Gas Exchange - Humans

Question 1

What is ventilation?

Answer 1

scientific term for breathing where air is constantly moving in and out of the lungs

Question 2

What happens during inhalation?

Answer 2

• external intercostal muscles and diaphragm contracts causing the ribcage to move upwards and outwards and the diaphragm flattens
• this increases the volume of the thoracic cavity
• as this increases the lung pressure decreases so that air flows from the trachea to lungs (always moves from high to low)

Question 3

When does inhalation/inspiration occur?

Answer 3

when air pressure in the atmosphere is greater than lungs forcing air into the alveoli (always moves from high to low)

Question 4

What does inhalation/inspiration require?

Answer 4

energy - it is an active process

Question 5

What occurs during exhalation/expiration?

Answer 5

• external intercostal muscles and diaphragm relaxes so the ribcage moves downwards and inwards and diaphragm curves upwards (dome shape) - the volume of the thoracic cavity decreases causing air pressure to increase in the lungs
• air is forced down pressure gradient and out of lungs (forced movement - requires no energy)

Question 6

What are the intercostal muscles?

Answer 6

antagonistic - as the internal contracts the external relaxes

Question 7

How does air move in the human gas exchange system?

Answer 7

air moves down the diffusion gradient
air enters nostrils/mouth and passes through: trachea (pipe protected by cartilaginous rings) → bronchi → bronchioles → alveoli (where gas exchange takes place)

Question 8

What are the alveoli?

Answer 8

air sacs where gas exchange occurs

Question 9

How are the alveoli adapted for efficient gas exchange?

Answer 9

• millions of alveoli
  → large surface area
• each wall of alveolus is made from a single layer of thin, flat cells (alveolar epithelium)
  → short diffusion pathway
• surrounded by a network of capillaries to remove exchanged gases
  → maintains concentration gradient - maintained by flow of blood (blood high in oxygen replaced by blood low in oxygen) and ventilation (air low in oxygen is continually replaced with air high in oxygen as you breathe)