the lungs

Question 1

what are the common features of exchange surfaces

Answer 1

• they have a large surface area
• they are moist
• they are thin
• they are permeable
• they have a mechanism to maintain the concentration gradient

Question 2

explain the alveoli

Answer 2

• they are well ventilated = ventilation movements ensure air is inhaled and exhaled from the lungs
• they have a good blood supply = they are covered with an extensive network of capillaries
• ensures the concentration gradient is maintained because the blood is always working

Question 3

what are the functions of the goblet cells

Answer 3

• they secrete mucus
• the mucus traps tiny particles
• reduces the chance of infection as any bacteria is removed from the lungs

Question 4

what is the role of the ciliated epithelium

Answer 4

• they have numerous tiny hair like structures
• they waft the mucus up the airway and back to the throat
• any mucus can then be swallowed and any bacteria will be killed by the stomach acid

Question 5

what is the role of smooth muscle

Answer 5

• they adjust the side of the airways
• they can contract which restricts the airways, this will reduce the diameter of the lumen
• restricts airflow in the lungs

Question 6

what is the role of elastic fibres

Answer 6

• they stretch when inhaling
• the alveoli expand
• the fibres will then recoil
• helps prevent the alveoli from bursting

Question 7

what is the role of the cartilage c rings

Answer 7

• support the trachea
• holds it open and prevents them from collapsing
• forms a c shape to still allow the oesophagus to expand when swallowing

Question 8

why are the alveoli thin

Answer 8

• they are only one epithelial thick
• there is a short diffusion pathway

Question 9

how do the alveoli maintain a concentration gradient

Answer 9

• they are covered in capillaries
• the blood is always moving

Question 10

explain ventilation in the lungs

Answer 10

• it allows the lungs to be supplied with fresh air to replace the used air
  this means that there is always a :
• higher concentration of oxygen in the lungs than the blood
• lower concentrations of carbon dioxide in the lungs than the blood

Question 11

what happens during inhalation

Answer 11

• the external intercostal muscles contract pulling the ribcage upwards and outwards
• this pulls out the inner pleural membrane which reduces the pressure in the pleural cavity
• the inner pleural membrane moves outwards, pulling on the lungs
• this causes the alveoli to expand
• the diaphragm contracts, making it go from a dome to a flattered shape
• the volume of the thorax is increased
• the pressure is decreased
• the air moves in

Question 12

what happens during relaxed exhalation

Answer 12

• the external intercostal muscles relax
• the ribcage falls under its own weight
• diaphragm relaxes and gut pressure pushes it back to the dome shape
• elastic recoil of lung tissue
• the volume of the thorax decreases
• the pressure increases
• air moves out

Question 13

what happens during forced exhalation

Answer 13

• the intercostal muscles contract, pulling the ribcage down and in
• abdominal muscles contract pushing the diaphragm upwards
• volume of the thorax decreases
• pressure increases
• air is forced out