The average consumer does not see these hairs, because they are singed off in the processing plant. Any mastication occurs in the gizzard. Many commercial poultry producers do not provide grit to their chickens, because they feed a ground feed of fine meal consistency that can be digested by the bird's digestive juices. The chicken has pneumatic bones, making its body lighter for flying, if it had not lost the ability to do so. There are 13 air sacs in the chicken's body, again to make the body lighter, and they are a functioning part of the respiratory system.
Chickens have comparatively short life spans.
Some live to be 10 to 15 years old, but they are the exception, not the rule. In commercial egg production, birds are about 18 months old when they are replaced by new, young stock. It takes close to six months for a female chicken to mature sexually and start laying eggs. Then, they are kept for 12 to 14 months of egg production. After that their economic value declines rapidly, so they are disposed of when they are about 18 months old.