Jackson 1 Flashcards
Lungs Regulate
blood pH
ventilation rate affects amount of CO2 in plasma
Lungs Provide microbial defense by means of
epithelial secretions –
lymphoid tissue in tract –
coughing and sneezing reflexes –
Lungs
6. Activate (or inactivate)
chemical messengers in blood –
e.g. convert angiotensin I to angiotensin II
Lungs 7. Defend against
blood clots – small blood clots get trapped in narrow vessels in lungs and are dissolved
Components and zones of the respiratory system
airways – series of tubes needed to exchange air between lungs and environment
lungs – site of gas exchange between air and blood
mechanical aids – skeletal muscles used to vary the volume of the thoracic cavity
upper airway – structures are
outside of the thoracic cavity
mouth/nose → pharynx → larynx → top of trachea
- conducting zone –
in thoracic cavity, but no gas exchange occurs
trachea → primary bronchi → secondary bronchi → tertiary bronchioles → bronchioles → terminal bronchioles
trachea and bronchi include cartilaginous rings and mucous glands –
bronchioles lose cartilage and glands, but add smooth muscle
respiratory zone – structures where
gas exchange can occur
respiratory bronchioles → alveolar ducts → alveolar sacs
respiratory bronchioles very
thin-walled; have alveoli in walls
Branching creates
parallel airways to maintain airflow and minimize increasing resistance to airflow. Compare this set-up to one in which multiple tubes simply become narrower.
Air is warmed and moistened – heat and water vapor are
exchanged with the blood in airway walls
Conducting zone protects against
microbes
goblet cells secrete mucus which can
trap airborne particles and pathogens;
cilia on epithelial cells move
mucus upwards to pharynx where it can be swallowed or expelled
Closed pneumothorax:
Pleural cavity pressure less than ATM
Open pneumothorax:
pleural cavity pressure = atm
tension pneumothorax:
pleural cavity pressure > ATM
Cystic fibrosis is a disease that
impairs the normal function of the conducting zone
Cystic fibrosis: mutation in genetic code for
Cl- channel reduces the amount of Na+ and Cl- secreted across the epithelium into mucus. This leads to there being less water in the mucus (due to osmosis)→ mucus is thick and dry
Cystic fibrosis: consequences of abnormal mucus -
infectious agents are trapped, but not expelled; airways are obstructed
Airflow is regulated by
bronchiolar smooth muscle
——- in alveoli provides time for exchange –
low rate of bloodflow
Microbial defense is provided by
pulmonary macrophage
Type I –
epithelial; gas exchange surface
Type II –
secrete surfactant
Macrophages – are considered the
3rd alveoli cells??
alveolar sacs are
~0.5 μm in diameter
distance between alveolus and capillary
≈ 0.2 μm
Respiratory gases are small non-polar molecules that diffuse down a “concentration” gradient - diffuse easily through plasma membranes, less easily through
body fluids
CO2 solubility = 77 mmol/L;
77 mmol/L;
O2 solubility =
2.2 mmol/L
Intrapleural fluid fills sacs (—– thick
10 – 20 μm thick)
Air flow is a function of the
pressure gradient and the resistance to flow within the airways
F =
ΔP/R
In the respiratory system, the pressure difference (ΔP) of concern is the difference between gas pressure in the lung/alveoli and atmospheric pressure (Palv - Patm )
If Palv < Patm, air flows
into lung (inspiration)
If Palv > Patm, air flows
out of lung (expiration)
Alveolar pressure changes in response to
changing the volume of the lungs according to Boyle’s Law
(P1 V1 = P2 V2 ),
transpulmonary (Ptp) =
Palv - Pip (Pip = interpleural pressure)
diaphragm contracts →
lowers floor of cavity → increases volume - inhale
external intercostals contract →
raise ribcage → increase volume - inhale
diaphragm relaxes →
raises floor of cavity → reduces volume - exhale.
external intercostals relax /internal intercostals contract→
lower ribcage → reduces volume - exhale
Palv equal Patm
between breaths (no air is moving)
Pip below
atmospheric pressure between breaths
Ptp = Palv – Pip;
lungs remain expanded
lungs tend to recoil inward –
chest wall tends to recoil outward –
net result is Pip is always subatmospheric
During inspiration – diaphragm
contracts → thorax expands
During inspiration:
Pip becomes
more negative
During inspiration: Ptp
increases so lung volume increases and air flows in until Palv = Patm
During expiration - diaphragm
relaxes → thorax compresses
During expiration: Pip becomes
less negative
During expiration: Ptp
decreases so lung volume decreases and air flows out until Palv = Patm
