Gas exchange in humans flashcards

11.1 Gas exchange in humans

Four features of gas exchange surfaces, with reasons

Large surface area: more diffusion at once. Thin surface: short diffusion distance. Good blood supply and good ventilation with air: both maintain a steep concentration gradient.

Route of air from the larynx to the gas exchange surface

Larynx → trachea → bronchi → bronchioles → alveoli.

Inspired vs expired air: oxygen, carbon dioxide, water vapour

Oxygen: about 21% in, about 16% out. Carbon dioxide: about 0.04% in, about 4% out. Water vapour: more in expired air.

Effect of physical activity on breathing

The rate and depth of breathing increase, then fall back gradually to resting values afterwards.

Gas exchange v ventilation

Diffusion across alveoli v air moving in and out.

Rate v depth of breathing

Breaths per minute v volume of air per breath.

Breathing in: muscles, ribs, diaphragm, volume and pressureExtended

External intercostals contract, internal intercostals relax; ribs move up and out; diaphragm contracts and flattens; thorax volume increases, so pressure falls below atmospheric and air flows in.

Function of cartilage in the tracheaExtended

Keeps the trachea open so it does not collapse when pressure falls during breathing in.

Why exercise increases the rate and depth of breathing (Extended chain)Extended

More aerobic respiration in muscles → more carbon dioxide in the blood → detected by the brain → increased rate and depth of breathing.

Ciliated cells (protecting the airways)Extended

Cilia beat and move mucus up to the throat, where it is swallowed.

Goblet cells v ciliated cellsExtended

Goblet cells make mucus, which traps pathogens and particles; ciliated cells move the mucus. Cilia do not trap anything.