The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. In chemical digestion, enzymes break down food into the small molecules the body can use.igestion begins in the mouth with the secretion of saliva and its digestive enzymes. Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis.
The stigma is generally in the center of the flower and stands up on the style, taller than the surrounding anthers. It usually has a gelatinous or visceral appearance, which is slightly damp and furry.
The ovary of the female flowers is surrounded by a many-scaled involucre. The withered stigma and style can be seen on these developing fruits. As the ovary enlarges, it pushes out of the involucre, which remains as the hat on top of the fruit, an acorn.