Exchange surfaces and breathing Flashcards
Why do multicellular organisms need specialised exchange surfaces?
Diffusion is too slow because:
- Some cells are deep within the body so the diffusion distance is too large
- Larger animals have a low surface area:volume ratio therefore it is difficult to exchange substances through a small surface area
- Higher metabolic rate so glucose and oxygen are used up quicker.
Describe the features of a specialised exchange surface and relate to specific cells.
- Microscopic hairs increase the surface area which helps increase absorption of water by osmosis and mineral ions by active transport - Root hair cell
- Made from a single layer of thin flat cells (alveolar epithelium) decreases diffusion distance for oxygen and carbon dioxide so increases rate of diffusion - alveoli
They have good blood supply and/or ventilation: - Alveoli - surrounded by good capillary network giving each alveolus its own blood supply
- Gills in fish - cappilary network keeps them well supplied with blood. Theyre also well ventilated helping maintain an oxygen concentration gradient increasing rate of oxygen diffusion.
Describe the function of goblet cells.
Secrete mucus which traps microorganisms in the inhaled air stopping them from reaching alveoli.
Found lining the airways.
Describe the function of cilia.
Beat the mucus to move it upward away from the alveoli towards the throat where it is swallowed - this prevents lung infections.
Found on the surface of cells lining the airways.
Describe the function of elastic fibres.
Help the process of breathing out - on breathing in the lungs inflate and the elastic fibres are stretched. Then, the fibres recoil to help push the air out when exhaling.
Found in the trachea bronchi bronchioles and alveoli.
Describe the function of smooth muscle.
Allows the diamter of the trachea bronchi bronchioles and alveoli to be controlled, During exercise, smooth muscle relaxes making the tubes wider so there is less resistance to air flow.
Describe the function of the rings of cartilage.
Provide support in the walls of the bronchi and trachea, collapsing when the pressure drops and you breathe in.
Describe inspiration in mammals.
The external intercostal and diaphragm muscles contract.
This causes the ribcage to move upwardsand outwards and the diaphragm to flatten increasing the volume of the thorax (space where the lungs are)
As the volume of the thorax increases the lung pressure decreases
This causes air to flow into the lungs
Inspiration is an active process so requires energy .
Describe expiration in mammals.
The external intercostal muscles and diaphragm muscles relax
The ribcage moves downwards and inwards
The thorax volume decreases making the air pressure increase
This forces air out of the lungs
Normal expiration is a passive process so does not require energy however if expiration if forced the internal intercostal muscles contract to pull the ribcage down and in.
What is tidal volume?
The volume of air that is inhaled OR exhaled with one breath at rest
What is vital capacity?
maximum volume of air that can be inhaled OR exhaled with one breath.
What is residual volume?
Volume of air left in the lungs after hardest possible exhalation
What is oxygen uptake?
Rate of oxygen consumption
What is the breathing rate?
Number of breaths per unit of time
Describe how a spirometer works.
- A spirometer has an oxygen filled chamber with a movable lid
- The person breathes through a tube connected to the oxygen chamber
- As the person breathes in and out of the tube the lid of the chamber moves up and down.
- Each time the lid goes down the pen on the kymograph goes down too, each time the lid goes up the pen on the kymograph goes up creating a spirometer trace.
- The soda lime in the tube the subject breathes into absorbs carbon dioxide.
