Mechanism of Breathing : Ventilation

Question 1

Define breathing

Answer 1

• result of pressure difference between lungs and air outside body
• pressure inside lungs is changed by lung volume changes

Question 2

Define ventilation

Answer 2

• exchange of gas bw lungs and surroundings
• includes inspiration and expiration

Question 3

Describe what happens during inspiration

Answer 3

• ext intercostal muscles contract to raise ribcage up and out
• diaphragm contracts and flattens
• thoracic cavity volume inc reducing pressure in lungs
• so air enters from outside, down the pressure gradient

Question 4

Describe what happens during expiration

Answer 4

• ext intercostal muscles relax so ribcage moves down and in
• int intercostal muscles contract to pull ribs down and in during forced expiration
• diaphragm relaxes and moves up
• thoracic cavity volume dec, inc pressure in lungs
• air forced out of lungs down a pressure gradient, aided by elastic recoil

Question 5

When are mechanical ventilators used?

Answer 5

• to assist breathing
• for patients with muscle weakness
• and severe lung infection

Question 6

Describe the gas exchange process between the alveoli and capillaries

Answer 6

OXYGEN
- as blood reaches capillaries surrounding alveoli
- the oxygen diffuses into blood
- across squamous epithelial cell membrane and endothelial wall of capillary
- moving from high to low conc of O2

CO2
- at same time co2 moves from blood into alveoli from high to low conc

BOTH / GENERAL
- both gases move in opposite directions diffusing from high to low conc
- heart then contracts and blood is circulated away from alveoli
- moving newly oxygenated blood away from lungs back to heart to be pumped around body

Question 7

Why does a concentration gradient need to be maintained by circulation of blood by heart and ventilation of air thru breathing?

Answer 7

• conc gradient is maintained at alveolar squamous epithelium
• to ensure gases diffuse efficiently in either direction + dont reach equilibrium

Question 8

How many membranes is there for oxygen to get to red blood cell from alveoli?

Answer 8

five

Question 9

Describe aerobic respiration in terms of oxygen and CO2

Answer 9

• oxygen is required for aerobic respiration + production of ATP
• CO2 is produced by aerobic respiration + has to be removed from respiring tissues

Question 10

Summarise the pathway of oxygen from the atmosphere to the blood via red blood cells

Answer 10

mouth - trachea - bronchi - bronchioles - squamous epithelium of alveoli - endothelium wall of capillary - red blood cell