Y12 MS - Gas Exchange (Complete)

Question 1

What is Ficks Law

Answer 1

The rate of diffusion is equal to:
(Surface area x concentration gradient) / diffusion distance

Question 2

How are the alveoli adapted for efficient gas exchange

Answer 2

Millions of alveoli provide a large surface area
Squamous epithelium cells are flattened for a short diffusion distance
Single layer of cells in the capillaries for a short diffusion distance
Large diffusion gradient for both oxygen and carbon dioxide
Concentration gradient maintained as the rich blood supply quickly removes oxygenated blood

Question 3

During human gas exchange in the alveoli, what structures must oxygen diffuse through

Answer 3

Squamous epithelium cells
Capillary walls
Tissue fluid
Membrane of red blood cells

Question 4

What structures does oxygen have to move through in the human respiratory system

Answer 4

Nostril
Trachea
Bronchi
Bronchioles
Alveoli

Question 5

How is breathing different from respiration

Answer 5

Respiration is the reaction oxygen + glucose —> carbon dioxide + water
Breathing is the gas exchange mechanism where oxygen and carbon dioxide are exchanged from the blood

Question 6

Overall where does gas exchange in humans take place

Answer 6

In the thorax

Question 7

Name all of the major structures involved in the human ventilation system

Answer 7

Trachea
Lungs
Bronchi
Bronchioles
Alveoli
Capillary network

Question 8

Describe the trachea

Answer 8

This is the airway which leads from the mouth and nose to the bronchi
It is lined with mucus-secreting goblet cells as well as small hairs named cilia which sweep microorganisms and dust away from the lungs
It also has rings of cartilage to allow it to flex and also prevent it from closing

Question 9

Describe the bronchi

Answer 9

There are two bronchi, one on the left and on the right at the bottom of the trachea. They are similar in structure to the trachea but narrower and lead to the bronchioles

Question 10

Describe the bronchioles

Answer 10

These narrow tubes carry air from the bronchi to the alveoli. As they are narrow they have no rings of cartilage to support them

Question 11

Describe the capillary network

Answer 11

An extensive network of capillaries which surround the alveoli and act as an exchange surface between the lungs and the blood
During gas exchange, oxygen diffuses from the alveoli and into the capillaries while carbon dioxide diffuses from the capillaries into the alveoli

Question 12

How is the trachea supported

Answer 12

With rings of cartilage which ensure the trachea stays open as well as allowing it to move and flex during breathing

Question 13

What can be found throughout the walls of the bronchi and bronchioles

Answer 13

Smooth muscle which helps regulate the flow of air into the lungs by dilating when more air is required and constricting when less is needed

Question 14

What is the equation for pulmonary ventilation

Answer 14

Pulmonary ventilation = ventilation rate x tidal volume

Question 15

What is the mechanism of breathing in

Answer 15

Breathing in causes the intercostal muscles to contract and the rib cage to move upwards and outwards
The diaphragm contracts and flattens so the volume of the thorax increases
This causes the pressure inside the thorax to decrease so air is drawn into the lungs

Question 16

What is the mechanism of breathing out

Answer 16

The external intercostal muscles relax and the internal intercostal muscles contract, pulling the ribs downwards and backwards
The diaphragm relaxes and returns to its dome-shape, reducing the volume of the thorax
This results in the pressure in the thorax increasing so the air is forced out

Question 17

What does it mean that the external and internal intercostal muscles are antagonistic

Answer 17

As one contracts, the other relaxes
Use this to help you describe the mechanism of breathing as inhalation / inspiration and exhalation / expiration are opposite processes

Question 18

Vital capacity

Answer 18

The maximum volume of air that can be inhaled or exhaled in a single breath

The level of this can be dependant on age, gender, weight and height

Question 19

Tidal volume

Answer 19

The volume of air we breath in and out at each breath at rest

Question 20

Breathing rate

Answer 20

The number of breaths per minute

This can be calculated from the spirometer trace by counting the number peaks or troughs in a minute

Question 21

Residual volume

Answer 21

The volume of air that is always present in the lungs

Question 22

Expiratory reserve volume

Answer 22

The additional volume of air which can be exhaled on top of the tidal volume

Question 23

What are spiracles

Answer 23

Insects have spiracles which are openings on the sides of the body lined with chitin
The spiracles can open and close by small muscles (like stomata) to control the flow of air and reduce water loss

Question 24

What are the major structures of the tracheal system in insects

Answer 24

Spiracles
Tracheae
Tracheoles

Question 25

What is the process of gas exchange in insects

Answer 25

Air enters into the tracheal system of the insect through the open spiracles and into the tracheae
The air moves through the trachea tube and into smaller tubes called tracheoles towrds the body cells
The ends of the tracheoles are lined with thin and moist surface membranes where gas exchange can take place
These thin membranes are surrounded by a fluid called haemolymph
The oxygen dissolves into the haemolymph fluid and diffuses into the insect body cells, moving from a high to low concentration
The carbon dioxide produced by respiration can diffuse from the cells, into the haemolymph and into the tracheoles from an area of high to low concentration

Question 26

What are the adaptations for gas exchange in the insect tracheal system

Answer 26

The thin surface membrane a the end of the tracheoles mean there is a short diffusion distance
The moist surface at the end of the tracheoles allows more rapid diffusion as the gases can dissolve into the haemolymph fluid
The extensive network of trachea and tracheoles mean there is a large surface area

Question 27

What are the major structures in the gas exchange of fish

Answer 27

Mouth
Gill arch
Gill filaments / lamellae
Operculum

Question 28

What is the process of gas exchange in fish

Answer 28

Water flows through the mouth of the fish
Water moves over the gills
As the water flows over the gill filaments, due to countercurrent flow oxygen diffuses down its concentration gradient from the water into the blood
Carbon dioxide diffuses down its concentration gradient from the blood into the water
The water is then forced out through the gills

Question 29

What is countercurrent flow

Answer 29

Where in the fish ventilation system, the flow of water is in the opposite direction as the flow of blood in the capillaries of the gill filaments
This means that the diffusion gradient is maintained across the gill filament

Question 30

How is the fish ventilation system adapted for efficient gas exchange

Answer 30

Countercurrent flow maintains a concentration gradient across the whole gill filament
Many gill arches on the gills and there are further gill filaments at right angles increase the surface area

Question 31

Describe the pathway taken by an oxygen molecule from the alveolus to the blood

Answer 31

The oxygen molecule moves across the alveolar epithelium and the epithelium of the capillary, into the blood