Describe the process through which a piece of ugali undergoes in man from the time of ingestion up to the time of absorption.

• The ugali is ingested into the mouth; The ugali is then masticated/chewed by the teeth to increase large surface area for the action of salivary amylase/ptyalin; The food mixes with saliva produced by salivary glands; Saliva contains mucus, water and enzyme ptyalin/salivary amylase.  Water softens the food, Mucus lubricates the food; ptyalin speeds up the conversion of starch to maltose;  ugali is made into boluses in the mouth; and then swallowed; The bolus moves along the oesophagus and peristalsis/by contraction and relaxation of circular and longitudinal muscles into the stomach; The digestion of starch stops in the stomach due to the presence of hydrochloric acid that denatures ptyalin/salivary amylase;
• The food moves into the duodenum by peristalsis in form of acidic chyme; where it mixes with the bile from the liver and pancreatic juice from the pancreas; bile salts being alkaline neutralize the acidic chyme, and provides an optimum pH/alkaline medium for the enzymes to act on carbohydrates; Pancreatic juice contains three enzymes out of the which enzyme pancreatic amylase speeds conversion of the remaining starch to maltose; When food reaches the ileum; it mixes with intestinal juice/succus entericus which contains several enzymes.  Maltase – speeds up the conversion of maltose to glucose; Lactase speeds up the conversion of lactose to glucose and galactose; Sucrase speeds up the conversion of sucrose into fructose and glucose;
• Absorption – glucose, which is  the end product of all carbohydrates diffuses through the epithelium of villi and capillary walls and  enters into the bloodstream, and is carried to the liver via hepatic portal veins;
• Assimilation – in the liver excess glucose is converted into glycogen and stored; The rest of the glucose is carried by the blood tissues which is oxidized during tissue respiration to release energy; √