The primary functions of gastrointestinal system are ingestion, digestion, absorption of nutrients and excretion of solid waste.
The body requires the consumption of nutrients to support physiological activity.
Proper function of the gastrointestinal system (GI) is essential for normal growth and for maintaining fluid and electrolytes balance.
For the assimilation of nutrients by the body, the bulk of the foodstuffs must first undergo mastication and digestion.
In this process, polymeric substances such as starches, proteins and triglycerides are broken down into their smaller segments “building blocks” of monomeric sugars, amino acids, fatty acids, etc., in preparation for absorption.
With the exception of most vitamins and inorganic substituent, this digestive breakdown process is necessary for absorption into the body.
It is also a factor in body defenses, preventing the potential absorption of “foreign” macromolecules. The GI tract is the largest immune system organ whose primary functions include the digestion and absorption of ingested nutrient and the protection of the body from ingested microorganism and noxious substances.
During digestion/hydrolysis if the polymeric nutrients (especially) the proteins), the vitamins and trace elements associated with them are released, allowing their more efficient absorption.
The large intestine absorbs water and electrolytes from entering content, which happens predominantly in the proximal half and stores fecal matter until defecation, which occurs in the distal half.
Absorption is the process by which the end products of digestion such as monosaccharides, amino acids, glycerol, fatty acid chains, vitamins, minerals and water – pass through the epithelial membranes in the small and large intestine into the blood or lymph system.
The mechanisms for digesting and absorbing major nutrients are fully mature in the premature and term infant.
Digestion and absorption of nutrients
