Radical Sphincter-Sparing Resection in Rectal Cancer
Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams in Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
The primitive gut tube is formed by the incorporation of the yolk sac, lined with endoderm, into the embryo. The primitive gut tube gives rise to the ‘visceral individuum’; these are the central unpaired organs such as the liver, stomach, spleen, intestine and rectum.92 The ‘somatic individuum’ develops simultaneously: this includes the paired organs such as the kidneys, ureters, external sphincter and the levator ani.92 At this stage of development the gut tube incorporates the foregut and hindgut, with the midgut still connected to the yolk sac via the vitelline duct. By the fifth week of development the gut tube is suspended throughout its length by a dorsal mesentery that contains blood vessels and lymphatics that traverse between the gut wall and the inner body wall. The hindgut includes the distal third of the transverse colon, the descending and sigmoid colon, the rectum, the upper third of the anal canal as well as part of the urogenital system (e.g. the bladder and urethra). In the hindgut this dorsal mesentery eventually condenses and develops into the mesorectum, which extends from the peritoneal reflection to taper at the level of the anal sphincter. The mesorectum represents the embryological delineation between the singular organs of the visceral individuum and the paired organs of the somatic individuum.92
The digestive system and the respiratory system
Frank J. Dye in Human Life Before Birth, 2019
A large part of the colon and the rectum have their origins in the hindgut (Figure 16.6). The caudal end of the hindgut is a blind tube ending at the cloacal membrane, the boundary between the rectum and the proctodeum (an inpocketing of ectoderm on the ventral side of the tail end of the embryo). The portion of the hindgut near the cloacal membrane is called the cloaca. From the cloaca's ventral surface, the allantoic diverticulum extends for a short distance into the umbilical cord. The urorectal septum grows between the hindgut and allantoic diverticulum toward the cloacal membrane, separating the cloacal membrane into an anal membrane and a urogenital membrane (see Figure 16.6). When the anal membrane ruptures during the seventh week, the anus opens to provide a passageway from the digestive tube into the amniotic fluid.
Neuroendocrine tumors of the gastrointestinal tract
Demetrius Pertsemlidis, William B. Inabnet III, Michel Gagner in Endocrine Surgery, 2017
The classical carcinoid syndrome (flushing and associated lability of blood pressure in 60%–85%, secretory diarrhea in 60%–80%, and bronchial constriction in 10%–20%) is found only in 20%–30% of patients with metastases. The syndrome is due to the secretion of vasoactive hormones from NETs [10]. These hormones include biogenic amines (5-hydroxytryptamine [5-HT or serotonin], 5-hydroxytryptophan [5-HTP], norepinephrine, dopamine, and histamine), peptides (bradykinin, kallikrein, and tachykinins [substance P, neurokinin A, and neuropeptide K]), and prostaglandins E and F. These are inactivated by first-pass metabolism in the liver, which is why patients are commonly asymptomatic when the NET is confined to its primary site in the GI tract, but become symptomatic when the NET spreads to the liver, affording the tumor the opportunity to secrete directly into the systemic circulation. The majority of cases of the carcinoid syndrome are associated with GI NETs, such as those in the jejunum, ileum, appendix, and cecum (so-called “midgut” NETs). In this group, about 20%–30% of patients present with the classical carcinoid syndrome [10]. Bronchial carcinoid tumors are associated with carcinoid syndrome in 10% of cases. “Hindgut” NETs in the colon and rectum are usually not associated with the carcinoid syndrome. Carcinoid syndrome can originate from metastatic pancreatic NETs secreting 5-HT, but this is rare.
Difference between right-sided and left-sided colorectal cancers: from embryology to molecular subtype
Published in Expert Review of Anticancer Therapy, 2018
Seung Yoon Yang, Min Soo Cho, Nam Kyu Kim
The endodermal gut tube created by body folding during the fourth week of gestation consists of a blind-ended cranial foregut, a blind-ended caudal hindgut, and a midgut open to the yolk sac through the vitelline duct [11]. The midgut forms the distal duodenum, jejunum, ileum, cecum, ascending colon, and proximal two-thirds of the transverse colon. The hindgut forms the distal third of the transverse colon, the descending and sigmoid colon, and the upper two-thirds of the anorectal canal. Just superior to the cloacal membrane, the primitive gut tube forms an expansion called the cloaca. During the fourth to sixth weeks, a coronal urorectal septum partitions the cloaca into the urogenital sinus, which will give rise to urogenital structures, and a dorsal anorectal canal [12]. As the right and left sides of the colon derive from different embryologic origins, anatomically, the proximal colon receives its main blood supply from the superior mesenteric artery with its capillary network being multilayered. The distal colon is perfused by the inferior mesentery artery. Between these two main sources, there is a watershed area located just proximal to the splenic flexure where branches of the left branch of the middle colic artery anastomose with those of the left colic artery. This area represents the border of the embryologic midgut and hindgut. Venous drainage of the colon largely follows the arterial supply with superior and inferior mesenteric veins draining both the right and left halves of the colon.
Comparative toxicity of three differently shaped carbon nanomaterials on Daphnia magna: does a shape effect exist?
Published in Nanotoxicology, 2018
Renato Bacchetta, Nadia Santo, Irene Valenti, Daniela Maggioni, Mariangela Longhi, Paolo Tremolada
Figure 2 shows sagittal sections from both controls and exposed samples. D. magna gut is composed by a short anterior region, the stomodeum or foregut, which is protected by a thick chitin layer with the function of transferring food from the mouth to the actual gut. This one, called midgut has anteriorly two diverticula or hepatic ceca, and both have digestive and absorptive functions. The final portion of the gut is called hindgut and is involved in the reabsorption of liquids (Quaglia, Sabelli, and Villani 1976). Microscopic analyses were performed mainly focusing at the midgut region, that is specifically involved in absorption. Contrary to controls, samples exposed to CNMs displayed large masses occupying the entire lumen of the gut (Figure 2(D–L)). These masses entered into contact with the apical cell portions, and in the most affected fields. caused disruption of the peritrophic membranes, whose role in protecting epithelial cells from mechanical damages was thus overcome. While at low concentrations some gut regions seemed to be perfectly conserved, at the highest concentrations the final portion of the midgut appeared completely altered. In these cases the epithelium was extremely reduced, the brush border eroded, and cells showed large empty spaces among them and between them and the basal lamina. These morphologies were mainly diffused in the 50 mg L−1 groups for all the tested CNMs.
Comparison of Right-side and Left-side Colon Cancers Following Laparoscopic Radical Lymphadenectomy
Published in Journal of Investigative Surgery, 2021
Han Deok Kwak, Jae Kyun Ju, Soo Young Lee, Chang Hyun Kim, Young Jin Kim, Hyeong Rok Kim
This retrospective study used prospective data for analysis. Between December 2009 and December 2014, 966 patients who underwent radical lymph node dissection were included. The right colon group included cecal, ascending, and hepatic flexure colon cancers, while the left colon group included splenic flexure, descending, sigmoid, and rectosigmoid junction colon cancers. The transverse colon is the boundary between midgut and hindgut, with no definite consensus in the literature on the origin, which is either the one-third or mid-portion of the transverse colon. The rectum, which is the transitional area between the hindgut and cloaca, was also excluded. In addition, patients with synchronous or multiple cancers and those with fewer than 12 harvested nodes, which could affect the comparison of sidedness, were also excluded. As most of the cases were performed with laparoscopic surgery, this analysis excluded open surgery, which represented <10%.
Related Knowledge Centers
- Ascending Colon
- Gastrointestinal Tract
- Inferior Mesenteric Artery
- Portal Venous System
- Sigmoid Colon
- Transverse Colon
- Descending Colon
- Colic Flexures
- Zoology
- Cecum