Gas Exchange In Humans Flashcards
What does air enter as you breathe in?
The trachea
What does the trachea split into? Where do these lead to?
2 bronchi, one bronchus leading to each lung.
What do bronchi branch off into?
Bronchioles - smaller tubes
What do Bronchioles end in?
Air sacs called alveoli
Where does gas exchange occur in humans?
At the alveoli
Where are the intercostal muscles found?
Between the ribs.
What are the 2 types of intercostal muscles?
Internal and external intercostal muscles
How is a large surface area achieved for efficient gas exchange in mammals?
Highly branched bronchioles leading to alveoli
Now is air moved across the exchange surface in mammals?
Tidal flow - flows in opposite directions in and out
How is the required gas delivered to respiring cells?
Red blood cells in blood vessels
What lines the alveoli?
A single layer of flattened epithelial cells and a network of pulmonary capillaries
What are the capillaries surrounding the alveoli lined with?
A single layer of endothelial cells
How thick are the capillaries surrounding the alveoli?
Very thin-one cell thick
Why is it beneficial for the capillaries to be narrow as the red blood cells pass through?
The capillaries are narrow so that red blood are flattened and squeezed through. This slows them down and increases surface area for diffusion.
Where are squamous epithelia found?
On the outer layer of the alveoli, lining the cheeks, inside blood vessels, lining the chambers of the heart
What are the adaptations of squamous epithelia?
Smooth, flat, very thin, packed closely together, single layer of flattened cells
Why are squamous epithelia important?
The layer of cells forms a thin cross-section which reduces the distance that substances have to move to pass through - it shortens the diffusion pathway
It is permeable, allowing for the easy diffusion of gases
Why is it important that the surface of the squamous epithelia is a low friction surface?
Low friction decreases the chance of clots forming
What 5 factors increase the rate of diffusion in mammals?
- The RBC’s are slowed as they pass through the pulmonary capillaries
- The RBC’s are flattened against the capillary walls
- The walls of capillaries and alveoli are very thin
- Alveoli have folds and there are many capillaries
- ventilation and circulation
Why does the slowing down of RBC’s as they pass through capillaries increase the rate of diffusion?
More time for efficient exchange of oxygen.
Why does the flattening of RBC’s against the capillary wall increase the rate of diffusion?
Reduces the distance between the alveoli and capillary therefore a shorter diffusion pathway
Why do thin walls increase rate of diffusion?
Shorter diffusion pathway
Why do folds in alveoli and many capillaries increase the rate of diffusion?
Increases the surface area
Why do ventilation and circulation increase rate of diffusion?
Ensure a concentration gradient is maintained
Define the term ventilation
The process by which air is constantly moved into and out of the lungs
What is inspiration (inhalation)?
When arr is forced into the alveoli because the pressure of the atmosphere is greater than the pressure inside the lungs
What happens during inspiration?
The external intercostal muscles and the diaphragm contract which causes the ribcage to move upwards and outwards and me diaphragm to flatten. The volume of the thorax increases as the diaphragm flattens. The pressure in the thorax decreases as volume increases. The pressure of air in the atmosphere is higher than the pressure inside the thorax. Air is drawn into the lungs. This is an active process and requires energy.
What happens during expiration?
The external intercostal muscles and the diaphragm relax (the internal ones remain relaxed unless expiration is forced). The volume of the thorax decreases as the diaphragm becomes domed. The pressure in the thorax increases as volume decreases. The pressure ‘of air in the atmosphere is lower than the pressure inside the thorax. Air is forced out of the lungs.
Is normal expiration active or passive?
It is passive as it doesn’t require energy.
What is the equation for pulmonary ventilation?
Pulmonary ventilation= tidal volume x ventilation rate
What is ventilation rate?
The breaths taken in one minute
What is pulmonary ventilation?
The measure of the amount of air that is moved into the lungs in one minute
Name the process by which oxygen passes from an alveolus in the lungs into the blood
Diffusion
Describe now oxygen in the air in the alveoli enters the capillaries
Diffusion across the alveoli epithelium
What is tidal volume?
The volume of air normally taken in at each breath when the body is at rest
What is forced expiratory volume (fev 1)
The maximum volume of air breathed out in one second
What is forced vital capacity? (Fvc)
The maximum volume of air that can be forced out of the lungs after a deep breath in
What is ventilation rate?
Number of breaths per minute
What is a spirometer? What’s it used for?
Amachine used to record measurements such as tidal volumes vital capacity etc.
What is residual volume?
Volume of air left in the lungs after forcibly breathing out
What is expiratory reserve volume?
The max volume of air that can be expelled from the lungs after normal expiration
What is inspiratory reserve volume?
The max volume of air that can be inhaled after a normal inspiration
Now do you work out % change in FEV1?
Final value - original value x100
Original value
What is a correlation?
A link/ relationship between 2 things that happen
What are the walls of the alveoli made from?
A single layer of thin, flat cells called alveolar epithelium
What protein can be found in the walls of the alveoli?
Elastin. It helps the alveoli return to their normal shape after inhaling or exhaling
Describe the route that air takes to get to alveoli
Moves down the trachea, bronchi and bronchioles into the alveoli this is down a pressure gradient
Describe the route oxygen takes to get into the blood
Alveoli, alveolar epithelium, capillary endothelium, blood
What 2 features do alveoli have that speed up diffusion+ gas exchange?
- A thin exchange surface: the alveolar epithelium is only one cell thick which means there is a short diffusion pathway
- a large surface area:more gas exchange can take place
Explain how gas exchange occurs at the alveoli
Air moves in and out of the alveolus. Blood enters the capillary from the rest of the body. It has a high concentration of carbon dioxide and a low concentration of oxygen. The alveolus has a high concentration of oxygen and a lower concentration of carbon dioxide. There is a net movement of carbon dioxide into the alveolus and a net movement of oxygen out of the alveolus. Blood goes to the rest of the body with A lower concentration of carbon dioxide and a higher concentration of oxygen
