specialised exchange surfaces
- Created by: aryan26
- Created on: 09-04-19 11:26
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- specialised exchange surfaces
- why do organisms need an exchange surface?
- Organisms need to exchange substances with their environment
- cells need to take in oxygen and glucose for aerobic respiration and metabolic processes
- and need to excrete waste products like carbon dioxide and urea
- multi-cellular organisms
- in single celled organisms the substances can diffuse directly
- the diffusion is quick because of the short distance
- in multi-cellular organisms diffusion is too slow because:
- some cells are deep within the body
- larger animals have a small SA:V ratio-difficult to exchange enough substances to supply a large volume through a small surface
- multi-cellular organisms have a higher metabolic rate so they use up oxygen and glucose faster
- in single celled organisms the substances can diffuse directly
- Organisms need to exchange substances with their environment
- Structures have different functions
- goblet cells- line airways and secrete mucus
- mucus traps microorganisms and dust to prevent them from reaching the alveoli
- cilia- on surface of the airways, they beat the mucus.
- This moves the mucus upwards away from the alveoli which helps prevent lung infections-
- elastic fibres- in the walls of the trachea, bronchi, bronchioles and alveoli.
- Help the process of breathing out, on breathing in the lungs inflate which stretches the fibres, then they recoil which pushes air out when exhaling
- smooth muscle- in the walls, allows their diameter to be controlled.
- During exercise the muscle relaxes making the tubes wider= less resistance to airflow
- rings of cartilage- in the walls of the trachea and bronchi and provide support.
- Strong but flexible and prevents the trachea collapsing when you breathe in
- goblet cells- line airways and secrete mucus
- increasing efficiency
- have a large SA
- -e.g. root hair cells: each branch of a root will be covered in microscopic hairs-gives the roots a large SA to increase the rate of absorbtion of water and mineral ions
- they are thin
- e.g. the alveoli: gas exchange surface in the lungs, made from a single layer of thin flat cells called the alveolar epithelium.
- O2 diffuses out into the blood and CO2 diffuses in the opposite direction. the thin epithelium helps decrease the diffusion distance which increases the rate
- e.g. the alveoli: gas exchange surface in the lungs, made from a single layer of thin flat cells called the alveolar epithelium.
- have a good blood supply and or ventilation
- e.g. fish gills: gas exchange surface in fish. O2 and CO2 are exchanged between fish's blood and the surrounding water.
- contain a large network or capillaries and are well ventilated- fresh water constantly passes over them. helps maintain a concentration grafient of O2
- e.g. fish gills: gas exchange surface in fish. O2 and CO2 are exchanged between fish's blood and the surrounding water.
- have a large SA
- In mammals the lungs are exchange organs
- 1-as you breathe in, air enters the trachea, which splits into two bronchi, each leading to a lung
- 2-each bronchus branches into smaller tubes called bronchioles-
- 3- the bronchioles end in small air sacs called alveoli where gases are exchanged
- 4- the rib cage, intercostal muscles and diaphragm work together to move air in and out
- why do organisms need an exchange surface?
- In mammals the lungs are exchange organs
- 1-as you breathe in, air enters the trachea, which splits into two bronchi, each leading to a lung
- 2-each bronchus branches into smaller tubes called bronchioles-
- 3- the bronchioles end in small air sacs called alveoli where gases are exchanged
- 4- the rib cage, intercostal muscles and diaphragm work together to move air in and out
- Structures have different functions
- goblet cells- line airways and secrete mucus
- mucus traps microorganisms and dust to prevent them from reaching the alveoli
- cilia- on surface of the airways, they beat the mucus.
- This moves the mucus upwards away from the alveoli which helps prevent lung infections-
- elastic fibres- in the walls of the trachea, bronchi, bronchioles and alveoli.
- Help the process of breathing out, on breathing in the lungs inflate which stretches the fibres, then they recoil which pushes air out when exhaling
- smooth muscle- in the walls, allows their diameter to be controlled.
- During exercise the muscle relaxes making the tubes wider= less resistance to airflow
- rings of cartilage- in the walls of the trachea and bronchi and provide support.
- Strong but flexible and prevents the trachea collapsing when you breathe in
- goblet cells- line airways and secrete mucus
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