| A | B |
|---|
| young-old | the majority of the elderly |
| old-old | the minority of the elderly |
| glaucoma | hardening of the eyeball due to the buildup of fluid |
| cataracts | thickening of the lens of the eye |
| B-cells | create antibodies that attack bacteria and viruses |
| T-cells | attack infected cells and strengthen other aspects of the immune system's functioning |
| compression of morbidity | limiting the time a person is ill |
| oxygen free radicals | unstable atoms with unpaired electrons that damage cells |
| Hayflick limit | the number of times a cell replicates before dying |
| primary aging | the universal changes that occur as we grow older |
| secondary aging | age-related changes that are caused by health habits, genes, and other conditions |
