hes quiz 100000000 Flashcards
Alveolar duct ….
opens to clusters of
alveoli
What are alveoli densely covered with
capillaries
gas exchange
simple diffusion across respiratory membranes
Type 1 alveolar cells
simple squamous epithelial cells
surrounded by flimsy basement
membrane
Type 2 alveolar cells
cuboidal epithelial cells scattered among type 1
Alveolar macrophages
fights bacteria, dust, debris,
Pulmonary artery for
oxygenation of blood
Pulmonary veins
return blood to heart
Bronchial arteries provide
oxygenated systemic blood to
lung tissue
Nervous innervation
Parasympathetic
Sympathetic
Visceral sensory fibers
Serous membrane surrounding lungs
Visceral pleura and Parietal pleura
What does the pleura do?
- Produce fluid to lubricate
surfaces and reduce friction
between layers - Maintains position of lungs
against thoracic wall - Create cavities to separate
major organs
Pleurisy
inflammation of
pleura (pneumonia)
Pleural effusion
fluid accumulation in pleural cavity
Transpulmonary pressure
Keeps air spaces of lungs open
Higher transpulmonary press = larger lung
Inspiration 1
Inspiratory muscles contract
Inspiration 2
thoracic cavity volume increases
Inspiration 3
Lungs are stretched; intrapulmonary volume increases
Inspiration 4
Intrapulmonary pressure drops to 1 mmhg
Inspiration 5
Air flows into the lungs down its pressure gradient until intrapulmonary pressure is 0. equal to atmospheric pressure
Expiration 1
Inspiratory muscles relax
Expiration 2
thoracic cavity volume decreases
Expiration 3
elastic lungs recoil passively; intrapulmonary volume decreases
Expiration 4
intrapulmonary pressure rises to 1 mmhg
Expiration 5
Air flows out of the lungs down its pressure gradient until intrapulmonary pressure is 0
Intrapulmonary pressure
Pressure inside the lungs decreases as lung volume increases during inspiration; pressure increases during expiration
Intrapleural pressure
Pleural cavity pressure becomes more negative as the chest wall expands during inspiration. Returns to initial value as chest wall recoils
Volume of breath
during each breath, the pressure gradients move 0.5 liters of air into and out of the lungs
Airway resistance: flow =
Flow = change in pressure / resistance
Alveolar Surface Tension
Liquid molecules attracted to each other vs. to gas molecules
Surfactant -> lowers surface tension and prevents alveolar
collapse
Lung compliance
Higher the lung compliance -> easier to expand lungs at any given transpulmonary pressure
Bronchus
conducting
Trachea
conducting
Alveolus/alveoli
respiratory
Larynx
conducting
Bronchioles
respiratory
Pharynx
conducting
conducting zones
not involved in gas exchange
Nose, pharynx, larynx, trachea,
bronchial tree
Pressure gradient
Gasses flow from high
–> low pressure
Atmospheric pressure
760 mmHg
Intra-alveolar (intrapulmonary) pressure – pressure within alveoli…
changes with
inspiration/ expiration
Intrapleural press
within pleural cavity
between visceral and parietal pleurae
Changes during breathing
* Always lower than intra-alveolar (~4 mm)
* Neg intrapleural press caused by forces
pulling visceral pleura from parietal pleura
* Volume change
Transpulmonary press
Intra-alveolar minus intrapleural (760-756=4 mm Hg)
Keeps air spaces of lungs open
* Higher transpulmonary press = larger lung
Inspiration
Boyle’s law:
* Vol dec -> Press inc
* Vol inc -> Pres dec
During deep, forced
inspirations (exercise)
accessory muscles further
increase thoracic vol
Expiration
At rest, lung elasticity more
a factor than muscle
contraction
Forced expiration from
contracting abdominal wall
muscles -> inc intra-
abdominal press -> forces
abdominal organs against
diaphragm and depress rib
cage
Physical Factors Influencing Pulmonary Ventilation
Airway resistance
Alveolar Surface Tension
Lung compliance
Airway resistance
major source is friction in the respiratory
passages
Small differences in pressure produce large changes in flow
Alveolar Surface Tension
force created by alveolar fluid
that resists lung distension
Alveolar film contains surfactant ->
lowers surface tension and
prevents alveolar collapse
Liquid molecules attracted to each other vs. to gas molecules
= surface tension
Lung compliance
the distensibility of lung tissue and
the thoracic cage
Higher the lung compliance ->
easier to expand lungs at any
given transpulmonary pressure
Anatomical dead
space
air in
airway that never
reaches alveoli
Alveolar dead
space
air within
poorly
functioning
alveoli
Perfusion
flow of blood in pulmonary capillaries
Fick’s Law of Diffusion: rate of gas exchange
Proportional to: Concentration gradient; Perfusion area; Diffusion constant
* Inversely related to membrane thickness
O2 vs. CO2
Solubility -> Greater for CO2 vs. O2
* Concentration gradient -> Greater for O2 (104 mm Hg) vs. CO2 (40 mm Hg)
CO2 diffuses
out of capillary into alveolus
O2 diffuses
cross
respiratory membrane from alveolus to capillary
