FOOD DIGESTION

FOOD DIGESTION is recognized as the process in the result of which eaten food is transformed into energy form suitable for our organism use. In the result of different physical processes and chemical reactions taking place under influence of digestive juices, nutrients (proteins, fats and carbohydrates) are changed to such extent that our organism is able to absorb them and use in metabolism process. Digestion takes place during the process of food movement through digestive system organs (mouth with all its structures, pharynx, oesophagus, stomach and bowels). Different auxiliary organs (salivary glands, pancreas, liver and gall bladder) are assisting digestion.

Physical processes

The main physical process during food digestion is disintegration of food mass: it happens both during chewing and in the result of rhythmic contractions of stomach and bowels. Such physical influences assist food dissolution and thorough blending of its particles with digestive juices that exude in our mouth, stomach and bowels. Besides it, contractions of digestion system walls together with periodical opening and closing of intestinal valves provide regular movement of food clot by small portions from one part of digestion system to another.

Chemical reactions

The main chemical reaction providing disintegration of proteins, carbohydrates and fats is hydrolysis provided by a set of ferments. In the course of this process nutrients appended to fragments of water molecules are decomposed into small dissoluble parts that can be assimilated by our organism.

Mouth digestion (salivary digestion)

Food Digestion process starts in our mouth: for 15-20 seconds the food we eat is kept in oral cavity where its size is reduced by chewing; it’s also blended with saliva and turns into food clot. Food size reduction is necessary for better contact with ferments of digestive juices. The finer food particles are the more intensive the process of their further digestion occurs due to broader contact surface with ferments. Saliva amount and its composition depend greatly on the quality of food we eat: the drier food is the more saliva is produced. At the same time, the quality and composition of saliva (and, to some extent, the degree of food digestion at this stage) also depend on stimulation of salivary glands. The very thought about food causes salivation; and presence of food in our mouth initiates the reflex process of saliva secretion and prolongs its time. Due to the fact that food remains in our mouth not for a long time, digestion is barely starts at this stage; the general digestive effect of saliva reveals itself only in out stomach.

Stomach digestion

A food clot needs approximately 6-9 seconds to get to our stomach from the mouth cavity. Here consumed food is digested with the help of ferments of stomach gland juice for 2-6 hours. Our stomach is the organ that appeared in the result of evolution to storage food and carry on starting stages of hydrolysis (food disintegration). An adult’s stomach can hold several kilos of food substances and liquids. Stomach juice contains hydrochloric acid and the following ferments: pepsin and gastricsin.`

Joint effect of stomach juice acid and ferments dissolve the majority of substances containing in consumed food: first of all it regards proteinic compounds.

The main role of ferments is to accelerate biochemical processes. They differ in accordance with their target: some ferments are produced to dissolve proteins; other ones – to dissolve carbohydrates and so on. They are unstable at high temperatures, active in particular mediums: for example, some ferments are active in acidic medium; other ones – in alkaline or neutral ones. Ferments are produced by secretory cells situated both separately in the form of glands and inside alimentary tube walls. Secretory cells receive necessary substances for ferment synthesis directly from blood and use a certain amount of energy to carry this process.

The period during which consumed food stays in the stomach depends on its composition: solid food that contains a lot of proteins stimulates stomach juice secretion more actively and remains in the stomach longer than liquid food containing less amount of proteins. Fats remain in the stomach for quite a long period while carbohydrates pass though it rather quickly. At the final stage of stomach digestion acidic liquid mass (chyme) is moved to bowels by means of peristaltic contractions.

Bowel digestion

The total length of bowels amounts approximately 6 metres; their glands secrete up to 2 litres of juice a day. The total surface of bowel walls is 3 times bigger than the total skin surface of our body.

Due to the fact that bowels have such broad surface, they appear to be the field of the most dramatic metamorphoses of the foot we eat. As some scientist use to say, here the process of cold nuclear fusion (turning of certain substances into other ones) takes place. That’s why the major digestive processes take place exactly in our bowels.

Bowel walls contain cells that synthesize and secrete different hormones. The weight of these cells is as big as the weight of the biggest endocrine glands! Up to the current moment there were discovered 7 types of endocrine cells, each of them produces a particular hormone.

Food Digestion Process (and especially protein digestion) is connected with increased energy expenditure. Normal work of our digestive organs depends to a great extent not only on balanced selection of food products but also on our nutrition regime.

Written by: Dennis Borisoff
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