3.1.1 Flashcards
Why is diffusion enough to supply the needs of single-celled organisms?
Metabolic activity is low, so oxygen demands and carbon dioxide production are relatively low. The SA: V ratio of the organism is larger.
What are the characteristics of effective exchange surfaces?
Increased surface area. thin layers, good blood supply, and ventilation to maintain the diffusion gradient
Describe the important features of the nasal cavity
- Large SA with good blood supply, which warms the air to body temperature
- Hairy lining, secreting mucus to trap dust and bacteria, which protects the lung tissue from irritation and infection
- Moist surfaces, increasing the humidity of the incoming air, which reduces evaporation from the exchange surfaces
Describe the structure of the trachea
The trachea is a wide tube supported by incomplete rings of cartilage, which stop the trachea from collapsing. They are incomplete to allow food to move down the oesophagus. The trachea and the branches are lined with ciliated epithelium
Describe ciliated epithelium tissue
Layer of ciliated epithelial cells with goblet cells between and below them.
What is the function of the goblet cells?
They secrete mucus onto the lining of the trachea, trapping dust and microorganisms. The cilia beat and move the mucus away from the lungs.
What are the bronchi?
The initial branches of the trachea. They are similar in structure to the trachea, but are smaller
What are the bronchioles?
Divisions of the bronchi. They have no cartilage, instead the walls contain smooth muscle. The contraction and relaxation of the smooth muscle changes the amount of air reaching the lungs. Bronchioles are lined with a layer of flattened epithelium, making some gas exchange possible
What are the alveoli?
Tiny air sacs, which are the main gas exchange surfaces in the body. The alveoli consist of a thin layer of thin, flattened epithelial cells, along with some collagen and elastic fibres, allowing for elastic recoil of the alveoli
Describe the main adaptations of the alveoli
Large SA. thin layers, good blood supply, good ventilation
What covers the inner surface of the alveoli?
A thin layer of a solution of water, salts, and lung surfactant. The lung surfactant allows the alveoli to remain inflated
Describe the process of inspiration
The diaphragm contracts, flattening and lowering. The external intercostal muscles contract, so the ribs move up and out. The thoracic volume increases, so pressure decreases. This causes air to be drawn, to equalise the pressure
Is inspiration active or passive?
Active
Describe the process of expiration
The diaphragm relaxes so it returns to its dome shape. The external intercostal muscles relax so the ribs move down and in. The thoracic volume decreases, so the pressure increases, so air moves out of the lungs until the pressure equalises.
What is tidal volume?
The volume of air that moves into and out of the lungs with each resting breath
What is the vital capacity?
The volume of air that can be breathed when the strongest possible exhalation is followed by the deepest possible intake of breath
What is the inspiratory reserve volume?
The maximum volume of air you can breathe in over and above a normal inhalation
What is the expiratory reserve volume?
The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
What is the residual volume?
The volume of air that remains in the lungs after the strongest possible exhalation
What is the total lung capacity?
The sum of vital capacity and residual volume
What is the breathing rate?
The number of breaths taken per minute
What is the ventilation rate?
The total volume of air inhaled in one minute (tidal volume * breathing rate)
What can be used to measure lung volume?
Spirometer, vitalograph, peak flow meter
How does gas exchange take place in insects?
Along the thorax and abdomen of most insects, there are small openings called spiracles. Air enters and leaves the system through them, but water is also lost. The spiracles are opened or closed by sphincters. Leading from the spiracles are tracheae. They carry the air into the body. They are held together by chitin. Tracheal fluid is present at the end of the tracheoles, which limits the penetration of air for diffusion
Describe gaseous exchange in bony fish
The mouth opens and the floor of the buccal cavity lowers. This lowers the pressure in the buccal cavity, and so water moves into it. The opercular cavity containing the gills expands. The buccal floor raises, so the water moves over the gills. The mouth then closes, and the operculum opens. Then, the volume of the opercular cavity decreases, so water is forced over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, so the flow of water is maintained.
How are bony fish adapted for gaseous exhange?
- The tips of adjacent fill filaments overlap. This increases resistance to flow of water over the gills surfaces, slowing down the movement of water.
- The water and the blood flow in opposite directions, ensuring a countercurrent exchange, maintaining the steep concentration gradient
