Respiration

Question 1

Why is breathing through nose better than through mouth?

Answer 1

• Nostrils lead to two nasal passages lined with moist mucous membranes
• Dust and bacteria trapped by mucus and hairs
• Air is warmed and moistened before entering lungs
• Sensory cells in mucous membrane may detect harmful chemicals

Question 2

Describe structures in trachea and their functions

Answer 2

-Goblet cells in nasal cavity and trachea: secrete mucus that traps dust particles and bacteria
-Ciliated epithelial cells in trachea:
cilia sweep mucus up trachea, then swallowed into oesophagus
-C-shaped cartilage rings in trachea: keep trachea open/ prevent trachea from collapsing when breathing in

Question 3

What are the adaptations of the lungs for efficient gaseous exchange?

Answer 3

1. The numerous alveoli in the lungs provide a large surface area for gaseous exchange
2. Wall of alveolus and blood capillaries is 1-cell thick. Shorter diffusion distance —> faster diffusion rate
3. a thin film of moisture on the surface of alveolus allows oxygen gas to dissolve in it
4. Walls of alveoli supplied by dense network of blood capillaries. Continuous flow of blood maintains concentration gradient of gases.

Question 4

Describe breathing mechanism for inspiration

Answer 4

Diaphragm contracts and flattens down

External intercostal muscles
contract and internal intercostal
muscles relax > rib cage is raised
upwards and outwards, sternum
moves up and forward

Thoracic volume increases, so
air is drawn into the lungs
as atmospheric pressure is higher
than pressure inside lungs

Question 5

Describe breathing mechanism for expiration

Answer 5

Diaphragm relaxes
and arches upwards.

External intercostal muscles relax
and internal intercostal muscles
contract > rib cage moves
downwards and inwards, sternum
moves down to original position

Thoracic volume decreases,
lungs are compressed and air
is forced out of the lungs
as pressure inside lungs is higher
than atmospheric pressure