Unit 1: Section 4 - Exchange Surfaces and Breathing

Question 1

Do smaller animals have high or low surface area to volume ratio?

Answer 1

High

Question 2

How can single celled organisms get substances into their cells?

Answer 2

The substances can diffuse directly in to the cell across the cell surface membrane. The diffusion rate is quick because the distance the substance has to travel is small.

Question 3

Why is diffusion across the outer membrane too slow in humans?

Answer 3

1) Some cells are deep within the body - there’s a big distance between them and the outside environment
2) Larger animals have a low SA:V ratio. It’s difficult to exchange enough substances to supply a large volume of animal through a small outer surface.

Question 4

When air is breathed in what is its route to the alveoli?

Answer 4

1) As you breathe in, air enters the trachea
2) The trachea splits into two bronchi - one bronchus leading to each lung
3) Each bronchus then branches off into smaller tubes called bronchioles
4) The bronchioles end in small ‘air sacs’ called alveoli where the gas is exchanged.

Question 5

What is an alveolus made of?

Answer 5

A single layer of thin, flat cells called the alveolar epithelium

Question 6

How does oxygen go from the alveoli into the haemoglobin?

Answer 6

Diffuses across the alveolar epithelium and the capillary endothelium and into the blood.

Question 7

What 3 characteristics do gas exchange surfaces have?

Answer 7

1) Large surface area, which increases rate of diffusion
2) They’re thin (often one layer of epithelial cells) - this provides a short diffusion pathway - increasing rate of diffusion.
3) Maintain a steep concentration gradient

Question 8

What is the role of goblet cells in the respiratory system?

Answer 8

They secrete mucus. The mucus traps micro-organisms and dust particles in the inhaled air, stopping them from reaching the alveoli.

Question 9

What is the role of cilia in the respiratory system?

Answer 9

Beats the mucus which moves it (along with the dust) upwards and away from the alveoli towards the throat, where it’s swallowed. This helps to prevent lung infection.

Question 10

What is the role of elastic fibres in the respiratory system?

Answer 10

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

Question 11

What is the role of smooth muscle in the respiratory system?

Answer 11

Allow the diameter of trachea, bronchi and bronchioles. During exercise the smooth muscle relaxes making the tubes wider. This means that there is less resistance to airflow and air can move in and out of the lungs more easily.

Question 12

What is the role of rings of cartilage in the respiratory system?

Answer 12

Found in the walls of trachea and bronchi, provide support. It stops the trachea and bronchi collapsing when you breathe in.

Question 13

What is the role of squamous epithelium cells in the respiratory system?

Answer 13

Gives a short diffusion pathway for oxygen and CO2 in the alveoli.

Question 14

See table on page 31 in book.

Answer 14

.

Question 15

Describe how inspiration happens.

Answer 15

1) Intercostal muscles and diaphragm contract
2) This causes the rib cage to move upwards and outwards and the diaphragm to flatten. This increases the volume of the thorax
3) This decreases the pressure to below atmospheric pressure
4) This causes air to enter the lungs
5) Inspiration is an active process - it requires energy

Question 16

Describe how expiration happens.

Answer 16

1) Intercostal muscles and diaphragm relax and becomes dome shaped
2) Ribcage moves downwards and inwards and becomes dome shaped
3) This increases the pressure to above atmospheric pressure
4) This causes air to leave the lungs
5) Expiration is a passive process - it doesn’t require energy

Question 17

What is tidal volume?

Answer 17

The volume of air in each breath

Question 18

What is vital capacity?

Answer 18

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

Question 19

What is breathing rate?

Answer 19

How many breaths are taken - usually measured per minute

Question 20

What is oxygen uptake?

Answer 20

The rate at which a person uses up oxygen

Question 21

How does a spirometer work?

Answer 21

1) The person breathes through a tube connected to the oxygen chamber
2) As the person breathes in and out, the lid of the chamber moves up and down
3) These movements are recorded by a pen attacked to the lid of the chamber - this writes on a rotating drum creating a spirometer trace
4) The soda lime in the tube where the person breathes into absorbs carbon dioxide.

Question 22

Why does the total volume of gas in the chamber decrease over time?

Answer 22

Because the air that is breathed out is a mixture of oxygen and CO2. Because the lime absorbs the CO2, the person only breaths in oxygen and because that is used up in respiration the total volume decreases.