BPK 306 Lecture Notes - Bronchiole, Gas Exchange, Frataxin

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Respiratory System #1
Introduction:
Primary fxn of pulmonary system:
oGas exchange (O2 uptake and CO2 removal @ appropriate fxning rates)
Body enhances RATE gas exchange
Study table of abbreviations
I. PULMONARY STRUCTURE AND FXN
A. Anatomy of the Respiratory System
Consists of nose, pharynx, larynx, trachea, bronchi, and lungs
Trachea
oHigher order bronchi
oAlmost completely surrounded by rings of cartilage. Cartilage helps
keep larger airways open
oAs bronchi gets smaller, cartilage gradually replaced by SM. SM
enables constriction and dilation of airway opening
oManipulate diameter of airways alters airway resistance, and how
much each lung area is ventilated
Fick’s Law of Diffusion:
oDiffusion rate = A*D*(P1 – P2)/T
oD proportional to solubility/sqrt(molecular weight)
Bronchial system
oSurface area enhancement:
Designed to enhance surface area for diffusion
About 23 bifurcations from trachea to alveoli
Bronchi – primary, secondary, tertiary bronchi terminal
and respiratory bronchioles alveolar ducts alveoli
300 million alveoli = 1 tennis court of SA. Enhances rate
of gas diffusion
Each alveolus enveloped by a bed of capillaries = incr SA
80% alveolar wall available for gas exchange when all caps
are open
Caps are 10 um diameter
Perfect for gas exchange
Only one RBC can fit through at a time
O2 diffusion distance minimized
oThickness Reduction:
Alveoli is 1 layer of epithelial tissue thick
Maximizes gas exchange rate
oAlveoli first occurs at about bifurcation 17, as buds
on bronchioles. Marks beginning of respiration zone. Section, prior
is conduction zone.
oAfter bifurcation 17 there’s dramatic incr in cross-
sectional area of bronchial tree
B. Pleural Space
Alveolar cells surround on outside by basement membrane. Basement
membrane has connective tissue (elastin and collagen)
oResults in an elastic lung (more so due to
arrangement of fibres, not individual molecs’ elasticity. Like nylon
stockings).
oThese elastic forces want lung to collapse
Pleural space is between
inside of chest wall and lung. A few milliliters in volume
Inner lining of thoracic cavity secretes pleural fluid
oPleural fluid allows lungs to slide over inner
chest wall when breathing.
oMakes lung stick to chest wall. Helps keep
lung open and counters elastic force of lung tissue
C. Removal of Inhaled Particles
Resistance greatest in higher order bronchi, but blockage occurs more often
in smaller bronchioles
Mucous:
a. Bronchial walls have goblet cells that excrete mucous. Cilia moves
mucous up bronchial system to glottis to be swallowed or spit out
b. Mucous layer 2 – 10 ug thick in trachea
c. Product of goblet cells, submucosal glands
d. Nonhomogeneous, adhesive, viscoelastic gel, composed of water,
carbs, proteins, lipids
Macrophages
a. Removes small particles that reach the alveoli (when fat drips on
heat source in BBQ or air pollution). No cilia, goblet cells or mucous
in alveoli.
D. EXTRAS
Cystic Fibrosis:
a. Autosomal recessive inherited disease of all exocrine glands
b. Caused by gene mutation on chromosome 7
c. Resuts in defective transmembrane regulator protein (cystic fibrosis
transmembrane conductance regulator). This is an alpha adrenergic
gated Cl- channel
d. Normally, elevated cAMP in epithelial cell opens Cl- channel.
i. Doesn’t happen in cystic fibrosis
ii. Leads to decr NaCl excretion to airways, sweat ducts,
pancreatic ducts.
iii. Leads to decr water excretion incr viscosity of secretions
iv. Viscous secretions plug airways and duct systems

Document Summary

Introduction: primary fxn of pulmonary system, body enhances rate gas exchange, study table of abbreviations, gas exchange (o2 uptake and co2 removal @ appropriate fxning rates) Pulmonary structure and fxn: anatomy of the respiratory system, consists of nose, pharynx, larynx, trachea, bronchi, and lungs, trachea keep larger airways open, higher order bronchi, almost completely surrounded by rings of cartilage. Cartilage helps: as bronchi gets smaller, cartilage gradually replaced by sm. Designed to enhance surface area for diffusion. About 23 bifurcations from trachea to alveoli. Bronchi primary, secondary, tertiary bronchi terminal and respiratory bronchioles alveolar ducts alveoli. 300 million alveoli = 1 tennis court of sa. Each alveolus enveloped by a bed of capillaries = incr sa. 80% alveolar wall available for gas exchange when all caps are open. Only one rbc can fit through at a time. O2 diffusion distance minimized: thickness reduction: Alveoli is 1 layer of epithelial tissue thick.