3.1 Gaseous Exchange

Question 1

What exchange system do small organisms use and what does it do

Answer 1

diffusion is used to take in all oxygen required and to get rid of carbon dioxide waste

Question 2

what are the 2 reasons that small organisms use diffusion

Answer 2

1. The metabolic activity of a single-celled organism is usually low, so the oxygen demands + CO2 waste production of the cell is low
2. The surface area to volume ration of small organism is large

Question 3

what is correlation between organism size and SA:V ratio

Answer 3

As an organism gets bigger the SA:V ratio decreases

Question 4

what is correlation between SA:V ration & gas exchange

Answer 4

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.

Question 5

how do increased S.A effect gas exchange

Answer 5

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.

Question 6

how do thin layers effect gas exchange

Answer 6

Thin layers: Reduces the distance that substances have to diffuse is short, making the process fast and effective.

Question 7

how does good blood supply effect gas exchange

Answer 7

Good blood supply: Good blood supply. Ensure substances are constantly developed, delivered. And removed from exchange services to maintain a steep concentration.

Question 8

how does ventilation effect gas exchange

Answer 8

Ventilation to maintain diffusion gradient: For a gas ventilation system helps maintain concentration gadient and makes the process more efficient.

Question 9

nasal cavity

Answer 9

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.

Question 10

trachea

Answer 10

• 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.

Question 11

bronchus

Answer 11

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.

Question 12

bronchioles

Answer 12

-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.

Question 13

Alveoli

Answer 13

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.

Question 14

adaptation of alveoli

Answer 14

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.

Question 15

inhalation

Answer 15

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

Question 16

exhalation

Answer 16

The External intercostal muscles relax which causes the internal intercostal muscles to contract which pulls the ribs downwards & inwards

The diaphragm relaxes and returns to domed position

The volume of the thorax decreases and the air pressure in the lungs increases and is greater the atmospheric pressure

This causes the air to move from high pressure in the lungs out to atmosphere pressure

Question 17

spirometer

Answer 17

is commonly used to measure different aspects of the lung volume or to investigate breathing patterns.

Question 18

tidal volume

Answer 18

Is the volume of air that moves into and out of the lungs with each resting breath. It is around 500 centimetres cubed in most adults at rest, which uses about 15% of the vital capacity of the lung.

Question 19

vital capacity

Answer 19

Is the volume of air that can be breathed in when the strongest possible inhalation is followed by the deepest possible intake of breath.

Question 20

inspiratory reserve volume

Answer 20

Is the maximum volume of air you can breathe in over and above a normal inhalation.

Question 21

expiratory reserve volume

Answer 21

Is the extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.

Question 22

residue volume

Answer 22

Is the volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.

Question 23

total lung capacity

Answer 23

Is the sum of the vital capacity and the residual volume.

Question 24

what is the breathing rate

Answer 24

The breathing rate is the number of breaths taken per minute

Question 25

what is the ventilation rate

Answer 25

The ventilation rate is the total volume of air inhaled in one minute.

Question 26

ventilation rate equation

Answer 26

Ventilation rate = tidal volume X breathing rate (per minute)