The respiratory system
major function
Major function:
-Supply oxygen for aerobic respiration and remove and dispose of carbon dioxide
Types/stages Respiration
Pulmonary ventilation
External respiration
Transport of respiratory gases
Internal respiration
Pulmonary ventilation:
breathing; the movement of air in and out of the lungs
External respiration:
Gas exchange between the blood and air filled chambers of the lungs
Transport of respiratory gases:
Movement of gases within the body, accomplished using the cardiovascular system (i.e. blood)
Internal respiration:
Exchange of gases between blood and tissues
Zones within the respiratory system
Conduction zone: rigid conduits for transport of air to respiratory passages
Respiratory zone: Site of gas exchange
Physical and chemical barriers in the nose Vibrissae: Olfactory mucosa: Respiratory mucosa: --Goblet cells: --Serous cells: ---Lysozyme: ---Defensins:
Vibrissae:
Olfactory mucosa:
-contains receptors for the sense of smell
Respiratory mucosa:
The Larynx
Once past the epiglottis, you reach the voice box
Sound production
Trachea
Long, flexible tube that directs air to the bronchi
Changes in structure
Cartilage structure changes:
-from rings, to plates, to none being replaced by elastic fibers (found throughout the respiratory tree)
The epithelium changes:
-From ciliated pseudostratified columnar, to columnar, to cuboidal, to squamous in the ducts and sacs
The amount of smooth muscle increases:
-allowing constriction of the passageways
The respiratory membrane
-Cuboidal (Type II) cells secrete surfactant
Other important structures and cells in the lungs
-Surrounded by elastic fibers
-Alveolar pores allow air pressure throughout the lung to be equalized if alveolar ducts collapse by disease or damage
-Alveolar macrophages (dust cells) destroy microorganisms and pathogens
Replace over 2 million per hour!
Lungs
Occupy the entire
Receive blood from the and are drained by the
Are surrounded by
Occupy the entire thoracic cavity except the mediastinal septum (surrounding the heart)
Receive blood from the pulmonary arteries (from the heart) and are drained by the pulmonary veins (toward the heart)
Are surrounded by pleura (parietal and visceral [serosa])
Lungs are surrounded by pleural fluid
Fluid acts as a
Fluid acts as a barrier, lubricant, and decrease surface tension between the lungs and body wall during breathing
The mechanics of breathing
Pressure is always described relative to
Patm =
If P = 756, then
Pressure is always described relative to atmospheric pressure (Patm)
Patm = 760 mmHg
If P = 756, then -4mmHg has occurred, causing a vacuum.
Intrapulmonary pressure
Palv is the pressure in the alveoli, rising and falling with the phases of breathing, but always equilibrating to external Patm
Pressure in the pleural cavity (Pip) also fluctuates, but is always negative related to the intrapulmonary pressure (intra-alveolar)
How is this negative pressure established (Pip)?
Two forces
Transpulmonary pressure
Two forces
Transpulmonary pressure
Pulmonary ventilation
Volume changes lead to
Volume changes lead to pressure changes, which lead to the flow of gases to equilibrate pressures
ΔV —> ΔP —-> F (flow of gas)
Boyle’s Law
If temperature is constant, the pressure of a gas is inversely related to its volume:
P1V1 = P2V2
P = pressure in mmHg V = volume in mm3 1 = initial condition 2 = resulting condition
Inspiration
-Muscles:
relationship between Palv and Patm
The uptake of air into the lungs (quiet inspiration)
Expiration
relationship between Palv and Patm
Physical factors affecting ventilation
drag:
Drag: friction of flowing molecules on surfaces
F = ΔP/R
F = flow P = pressure, where ΔP = (Patm – Palv) R = resistance