Term | Definition |
Absorption | The "taking in" of substance particles, generally in molecular or ion form. |
Anaerobic bacteria | Bacteria that survive in the absence of oxygen. E. Coli is an example. |
Anus | The posterior opening of the digestive tract, protected by the anal sphincter. |
Appendix | A fingerlike vestigial protection from the caecum. No function |
Bile | A liver secretion that passes through the bile duct into the duodenum. Bile emulsifies lipids. |
Capillary | The smallest type of blood vessel. The walls of capillaries are only one cell thick thus facilitating capillary-tissue fluid exchange. |
Cardiac sphincter | The muscular constriction along the gastro-intestinal tract located where the esophagus meets the stomach. |
Chemical digestion | The hydrolytic reactions that reduce food molecules to monomers by enzymatic activity. |
Digestive enzyme | Hydrolytic enzyme that chemically breaks food molecules into monomers. |
Digestive tract | This is the tube that conducts food through the body from the mouth to the anus. |
Duodenum | The first portion of the small intestine. This is where majority of the digestive activity takes place. |
Emulsification | The making of an emulsion by the physical suspension of immiscible substances into a solute. |
Epiglottis | The ventral flap of tissue on the top of the trachea (the glottis), just anterior of the larynx. |
Esophagus | The esophagus is located dorsal to the trachea. It extends from the base of the pharynx to the cardiac sphincter. |
Gall bladder | A thin-walled storage sac attached to the underside of the liver. The gall bladder contains bile. |
Gastric juice | The digestive secretion produced by the stomach. Gastric juice is released as a result of the action of the hormone, gastrin. |
Hydrochloric acid (HCL) | This acid is a component of gastric juice. As such, it converts pepsinogen to the active enzyme, pepsin, which breaks some peptide bonds starting the digestion of proteins in the stomach, |
Insulin | A protein hormone that is produced by the beta cells of the islets of Langerhans in the pancreas. Insulin promotes the uptake and utilization of blood sugar by cells. Insulin lowers blood sugar. |
Intestinal juice | The digestive secretion of the small intestine. Intestinal juice contains a variety of enzymes that complete the chemical digestion of food. |
Lacteals | The beginnings of the lymphatic system in the villi of the small intestine. The lacteals transport the products of fat digestion away from the intestines. |
Large intestine (colon) | The large intestine begins at the ileocaecal valve, has four major sections: ascending, transverse, descending colons and the rectum. |
Lipase | Produced by the pancreas and enters the duodenum as a component of pancreatic juice. The products of its activity are fatty acids and glycerol. |
Liver | The largest inner organ of the body. The liver is located posterior to the diaphragm and has many functions including the production of bile, the conversion of ammonia into urea, storage of glucose as glycogen, production of globulins. |
Maltase | The disaccharides that catalyses the hydrolysis of maltase as well as the dehydration synthesis of glucose molecules to make maltose. |
Microvillus | Membranous extensions of the cytoplasm of columnar epithelial cells that line the villi. The microvillus increase the contact surface area of the villi against the intestinal lumen, thus increasing the absorption of the products of digestion. |
Nuclease | A nucleic acid-digesting enzyme. Nucleases are components of both pancreatic juice and intestinal juice. |
Pancreas | The gland posterior to the stomach that has both endocrine and exocrine functions. As an endocrine gland, its islets of Langerhans produce the hormones insulin and glucagon. |
Pancreatic amylase | The component of pancreatic juice that digests starch into maltose. |
Pancreatic juice | The exocrine secretion from the pancreas. Pancreatic juice contains pancreatic amylase, trypsin, lipase, nucleases, sodium bicarbonate, and water. |
Pepsin | A protease enzyme. Pepsinogen is a component of gastric juices. HCl, another component of gastric juice, activates it. |
Pepsinogen | Inactive form of pepsin. HCl activates it into pepsin. |
Peptidase | An enzyme that breaks peptide bonds, Peptides of various sorts are components of intestinal juice. |
Peristalsis | Smooth muscle contractions long tubular structures. It is the result of the coordinated contractions of both longitudinal and citcular muscles. |
pH | A measure of the amount of hydrogen ions in a solution. A solution with a pH of 7 is neutral. |
Pharynx | The region at the back of the mouth where both food and air travel. |
Physical digestion | The mechanical breaking apart of food materials in the digestive system. |
Protease | A protein-digesting enzyme. Typically, to avoid their production in a cell, proteases are produced in an inactive form. |
Pyloric sphincter | This is thee muscular constriction at the bottom of the stomach. The pyloric sphincter relaxes to permit small amounts of acid chyme into the duodenum at a time, so it can be neutralized and digested further. |
Rectum | The last portion of the large intestine. The rectum stores and compacts feces until defecation. |
Salivary amylase | This is the starch digesting enzyme that is a component of saliva. It has an optimum pH of about 7.0 in contrast to pancreatic amylase, which has an optimum pH of just over 8.0. |
Salivary gland | One of three sets of exocrine glands that deliver mucus and salivary amylase to the mouth. |
Salivary juice (Saliva) | A combination of salivary amylase and mucus that is produced and delivered to the mouth through ducts from the salivary glands. |
Small intestine | The longest portion of the gastrointestinal tract lying between the stomach and the large intestine. It is subdivided into three parts; the duodenum, the jejunum and the ileum. |
Sodium bicarbonate | The buffering component of pancreatic juice. The bicarbonate ions maintain the pH of chyme at about 8.2 which is optimal for the function of the pancreatic enzymes. |
Stomach | A significant organ in the digestive system lying between the cardiac ad pyloric sphincters. |
Swallowing | A reflexive action that initiates the movement of a ball of food down the esophagus. Swallowing is controlled by the medulla oblongata. |
Trypsin | A protease enzyme component of pancreatic juice. Trypsin is produced as trypsinogen, a precursor. It is activated by enterokinase. |
Villus | The finger like projections along the inner wall of the ileum. These contain blood capillaries and a lacteal and function for the absorption of the products of digestion. |