gastrointestinal tract (digestive system)

6.5 to 9 meters long

they move from the lumen of the digestive tract into the bloodstream

epithelium and also coated with moist mucus for protection

mouth through the pharynx to the oesophagus, stomach, small intestine and large intestine. The large intestine terminates in the rectum and anus

Chewing mixes food with saliva which contains amylase which breaks down starch. Once food is swallowed, the chewed food is known as bolus. Bolus is pushed along from the esophagus into the stomach by waves of muscle contractions known as peristalsis

enzymes are released which aids further digestion and absorption. The stomach mixes and stores ingested food, also it produces hydrochloric acid (HCl, pH 1.5), pepsins, mucus, and intrinsic factor. These substances make up the gastric juice which when mixed with the ingested food produces a paste known as chyme; acidity of the gastric juice also kills microbes

Food is chemically broken down into nutrients small enough to be absorbed. Pancreas releases amylase, Trypsin, lipase and nucleases which digests carbohydrates, proteins, fats and nucleic acids The liver produces bile whilst the gallbladder stores it, bile aids in the digestion and absorption of fats. The hepatic portal vein diverts nutrient-rich blood from the small intestine to the liver, allowing the liver to process and store these nutrients into macromolecules such as glucose to glycogen, storage of Vitamin D

digested nutrients and fluid pass from the lumen wall into blood or lymph. The small intestine is the location of most digestion and absorption. Chyme along with enzymes from pancreas, liver and gallbladder first enters the duodenum, most digestion and absorption takes place in the jejunum. Some nutrients such as vitamin B12 are absorbed in the ileum while residues are on its way to the large intestine. The structure of the small intestine aids absorption; microvilli (finger like projections) provide a vast surface area for absorption

undigested and unabsorbed remnants are excreted from the end of the GIT. The large intestine is the area where water, salts and certain vitamins are reabsorbed from food and remaining material is eliminated as feces. Bacteria in the large intestine produce some vitamins (Vitamin K and B12) which are absorbed.

page 16

salivary amylase, salivary glands, polysaccharide, disaccharide pancreatic amylase, pancreas, polysaccharide, disaccharide

pepsins, stomach lining, proteins, protein fragments trypsin, pancreas, proteins, protein fragments carboxypeptidase, pancreas, proteins, amino acid

lipase, pancreas, triglycerides, fatty acids

pancreatic nucleases, pancreas, DNA and RNA, nucleotide

A water-soluble vitamin involved in the metabolism of every cell of the human body.

A painful, burning sensation that occurs in the chest or throat when stomach acid backs up into the esophagus

chronic condition that affects the large intestine

An impaired ability to digest lactose, a sugar found in milk and other dairy products. Usually occurs due to deficiency of lactase.

Damage to the epithelium or mucous membrane of a internal organ.

An inherited disorder that affects the cells that produce mucus, sweat and digestive juices resulting in severe damage to the lungs, digestive system and other organs in the body.

A chronic digestive and immune disorder triggered by eating foods containing gluten such as bread. It results in the damage of the small intestine.

A group of fat-soluble vitamins that play a role in blood clotting, bone metabolism, and regulating blood calcium levels