3. Lung Ventilation Flashcards
Why do trachea and bronchi have C-shaped rings of cartilage but the bronchioles do not?
Cartilage keeps the airways open
By being C shaped, with the open side next to the oesophagus, means that the trachea maintains its shape without endangering or being endangered by the oesophagus.Also the C shape allows the trachea to expand during inspiration.
As the branching bronchi get smaller and smaller, the proportion of cartilage in their walls decreases, while the amount of smooth muscle increases. This arrangement makes it possible to change the diameters of the small bronchi and bronchioles
Expiration
Rib Cage gets smaller Diaphragm relaxes and moves up TC Volume decreases Pressure increases Recoil of elastic lungs External intercoastals relax
Inspiration
Rib Cage expands up and out Diaphragm contracts and moves down TC Volume increases External intercoastals contract Pressure decrease Air flows in the equalise pressureq
The Mechanism of breathing
The steep concentration gradient across the gas exchange surface is maintained in to ways: by blood flow on one side and ventilation on the other.
These movements are transmitted to the lungs via the pleural sac surrounding each lung.
The outer membrane is attached to the thorax and the inner membrane is attached to the lungs.
Between the membranes is the pleural fluid, which is incompressible, so if the thorax moves, the lungs move too.
The alveoli are elastic and collapse if not held stretched by the thorax (as happens in stab wounds).
Forced expiration
The abdominal muscles contract, pushing the diaphragm upwards
The internal intercostal muscles contract, pulling the ribs downward
This gives a larger and faster expiration, used in exercise
Ciliated columnar epithelial tissue
Colum-shaped ciliated cells with hair-like structures called cilia covering an exposed cell surface
Line the trachea in the respiratory system in order to protect the lungs from infection
Cilia sweep pathogens away from the lungs
Goblet cells in columnar epithelial tissues
Colum shaped cells in the respiratory tract as well
Goblet cells are specialised for secreting mucus - a mixture of glycoproteins and proteoglycans synthesised in the ER and Golgi
Secrete mucus to protect the lungs and prevents unwanted particles reaching the lungs from the air we breathe
Prevents bacteria reaching the alveoli
Where else are secretions used in the respiratory system?
Pleural membranes
- are serous membranes
- one side lines body cavity wall and the other lines lungs
- secrete serous fluid that reduces friction and enables the membranes to slide over each other
- prevent lungs adhering to body cavity wall
Surfactant in alveoli
surface of alveoli has to be moist so oxygen can dissolve in the water before it can diffuse through into blood in capillaries
Prevents sticking of membranes together in ‘bunches
Tidal volume
This is the amount of air exchanged in a single breath.
Approximately 500 cm3 at rest.
Increases significantly with exercise.
Vital capacity:
This is the maximum volume of air that can be exchanged in a single breath.
Made up of:
Inspiratory reserve
Expiratory reserve
Tidal volume.
Approx 4 to 4.5 dm3.
Depends upon body size, gender, exercise.
Breathing rate:
Spirometer trace has series of peaks and troughs.
Peak to peak (or trough to trough) is one breath.
Count the number in a minute.
Total air breathed per minute (pulmonary ventilation) is:
Tidal volume x breathing rate.
Oxygen consumption:
The air breathed into the spirometer has the CO2 removed by the soda lime:
volume of gas decreases
decrease is equivalent to oxygen consumption
calculate gradient for O2 consumption.
Gradient steeper during exercise.
