Download Non Respiratory Gas Exchange

Nonrespiratory Functions of the
Lung
Pulmonary Defense Mechanisms
Nonrespiratory Functions of the
Pulmonary Circulation
Metabolic Functions of the Lung
Pulmonary Defense Mechanisms
Air Conditioning
Olfaction
Filtration and Removal of Inspired Particles
Filtration and Removal of Inspired Particles
Filtration of Inspired Air
Removal of Filtered Material
Reflexes: Cough and Sneeze
The Mucociliary Escalator
Mechanisms of the Terminal Respiratory Units
Alveolar Macrophages
Other Methods Of Particle Removal or
Destruction
Figure 10-1
sphenoidal sinus
turbinates
adenoid tissue
orifice of auditory
tube
uvula
epiglottis
antrum
ethmoidal sinus
septum
middle meatus
turbinates
antrum
Sphenoidal sinus
Turbinates
Adenoid tissue
Orifice
of
auditory
tube
Uvula
Ethmoidal sinus
Epiglottis
Tongue
Turbinates
Antrum
Septum
Filtration of Inspired Air
Hairs at the inlet filter particles greater than 10-15µ
Nasal turbinates force inspired air to pass in narrow
streams so particles pass close to either the nasal
septum or mucosa of the turbinates and impinge
directly on mucosa or settle by gravity
Particles greater than 10µ are almost completely
removed in the nose, along with some smaller ones
Particles between 2 - 10µ usually settle on the mucuslined walls of the trachea, bronchi, and bronchioles
Particles between 0.3 and 2.0µ and all foreign gases
reach the alveolar ducts and alveoli
Particles less than 0.3µ in diameter usually remain as
aerosols and are almost entirely expired
Particles removed may include: silica, asbestos, inert
dust, bacteria
Mucociliary Escalator
Cilia line entire respiratory tract (except part of
pharynx, anterior 1/3 of nose, and the terminal
respiratory units)
Beat 600-900 times/min
Appear to be coordinated so sheet of mucus (containing
trapped foreign particles) secreted by goblet cells and
mucous glands is propelled toward the pharynx where
is it swallowed or expectorated
Mechanism of control is not well understood. Nerves do
not appear to be involved. Inhaled irritants may slow
down or "paralyze" cilia
Figure 10-2
Alveolar Macrophages
Large mononuclear ameboid cells - scavenge the
alveolar surface and engulf inhaled particles
Contain lysosomes capable of killing bacteria
Many other functions, including secretion of
components of immune and inflammatory responses
such as cytokines, arachidonic acid derivatives,
enzymes, and growth factors
Life span 1-5 weeks
Appear to emigrate to the sheet of mucus on the walls of
terminal bronchioles and "ride" up to larger airways
Figure 10-3
Other Methods of Particle Removal or
Destruction
Reach the mucus sheets by upward movement of
the alveolar fluid lining
Penetrate into the interstitial space for
phagocytosis by tissue histiocytes, and/or
entrance into the lymphatic channels
Particles may also be destroyed by surface
enzymes (lysozymes, lactoferrin) or removed
by immunologic reactions (interferon,
complement, etc.)
mucociliary escalator
pulmonary arteriole
Figure 10-4
bronchial-associated
lymphoid tissue
terminal bronchiole
centripetal lymphatics
respiratory bronchiole
alveolar sac
bronchoalveolar
junction
pleura
alveolar macrophage
cell and/or particle pathway
particle
fluid absorption pathway
Integrated System for Defense of the Respiratory Tract
Natural Mechanical Defenses
Filtration and impaction remove particles
Sneeze, cough, and bronchospasm expel particles
Epithelial barriers and mucus limit particle penetration
Natural Phagocytic Defenses
Effected by airways, interstitial, and alveolar macrophages;
polymorphonuclear leukocytes
Phagocytosis of particulates, organisms, and debris
Microbicidal and tumoricidal activities
Degradation of organic particles
Integrated System for Defense of the Respiratory Tract
Acquired Specific Immune Defenses
Humoral immunity
Effected by B lymphocytes
Biologic activities mediated by specific antibody
Augments phagocytic and microbicidal defense mechanisms
Cell-mediated immunity
Effected by T lymphocytes
Biologic activities mediated by:
Delayed-type hypersensitivity reaction
T cell cytotoxicity
Augments microbicidal and cytotoxic activities of macrophages
Mediates subacute, chronic, and granulomatous inflammatory
responses
Nonrespiratory Functions of the
Pulmonary Circulation
Reservoir for left ventricle
Filter to protect the systemic circulation
Fluid exchange and drug absorption
Figure 10-5
200
arterial pressure,
mmHg
100
0
120
SVC pressure,
cmH2O
0
220
260
distal PA pressure, 230
mmHg
0
aortic flow, ml/s
300
200
100
0
PA flow, ml/s
300
200
100
0
balloon occlusion
ECG
Metabolic Functions of the Lungs
Uptake or conversion by lungs of chemical
substances in mixed venous blood
Formation of chemical substances in lungs and
release for local use: surfactant, histamine,
serotonin, leukotrienes, PAF, PG’s, etc.
Release into blood of substances stored in
pulmonary tissues or cells, including
macrophages: bradykinin, histamine,
serotonin, PGE2, PGF2 , heparin, etc.
Uptake or Conversion by the Lungs
of Chemical Substrates in Mixed Venous Blood
SUBSTANCE IN
MIXED VENOUS BLOOD
RESULT OF A SINGLE PASS
THROUGH THE LUNG
Prostaglandins E1, E2, F2
Prostaglandins A1, A2, I2
Leukotrienes
Serotonin
Acetylcholine
Histamine
Epinephrine
Norepinephrine
Isoproterenol
Dopamine
Bradykinin
Angiotensin I
Angiotensin II
Vasopressin
Oxytocin
Gastrin
ATP, AMP
Almost completely removed
Not affected
Almost completely removed
85-95 % removed
Inactivated by cholinesterases in blood
Not affected
Not affected
Approximately 30% removed
Not affected
Not affected
Approximately 80% inactivated
Approximately 70% converted to Ang II
Not affected
Not affected
Not affected
Not affected
40 - 90% removed
Figure 10-6
Air
TM
Aqueous
subphase
MAC
LB
MVB
Type I cell
Type I cell
G
ER
Interstitium
Type II
cell
Basal membrane