Resp 4 Flashcards
Scientists initially assumed the major determinant of lung compliance and lung recoil were….
elasticity of pulmonary cells and ECM (elastin and collagen)….FALSE
A major determinant of lungs elastic recoil is…
surface tension
surface tension
measure of force acting to pull a liquid’s molecules together at an air-water interface
Laplace’s equation
P=(2T)/r; T=surface tension (~70dynes/cm), r=bubble radius
surfactant
a detergent-like molecule secreted by Type II alveolar cells that reduces surface tension to ~25dynes/cm or less; increasing compliance
What is surfactant composed of?
90% phospholipids, 10% protein
How does surfactant reduce surface tension?
By decreasing density of water molecules at air-water interfaces
Smaller alveoli have ____ surfactant because…
more; it equalizes the pressure between large and small alveoli
Rapidly expanding alveolus vs slowly expanding alveolus
-rapidly expanding alveolus greatly reduces surface density of surfactant and increase surface tension and elastic recoil, putting a “brake” on expansion
Infant Respiratory Distress Syndrome
affects 1% of new borns; developmental insufficiency of surfactant production and immaturity of the lungs
Prevention of Infant Respiratory Distress Syndrome
glucocorticoid injection to the mother
Treatment of Infant Respiratory Distress Syndrome
- artificial surfactant
- continuous positive airway pressure (CPAP)
- intubation
90% of airway resistance occurs in….
trachea and bronchi
Major determinant of bronchoconstriction/dilation (diameter)
CO2
high levels of CO2 cause..
dilation
low levels of CO2 cause..
constriction
histamine
released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries
Asthmatic airways have…
wall-inflamed and thickened
Asthmatic airway during attack
- air trapped in alveoli
- tightened smooth muscled
In respiratory system effectiveness of ventilation is determined by..
total pulmonary ventilation; volume of air moved into and out of lungs each minute
total pulmonary ventilation =
ventilation rate x tidal volume
alveolar ventilation =
ventilation rate x (tidal volume - dead space)
PO2 and PCO2 remains ______________ during quiet respiration
relatively constant
As alveolar ventilation increases…. alveolar PO2 ________ and PCO2__________.
increases, decreases (and vice versa)
Perfusion
blood flow
perfusion is absent at the..
apex of lungs due to more negative intrapleural pressure (gravity)
Pulmonary arterioles primarily influenced by….
decreasing O2 levels
Bronchioles are sensitive to….
CO2 levels; dilating with increasing levels and constriction with decreasing levels
