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Alimentary Canal Another name for the digestive system; defined as a hollow tube that extends from the mouth and ends at the rectum. Oral Cavity Also known as mouth; where foods and liquids first enter the digestive tract. Teeth Crush and tear food into small round pieces forming a bolus. Bolus A mass of food ready to be swallowed. Tongue The muscular organ attached to the back of the mouth and functions in tasting, swallowing, chewing, and speaking. Salivary Glands Secrete saliva which is a digestive juice that facilitates chewing, swallowing, and initiates carbohydrate digestion. Parotid Salivary Glands Lie anterior to the ear on each side of the head and produce watery saliva containing salivary amylase, which is responsible for breaking down carbohydrates. Sublingual Salivary Glands Located under the tongue and secrete mucous. Submandibular Salivary Glands Located on each side of the jaw bone and secrete a watery mucous containing salivary amylase. Pharynx Located behind the nose, mouth, and larynx. Also known as the throat. Serves both digestive and respiratory systems. Nasopharynx Lies just posterior to the nasal cavity. Oropharynx Lies inferior to the nasopharynx and extends to the base of the tongue. Laryngopharynx Lies inferior to the oropharynx and is the entrance to the esophagus. Larynx Contains the vocal cords and epiglottis; lies anterior of the pharynx. Epiglottis A lid-like flap of elastic cartilage tissue attached to the root of the tongue and is covered with a mucous membrane; prevents food from entering the lungs. Ventral Body Cavity Contains organs of the respiratory, cardiovascular, digestive, urinary, and reproductive systems; divided into thoracic and abdominopelvic cavities by the diaphragm. Peritoneum A serous membrane that lines the peritoneal cavity. Visceral Peritoneum A membrane that covers enclosed organs. Esophagus Straight, collapsible, muscular tube about ten inches in length that connects the pharynx to the stomach. Peristalsis A wave of muscular movement that pushes food through the digestive system. Esophageal Sphincter A circular piece of muscle tissue that keeps food from going back into the esophagus once it enters the stomach. Stomach Primarily a reservoir that permits digestion to take place gradually with limited absorption. Large and J-shaped, and located within the peritoneum below the diaphragm. Chyme A semi-solid mixture of food and gastric juices that's propelled into the small intestine. Mucous Cells Located in the lining of the stomach where the gastric glands are contained. Secrete mucous, which provides protection for the stomach walls. Parietal Cells (Proton Pumps) Large cells that are located on the margin of the gastric glands. Secrete both hydrochloric acid and intrinsic factor. Hydrochloric Acid A secretion of the parietal cells that is necessary to activate protein-digesting enzymes. Intrinsic Factor A secretion of the parietal cells that is important for the absorption of dietary vitamin B12. Chief Cells Located in the gastric glands and secrete pepsinogen. Pepsinogen Secreted by chief cells. A precursor for pepsin, which is a major protein-digesting enzyme responsible for breaking down proteins into polypeptides. Endocrine Cells Located in the gastric glands and secrete gastrin and regulate secretion and motility. Pyloric Sphincter Opening at the end of the stomach. A ring-like muscle that opens to allow chyme into the first portion of the small intestine. Small Intestine A portion of the digestive tract that is approximately 23 feet in length. A major site of absorption and extends from the pyloric sphincter to the cecum, at the beginning of the large intestine. Duodenum First portion of the small intestine. Shaped like a horse-shoe and is about 8-11 inches long. Receives digestive juices from the liver and pancreas which is added to the chyme. Jejunum Second portion of the small intestine. Joins the duodenum to the ileum. Bulk of chemical digestion and nutrient absorption occurs here and it is roughly nine feet in length. Ileum Final portion of the of the small intestine that ends at the cecum, which opens into the large intestine. Villi Fingerlike projections that carpet the small intestine and increase the absorptive surface area. Nutrients in food are absorbed through these. Large Intestine Extends from the termination of the ileum to the anus. Major functions include re-absorption of water and compaction of the intestinal contents into poo. =] Re-absorption of important vitamins, and storage of fecal matter prior to defecation. Cecum Where the small intestine meets the large intestine. Receives waste material and begins the process of compaction. Appendix A short, worm-like projection that extends from the cecum that's function is not fully known. Colon Extends from the cecum to the rectum. Absorbs water, minerals, and vitamins from intestines. Eliminates undigested material during defecation. Ascending Colon Upward portion of the large intestine. Transverse Colon Portion of the large intestine that goes across the abdominal cavity from the right to the left. Descending Colon Portion of the large intestine going down to the sigmoid colon. Sigmoid Colon Portion of the large intestine going from the descending colon to the rectum. Rectum The terminal part of the large intestine and controls the defecation reflex. Anus Terminal opening of the anal canal. Internal and external sphincters which controls the exit of fecal matter. Accessory Organs Organs that play a direct role in digestion, but are not a part of the alimentary canal. Liver Largest organ in the body. Responsible for metabolic regulation, hematological regulation, and bile production. Gallbladder A small organ that stores and concentrates the bile that is made in the liver until it is needed in the digestive proces. Bile A yellow, brownish, or olive-green liquid that emulsifies fat into microscopic globules and dilutes and neutralizes stomach acid in the small intestine. Pancreas An organ that has both endocrine and exocrine functions. Pancreatic Juice An alkaline mixture of digestive enzymes, water, and ions. Ingestion Occurs when materials enter the digestive tract via the mouth. An active process involving conscious choice and decision making. Mechanical Processing Crushing and shredding that makes materials easier to propel along the digestive tract. Digestion Refers to the chemical breakdown of food into small organic fragments suitable for absorption by the digestive epithelium. Secretion The release of water, acids, enzymes, buffers, and salts by the epithelium of the digestive tract, and by glandular organs. Absorption The movement of organic substrates, electrolytes, vitamins, and water across the digestive epithelium and into the interstitial fluid of the digestive tract. Excretion The removal of waste products from the body fluids.