Chapter 7 Exchange surfaces and Breathing Flashcards
(36 cards)
For amoeba (single celled organism), transporting materials into and out of the cell happens via simple diffusion. Why do larger organisms require adaptions to increase efficiency of exchange?
Single celled organisms have:
> A large surface area : volume - This means they have a large surface area to diffuse by to fill up a relatively smaller space.
> Lower metabolic activity - They have a lower metabolic demand for things like glucose, oxygen and water, because they have less complex systems.
> Short diffusion distance - Distance by which substances diffuse from outside of the cell to the centre inside, is small, which gives a higher diffusion rate.
What are the features of specialised exchange surfaces?
> Increased surface area - Overcoming the limitations of low SA:V in larger organisms (villi in small intestine, root hair cells).
Thin layers - Thin layer; short diffusion distance; faster diffusion rate.
Good blood supply - Ensures substances are constantly diffused from blood to exchange surface; maintains a steep concentration gradient for diffusion.
Ventilation to maintain diffusion gradient- A good ventilation system means there is a constant supply of oxygen in, and constant remove of carbon dioxide to maintain concentration gradients.
Describe the movement of air (to alveoli) in the human gas exchange system.
> Nose
Nasal cavity
Trachea
Bronchi
Bronchioles
Alveoli
How is the nasal cavity adapted to taking in air?
> The nasal cavity has a large surface area with a good blood supply, which warms the air to body temperature.
It has a hairy lining that secretes mucus to trap dust and bacteria (protecting lung tissue from irritation and infection).
How is the trachea in humans adapted to its function?
The trachea carries air from the nasal cavity to bronchi.
> The trachea is supported with C-shaped rings of cartilage, to prevents the trachea from collapsing down on itself. It is C-shaped as it allows for movement of food down the adjacent pipe, the oesophagus.
> The trachea is lined with goblet cells and ciliated epithelium. The goblet cells secretes mucus (made of glycoproteins) which traps any bacteria and pathogens in the trachea, stopping them from reaching the lungs. The cilia then sweeps this mucus back up to be coughed up.
> The tracheal walls are made of smooth muscle. The trachea is able to contract and recoil due to the elastic fibres in trachea wall. The contraction of smooth muscle reduces the size of the lumen in the trachea, possibly to reduce airflow to the lungs in the presence of harmful substances.
How are the bronchioles adapted to its function?
The bronchioles carries air from the bronchi to alveoli.
> The bronchioles also contains some smooth muscles in its walls, so when it constricts, it is able to reduce airflow to the lungs.
> The walls of the bronchioles is made up of a thin layer of flattened epithelium, making some gas exchange possible.
How are the alveoli adapted to its function?
The alveoli is the site of gas exchange is humans.
> The alveoli has high surface area. Each individual alveoli is very small in size, giving a high SA:V. But with millions of alveoli in the lungs, this increases the surface area greatly, giving a faster diffusion rate.
> Short diffusion distance - Each alveoli has one layer of squamous epithelial cells in its walls.
> Maintained concentration gradient- Each alveoli is surrounded by a network of capillaries, with a good blood supply that is constantly exchanging gases.
> Elastic tissues in the walls of the alveoli allows the alveoli to expand as air is drawn in (and then recoil).
Describe the process of inspiration in humans.
> The diaphragm contracts and moves downwards.
External intercostal muscles contract.
Ribcage is pulled upwards and outwards.
The volume of thorax (chest cavity) increases.
The pressure in the thorax drops below atmospheric pressure.
Causes air to flow in the lungs.
Describe the process of expiration in humans.
> The diaphragm relaxes.
External intercostal muscles relax.
Internal intercostal muscles can contract, if air is being pushed out forcefully (forceful expiration).
Ribcage is pulled inwards and downwards.
The volume of the thorax decreases.
The pressure in the lungs increases and rises above atmospheric pressure.
Air moves out of the lungs.
What is the difference between normal expiration and forcefully exhaling (like during exercise, sneezing or coughing)?
Normal expiration is a passive process, where the internal intercostal muscles do not contract. When someone forcefully exhales, the intercostal muscles contracts which requires energy- it is not passive.
Describe how a floating chamber spirometer works.
> A floating chamber spirometer consists of a chamber of air or medical grade oxygen floating on top of a tank of water.
During inspiration, air is drawn from the chamber so the lid moves down.
During expiration, air returns to the chamber, raising the lid.
These movements are recorded by a data logger.
What precautions should be taken when using a spirometer?
> The subject should be healthy (free from asthma).
Soda lime should be fresh and functioning.
There should be no air leaks in the apparatus (it can give inaccurate results).
Sterilised mouthpiece.
Water chamber should not be overfilled.
What is the purpose of soda lime in a spirometer?
The soda lime is absorbed by carbon dioxide, so the data logger solely gives an indication of oxygen consumption.
What is tidal volume?
The air inhaled and exhaled when at rest.
What is vital capacity?
A measurement of maximum volume of air an individual can breathe in after strongest possible exhalation.
What is inspiratory reserve volume?
The maximum volume of air you can breathe in over and above normal inhalation.
What is expiratory reserve volume?
The extra amount of air you can force out of your lungs over and above normal tidal volume of air you breathe out.
What is residual volume?
The volume of air that remains in the lungs so they don’t collapse.
What is total lung capacity?
This is the sum of vital capacity and residual volume.
What is breathing rate?
Number of breaths taken per minute.
What is ventilation rate?
This is the volume of air inhaled in one minute. It is calculated by:
Tidal volume x Breathing rate
How is oxygen transported in the body of an insect?
In an insect’s body, oxygen is transported via body fluids. These body fluids acts as both blood and tissue fluid.
Describe the movement of air through an insect.
Air enters through the spiracles.
The air travels to the trachea.
The air reaches the tracheoles. Near the ends of the tracheoles is where gas exchange occurs, as the end of the tracheoles are found near muscles.
What is the function of the spiracles in an insect? How is it adapted to its function?
The spiracles are little holes found on the surface of the body of the insect, and it is where air enters. Gases are able to enter the insect through this, but water can also be lost. To maximise gas exchange and reduce water loss, the spiracles have adaptions where it can open and close, with the help of sphincters. So, when an insect is inactive and has a low demand for oxygen, the sphincters closes the spiracles to reduce water loss.
