exchange and breathing. Flashcards
What is an exchange surface?
A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other.
What is exchange like in single-celled organisms?
Diffusion is quick: Short diffusion distance, relatively high SA : Volume ratio.
What is exchange like in multicellular organisms?
Diffusion is slow: Some cells are too deep within the body, large diffusion distance, low SA : Volume ratio, high metabolic rate.
Adaptations of exchange surfaces?
- Increased surface area.
- Thin.
- Good blood supply or ventilation (maintain concentration gradient).
Examples of exchange surfaces?
- Root hair cell.
- Alveoli.
- Gills.
How are root hair cells adapted for exchange?
- Thin cell well:
Short diffusion distance. - Large surface area (each branch covered in millions of microscopic hairs):
Increases rate of absorption.
How are alveoli adapted for exchange?
- Thin (made from a single layer of cells called the alveoli epithellum): Short diffusion distance.
- Good blood supply (surrounded by a large capillary network):
Maintains concentration gradient. - Good ventilation (air is constantly being replaced by the lungs): Maintains concentration gradient.
- Moist lining:
Increases humidity, reducing evaporation.
How are gills adapted for exchange?
- Well-ventilated (water constantly moving over gills):
Maintains concentration gradient. - Good blood supply:
Maintains concentration gradient.
Explain what happens when inhaling (inspiration).
- Diaphragm contracts and flattens (pushes digestive organs down).
- Intercostal muscles contract.
- Ribs move outwards and upwards.
- Volume of chest cavity increases.
- Pressure in chest cavity drops below atmospheric pressure.
- Air moves in to lungs down a pressure gradient.
Explain what happens when exhaling (expiration).
- Diaphragm relaxes and is pushed up by displaced organs underneath.
- Intercostal muscles relax.
- Ribs move inwards and downwards.
- Volume of chest cavity decreases.
- Pressure in lungs increases above atmospheric pressure.
- Air moves out of lungs down a pressure gradient.
Describe the nasal cavity.
- Large SA with good blood supply: warms air to body temperature.
- Hairy Lining: protects lung from irritation and infection.
- Moist surface: increases humidity of air, reducing evaporation.
Describe the bronchus.
- Similar to trachea but smaller.
- There are two, each leading to a different lung.
Describe the trachea.
- Supported by strong, flexible cartilage.
- Goblet cells secret mucus to trap dust and microbes.
- Ciliated epithelium moves mucus away from the lungs.
Describe the alveoli.
- Elastic tissues: allow alveoli to stretch and recoil.
- Inner surface of alveoli is covered with a layer of water, salts and lung surfactant.
- Oxygen dissolves into water before diffusing but could also evaporate. Aims to reduce water loss.
Describe the bronchioles.
- Contains smooth muscle which contracts and relaxes to change the amount of air that reaches the lungs.
- Lined with epithelium to make gas exchange possible.
Define tidal volume.
Volume of air moved in and out of the lungs with each breath when at rest. Approximately 0.5dm cubed and provides the body with enough oxygen for its resting needs while removing enough carbon dioxide to maintain a safe level.
Define vital capacity.
The largest volume of air that can be moved into and out of the lungs in one breath. Approximately 5dm cubed but varies between men and women, or a person’s size and age. Regular exercise increases vital capacity.
Define residual volume.
Volume of air that always remains in the lungs, even after the biggest possible exhalation. Approximately 1.5dm cubed.
Define dead space.
Air in the bronchioles, bronchi and trachea. There is no gas exchange between this air and the alveoli/blood.
Define inspiratory reserve volume.
How much more air can be breathed in (inspired) over and above the normal tidal volume when you take a big breath. This reserve is called upon when exercising.
Define expiratory reserve volume.
How much more air can be breathed out (expired) over and above the amount that is breathed in a tidal volume breath.
Define spirometer.
A device designed to measure the volume of air entering and leaving the lungs during breathing. A kymograph (a revolving drum wrapped in graph paper) records a trace which corresponds to the person’s breathing pattern.
Define peak flow meter.
- Simple device used to measure the rate at which air is expelled from the lungs.
- People who have asthma often use these to monitor how well their lungs are working.
How do spirometers work?
- Oxygen breathed in from the spirometer is used in respiration so is not exhaled.
- Carbon dioxide is released in respiration and exhaled back into the spirometer.
- Carbon dioxide absorbed by soda lime.
- Volume of air in chamber decreases over time.
- We can use this to measure oxygen uptake.
