The Digestive (Gastrointestinal) System and Its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
The pancreas, located behind the stomach, contains digestive exocrine cells in addition to its endocrine function. Pancreatic enzymes are capable of digesting fats, carbohydrates, and proteins, and they are carried by an alkaline bicarbonate solution that neutralizes stomach acid. These juices act to convert the chemical environment from acidic to alkaline, which is more amenable to the intestines. Although the liver lies outside the digestive tract, it is considered a part of this system because of its many functions relating to digestion. It modifies all types of food substances, including fats, to enable utilization by body tissues. The gallbladder, a small, pear-shaped, sac-like organ located under the right lobe of the liver, serves as a storage area for excess bile before it passes into the duodenum.
Introduction
Paul Ong, Rachel Skittrall in Gastrointestinal Nursing, 2017
The digestive system is divided into two parts: the gastrointestinal tract and the accessory organs. The gastrointestinal (GI) tract is made up of a number of organs that are directly involved in the process of digestion: mouth, pharynx, oesophagus, stomach, small intestine, large intestine and rectum (Figure 1.1). The accessory organs are a group of organs that assist in the process of digestion, and they include the teeth, tongue and gallbladder, which facilitate digestion. There are also a number of digestive glands such as the salivary glands, liver and pancreas that produce secretions that assist in the process of digestion but are not considered part of the gastrointestinal tract. This is why they are termed accessory organs (Figure 1.2). These organs are constructed of specialised cells that perform different complex functions. How the cells are specialised is dependent upon the function they perform.
Basic medicine: physiology
Roy Palmer, Diana Wetherill in Medicine for Lawyers, 2020
The functions of the gastrointestinal tract include transport, secretion of digestive juices, absorption of nutrients and clearance of waste. Besides the hollow tube of the alimentary canal (Figure 1.3), the gastrointestinal system comprises the biliary tract and pancreas, which are concerned with digestion, and the liver where much of the body’s metabolism takes place—notably the biochemical processes by which nutrients are converted into energy and building blocks such as albumin (the main protein in the blood). Entry of food into the mouth stimulates the flow of saliva and gastric (stomach) juice; in fact, even the thought of food can induce salivation, as Pavlov showed in dogs. Swallowing, which starts as a voluntary exercise and continues involuntarily, transmits the bolus of food from the mouth to the stomach via the oesophagus (gullet). In the stomach food is physically mashed up by muscular contraction, and the process of digestion is begun by the proteolytic (protein-splitting) enzyme pepsin. Pepsin works at an acidic pH, and the strong hydrochloric acid secreted by the gastric lining also sterilizes the food; excess gastric acid contributes to duodenal ulcer disease.
Intracameral Gnathostomiasis: A Case Report and Literature Review
Published in Ocular Immunology and Inflammation, 2023
Wijak Kongwattananon, Thanaporn Wiriyabanditkul, Waraluck Supwatjariyakul, Thanapong Somkijrungroj
Under light microscope, an advanced third-stage larva of G. Spinigerum is found ranging in size from 2.30 mm to 4.40 mm long and 0.25 mm to 0.43 wide.20 It consists of three parts. The first part is the lip. The second part is the cephalic bulb with a characteristic of four transverse rows of hooklets on its surface. The third part is the body, which has more than 250 transverse rows of cuticular spines encircling the body. The digestive tract comprises a muscular esophagus and an intestine opening down to the anus near the posterior end. Scanning electron microscope can reveal external morphology of the larva in more detail. The mouth of larva is cup-shaped with a pair of lateral lips and labial papillae.7,12 The cephalic bulb is distinguished from the body by collar tissue and has four circumferential rows of hooklets.7 Each row bears 45 to 50 hooklets.7 Cervical papillae is typically found between 9th and 10th rows of body cuticular spines.21
Cellulolytic bacteria in the large intestine of mammals
Published in Gut Microbes, 2022
Alicia Froidurot, Véronique Julliand
The large intestine of mammals (Figure 3) is a fermenter in which environmental conditions are favorable to microbial activity. It is the part of the digestive tract that follows the small intestine and begins at the cecum and includes the appendix (humans only), colon, rectum, and anus.32 The large intestine contains a minority of microorganisms that are able to degrade cellulose, including bacteria, and certain anaerobic eukaryotes (fungi and protozoa).16,33 In contrast, the abundance of microorganisms growing on soluble polysaccharides resulting from the “primary” cellulose degradation is high.16,34 In the present review, cellulolytic bacteria were focused. Despite their small quantity, cellulolytic bacteria play a crucial role, i.e., a “keystone” role, in this process, as their absence would, e.g., greatly decrease the degradation and utilization of an important substrate, thus affecting the remainder of the microbial community.33
The Effects of Perioperative Probiotics on Postoperative Gastrointestinal Function in Patients with Brain Tumors: A Randomized, Placebo-Controlled Study
Published in Nutrition and Cancer, 2023
Mengyang Jiang, Xiaoyu Zhang, Yiqiang Zhang, Yang Liu, Ran Geng, Haixia Liu, Yongxing Sun, Baoguo Wang
The primary functions of the gastrointestinal tract are motility, secretion, absorption, and serving as a barrier. Nervous system disorders affecting gastrointestinal function are characterized primarily by abnormalities in motility rather than secretion (6). Gastrointestinal motility is regulated at multiple levels, including the central and enteric nervous systems as well as the microbiome (26,27). Surgery-induced stress and inflammatory responses activate the sympathetic and enteric nervous systems, leading to gastrointestinal dysfunction and thus disturbing motility and transit (28). This process involves the immune system, inflammatory cells, reactive enteric glia, neurons, smooth muscle cells, epithelial cells, and the microbiome in the intestinal lumen (8). Postoperative gastrointestinal dysfunction can not only cause short-term complications, but may also lead to long-term complications after inflammation subsides (29). The incidence of postoperative gastrointestinal dysfunction in adults with neurological diseases is more than twice that for individuals with non-neurological diseases (2).