Exchange surfaces

Question 1

What happens in inspiration?

Answer 1

• External intercoastal muscles contract
• Ribcage moves up and out
• Diaphragm contracts and flattens
• Volume of thorax (the space where the lungs are) increases
• Pressure inside thorax decreases
• Air is drawn in

Question 2

What happens in exhalation?

Answer 2

• External intercostal muscles relax
• Ribcage moves down and in
• Diaphragm relaxes and becomes dome-shaped
• Volume of thorax decreased
• Pressure inside thorax increases
• Air is forced out

Question 3

What is the role of goblet cells in the gaseous exchange system?

Answer 3

Secrete mucus
-> the mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli.

Question 4

Location of goblet cells?

Answer 4

Lining the airways (in the trachea and bronchi)

Question 5

Location of cilia?

Answer 5

On the surface of cells lining the airways

Question 6

What is the role of cilia in the gaseous exchange system?

Answer 6

Beat the mucus
-> This moves the mucus (plus the trapped microorganisms and dust) upward away from the alveloi towards the throat, where its swallowed.
-> this helps prevent lung infections

Question 7

Location of elastic fibres?

Answer 7

The walls of the trachea, bronchi, bronchioles and alveoli

Question 8

What is the role of elastic fibres in the gaseous exchange system?

Answer 8

Help the process of breathing out
-> On breathing in, the lungs inflate and the elastic fibres are stretched.
-> Then the elastic fibres recoil to help push air out when exhaling.

Question 9

Location of smooth muscle?

Answer 9

In the walls of the trachea, bronchi and bronchioles

Question 10

What is the role of smooth muscle in the gaseous exchange system?

Answer 10

Controls the diameter of the trachea, bronchi and bronchioles.
-> During exercise the smooth muscle relaxes, making the tubes wider. This means there’s less resistance to airflow and air can move in and out of the lungs move easily.

Question 11

Location of rings of cartilage?

Answer 11

In the walls of the trachea and bronchi

Question 12

What is the role of rings of cartilage in the gaseous exchange system?

Answer 12

Provide support
-> Strong but flexible- stops the trachea and bronchi collapsing when you breathe in and the pressure drops.

Question 13

What is the tidal volume?

Answer 13

The volume of air in each breath- usually about 0.4dm^3

Question 14

What is vital capacity?

Answer 14

The maximum volume of air that can be breathed in or out

Question 15

What is breathing rate?

Answer 15

How many breaths are taken (usually in a minute)

Question 16

What is oxygen consumption/ oxygen uptake?

Answer 16

The rate at which an organism uses up oxygen (e.g. the number of dm^3 used per minute).

Question 17

What do fish have because of their large size?

Answer 17

A very low surface area to volume ratio.

Question 18

Where does oxygen enter the fish?

Answer 18

Oxygen rich water enters the fish through the mouth and then passes over the gills.

Question 19

What happens in the gills of fish?

Answer 19

Oxygen diffuses from water into the blood and carbon dioxide diffuses from the blood into the water.

Question 20

How does water leave the fish?

Answer 20

Through the operculum opening

Question 21

What do gills consist of?

Answer 21

Several bony gill arches, and extending from each gill arch a large number of gill filaments. Gill filaments are covered with numerous gill lamellae.

Question 22

Where does gas exchange take place in fish?

Answer 22

The gill lamellae

Question 23

How are gill lamellae adapted for efficent gas exchange?

Answer 23

• Massive surface area for gases to diffuse over
• Very short diffusion distance through the walls of the lamellae and into the bloodstream.
• Extensive network of blood capillaries

Question 24

What maintains the steep concentration gradient for oxygen in fish?

Answer 24

Once oxygen diffuses into the blood it is carried away

Question 25

What is the direction of blood and water in fish?

Answer 25

Opposite directions (a counter-current system)

Question 26

What is the major advantage of counter-current systems in fish?

Answer 26

Always maintains a steep concentration gradient for oxygen

Question 27

How do bony fish maintain constant water flow through the gas exchange system- step 1?

Answer 27

The fish opens its mouth, which lowers the floor of the buccal cavity. The volume of the buccal cavity increases, decreasing pressure inside the cavity. This casues water to flow into the buccal cavity.

Question 28

How do bony fish maintain constant water flow through the gas exchange system- step 2?

Answer 28

When the fish shuts its mouth the floor of the buccal cavity raises. This decreases the volume and increases the pressure inside the cavity. Water flows from the buccal cavity (high pressure) into the gill cavity (low pressure).

Question 29

How do bony fish maintain constant water flow through the gas exchange system- step 3?

Answer 29

As water enters the pressure in the gill cavity builds up an causes the operculum to be forced open and water to exit the fish. The operculum is then shut when the floor of the buccal cavity is lowered at the start of the next cycle.