Endosymbiotic theory is a theory of evolution that eukaryotes came from prokaryotes. Mitochondria and chloroplasts both have the double membranes. Each of them also contain genetic material that are replicated with a separate cell cycle. Both organelles have their own ribosomes.
The events of inspiration begins with the;
Impulses are conducted on the phrenic nerve to muscle fibers in the diaphragm contracting them.
As the dome shaped diaphragm moves downward the thoracic cavity expands.
At the same time the external intercostal muscles may contract raising the ribs and expanding the thoracic cavity further.
The intra-alveolar pressure decreases
Atmospheric pressure greater than intra-alveolar pressure forces the air into the respiratory tract through the air passages.
The lungs fill with air.
