Exchange Surfaces Flashcards
Why is diffusion alone enough to supply the needs of single-called organisms?
1- Metabolic activity of a single-celled organism is usually low, so O2 demands and CO2 production are relatively low
2- SA:V ratio of organism is large
Give 4 features of effective gaseous exchange surfaces
1- Increased SA; provides area needed for exchange
2- Thin layers; diffusion distance is shorter
3- Good blood supply; ensures a steeper conc gradient for more diffusion, substances are constantly delivered and removed
4- Ventilation; maintains diffusion gradient
Give 3 important features of the nasal cavity
1- Large SA with good blood supply; warms air to body temperature
2- Hairy lining; secretes mucus to trap dust/bacteria, protecting lungs from irritation/infection
3- Moist surfaces; increase humidity of incoming air, reducing evaporation from exchange surfaces
What does the trachea do?
The main airway carrying clean, warm, moist air from the nose down into the chest
What are the adaptations of the trachea?
- Incomplete rings of cartilage
- Lined with ciliated epithelium
What is the advantage of having incomplete rings of cartilage in the trachea?
Stop the trachea from collapsing
What is the advantage of the trachea being lined with ciliated epithelium?
- Have goblet cells to secrete mucus to trap dust and microorganisms
- Have cilia to beat and move mucus/dirt/microorganisms away from lungs
What are bronchi?
Where the chest cavity divides to form a left and right bronchus, similar in structure to the trachea but are smaller
What are the bronchioles?
Where the bronchi divide
What are the adaptations of bronchioles?
- No cartilage rings
- Walls contain smooth muscle
- Lined with a thin layer of flattened epithelium
What is the advantage of bronchioles having a wall containing smooth muscle?
- Allows contraction (constrict)
- Allows relaxation (dilate)
- Changes amount of air reaching lungs
What is the advantage of bronchioles being lined with flattened epithelium?
Makes some gaseous exchanges possible
What are alveoli?
Tiny air sacs, which are the main gas exchange surfaces of the body
What are the alveoli made of?
- A layer of thin, flattened epithelial cells
- Collagen and elastic fibres
What is the advantage of the alveoli consisting of elastic fibres?
- Allow the alveoli to stretch as air is drawn in
- Allow elastic recoil; helps squeeze air out when they return to resting size
Give 4 main adaptations of the alveoli
1- Large SA
2- Thin layers
3- Good blood supply
4- Good ventilation
What is the advantage of the alveoli having a large SA?
For increased rate of diffusion
What is the advantage of the alveoli having thin layers?
Single epithelial cell thick for short diffusion distance
What is the advantage of the alveoli having a good blood supply?
Maintains a steep concentration gradient for more diffusion
What is the advantage of the alveoli having good ventilation?
Maintains a steep diffusion gradient for O2 and CO2 between blood and air in the lungs
What is ventilation?
Air moving in and out of the lungs as a result of pressure changes in the thorax brought about by breathing movements
What is the thorax?
Chest cavity
What is the diaphragm?
A broad, domed sheet of muscle, which forms the floor of the thorax
What is inspiration?
Breathing in
What happens to the diaphragm during inspiration?
Contracts
Flattens
Lowers
What happens to the external intercostal muscles during inspiration?
Contract
Ribs move upwards + outwards
What happens to the volume of the thorax during inspiration?
Increases
What happens to the pressure of the thorax during inspiration?
Decreases so is lower than the pressure of the atmospheric air
What is expiration?
Breathing out
What happens to the diaphragm during expiration?
Relaxes
Moves up
What happens to the external intercostal muscles during expiration?
Relax
Ribs move down + inwards
What happens to the volume of the thorax during expiration?
Decreases
What happens to the pressure of the thorax during inspiration?
Increases so is higher than the pressure of the atmospheric air
What is a spirometer used to measure?
- Different aspects of the lung volume
- Investigate breathing patterns
What is tidal volume?
The volume of air that moves into and out of the lungs with each resting breath
What is vital capacity?
The volume of air that can be breathed in when the strongest possible exhalation is followed by the strongest possible inhalation
What is residual volume?
The volume of air left in your lungs when you exhale as hard as possible
What is total lung capacity?
Sum of vital capacity and residual volume
What is breathing rate?
The number of breaths taken per minute
What is ventilation rate?
The total volume of air inhaled in one minute
How do you calculate ventilation rate?
Tidal volume x breathing rate
