pulmonary ventilation Flashcards
air moves in and out lungs cos of what
pressure diff
high to low
explain boyles law
Gas law
States that the pressure
of a gas is inversely proportional to its volume
P1V1=P2V2
explain muscle respiration in terms of when breathing in
Inspiration
breathing in, inhalation
Diaphragm
constriction causes dome to flatten
Muscles that elevate ribs & sternum e.g.,
- External intercostals
- Pectoralis minor
- Scalenes (neck)
increase size of thoracic cavity
explain muscle respiration in terms of breathing out
Active Expiration
breathing out, expiration
Muscles that depress ribs & sternum e.g.,
- Internal intercostals
- Abdominal muscles
decrease size of thoracic cavity
Passive Expiration
elastic lung recoil:
- Elastic fibres in alveolar wall
- Surface tension of fluid film lining alveoli
name the muscles of inhalation
sternocleidomastoid
scalenes
external intercostals
diaphragm
name the muscles of exhalation
internal intercostals
external oblique
internal oblique
transversus abdominis
rectus abdominis
explain the changes of thoracic cavity during inhalation and exhalation
on inhalation the sternum moves outwards
on inhalation the diaphragm contacts and moves downwards
air movement results from diff between what
atmospheric pressure (760mmHg)
and
Alveolar pressure
Palv (inside alveolus)
- Decrease = air moves into lungs
summarise the cycle of air movement
at rest (diaphragm relaxed):
- alveolar pressure = 760mm Hg
during inhalation (diaphragm contracting):
- alveolar pressure = 758mm Hg less than the atmospheric = so air moves in
during exhalation (diaphragm relaxing):
- alveolar pressure = 762 mm Hg, more than atmosphereic = so air moves out
atmospheric pressure is remained at 760mm Hg throughout cycle
what is pleural cavity
space between lung & chest wall
what is found inside pleural cavity
Pip (written as = big P, tiny ip)
what happens if If Pip < Palv
alveoli expand (= normal)
what is Pneumothorax
If air enters pleural cavity, Pip= atmospheric pressure
alveoli cannot expand
lungs collapse
what can be seen in an Pneumothorax CT scan
Lung collapsed
Dark, air-filled space
name 3 other factors that affect rate of pulmonary airflow
Surface tension of alveolar fluid
Lung compliance
Airway resistance
explain the 3 factors that can affect rate of pulmonary airflow
Surface tension of alveolar fluid:
- Overcome by surfactant
lipoprotein molecules in alveolar fluid prevent alveoli collapsing & allowing lungs to expand
- Less surfactant in premature infants causes
‘respiratory distress syndrome’
Lung compliance
- Capacity for stretching
Airway resistance
- Controlled by pressures and airflow
what causes interpleural pressure
pleural cavity
with can lead to pneumothorax
what is the Role of Surfactant in Lung
Decreases surface tension of alveoli to prevent them from collapsing.
describe the diff between immature vs mature lung
Immature lung:
Not conducive to gas exchange
Mature lung:
Larger surface area
what does lung compliance mean
Effort required to stretch lungs & thoracic wall
explain high compliance
high compliance = easy expansion
e.g., thin balloon has high compliance as easy to inflate
how is there effort required to stretch the lungs and thoracic wall
Elastic forces of the lung:
presence of elastic & collagen fibres
surface tension.
explain airway resistance
Resistance of the respiratory tract to airflow
- during inhalation and exhalation
Decreases as diameter of airways increases
- walls pulled outwards, smooth muscle relaxation
explain air volume as we breathe
Only small proportion of air in lungs exchanged during single, quiet respiratory cycle
- inhale + exhale
Increase by inhaling more vigorously & exhaling more completely
Maximum effort of inspiration
- Volume of air in lungs = Total lung capacity
name the 4 pulmonary volumes
tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
explain the pulmonary volumes tidal volume
amount of air moved into or out of lungs during a normal inspiration or exhalation (~500ml)
explain the pulmonary volume Inspiratory reserve volume
amount of air that can be inspired forcefully after inspiration of normal tidal volume (~3100ml)
explain the pulmonary volume Expiratory reserve volume
amount expired forcefully after normal expiration (~1200ml)
explain the pulmonary volume Residual volume
still remaining in respiratory passages & lungs after most forceful expiration (~1200ml)
what are pulmonary capacities
Sum of two or more pulmonary volumes
name the 4 pulmonary capacities
Inspiratory capacity
functional residual capacity
vital capacity
total lung capacity
explain the pulmonary capacity: Inspiratory capacity
tidal vol + inspiratory reserve vol
amount can inspire maximally after normal expiration (~3600 ml)
explain the pulmonary capacity: Functional residual capacity
expiratory reserve vol + residual vol
amount remaining in lungs after normal expiration
(~2400 ml)
explain the pulmonary capacity: Vital capacity
inspiratory reserve vol + tidal vol + expiratory reserve vol
max can expel after max inspiration (~4800 ml)
explain the pulmonary capacity: Total lung capacity
inspiratory reserve vol + expiratory reserve vol + tidal vol + residual vol (~6000ml)
explain how we measure these volumes and capacities
Spirometry:
process of measuring volumes of air that move in & out of respiratory system
Spirometer:
device used to measure these pulmonary volumes
- Values obtained useful in diagnosing problems with pulmonary ventilation, e.g., asthma.
