Gas Exchange - Mammals Flashcards
What are the two types of airways in mammalian lungs?
Conducting and respiratory
What are conducting airways? What structures are conducting airways?
Sections of the respiratory tract where no gas exchange occurs. Include trachea, bronchi, and terminal bronchioles
What are respiratory airways? What structures are respiratory airways?
Sections of the respiratory tract where gas exchange occurs. Include respiratory bronchioles, alveolar ducts, and alveolar sacs
What muscle controls breathing?
Diaphragm
What is the structure of the alveoli?
Polygonal, flattened walls, wrapped in capillaries and suspended in collagenous matrix
Why is diffusion between the blood and alveoli so efficient?
Distance is very short and the walls of both the alveoli and capillaries
Does only diffusion move air around in the lungs?
No, bulk flow via convection is used first to move large amounts of air
What is important about the air in the alveoli?
There is always air in there and it is motionless, so oxygen needs to diffuse across the final distance
Why is it critical that the alveoli always have air in them?
Prevent collapse
What are the 3 types of cells in the alveoli?
Type 1, type 2 and macrophages
What do type 1 cells do?
Gas exchange
What do type 2 cells do?
Secrete surfactants
What do macrophages do?
Destroy pathogens
What does the surfactant do?
Maintains surface tension of water droplets in the alveoli and prevents the alveoli from collapsing. Decreases surface tension of a liquid and decreases the recoil tendency
What happens to a smaller alveolus if there’s no surfactant?
It collapses into a larger one
Are all alveoli the same size?
No, some are larger than others
How much surfactant will be in a small alveolus compared to a larger one?
More in the smaller one to prevent collapse into the larger one
What is the surfactant made of?
Amphipathic lipoproteins
What is recoil tendency?
The elastic recoil of the alveoli that aids in exhalation
What are the two things that help with the recoil tendency of the alveoli?
Water drops and surfactant
What is the pleural sac?
Small fluid filled sac between the lung and chest wall
What is atelectasis?
Collapse of the alveoli
What is the pressure inside the pleural sac?
756 mmHg
Why is it so important that the intrapleural pressure is less than the atmospheric pressure?
Prevents alveolar collapse and maintains integrity of the lungs
Why does the pleural sac need to be filled with fluid?
Allows the walls of the sac to slide past each other during respiration
What is one of the major factors that stretches the lungs in the thoracic cavity throughout ventilation to prevent collapse of the lungs?
Cohesiveness of water
What is pneumothorax?
Collapsed lungs, the physical penetration of the pleural sac from injury
What are the two types of pneumothorax?
Traumatic and spontaneous
What is traumatic pneumothorax?
Chest wall is punctured
What is spontaneous pneumothorax?
Punctured lung
What are the two phases of tidal ventilation?
Inspiration and expiration
What is happening to the diaphragm, the intercostal muscles, and the pleural sac during inspiration?
Diaphragm and intercostal muscles contract and expand the thoracic cavity, and the expansion pulls on the outer layer of the pleural sac and creates the negative pressure
What happens during expiration?
Diaphragm and intercostal muscles relax, abdominal muscles contract
What is the transmural pressure?
The difference between the intrapleural pressure and the intra-alveolar pressure
How does the transmural pressure change during inspiration and expiration?
Increases during inspiration and decreases during expiration
Why is transmural pressure important?
Need to stretch the lungs in the thoracic cavity throughout the ventilation cycle to prevent collapsing during expiration
How do we measure transmural pressure?
A spirometer
What is tidal volume?
The total amount of air moved by one ventilatory cycle (Vt)
What is inspiratory reserve volume?
The maximum amount of air able to be inhaled
What is expiratory reserve volume?
The maximum amount of air able to be expired
What is residual volume?
The amount of air that is always in the lungs
What is vital capacity?
The sum of the tidal volume, inspiratory reserve volume, and expiratory reserve volume
What respiratory adaptation is seen in animals with long necks?
Increase tidal volume to compensate for additional dead space
What is the difference between respiratory minute volume and alveolar minute volume?
Alveolar minute volume takes the dead space into account
What happens to respiratory minute volume and alveolar minute volume during exercise?
They both increase
How are cardiac output and ventilation related?
Both increase proportionally, the ratio stays at about 1
What is the prefusion ratio?
Cardiac output
What are the two forces that keep the thoracic wall and lungs in close application?***
Cohesiveness of water
Transmural pressure gradients
