How alveoli in the lungs are adapted for gaseous exchange

Alveoli :

at the end of bronchiole there are bubble like structures, called alveoli
around 300 million alveoli in each lung → creates large SA for gaseous exchange
each alveolus has a layer of moisture (surfactant) on the inside and a thin wall (one cell thick)
each alveolus surrounded by a network of blood capillaries
walls of capillaries are also thin (one cell thick) → creates a short diffusion distance for gaseous exchange

from inhaled air → dissolves in the alveolus’s surfactant moisture layer and moves by diffusion through wall of alveolus into the blood capillary next to it, where it enters the red blood cell
red blood cell → contain a dark red protein called haemoglobin that the oxygen binds to for transporting oxygen to all the cells around the body, where it’s used for aerobic respiration to release energy
diffusion - movement of particles from a region of high concentration to a region of low concentration until an equilibrium is reached → in the alveoli, there is a high concentration of oxygen, in the blood there is a low concentration to allow diffusion to occur

dissolved in the watery part of the blood called plasma
moves by diffusion from the blood through the walls of the capillary and into the alveolus
exhaled from the lungs
in the plasma → high concentration of CO2, in the alveoli → low concentration of CO2, allows diffusion to occur

blood moves quickly due to the heart contracting, means a large volume of O2 and CO2 can be exchanged in a short time
moving blood maintains the concentration gradient, allowing the diffusion of CO2 and O2 to occur