Module 3.1.1 Flashcards
Why does the body need exchange surfaces?
All cells need a supply of oxygen and nutrients to survive.
They also need waste products removed so they don’t cause a toxic build up.
What are the 3 main factors that affect the need for an exchange system?
Size
Surface area to volume ratio
Level of activity
How does size affect the need for an exchange system?
In very small organisms (single celled) all cytoplasm is very close to the environment. Simple diffusion is enough.
Multicellular organisms have many layers of cells and so the diffusion pathway is too long and diffusion is too slow to enable a supply to inner cells.
Why does surface area to volume ratio affect the need for an exchange system?
Small organisms have a small surface area but they also have a small volume. Their SA is large compared to volume. They have a large SA:V ratio.
Large organisms have a large SA but a larger volume. As size increases, SA:V ratio decreases.
How does level of activity affect the need for an exchange system?
Large organisms have a high metabolic rate so need to exchange lots of material quickly, metabolic activity uses energy from food and requires oxygen to release energy in aerobic respiration.
The cells of an active organism need good supplies of nutrients and oxygen to supply energy.
What are the features of an efficient exchange surface?
Increased SA.
Thin layers.
Blood supply.
Ventilation.
Why is increased SA a good feature of an exchange system?
Provides a larger area over which the exchange of materials occurs.
Overcomes limitations of SA:V ratio of larger organisms.
Why are thin layers a good feature of an exchange system?
Creates a short diffusion pathway.
Increases speed and efficiency of exchange.
Why is blood supply a good feature of an exchange system?
Maintains a steep conc gradient for diffusion and ensures the exchanged substances are constantly moving to the area needed/removed from an area.
Why is good ventilation a good feature of an exchange system?
Maintains the diffusion gradient for gases, makes the processes faster and more efficient.
What do larger organisms require specialised gas exchange and transport systems?
To transport substances such as oxygen and nutrients to their cells efficiently.
Where does gas exchange occur in insects, fish and mammals?
Gills, spiracles and lungs.
What is the pleural cavity?
It is a double membrane that encloses both lungs. The space between these membranes is called the pleural cavity and is filled with a small amount of pleural fluid.
What does the pleural cavity do?
The fluid inside lubricates the lungs. It also adheres to the outer walls of the lungs to the thoracic (chest) cavity by water cohesion, so that the lungs expand with the chest while breathing.
What are the features of the nasal cavity and how do they help gas exchange?
Large SA and good blood supply - warms the air as it passes into the body.
Hairy lining - hairs trap dust and bacteria in mucus and prevent them from reaching the lungs, which could cause infection.
Moist surfaces - increases the humidity of the incoming air, this reduces the evaporation of water in the lungs.
This means that after the air has passed through the nasal cavity, the air entering the lungs is a similar temperature and humidity to the air already there.
What are the features of the trachea?
Supported by a layer of cartilage that holds the trachea open and prevents it from collapsing.
The rings are incomplete to allow it to bend when food is swallowed down the oesophagus behind.
Gaps between the cartilage is filled with smooth muscle and elastic fibres.
The cartilage, muscle and elastic fibres hold the trachea open but allow flexibility during inspiration and expiration.
The trachea is lined with ciliated columnar epthelial cells and goblet cells that prevent dust and bacteria from entering the lungs.
Blood vessels warm the air.
What are the bronchus and what are their function?
They are extensions of the trachea that split into two for the left and right lung.
Has a v. similair structure to trachea but smaller.
Cartilage rings hold the pipes open.
What are the bronchioles and what are their functions?
The bronchus splits into much smaller bronchioles.
They are about 1nm or less in diameter.
No cartilage and are held open by smooth muscle.
When this muscle contracts the bronchioles contract, this affects the air flow to the lungs.
Lined with a thin layer of columnar/cuboidal epithelial tissues making some gas exchange possible
How does asthma affect the brochioles?
Cells lining the bronchioles release histamines (making epithelial cells inflamed and swollen). These histamines stimulate goblet cells to release excess mucus and smooth muscles in bronchioles walls to contract.
Airways narrow and fill with mucus.