human breathing system

Question 1

what are the pleural membranes and their function

Answer 1

• they line the thorax and cover each lung the fluid between membranes prevents friction between lungs and chest cavity

Question 2

what is the tracheas function

Answer 2

a flexible airway bringing air to the lungs

Question 3

outline inspiration

Answer 3

1) external intercostal muscles contract and the ribs pull up and out
2) the diaphragm contracts and flattens
3) increases volume and decreases pressure below atmospheric pressure so air is forced into the lungs

Question 4

outline exhalation

Answer 4

1) external intercostal muscles relax causing ribs to move down and in
2) diaphragm relaxes causing it to dome upwards
3) decreases the volume and increases pressure above atmospheric pressure so air is forces out the lungs

Question 5

what is surfactant

Answer 5

made up of moist secretions containing phospholipids and proteins- it coats the alveoli decreasing surface tension preventing the alveoli from collapsing when air pressure is too low

Question 6

what are the essential features of alveoli

Answer 6

• large surface area to volume ratio
• gases dissolve in the surfactant layer of the alveoli
• only one cell thick so short diffusion pathways
• maintained conc gradient from large network of capillaries

Question 7

outline how gases move in and out the alveoli

Answer 7

deoxygenated blood enters the capillaries surrounding the alveoli
oxygen diffuses out the air in the alveoli into the red blood cells in the capillaries down the conc gradient
CO2 diffuses out the plasma in the capillary into the air of the alveoli