I'm assuming you meant and frailness not fertility, in which case it is the oldest old period
As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion.Mar 4, 2016
This is cellulose,because humans lack enzymes to break it down
Explanation:
Mark me brainliest if it helps you
nonliving and abiotic.
The Central Nervous System<span> (CNS) includes all of the nerves of the Brain and Spinal Cord.</span>
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The Peripheral Nervous System (PNS) includes all of the nerves both sensory and motor connecting the CNS to the muscles, organs, and sensory structures of the body.</span>
