Encyclopedia entry
Hypophysis
In one study of 54 unselected cases, "anterior pituitary tissue" was found in the pharyngeal mucosa.
Variant archive
The articles published on the portal, most recent first.
854 published articles
In one study of 54 unselected cases, "anterior pituitary tissue" was found in the pharyngeal mucosa.
Congenital bilateral absence of the vas deferens without associated kidney and urinary tract anomalies has been reported. Reference Godard, E. (1859) Note sur l'absence congénitale du canal excréteur et du réservois de la semenence, le testicule existant. Soc. Biol. Comptes Rendus des Séances et Mémoires. 11:329-342.
The appendix may be found almost anywhere in the abdominal cavity depending upon its development and the rotation of the gut. In situs inversus it will be found in the lower left quadrant of the abdomen. Depending on its length, it may lie in the true pelvis. It usually varies in size from less than 5mm (1/4 inch) to 230mm (9 1/4 inch) in length. According to Broedel, the longest appendix recorded was 33 cm (13 inches) (Kelly and Hurndon) The appendix may be absent or duplicated. Three appendices in one individual has been reported. Appendicular diverticula may occur.
In complete transposition of the viscera, the stomach will lie on the right side. Congenital hourglass constriction of the stomach is rare (46 of 50 cases reported, however, were in women). Congenital stenosis of the pylorus occasionally occurs. There may also be a doubled or tripled pyloric antrum, or the antrum may be replaced by a tube with thickened walls. The fundus of the stomach sometimes has a diverticulum. The stomach may be partially retroperitoneal (along with the spleen and left lobe of the liver). This is usually associated with defective mesenteries and omenta.
Notches on the anterior, posterior, and inferior borders, and fissures on the diaphragmatic surface of the spleen have been reported. The anterior border was free of notches in eight of 113 specimens examined; most commonly there were two notches, but in one case there was seven. Notches on the posterior border occured in 32% of cases and on the inferior border in 8%. The fissures on the diaphragmatic surface do not appear to represent the persistence of a primitive lobulation. When the spleen is absent, the splenic artery terminates in the pancreas.
The small intestine, which measures 7m immediately postmortem, may measure 2-4m (or less) in the living. Postmortem lengths vary between 5 and 8 m, and length may be correlated with stature.
Variations in the size of the tongue have been reported (microglossia and marcoglossia). Because of the embryological origin of the thyroid gland at the base of the tongue, thyroid cysts and tumors may be located in the tongue around the foramen cecum, In one study, this was reported to have occurred in 3 of 800,000 patients. See thyroid for additional cases. The tongue may be doubled.
The principal variations of the pharynx are due to the persistence of the visceral clefts or to irregularities in their position. Various cases of this type have been described as pharyngeal diverticula or cervical fistulae. A pituitary nodule has been found in the pharyngeal wall.
One of the most interesting but rare variations of the pancreas is the condition known as the annular pancreas. The duodenum (usually its descending part) is surrounded by a ring of pancreatic tissue continous with the head of the pancreas. There may be a constriction of the duodenum at the location of the ring, with dilations above and below. It is generally considered that the ventral rudiment of the pancreas consists of a right and left part. The left part usually atrophies but may persist, or the right half may exhibit excessive growth and surround the pancreas.
Palatine tonsils exist as two types: pedunculated or buried. The pedunculated type is nearly spherical and attached by a small base to a shallow tonsillar sinus. The buried type is attached by a broad base to a deep sinus. If the buried type is abnormally enlarged the condition may be obscure by tonsillar folds.
The submandibular gland has been found intimately associated with or fused with the sublingual gland; its bilateral absence has also been reported. The sublingual gland has a variable relation to the mandible. Accessory or isolated groups of cells are found in the oral cavity. They have been reported in the crypts of the palatine tonsils, the soft palate, hard palate, cheeks and lips. These are primarily mucous secretory cells similar to those found in the sublingual and submandibular glands.
A common mesentery for the jejunum, ileum, ascending colon, and any part or all of the transverse colon has been reported. The greater omentum may be defective with consequent continuity between the abdominal cavity and omental bursa.
The liver is not subject to great or frequent deviation from its usual form and relation. It has been found without any division into lobes. On the other hand, a case has been recorded in which the adult liver was divided into 12 lobes, and similar cases of of excess lobes have been observed. A detached portion, forming a sort of accessory liver, is occasionally found appended to the left extremity of the gland by a fold of peritoneum containing blood vessels.
A case of double lip has been reported. Reference Mason, M.L., Anson, B.J. and L.E. Beaton. (1940) The surgical and anatomical aspects of a case of double lip. Surg., Gynecol. Obstet. 70:12-17.
The colon is usually found to be either retroperitoneal or intraperitoneal depending on the presence or absence of a mesentery or, another term, mesocolon. In a study of 100 subjects by Treves, 52% of ascending and descending colons did not have a mesocolon, hence they were by definition retroperitoneal. In 14%, both divisions of the colon had a distinct mesocolon (therefore, they were intraperitoneal along with the transverse and sigmoid divisions of the colon). In 12%, the ascending colon had a mesentery and 22% of the descending colons were suspended in a mesentery.
Heterotopic islands of pancreatic tissue has been found in the wall of the jejunum
The ileum may be doubled. A tubular or conical diverticulum (Meckel's diverticulum) arises from the ileum in about one in 100 subjects (367 found in 40,439). Its average position is about 52cm (varying from 15 to 100cm) proximal to the ileocolic junction, but it has been observed anywhere from 2.7 to 300cm proximal to the junction. The diverticulum usually arises from the ileum on the side opposite the attachment of the mesentery. Miyabara, et al and others reported a study of ileal diverticula in 1816 late fetal and neonatal cadavers. They found 61 individuals with diverticula (3.4%).
The gallbladder may be absent, in which case the hepatic duct is dilated within the liver or in some part of its course. In three studies, the congenital absence of the gallbladder was reported as follows. In 1) 18,350 autopsies the incidence of absence was 0.065%; 2) in 7,919 autopsies, 0.075%; and 3) in 3,661 autopsies, 0.03%. The gallbladder and cystic duct may be absence. Somtimes the gallbladder is irregular in form or constricted across its middle; more rarely, it is partially divided in a longitudinal direction.
The upper part of the esophagus may communicate with the trachea by a congenital fistula, the result of arrested development in which this part of the foregut becomes divided into an alimentary and respiratory tube. This condition may be associated with atresia of the upper end of the esophagus. Diverticula occasionally occur, especially on the posterior wall, and the esophagus may become considerably dilated just above the point where it pierces the diaphragm.
The position of the duodenum does not vary greatly. The third part of the duodenum generally crosses in front of the third lumbar vertebra, and not infrequently it is as low as the fourth; it rarely comes into relation with the fifth lumbar (three of 337 subjects). In four cases the duodenum ended on the right side of the vertebral column. The duodenum may be duplicated and duodenal diverticula are not uncommon. They are usually single, consist of all the coats of the intestine, and project from the concave side of the duodenum and, consequently, toward the pancreas.