3.1 Flashcards
Explain the need for a specialised exchange surface
- small surface area to volume ratio
- living things need to obtain O2, nutrients, water + CO2 (in plants). They also need to be able to remove waste substances such as CO2, urea and O2 (plants) before they reach toxic levels, this exchange needs to happen quickly.
Explain the features of an efficient exchange surface
- large surface area
- a thin barrier to reduce the diffusion distance, barrier must be permeable to the substances being exchanged
- good blood supply so it can maintain a steep concentration gradient so that diffusion can occur rapidly
What is the alveoli?
Tiny folds of the lung epithelium to increase surface area
What are bronchi and bronchioles?
Smaller airways leading to the lungs
What is the diaphragm?
A layer of muscle between the lungs
What are the intercostal muscles?
Muscles between the ribs. Contraction of the external intercostal muscles raises the ribcage
What is the trachea?
The main airway leading from the back of the mouth to the lungs
What is ventilation?
The refreshing of air in the lungs, so that there is a higher oxygen concentration than in the blood, and a lower carbon dioxide concentration
Describe the mechanism of ventilation in mammals during inspiration/inhalation
- The diaphragm contracts to move down and become flatter - the displaces the digestive organs downwards
- The external intercostal muscles contract to raise the ribs
- The volume of the chest cavity is increased
- The pressure in the chest cavity drops below atmospheric pressure
- Air is moved into the lungs
Describe the mechanism of ventilation in mammals during exspiration/exhalation
- The diaphragm relaxes and is pushed up by the displaced organs underneath
- The external intercostal muscles relax and the ribs fall; the internal intercostal muscles can contract to help push air out more forecfully - this usually only happens during exercise or coughing or sneezing
- The volume of the chest cavity is decreased
- The pressure in the lungs increases and rises above the pressue in the surrounding atmosphere
- Air is moved out of the lungs
What is cartilage?
A form of connective tissue
What is ciliated ephithelium?
A layer of cells that have many hair-like extensions called cilia
What are elastic fibres?
Protein fibres that can deform and the recoil to their original size
What are goblet cells?
Cells that secrete mucus
What is smooth muscle?
Involuntary muscle that contracts without the need for conscious thought
What is the use of ciliated epithelium?
They line airways and move mucus to the top of the airway, where it is swallowed.
What is the use of goblet cells?
Goblet cells in the epithelium release mucus, which traps pathogens
What is the use of cartilage?
The trachea and bronchi are supported by C-shaped rings of cartilage which prevents collapse during inspiration. The C-shape allows room for food to pass down the oesophagus and allows flexibility
What is the use of elastic fibres?
The alveolus walls contain elastic fibres that stretch during inspiration but then recoil to help push air out during expiration.
What is breathing rate?
The number of breaths per minute
What is oxygen uptake?
The volume of oxygen absorbed by the lungs in 1 minute
What is tidal volume?
The volume of air inhaled or exhaled in one breath, usually measured at rest
What is a spirometer?
A device that can measure the movement of air into and out of the lungs
What is vital capacity?
The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath
What is residual volume?
The volume of air that remains in the lungs after forced expiration
What is the buccal cavity?
The space inside the mouth
What is countercurrent flow?
When 2 fluids flow in opposite directions
What are gill filaments/primary lamellae?
Slender branches of tissue that make up the gill.
What are the secondary lamellae/gill plates?
Folds of the filament to increase surface area
What is the operculum?
A bony flap that covers and protects the gills
What is the spiracle?
An external opening or pore that allows air in and out of the tracheae
What is the tracheal fluid?
The fluid found at the ends of the tracheoles in the tracheal system
What is the tracheal system?
A system of air-filled tubes in insects
Why does countercurrent flow occur?
Blood flows in an opposite direction to water which creates a countercurrent flow, absorbing the maximum amount of oxygen + ensures there is a steep concentration gradient between oxygen and water. (concentration of O2 is always higher in the water than in the blood)
What can the buccal cavity do?
- Lower, this increases volume +decreases pressure meaning water is sucked in
- Close, raising the floor, decreasing volume+ increasing pressure which forces water out and across gill filaments/primary lamellae, increased pressure also forces operculum open to water leaves the gills
Do insects have an open or closed circulatory system?
Open circulatory system
How does air get to insects respiring tissues?
Through an insects air-filled tracheal system which supplies air directly
How does air enter an insect?
Through the spiracles (pores)
Where does gas exchange occur in an insect?
Between the air in the tracheole and the tracheal fluid.
How can you increase the surface area of an insect?
- Tracheal fluid can be withdrawn into the body fluid
- Tracheal system can expand and have flexible walls
- Movement of wings can alter volume of thorax
- Locusts can alter volume of abdomen by specialised breathing movements
