Lung is a mechanical organ
• Built similar to pyramids (apex at top, base at
bottom, with segments)
• Packaging problem (55% on R, 45% on L)
• Major properties are
– Dry
– Inflated
Segmental Anatomy: redundancy
• Purpose of segments
– Prevent spread of infection
– Prevent complete obstruction from an inflated
foreign body
• Lobes have more than one segment (20
total)
– Upper
– Middle
– Lower
Air is distributed in proportion to
segmental volume
• Maintain volume similar to a submarine
• Ventilation is matched to volume: regional
ventilation = regional volume
Move during sleep; give lungs
negative pressure to prevent
atelectasis: airlessness
Carina: branch point in the lungs
• Bronchiole tree is not symmetrical
• Food must pass from front to back and air
from back to front
– Can be problem in the old and the young
– Glottis defends the airway
Larnyx: rigid, cartilagenous box
• Narrowest part of the system
• “V” is front: vocal cords
• Vocal cords move in synchrony with
diaphragm
Trachea: ~ vacuum hose
• Posterior is muscle, anterior is cart. Rings
• Muscle allows ability to cough
• Posterior utilized to expel objects: blow
gun or spit wad effect
COPD: chronic obstructive
pulmonary disease
• Exhalation is restricted
RLD: restrictive lung disease
• Inhalation is restricted
Air moves across a pressure
gradient
Muscles of inspiration (Active)
• Diaphragm
• External intercostals (bucket handles)
• Inspiration is active
Muscles of expiration (intercostals
are stabilization) (usually passive):
• Rectus abdominus
• Obliques
• Lats
Diaphram originates in the chest
wall and inserts on the central
tendon:
• Three muscles, right, left costal, and cural
components
• Criss-cross in the back to allow for the
esphogus, vena cava, etc.
Flow is swirly, not turbulent, difficult
to characterize the flow in the
upper airways to simplify, assume
Ohms law:
• Resistance (R) = change pressure/flow
• Or flow = change in pressure/R
Velocity (U = flow/area)
• Need low pressure for inspiration: 5 cm/H2O
• Inhale pressure has capacity for 120 cm/H2O
• Maximal inspiratory pressure (MIP) usually
occurs at FRC (functional residual capacity), low
lung volumes, usually about -80 – -100 cm/H2O
• MEP: occurs at high lung volumes, recoil of
diaphragm (100-110 cm/H2O)
• Due to length tension relationship
Disease states: greater pressure
for adequate flow (obstructive
airway disease)
Delta Vt/Delta pressure =
compliance
• High compliance: emphysema
• Increase pressure
– Increase chest wall diameter
– Compress abdominal space
Total Lung Capacity (TLC)
determined by:
•
•
•
•
Wt, gender, age, ht
Compliance
Surfactant
Insp/expir. muscle strength
Conducting airways have
cartilage, lower do not:
interdependent
Alveoli are connected via smooth
muscle and connective tissue:
one opens, all open to prevent
atelectasis
Mucosal clearance: similar to
flypaper, lubricates and protects:
• Hydrates
• Provides protective surface
• Collect debris
Goblet cells: secrete sticky,
tenacious mucous
Submucosal glands are less
sticky, make islands
Debris is moved up on islands
to carinas via cillia “beating”
• Clean from periphery to the central
• Mucocilliary escalator
Cystic Fibrosis: does not
regulate sol (soluable) phase
• Cillia are too deep, below the surface,
cannot beat effectively, bacteria can
overgrow
Peripheral airways have laminar
flow, allows for diffusion
Alveoli have pores for gas
diffusion, collateral airflow
Two types of ventilation:
• Pulmonary: air is brought into lungs and
exchanged with air in lungs (Ve)
• Alveolar: exchange of gases between
alveoli and capillaries