Topic 3: Gas exchange Flashcards
Describe the process on how air enters the lung.
Air flows in through the mouth and nose then down the trachea which splits into two bronchi which branches off into bronchioles. Bronchioles end in small sacs known as alveoli.
Where does gas exchange in animals take place?
In the capillaries surrounding the alveoli
What is each lung surrounded by and how does it help the lung?
A membrane and the pleural cavity is filled with pleural fluid.
This lubricates the lung and helps the lung adhere to the walls of thoracic cavity by water cohesion.
Which allows the lungs to expand with the chest during inhalation.
Where is cartilage found and what is its function?
-Trachea and Bronchus
provides strength to trachea and bronchus
holds the airway open-prevents collapse of airway when pressure falls
Where is the surfactant found and what is its function?
-Coats the surface of lungs
Phospholipid layer which maintains moisture but reduces surface tension to stop alveoli collapsing when air pressure falls.
Where is smooth muscle found and what’s its function?
-Lining of trachea and bronchioles
Can contract to constrict the airways
Where is goblet cells found and what is its function?
-Lining of trachea and bronchioles
Secrete mucus which traps harmful particles which are breathed into the lungs.
Where are ciliated epithelial cells found and what is its function?
-Lining of trachea and bronchioles
Beat regularly to move mucus up the airways towards the mouth to be removed.
Helps keep the airway clear and prevent infections
Where are elastin found and what is its function?
-Lining of alveoli and all airways
Allows lug tissue to stretch and recoil.
Allows alveoli to return to original shape after exhaling.
Where are the squamous epithelium cells found and what is its role?
-Lining of the alveoli
Gives a short diffusion distance pathway for gases.
How is the alveoli adapted for gas exchange?
-Alveolar squamous epithelium and capillary squamous epithelium are flattened and only one cell thick
-Highly folded (large number of alveoli)
-Capillaries that surround the alveoli are very narrow
- Large number of capillaries surrounding the alveoli
-Constant ventilation and circulation.
How does the squamous epithelium being very thin increase diffusion?
It creates a short diffusion distance for gases.
How does narrowed capillaries increase diffusion?
Red blood cells are slowed down to squeeze through one at a time increasing the time for diffusion.
How does having a large number of alveoli increase diffusion?
Increases surface area for gas exchange
How does large number of capillaries surrounding the alveoli increase diffusion?
Provides the alveoli with a rich blood supply
How does constant ventilation and circulation increase diffusion?
Ensures concentration of oxygen in alveoli is higher and concentration of carbon dioxide is lower than the blood, maintaining a steep concentration gradient.
What happens during inspiration (inhalation)
-Diaphragm contracts and flattens whilst the ribcage moves up and out due to external intercostal muscles contracting.
-This increases the volume of the thoracic cavity and decreases the pressure, allowing air to move into the trachea down the pressure gradient.
-Internal intercostal muscles relax.
What happens during expiration (exhalation)?
Diaphragm relaxes whilst the rib cage moves down and in
This causes the volume to decrease and the pressure in the thoracic cavity to increasing, forcing air out.
External intercostal muscle relaxes whilst internal intercostal muscle contracts.
How is air supplied to respiring tissues in an insect?
Air enters through spiracles which travels down the trachea, splitting into tracheoles which continue dividing until they penetrate into individual body cells.
-Therefore gases are directly exchanged between cells.
How does the insects tracheole having thin walls increase rate of diffusion?
Shortens diffusion distance of gases to cells
How does the insects tracheole being highly branched increase the rate of diffusion?
Increases surface area for diffusion
There is fluid in the ends of the trachea where it joins tissues.
How does this increase the rate of diffusion in insects?
- Gas exchange from air to liquid occurs in the tracheole which allows gases to diffuse to tissues faster
- Tracheal fluid can be withdrawn into the body fluid to increase the surface area of the tracheole exposed to air
How does spiracles having the ability to close increase the rate of diffusion?
Builds up the CO2 concentration gradient, allowing it to diffuse faster
How does ventilation occur in insects?
- Contracting muscles between each body segment
The insect can compress the tracheae, pumping gases in and out of the body.
