What is the structure of the lungs?
Lungs connect to the trachea and split into two branches called bronchi. These split into smaller branches called bronchioles, which end in alveoli.
What is the structure of the alveoli?
Sac structures made up of simple squamous cells, surfactant (prevents collapse), and covered with capillaries.
What is the function of alveoli? Why do they possess the qualities they have?
They are thin (one cell thick) and permeable to allow oxygen and CO2 exchange with the capillaries. They filter oxygen into the capillaries and remove CO2 in a process known as diffusion. They have a large surface area with many chambers to increase surface area and maximise diffusion.
Why do your bronchi branch off into many bronchioles?
To increase surface area.
What is the function of cilia?
Removal of foreign particles using a wave-like motion. They line the trachia and lungs and move mucus, germs and other partivles towards the mouth to be coughed or sneezed out.
How does ventilation (breathing) take place?
The diaphragm contracts, moving down. Intercostal muscles enlarge the chest, moving the rib cage up and out which increases the volume of the lungs and decreases pressure within them. This causes oxygen rich air to be drawn in through the trachea from the oral cavity (mouth) or nasal chambers (nose). This air reaches the alveoli which exchange gas through diffusion. The diaphragm and intercostal muscles relax, increasing pressure in the lungs. This forces oxygen-depleated air/CO2 to be exhaled through the mouth or nasal chambers.
How is oxygen exchanged?
The walls of the alveoli and capillaries are one cell thick, allowing for oxygen molecules to pass through. Once oxygen passes through the alveoli, the iron in the hemoglobin proteins present in erythrocytes (RBCs) binds to the oxygen.