The small intestine
Paul Ong, Rachel Skittrall in Gastrointestinal Nursing, 2017
Goblet cells secrete mucous and are abundant in the crypts of Lieberkühn. Crypts are intestinal glands which can be described as invaginations between the villi. The mucous provides protection against chemical damage from enzymes and mechanical damage caused by friction as chyme moves through the lumen. The enterocytes are involved in both digestion and absorption. Their surfaces are covered with microvilli which play a major role in increasing the surface area. These microvilli form what is often termed a ‘brush border’ of hair-like fibres. Attached to these are a number of important enzymes which enter into the lumen of the small intestine. These enzymes perform a vital function of breaking down food material that comes into contact with the brush border. Once these materials are broken down they are then absorbed by the enterocytes. As enterocytes are shed from the villi into the lumen they disintegrate and release their enzymes into the lumen. Within the intestinal glands are enteroendocrine cells which produce intestinal hormones which are released into the lamina propria and diffuse into the capillary blood vessels. These play a role in the coordination of digestive activities, and important ones include gastrin, cholecystokinin (CCK) and secretin. Figure 5.5 provides an overview of regulation of pancreatic and hepatobiliary secretions showing hormonal pathways.
Exposure
Frank A. Barile in Barile’s Clinical Toxicology, 2019
Oral administration of drugs and toxins is by far the most popular route of exposure. Oral administration involves the presence of several physiological barriers, which must be penetrated or circumvented if an adequate blood concentration of the compound is to be achieved. The mucosal layers of the oral cavity, pharynx, and esophagus consist of stratified squamous epithelium, which serves to protect the upper gastrointestinal (GI) lining from the effects of contact with physical and chemical agents. Simple columnar epithelium lines the stomach and intestinal tracts, which function in digestion, secretion, and some absorption. Immediately underlying the epithelium is the lamina propria, a mucosal layer rich in blood vessels and nerves. Mucosa-associated lymphoid tissue (MALT) is layered within this level, where prominent lymphatic nodules sustain the presence of phagocytic macrophages and granulocytes. Salivary and intestinal glands contribute to the digestive process by secreting saliva and digestive juices. The submucosa, muscularis, and serosa complete the strata that form the anatomical envelope of the GI tract. Enteroendocrine and exocrine cells in the GI tract secrete hormones and in the stomach, secrete acid and gastric lipase. Tables 5.1 and 5.2 illustrate select toxic substances and routes of exposure, including dermal and ocular routes, and their suspected clinical effects.
Anatomy and Physiology of the Autonomic Nervous System
Kenneth J. Broadley in Autonomic Pharmacology, 2017
The autonomic nervous system controls the internal involuntary functions of the body. These are the functions concerned with the maintenance of a constant internal environment, that is, homeostasis. The major activities and systems under the control of the autonomic nervous system include digestion, the cardiovascular system (such as the blood pressure), blood chemistry, breathing and body temperature. Control of these functions is below the level of consciousness, hence the term involuntary nervous system. The major cellular structures that are innervated by the autonomic nervous system are smooth muscle, cardiac muscle, glandular tissue and adipocytes (fat cells). Thus, the digestion of food occurs by the secretion of digestive enzymes from the intestinal glands of the intestinal mucosa and rhythmic contraction and relaxation of circular and longitudinal smooth muscle arranged in the intestinal wall propels the chyme along and chums it up to aid digestion. We are unaware of this process and have little conscious control over it. The autonomic nervous system modulates this digestive activity by either speeding or attenuating.
Zhizhu decoction alleviates slow transit constipation by regulating aryl hydrocarbon receptor through gut microbiota
Published in Pharmaceutical Biology, 2023
Yong Wen, Yu Zhan, Shiyu Tang, Fang Liu, Rong Wu, Pengfei Kong, Qian Li, Xuegui Tang
Histopathological analysis of the colonic tissue showed that the colonic tissue of mice in the control group had complete structures of mucosa, submucosa, muscularis and outer membrane, the mucosa was covered with single columnar epithelial cells, and a large number of intestinal glands were found in the lamina propria. However, in the model group, some areas of colonic tissue were characterized by mucosal necrosis, loss of epithelial cells in the necrotic area, necrotic of intestinal glands in the lamella propria, and the tubular structure was absent, only necrotic cell fragments and a few lymphocytes or neutrophils were observed. After treatment with all doses of ZZD and positive drugs, the damage to colonic tissue was significantly improved. The colon structure was relatively complete, the epithelial cells were arranged in a more orderly manner, and only a few intestinal glands were necrotic in the lamina propria, with slight inflammatory cell infiltration (Figure 2(A)). In addition, the thickness of mucosa tissue and muscle layers was also determined. The analysis revealed that compared with the control group, the tissue thickness was significantly reduced in the model group. However, the above effects were significantly reversed following mice treatment with different doses of ZZD (p < 0.05; Figure 2(B)).
Comparative study on the gastrointestinal- and immune- regulation functions of Hedysari Radix Paeparata Cum Melle and Astragali Radix Praeparata cum Melle in rats with spleen-qi deficiency, based on fuzzy matter-element analysis
Published in Pharmaceutical Biology, 2022
Yugui Zhang, Jiangtao Niu, Shujuan Zhang, Xinlei Si, Tian-Tian Bian, Hongwei Wu, Donghui Li, Yujing Sun, Jing Jia, Erdan Xin, Xingke Yan, Yuefeng Li
The upper part of the small intestine starts from the pylorus of the stomach, and its lower part is connected with the large intestine via the ileocecal valve, which is divided into duodenum, jejunum and ileum. The HE staining results of duodenum, jejunum and ileum showed obvious injuries in SQD model compared with normal. The main reason may be related to the diarrhoea symptoms of SQD rats. Three parts of the small intestine had more crypt cells, the villi were shortened and indistinct, the villi tips were partially necrotic and detached, the villus epithelial cells were damaged and detached, and edoema was obvious. The intestinal glands were obviously degenerated, and the submucosa was slightly congested and severely oedematous, with a small amount of inflammatory cell infiltration. After treatment, the number, arrangement and morphological structure of glandular cells in each part of the small intestine were significantly improved, the length of villi increased, and edoema was relieved. In particular, HRPCM (18.9 g/kg) and ARPCM (18.9 g/kg) were more significant (Figure 10).
Anticoccidial effect of Fructus Meliae toosendan extract against Eimeria tenella
Published in Pharmaceutical Biology, 2020
Ting Yong, Meng Chen, Yunhe Li, Xu Song, Yongyuan Huang, Yaqin Chen, Renyong Jia, Yuanfeng Zou, Lixia Li, Lizi Yin, Changliang He, Cheng Lv, Xiaoxia Liang, Gang Ye, Zhongqiong Yin
The structure of the caecum in the normal group was normal (Figure 3(A)), while the caecum in the untreated group had serious lesions. Due to the large number of oocysts in the intestinal mucosa, the intestinal gland was disorganized (Figure 3(B)). Compared with the untreated group, the number of oocysts in the intestinal mucosa of the pre-treated groups was decreased (Figure 3(C–F)), and that of the FMTE-H group was the least (Figure 3(D)). In the normal group, the appearance of the liver was normal (Figure 3(G)). In the untreated group, the hepatocytes were swollen, and serious vacuolar degeneration, disappeared hepatic cord and narrowed hepatic sinuses were observed (Figure 3(H)). In the pre-treatment group, there were varying degrees of granular and vacuolar degeneration (Figure 3(I–L)). In the FMTE-H group, mild vacuolar degeneration of hepatocytes and inflammatory cell infiltration were found in the marginal area of hepatic sinuses (Figure 3(J)). In the normal group, the structure of kidney was normal (Figure 3(M)), but in the untreated group, the epithelial cells of renal tubules were swollen, even with severe granular degeneration and vacuole degeneration, which resulted in the narrowing of renal tubules and the shedding of cells in the tubules (Figure 3(N)). In the pre-treatment group, there were different degrees of granular and vacuolar degeneration and inflammatory cell infiltration in kidney (Figure 3(O–R)). Compared with other pre-treatment groups, the appearance of kidney was normal, and the epithelial cells of renal tubules had slight granular degeneration and vacuole degeneration in the FMTE-H group (Figure 3(P)).