Glossary Absorption After digestion, the basic elements of food are absorbed by active and passive transport across the membranes of cells lining the small intestine Acetylcholine A neurotransmitter released by the vagus nerve in response to the sight, smell and taste of food. Active transport An energy-dependent process in which certain substances are able to cross cell membranes against a concentration gradient Antrum The area of the strongest muscular contractions in the stomach, where food is kneaded and churned before being passed to the duodenum Autonomic nerves Nerves responsible for the control of bodily functions that are not under conscious control Bile A fluid produced in the liver and concentrated in the gall bladder that is delivered via the common bile duct to the duodenum when required for fat digestion Caecum The first section of the large intestine. The caecum is a pouch and is the widest section of the large intestine, located in the lower right hand side of the abdomen Cardiac sphincter Another name for the lower oesophageal sphincter Chemoreceptor trigger zone An area of the brain that triggers the vomiting reflex when stimulated Chyme Partially digested food Colon Part of the large intestine; divided into ascending, transverse, descending and sigmoid sections. It absorbs water to concentrate the faeces and draws some salts into the colon for elimination. Colonic bacteria are present in large quantities Columnar epithelial cells Column-shaped cells that line the inside of the small intestine Corpus The corpus (or corpus ventriculi) is the 'body' of the stomach. The muscles relax when food enters the stomach to accommodate large volumes Dependency A state that occurs when a person is addicted to a substance Digestion The process by which food is broken down into its basic elements: saccharides (from starch and sugars) amino acids (from protein) fatty acids and glycerol (from fats) Duodenum The first part of the small intestine, about 25cm long Dyspepsia From a Greek word meaning 'bad digestion'. Includes symptoms confined to the stomach area involving discomfort, griping or stomach cramps, churning sensations, feelings of bloating, nausea and flatulence. These symptoms are all related to eating, but come on at different times after eating, depending on the cause Elimination Excretion of waste products of digestion and metabolism from the body via faeces; can also refer to urine, sweat, tears and expiration Endoscopy A diagnostic technique for examining the inside of the gastrointestinal tract through a slim tube or endoscope Fundus Part of the stomach. The muscles in the fundus relax when food enters the stomach Gastrin A hormone released in response to food arriving in the stomach that stimulates acid secretion both directly by acting on the parietal cells, and indirectly by stimulating the release of histamine Gullet Another name for the oesophagus H2 antagonist A drug that inhibits the H2 histamine receptor Heartburn A painful burning sensation behind the breastbone caused by reflux of acid from the stomach into the oesophagus Helminth Another name for a worm Histamine A hormone that acts on histamine (H2) receptors on the parietal cells to stimulate gastric acid secretion Ileo-caecal valve The valve joining the ileum to the caecum and marking the junction between the middle and lower parts of the intestine Ileum The lower section of the small intestine (3.6m in length) that is the main site for absorption, facilitated by its very large surface area Ingestion The first stage in processing food; taking it into the body and passing it to the stomach Irritable bowel syndrome (IBS) An abnormality of function, rather than structure of the small intestine and colon. Symptoms can include one or more of the following: abdominal pain, either sharp and colicky or a dull ache bloating and distension of the abdomen diarrhoea, sometimes with mucus present constipation excessive wind changed stools rectal discomfort Jejunum The middle section of the small intestine (about 2.7m long) that connects the duodenum and ileum and is mainly concerned with digestion Large intestine Part of the gastrointesinal tract that extends from the caecum to the anus, and includes the caecum, colon, rectum and anus. It is wider than the small intestine and has a pouched appearance Lower oesophageal sphincter (LOS) The ring of muscle at the lower end of the oesophagus, also called the cardiac sphincter. it is normally closed but relaxes when on swallowing to allow food and liquid into the stomach. The cardiac sphincter is firmly closed during peristalsis to prevent reflux of food, gastric contents and air back into the oesophagus from the stomach Motility The degree of mobility of the gastrointestinal tract, which contributes to the movement of food and digested food products through the tract Mucosa The lining of muscle, connective tissue, secretory cells and glands in the gastrointestinal tract Nausea A feeling of queasiness, when the sufferer believes they are about to vomit Oesophagus A muscular tube about 25cm long, connecting the pharynx to the stomach Pancreatic juice A fluid containing digestive enzymes produced by the pancreas that is released into the duodenum when triggered by food arrival Parietal cell A specialised cell in the stomach wall that produces and secretes hydrochloric acid Passive transport A process in which substances cross cell membranes without using energy, e.g. by diffusion Peptic ulcer An identifiable lesion in the stomach or duodenum, related to the acid contents of the stomach Peristalsis The involuntary muscular movements responsible for the propulsion of food through the gastrointestinal tract from the oesophagus to the anus pH A measure of the acidity or alkalinity of a solution. A pH of 7.0 indicates a neutral solution; a pH below 7.0 indicates an acid and a pH above 7.0 indicates an alkali Pharynx The canal leading from the mouth to the oesophagus. Another name for the throat Postprandial Occurring after eating Pyloric sphincter The ring of muscle at the base of the stomach that is normally contracted to prevent food leaving the stomach before gastric digestive processes are complete and to stop chyme returning to the stomach from the duodenum Pyloric stenosis A condition in which the outlet from the stomach to the small intestine is constricted by thickened muscle Rectum The muscular sac that stores faeces immediately before defaecation. Distension of the rectum by faeces triggers the urge to defaecate Reflux Flow of digested food against the normal direction of movement Small intestine The middle part of the gastrointestinal tract leading from the pyloric sphincter at the base of the stomach to the ileo-caecal valve at the beginning of the caecum. In total, the small intestine is over 6m long and includes the duodenum, jejunum and ileum. most digestion and absorption takes place in the small intestine Smooth muscle Involuntary muscle that is not under the conscious control of the brain Stomach The muscular bag in which food is mixed and stored before digestion begins Surfactant A wetting agent Villi Tiny (1mm) finger-like projections throughout the gastrointestinal tract that increase the surface area in the small intestine and assist propulsion of contents Vomiting The act of being sick