3.1 - Specialised Exchange of Gases

Question 1

Describe the process by which bony fish respirate

Answer 1

Fish opens its mouth, lowering the buccal cavity
The volume of the buccal cavity increases therefore decreasing the pressure causing water to be sucked in
When the fish closes its mouth, the buccal cavity is raised
This decreases the volume and increases the pressure
The increased pressure forces water out of the cavity across gill filaments
This causes the operculum to open
This allows the water to move out of the gills down a pressure gradient.

Question 2

Describe inspiration in the lungs

Answer 2

Rib muscles contract causing the ribs to move up
The diaphragm muscles contract which makes the diaphragm move down and out
The volume of the lungs increase
The pressure of air decreases below atmospheric pressure
Air enters the lungs to equalise the pressure.

Question 3

Describe expiration in the lungs

Answer 3

Rib muscles relax
Ribs move down and in
Diaphragm muscles relax, causing diaphragm to move up
The volume of the lungs decreases
The pressure inside the lungs increases above atmospheric pressure

Question 4

Describe respiration in larger insects

Answer 4

Flexible walls to ventilate
They can squeeze in and out
Movements of the wings can change the volume of the thorax
Locust in particular can change the volume of their abdomen by closing and opening valves in their spiracles

Question 5

Ventilation in insects

Answer 5

Air enters pores in their abdomen called spiracles
Air comes through a tube called trachea
These then split into tracheoles which are filled with tracheal fluid
The gases will diffuse in the tracheal fluid where it will diffuse into the cells

Question 6

Oxygen transport in insects

Answer 6

Tissue fluid and blood fluid are the same(hemolymph)

Insects have a tracheal system

Question 7

What are the features of a good specialised exchange surface?

Answer 7

Thin walls for short diffusuion
Large SA:V ratio for rapid rate of diffusion
Moist so gases can dissolve first
Good blood supply and well ventilated to maintain a steep concentration gradient

Question 8

What is the function of the trachea?

Answer 8

Carries fresh, clean air from the environment into the lungs

Question 9

What are the features of the trachea?

Answer 9

C - shaped cartilage - stops airways collapsing due to pressure in thorax
Goblet cells - lines walls of trachea and secrete mucus to trap pathogens
Ciliated epithelium - waft mucus up to the pharynx to be swallowed and digested
Smooth muscle - allows the airways to contract and expand under pressure
Elastic fibres - h

Question 10

Features of bronchus?

Answer 10

Smooth muscle 
Elastic fibres
C - shaped cartilage
Ciliated epithelium 
Goblet cells

Question 11

What is the function of the bronchus?

Answer 11

They carryinspired air from environment to the alveoli for gas exchange

Question 12

Features of bronchiole

Answer 12

Smooth muscle - contract to control amount of air entering lungs, contract and dilate
Ciliated epithelium
Elastic fibres 
Cartilage - 
Goblet cells(only in larger ones)

Question 13

Function of bronchiole

Answer 13

Carry oxygen rich air into the lungs and take carbon dioxide out of the lungs

Question 14

List adaptations of alveoli and describe how they aid its function

Answer 14

Good blood supply so gases can easily diffuse in and out of the blood
Well ventilated - maintain steep concentration gradient with blood
Moist lining - gases can dissolve first before entering blood
Folded - increases their surface area, more oxygen from bronchioles can diffuse into blood
Contain a lung surfacant - stops alveoli collapsing and sticking together
Contain collagen and elastic fibres that can stretch out and recoil to squeeze air out, stops alveoli exploding
Squamous epithelium - thinner walls for a shorter diffusion distance for gases

Question 15

What happens during an asthma attack?

Answer 15

Cells lining bronchioles secrete histamines
Causes epithelial cells to swell and become inflamed
Smooth muscle in bronchioles contracts airways
Mucus is secreted which reduces air flow through lungs

Question 16

What is tidal volume?

Answer 16

Volume of air moving in and out of lungs in one resting breath

Question 17

What is vital capacity?

Answer 17

Largest volume of air that can be moved in and out of the lungs in one breath

Question 18

What is expiratory reserve volume?

Answer 18

The volume of air that can be exhaled above the normal tidal volume

Question 19

What is residual volume?

Answer 19

The volume of air left in the lungs following the strongest possible exhalation

Question 20

How to find breathing rate?

Answer 20

Number of breaths per minute

Question 21

What is total lung capacity?

Answer 21

Vital capacity + residual volume

Question 22

How to work out ventilation rate

Answer 22

Volume of air breathed in per minute x tidal volume

Question 23

What is the function of a spirometer?

Answer 23

Measure how much air is breathed out of the lungs between exhalations and inhalations

Question 24

What is the operculum and what is its function?

Answer 24

A bony flap that protexts the gills

Helps maintain a constant flow of water through the gills

Question 25

Why would a fish die in air?

Answer 25

Gill stacks need a constant flow of water to stay separated and have a larger surface area.
In air they would stick together and the surface area would be too small for gas exchange

Question 26

How are fish gas exchange system adapted for their function?

Answer 26

Large surface area provided by gill filaments
Rich blood supply from lamallae
Thin walls - shorter diffusion
Countercurrent flow - concentration gradient maintained by counter flow of water in opposite direction to blood flow, oxygen constantly moving into blood by diffusion. Happens as oxygen concentration always higher than oxygen concentration.

Question 27

What is the function of the c - shaped cartilage?

Answer 27

Keep airways open and prevent collapse during inspiration when there is a low pressure in the thorax
also allows some flexibility to move neck without constricting airways

Question 28

What is the function of the smooth muscle?

Answer 28

Contracts to constrict airways
Reduces flow of air (reduces harmful substances going into lungs;
asthma)

Question 29

What is the function of the elastic fibres?

Answer 29

DO NOT CONTRACT/RELAX
Stretch when smooth muscle contracts
Recoil (when smooth muscle relax) to help dilate the airway again

Question 30

What is the function of goblet cells(not in smallest bronchioles)?

Answer 30

Secrete mucus which traps bacteria and other particles to be removed from the lungs to reduce infection

Question 31

What is the function of the ciliated epithelium?

Answer 31

Waft to and fro to remove mucus from airways up to throat

Question 32

Function of the blood vessels

Answer 32

Give good blood supply to lung tissue e.g. smooth muscle with oxygen for aerobic respiration or alveoli

Question 33

Through what system does a fish respirate/gain a constant flow of oxygen into the blood?

Answer 33

Countercurrent Flow
Blood in capillaries moving opposite direction from water flow
So concentration of oxygen in water is always higher than in the blood
Therefore oxygen constantly moves into the bloodstream, more efficient method than reaching an equilibrium

Question 34

Countercurrent flow system in fish

Answer 34

• Blood always meets water with higher oxygen concentration
• Therefore there is always a concentration gradient along the entire surface of the gill
• Therefore there is always diffusion along the entire surface of the Gill of oxygen into the blood