; I may ask you any combination of formulas.
Volume:
ERV= Expiratory reserve volume
IRV= Inspiratory reserve volume
VT= Tidal Volume
Capacity:
FRC (Functional residual capacity)=RV(Residual volume)+ ERV (Expiratory reserve volume)
IC (Inspiratory capacity)= IRV + VT
VC (Vital capacity)= IC + ERV or VC=IRV +TV+ERV
TLC (Total lung capacity) = VC + RV
Tidal Volume (TV)
The volume of each breath; (resting level breathing)
IRV
Additional air that could further be inhaled with maximum effort after quiet inhalation
ERV
Additional air that could be exhaled with maximal effort after quiet exhalation
RV
Air left in the lungs after maximal expiratory effort
TLC
SUm of all four volumes
FEV1
(Forced Expiratory Volume in 1 second)
- should be 80% of VC in healthy adult young human.
Alveoli function
Site for gas exchange
–> Alveolar air, AV
Anatomic Dead-space
Conductive airways = nares to terminal bronchioles
Alveolar dead-space
Poorly perfused alveoli, limited or no exchange
Physiologic dead-space
Anatomic + Alveolar dead-space
Dead-space/tidal volume or DV/TV
The fraction of each breath ventilating the dead-space
30 % in dogs
50-75% in cattle, horse
Because dead space is relatively constant what does it affect
TV, f or both are responsible for altering the amount of air ventilating the alveoli during exercise & thermoregulation due to dead space being constant
Heat Stress
Dogs (panting): small TV, increased f, increased Dead-space (DS) ventilation, evaporation, heat loss
Large animals: increased f, increased DS ventilation, heat loss
Cold Stress
Need to increase metabolism ( increased O2 consumption, CO2 production that needs to be eliminated)
Increased alveolar ventilation (increase TV), decrease DS ventilation
decrease f, decrease DS ventilation
