Mammalian Respiratory System

Question 1

What is gaseous exchange and why is it performed?

Answer 1

Gaseous exchange involves the transfer of gases between organism’s internal and external environment by diffusion across cell membranes.

Gases are required by the organism to carry out specific functions, and some gases are wastes that need to be expelled.

Question 2

What are the main two gases exchanged in animals, and why?

Answer 2

Oxygen is taken in as it is required for cellular respiration to release the energy from nutrients it has consumed.

Carbon dioxide, produced by respiration, must be removed as it can build up and make the cell acidic, altering enzyme function.

Question 3

What main characteristics do all respiratory systems have?

Answer 3

1. A large surface area - involves branching, folding and flattening, allows for faster rate of diffusion
2. Thin, moist surfaces - ensure gases are dissolved for easier diffusion, thinness decreases distance travelled
3. Close proximity to circulatory system for quick distribution
4. Greater concentration of required gas on one side of membrane to maintain concentration gradient (greater difference, faster diffusion) (Eg. oxygen in high concentration in external environment to organism)

Question 4

Why are the respiratory systems of mammals inside their body?

Answer 4

This reduces the water loss from the respiratory surface

Question 5

Describe the structure of alveoli

Answer 5

Thin-walled air sac, surrounded by capillaries.

Increased SA is achieved by 300 million alveoli sacs. Each alveolus has folding of the interior lining.

Each alveolus is one cell thin, these cells are flattened.

All surfaces are moist - air inside is saturated with water vapour, inside is lined with mucus - ensures dissolved gases

280 million capillaries surround the alveoli.

Question 6

Describe the movement of oxygen and carbon dioxide across the respiratory membrane in relation to their concentration gradients

Answer 6

Oxygen diffuses from where it is most concentrated in the alveoli into the capillaries where it is less concentrated.

Carbon dioxide is more concentrated in the capillaries and diffuses out into the alveolar space.

Question 7

Describe the movement of the diaphragm and the internal intercostal muscles during breathing

Answer 7

Breathing in, the diaphragm contracts, moving down and increasing lung volume. Breathing out, the diaphragm relaxes and moves up.

Internal intercostal muscles can move the ribs up or down to further increase inhalation and exhalation volume.

Question 8

Outline the progression from bronchus to alveoli

Answer 8

The bronchus is the main branch within the lung. There are two bronchi, stemming from the trachea. Bronchioles are the smaller branches of bronchi, and the alveoli are the ends of the bronchioles, which are the sites of gas exchange.