7.2 - Mammalian Gaseous System

Question 1

Why do humans need an exchange system?

Answer 1

• Big, so small SA:V
• Metabolically active and maintain temperature
• Require a lot of O2 and removal of CO2

Question 2

Why is the nasal cavity important?

Answer 2

• a large SA with a good blood supply which warms the air to body temperature
• hairy lining that secretes mucus to trap bacteria, protecting lung tissue for infection
• moist surfaces which increase humidity of incoming air, reducing evaporation

Question 3

Why is the trachea important?

Answer 3

• carries clean, warm, moist air from nose to chest,
• wide tube supported by cartilage that hold it open. They are incomplete so food can move through the oesophagus, allows flexibility
• Lined with ciliated epithelium cells and goblet cells. The goblet cells produce mucus and the cilia move it away from the lungs to be digested

Question 4

What is the Bronchus?

Answer 4

• Trachea divides to form the left bronchus, leading to the left lung. They are the same structure as the trachea, but smaller.

Question 5

What are bronchioles?

Answer 5

• The bronchus divides to form small bronchioles
• These have a diameter of 1mm
• They have no cartilage, has elastin instead.
• Their walls are lined with smooth muscle for easier exchange
• The muscle contracts and cause the bronchioles to contract and vice versa, changing the amount of air reaching the lungs
• Flattened epithelium for better gas exchange

Question 6

What are the alveoli

Answer 6

• Tiny air sacs unique to mammalian lungs
• diameter of 200-300 micrometers
• layer of thin epithelium cells for better exchange
• made from collagen and elastin for elastic recoil.

They have the 4 components of a good exchange surface
They also have surfactant (solution of water +salts) that keeps the alveoli inflated

Question 7

Describe Inspiration

Answer 7

• Diaphragm contracts and pulls down
• External intercostal muscles contract, moving the ribs outwards and up
• This increases the volume inside the Thorax
• Pressure decreases in the Thorax
• Air is drawn through the Trachea into the lungs to equalise the pressure

Question 8

Describe Expiration

Answer 8

• Diaphragm relaxes
• External Intercostal muscles relax, ribs move down and inwards
• Volume decreases and pressure increases in the Thorax
• air is drawn out until the pressure is equalised