3.1 Gaseous Exchange Flashcards
What exchange system do small organisms use and what does it do
diffusion is used to take in all oxygen required and to get rid of carbon dioxide waste
what are the 2 reasons that small organisms use diffusion
- The metabolic activity of a single-celled organism is usually low, so the oxygen demands + CO2 waste production of the cell is low
- The surface area to volume ration of small organism is large
what is correlation between organism size and SA:V ratio
As an organism gets bigger the SA:V ratio decreases
what is correlation between SA:V ration & gas exchange
if there’s a smaller SA:V ratio it increases the distance needed to travel from the outside to reach the cells at the centre of the body. This makes it difficult to absorb enough oxygen through the available S.A to meet the body’s needs.
how do increased S.A effect gas exchange
Increased surface area: Specialised cells like villi and root hair provide a larger surface area needed for exchange and overcomes limitation of surface area to volume ratio.
how do thin layers effect gas exchange
Thin layers: Reduces the distance that substances have to diffuse is short, making the process fast and effective.
how does good blood supply effect gas exchange
Good blood supply: Good blood supply. Ensure substances are constantly developed, delivered. And removed from exchange services to maintain a steep concentration.
how does ventilation effect gas exchange
Ventilation to maintain diffusion gradient: For a gas ventilation system helps maintain concentration gadient and makes the process more efficient.
nasal cavity
Has a large surface area with a good blood supply Which warms the air to body temperature.
A heavy lining which secrets mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection.
Moist surfaces which increase the humidity of the incoming air, reducing evaporation from the exchange services.
trachea
- main airway for carrying clean , warm , moist air to chest cavity
- Contains incomplete rings of strong cartillage to stop it collapsing
- The trachea and its branches are lined with a ciliated epithelium with global cells between and below the epithelial cells. Goblet cells secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining.
bronchus
In the chest cavity, the trachea divides to form the left bronchus leading to the left lung & the right bronchus leading to the right lung. They are similar in structure to the trachea, with the same supporting rings of cartilage, but they are smaller.
bronchioles
-The walls of bronchioles contain smooth muscle.
-When the smooth muscle contracts, the bronchioles constrict, meaning close.
-When it relaxes, the bronchioles dilate, which means open. This changes the amount of air reaching the lungs.
-Bronchioles are lined with a thin layer of flattened epithelium, making some gases exchange possible.
Alveoli
Alveoli is singular for Alveolus. They are tiny air sacs which are the main gas exchange surface of the body. Each of alveolus has a diameter of around 200 to 300 micrometres and consist of a layer of thin flattened epithelium cells along with some collagen and elastic fibres which are composed of elastin. These elastic tissues allow the alveoli to stretch as air is drawn in. When they returned to their resting size, they help squeeze the air out. This is known as the elastic recoil of the lungs. The alveoli epithelium cells are very thin to minimise diffusion distance. Each alveolus is surrounded by a network of capillaries to remove the exchanged gasses and therefore maintain the concentration gradient. There is high concentration of carbon dioxide in the capillary and low concentration of oxygen. In the alveoli there is low concentration of carbon dioxide, so the carbon dioxide diffuses from the capillary into the alveoli. The alveoli contain a high concentration of oxygen which then diffuses into the capillary.
adaptation of alveoli
Large surface area: There are 300-500 million Alveoli per adult lung. The alveolar surface area for gaseous exchange in the 2 lungs combined is about 50-75 m cubed. This large surface area allows for greater gas exchange
Thin Layers: Both the Abiola and capillaries that surround them have walls that are only a single epithelial cell deck, so the diffusion distance between the air in the Alveolus and the blood in the capillaries are very short.
Good blood supply: The millions of Aveo lie in each lung are supplied by a network of around 280 million capillaries. The constant flow of blood through these capillaries brings carbon dioxide and carries off oxygen, maintaining a steep concentration gradient for both carbon dioxide and oxygen between the air in the alveoli and the blood in the capillaries.
Good ventilation: Breathing moves air in and out of the alveoli, helping maintain steep diffusion gradients for oxygen and carbon dioxide between the blood and the air in the lungs.
inhalation
The external intercoastal muscles contract which causes the rib cage to move upwards while the internal intercoastal muscles relax
The diaphragm contracts and flattens from dome position
The volume of the thorax increases and the air pressure in the lungs to decrease until it is slighlty lower than the atmospheric pressure
As a result, air moves down the pressure gradient and rushes into the lungs and air is drawn in
