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| Description: The internal ears develop first. This also begins about 22 days after fertilization. The surface ectoderm thickens to form otic placodes that appear on either side of the hindbrain (rhombencephalon). They form otic pits that pinch off to form otic vesicles. Smell and taste are not affected by aging until around age 50 when the gradual loss of receptors and the slower rate of regeneration have an affect. The lens begins to lose elasticity and has difficulty focusing on close objects (presbyopia). This begins around age 40. Muscles of the iris weaken and react more slowly to light and dark causing elderly people to have difficulty adjusting to changes in lighting. Retinal diseases such as macular disease, detached retina and glaucoma (damage to the retina due to increased intraocular pressure) occur more frequently in the elderly. By about age 60, approximately 25% of individuals experience a noticeable hearing loss. Age associated loss is called presbycusis. Tinnitus (ringing in the ears) and vestibular imbalance also occur more frequently in the elderly. Picture Stats: Views: 309 Filesize: 869.58kB Height: 900 Width: 990 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=41426 |