Each alveolus is coated with a thin layer of liquid containing _______________, and is surrounded by an extensive network of capillaries
Surfactant
____________ lowers the surface tension of the alveoli and facilitates gas exchange across the membranes.
surfactant
The lungs are surrounded by 2 membranes called:
1. _______________
2. _______________
1. visceral pleura
2. parietal pleura
The space between the two pleura is called the________________.
Intrapleural space
The pressure between the ___________ and the _____________ prevents the lungs from collapsing.
intrapleural space
lungs
Inhalation
*diaphragm contracts & flattens
*external intercostal muscles contract, pushing the rib cage and chest wall up and out
*thoracic cavity increases in volume
*This volume increase causes a decrease in intrapleural pressure - causes the lungs to expand and fill with air
*This is referred to as negative - pressure breathing because air is drawn in by a vacuum.
Exhalation
*passive process
*lungs and chest wall are highly elastic, and tend to recoil to their original position
*thoracic cavity volume decreases --- causes an increase in pressure in the intrapleural space
*During forced exhalation, the internal intercostal muscles contract.
*Surfactant reduces the high surface tension of the fluid lining of the alveoli, preventing alveolar collapse during exhalation.
Ventilation is regulated by neurons located in the __________________, whose rhythmic discharges stimulate the intercostal muscles and/or the diaphragm to contract.
Medulla oblongata
The neural signals of the oblongata can be modified by _____________, which respond to changes in the pH and the partial pressure of CO2 in the blood.
chemoreceptors - example in the aorta
When the partial pressure of CO2 rises, the medulla oblongata stimulates an increase in the rate of ventilation.
a. true
b. false
true
Hyperventilation _________ the partial pressure of CO2 in the blood below normal.
a. increases
b. decreases
b. decreases
An instrument called a ______________ measures the amount of air normally present in the respiratory system and the rate at which ventilation occurs.
spirometer
The maximum amount of air that can be forcibly inhaled and exhaled from the lungs is called the _________________.
Vital capacity
The amount of air normally inhaled and exhaled with each breath is the ____________________.