Human gas exchange

Question 1

What does the cartilage do in human gas exchange

Answer 1

• Cartilage is a strong and flexible and found in many places
  . One place is in rings along trachea, called tracheal rings they support the trachea and ensures it stays open, while allowing it to move and flex as we breathe

Question 2

What is a specialised tissue in human gas exchange

Answer 2

Ciliated epithelium - specialised cell along the trachea down to the bronchi. Each cell has small projections of cilia which sweep mucus away from the lungs and the epithelium itself

Question 3

What is the structure of the humans gas exchange

Answer 3

Air enters the trachea. The trachea splits into 2 bronchi (one bronchus to each lung). They then branch off into bronchioles. The bronchioles end with alveoli’s the sight of gas exchange

Question 4

What are the intercostal muscles

Answer 4

Muscles found between the ribs
internal intercoastal and external intercoastal

Question 5

What is the process of inhalation

is this an active or passive process

Answer 5

• External intercostal muscles contract which moves the ribcage up and out
• The diaphragm contracts and flattens
• The volume of the thorax increases and pressure decreases to below atmospheric pressure
• Air will flow in from an area of high pressure to low pressure (down concentration gradient) so it flows down the trachea into the lungs
  Active process so requires energy

Question 6

What happens during exhalation

Answer 6

• The external intercoastal muscles relax and the ribcage moves down and in
• The diaphragm relaxes and becomes dome-shaped
• Volume of the thorax decreases and the pressure inside the thorax increases
• Air is forced out by the recoil of elastic fibres surrounding the alveoli’s

Question 7

Is exhalation an active or passive process
What happens if it is forced?

Answer 7

Usually a passive process
In forced exhalation (e.g. blowing candles out) the external intercoastal muscles relax and the internal intercoastal muscles contract pulling the ribcage further down and in

Movement of 2 sets of intercoastal muscles is said to be antagonistic (opposite)

Question 8

How do you work out the PVR

Answer 8

PVR (dm^3/min)=
Tidal volume (dm^3) x Breathing rate (per min)

Question 9

What is the PVR

Answer 9

Pulmonary ventilation rate

Volume of air breathed (in or out) in one minute

Question 10

What is gas exchange like in the alveoli

Answer 10

-Surrounded by capillaries
- Diffusion of carbon dioxide out of the capillaries into the alveoli due to there being a high concentration of carbon dioxide in the capillaries (one cell think)
- Diffusion of oxygen out of the alveoli into the capillaries due to there being a higher concentration of oxygen inside the alveoli’s

Question 11

What are the adaptations of the alveolar epithelium

Answer 11

• Alveoli are tiny air sacks and there are 300 million in each human lung creating a large surface area
  -The alveoli epithelium cells are very thin (one cell thick) to minimise diffusion distance
• Each alveolus is surrounded by capillaries to remove exchanged gases and they have a constant flow of blood (e.g. to transport oxygenated blood) to maintain a concentration gradient