osteoporosis
osteoporosisosteoporosis
bones
While the word porous isn't generally used in medical terminology, -porotic is the medical terminology combining form meaning porous. For instance, osteoporotic means a condition of more porous bones.
Bones.
epiphyses
Spongy bones are not literally spongy. These bones are just extremely porous giving the appearance of looking like spongy material.
ostoperosis
calcium,
Oseteoporosis. "Osteo" is the root word meaning "bones", and the "porous" part indicates that the bones aren't as solid as they should be.
Hollow light weight bones means less weight, which results in a bird using less energy to fly and making it easier for the bird to take off from the ground.
Condition caused by calcium deficiency; bones become porous, weak, and fragile.
The correct spelling is "osteoporosis" (condition leaving bones porous and brittle).