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Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
Revati Phalkey, Naima Bradley, Alec Dobney, Virginia Murray, John O’Hagan, Mutahir Ahmad, Darren Addison, Tracy Gooding, Timothy W Gant, Emma L Marczylo, Caryn L Cox
The small intestine – is concerned primarily with the absorption of sugars or carbohydrates and produces the related enzymes maltase, sucrase and lactase. Though the nerve supply to the small intestine is both from the parasympathetic and sympathetic nervous systems, these nerves regulate motility or contractions of the small intestine (peristalsis) and have no role in the production of the digestive enzymes. The absorption of food takes place mainly in the small intestine. Amino acids and fats are also absorbed here.
Tissue Engineering in Reconstruction and Regeneration of Visceral Organs
Published in Rajesh K. Kesharwani, Raj K. Keservani, Anil K. Sharma, Tissue Engineering, 2022
Soma Mondal Ghorai, Sudhanshu Mishra
The small intestine is segmented into three regions: these are the duodenum, jejunum, and ileum (Spoerri, 1949). Duodenum is the shortest of 25.4 cm and begins after the pyloric sphincter followed by jejunum of 0.9 m and ileum is the longest of about 1.8 m in length. Ileum is also the thickest and most vascular with well-developed folds than the other two. The entire intestine is innervated by parasympathetic nerve fibers from the vagus nerve and sympathetic nerve fibers from the thoracic splanchnic nerve. Intestine is also accompanied by a well-circulated portal system with the superior mesenteric artery and superior mesenteric vein as the main artery and vein to collect the nutrient-rich blood and carry it to the liver via the hepatic portal vein. Anatomically, intestine is composed of mucosa and submucosa and a highly absorptive surface area with numerous villi and microvilli and more than 600-fold, circular folds. Special lymphoid organ Peyer’s patches are seen within the submucosa of the intestine, which impart immunity from the invading pathogens (Figure 7.7A).
Deep Learning in Medical Image Classification
Published in R. Sujatha, S. L. Aarthy, R. Vettriselvan, Integrating Deep Learning Algorithms to Overcome Challenges in Big Data Analytics, 2021
Problems, such as, irritation, hemorrhage, disease, and cancer in the gastrointestinal tract are the main causes of indigestion and improper absorption. Peptic or stomach ulcer is the bleeding caused in the upper GI tract. Tumors, gastric cancer, and colonic diverticulitis cause large bowel hemorrhage. Because of abnormal blood vessels, celiac sprue, Crohn’s illness, gastric tumors, peptic ulcers, and GI bleeding are issues that trouble the small intestine. Current imaging innovations such as endoscopy, enteroscopy, endoscopy of remote cases, tomography, and MRI play a huge role in the determination of these gastrointestinal tract issues.
Microplastics and human health: Integrating pharmacokinetics
Published in Critical Reviews in Environmental Science and Technology, 2023
The main routes of exposure to microplastics for humans consist of ingestion, inhalation, and dermal contact. The digestive system is important in the digestion and absorption of nutrients and electrolytes, which occur mainly in the small intestine. The small intestine may also play an important role in the absorption of microplastics (Figure 1). Contact of microplastics with the intestinal mucosa is dependent on their ability to cross the intestinal mucus, facilitated through a formation of a corona of organic matter or intestinal contents (Powell et al., 2007) or due to small particle sizes (Szentkuti, 1997). After crossing the intestinal mucus, particles come in contact with the intestinal epithelium, being internalized by the following mechanisms: (i) transcytosis, the uptake and transport of smaller particles by enterocytes; (ii) internalization by M cells (e.g. micropinocytosis, phagocytosis, and receptor-mediated endocytosis) or other cells in the intestinal mucosa adjacent to Peyer’s patches; (iii) paracellular transport, through gaps between cells dependent on concentration gradients and particle sizes, increasing when tight junction integrity is compromised; (iv) persorption through gaps in the villi during cell turnover (desquamation zones), openings of tight junctions during the migration of macrophages, or damage to the epithelium (e.g. erosion and ulceration), for larger particles (e.g. 7–70 µm); (v) uptake by migratory phagocytes (e.g. intestinal macrophages and dendritic cells) directly from the intestinal lumen (Delon et al., 2022).