Download The Respiratory System Organization of the Respiratory System

The Respiratory System
Functions:
Moves air to and from the gas-exchange sites where
diffusion occurs between air and circulating blood.
Provides non-specific defenses against pathogenic
invasion.
Permits vocal communication.
Helps control pH of body fluids.
Anatomy and Physiology for Engineers
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Organization of the Respiratory System
Anatomy and Physiology for Engineers
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Nose, Nasal Cavities and Pharynx
Air enters through nostrils, communicates to nasal cavity.
Nasal septum divides nose into left and right sides.
Nasal conchae: ridges within nasal cavity.
Produces disturbances in air flow, enhancing mixing and filtration.
Respiratory epithelium: ciliated cell layer (goblet cells and mucous
glands).
Cilia sweep debris and pathogens into pharynx (throat).
Nasal cavity also flushed by mucus produced by nasal sinuses and by
tears through nasolacrimal duct.
Anatomy and Physiology for Engineers
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Pharynx (throat)
Throat is shared by digestive and respiratory tracts.
Dense concentration of ciliated cells.
Cystic fibrosis:
Genetic disorder (chromosome 7).
Bacterial infection and associated heart failure.
Mucus becomes too viscous to be transported by cilia.
Leads to frequent bacterial infections.
Anatomy and Physiology for Engineers
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The Larynx (Voice Box)
Incoming air leaves pharynx through glottis (narrow
opening protected by larynx).
3 large cartilages support larynx.
Epiglottis prevents entry of liquids or solid food into respiratory
system.
Thyroid cartilage protects anterior and lateral surfaces of larynx.
“Adam’s Apple”
Cricoid cartilage provides posterior support to larynx.
Two pairs of ligaments extend across larynx between
thyroid cartilage and 3 smaller cartilages.
False and true vocal cords.
Anatomy and Physiology for Engineers
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The Larynx (Voice Box)
Anatomy and Physiology for Engineers
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The Trachea (Windpipe)
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The Bronchi and Bronchioles
Trachea branches into right and left bronchi.
Bronchi are histologically similar to trachea.
Rapid branching.
~ 1 mm -> bronchioles.
Bronchioles parallel arterioles in function.
Varying diameter controls local flow.
Sympathetic stimulation causes relaxation of smooth muscles around
bronchioles.
Last part: terminal bronchioles (0.3 -0.5 mm diameter)
Each terminal bronchiole supplies air to a lobule of the lung.
Lobule: segment of lung tissue bound by connective tissue partitions,
supplied by a single terminal bronchiole, and accompanied by
pulmonary arteries and veins.
Anatomy and Physiology for Engineers
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Alveolar Ducts and Alveoli
Respiratory bronchioles open
into alveolar ducts.
Alveolar ducts end at alveolar
sacs (alveoli).
Gas exchange occurs at alveoli
surfaces.
Each lung: 150 x 106 alveoli.
Alveolar surface ~ 140 m2.
Thin squamous epithelium.
Alveolar macrophages
consume dust particles.
Surfactant cells release
surfactant -> decrease surface
tension (prevents collapse of
alveolar walls.)
Anatomy and Physiology for Engineers
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The Respiratory Membrane
Gas exchange occurs across this membrane.
3 components:
Squamous epithelial cells lining the alveoli.
Endothelial cells lining adjacent capillary.
Fused basement membranes between alveolar and endothelial cells.
Diffusion across membrane is rapid:
Diffusion distances are small (thickness: ~ 0.1 µ).
Both O2 and CO2 are lipid soluble.
Pneumonia
Develops due to pathogenic infection of lobule.
Infection --> inflammation --> fluid leaks into alveoli --> respiratory function
decreases.
Bacterial infection usually involves bacteria normally found in lining of upper
respiratory tracts.
Retardation of pathogenic defense system in these tracts (smoking, immune
compromise) allows bacteria to evade defense system and migrate into
alveoli.
Anatomy and Physiology for Engineers
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The Lungs
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The Pleural Cavities
Thoracic cavity is the shape of a broad cone: base is the
diaphragm; walls are rib cage; apex is entrance to respiratory
& digestive tracts.
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Respiratory Physiology
Process of respiration involves 4 key steps:
Pulmonary ventilation (breathing - convection).
Gas diffusion across respiratory membrane
(diffusion).
Storage and transport of oxygen and carbon
dioxide (convection).
Exchange of oxygen and carbon dioxide between
blood and interstitial fluids (diffusion).
Anatomy and Physiology for Engineers
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Pressure-Volume Relationship During Ventilation
Anatomy and Physiology for Engineers
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Gas Exchange at the Respiratory Membrane
Process of gas exchange
depends on:
Partial pressures of O2 and
CO2.
Portion of pressure
contributed by each gas.
Ex: atmospheric pressure:
PN2 + PO2 + PH2O + PCO2
O2 ~ 21% of atmospheric
gas -> PO2 ~ 20% 760 mm
Hg = 159 mm Hg.
Diffusion from gas into liquid
& vice-versa.
Anatomy and Physiology for Engineers
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O2 & CO2 Pickup and Delivery
O2 and CO2 have very limited solubility in plasma
~1.5% of O2 molecules found in solution.
~ 7% of CO2 in solution.
Remaining O2 transported by binding onto iron
atoms of the hemoglobin (Hb) molecule.
Hb + O2 ¤ HbO2
Release of O2 from Hb molecule depends on PO2 in
surrounding tissue, pH, temperature.
CO2 binds to globin portion of Hb (~23%).
Remaining transported by conversion to carbonic acid
(H2CO3 ¤ H+ + HCO-3).
Anatomy and Physiology for Engineers
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Control of Respiration
Respiratory centers: 3 pairs of loosely organized nuclei in
reticular formation of pons and medulla.
Control respiratory rate and intensity.
Inspiration
Inspiration
(2 seconds)
Inspiratory
Muscles
contract
Inspiration
Occurs
Inspiratory
Muscles
contract
Doral
Respiratory
Group
Active
QUIET
RESPIRATION
Doral
Respiratory
Group
Inhibited
Inspiratory
Muscles
Relax
Passive
Expiration
Occurs
Expiration
Occurs
Doral
Respiratory
Group
Inhibited
Expiratory
Muscles
Relax
Doral
Respiratory
Group
Active
FORCED
RESPIRATION
Inspiratory
Muscles
Relax
Ventral
Respiratory
Group
Inhibited
(3 seconds)
Anatomy and Physiology for Engineers
Ventral
Respiratory
Group
Active
Active
Expiration
Occurs
Expiratory
Muscles
Contract
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Control of Respiration
Higher order centers also
control pace and depth
of respiration.
Indirectly via pons.
Directly via stimulation
of respiratory muscles.
Voluntary and
involuntary control.
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Review Questions
During maximal exercise, hemoglobin
releases more O2 to active skeletal muscles
than at rest. Why ?
Why would obstruction of the airways affect
body’s pH ?
Explain physiology of “bends” or
decompression sickness.
Describe a possible pulmonary treatment for
an infant born prematurely (22-25 weeks).
Anatomy and Physiology for Engineers
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