Variants and anomalies of development of digestive organs

Lips. A complete or partial cleft of the upper lip is possible, most often lateral to its median groove ("harelip"). Sometimes the cleft from the upper lip extends to the wing of the nose. Rarely, the cleft of the upper lip reaches the olfactory region of the nose or, bypassing the wing of the nose laterally, reaches the orbit and divides the lower eyelid. Clefts of the lower lip are possible. The absence of one or both lips is extremely rare. Asymmetric widening of the oral cleft to one or both sides (macrostoma) is possible. A decrease in the oral cleft is observed (microstoma).

Palate. There is a cleft of the hard palate - non-fusion of the palatine processes of the maxillary bones ("cleft palate"). This anomaly can be combined with a cleft of the soft palate. Various combinations of "cleft palate" and "hare lip" are observed. Sometimes in this case the alveolar process of the upper jaw is separated from the rest of the maxillary bone by a deep cleft on one or both sides. Bifurcation of the uvula of the soft palate is possible. The uvula is sometimes displaced and strengthened by the base on the posterior edge of the vomer. The size and shape of the uvula also vary. The muscles of the soft palate vary due to the different degree of possible non-fusion of both halves of the palate. Sometimes there is a wing - a tubular muscle, originating on the medial pterygoid muscle. The pterygotube muscle is woven into the thickness of the mucous membrane of the auditory tube. Often, in the thickness of the palatine aponeurosis, there is a small muscle that lifts the soft palate, starting at the hook of the pterygoid process.

Teeth. The number of teeth and their relative positions are subject to significant fluctuations. Between the crown and the root of the medial incisors, there is a ring-shaped or convex thickening of the enamel, which occurs due to pressure from the antagonist tooth. On the inner surface of the upper lateral incisors, near the back of their root, there is sometimes a tubercle. The canines (especially the lower ones) are often rotated along their axis and bent outward. In rare cases, the canines do not erupt. Sometimes the canines develop later than the adjacent teeth, therefore, due to the lack of space in the dental row, they grow to the side. Premolars may be missing completely or partially. The number of roots in molars may vary. Often the roots converge or diverge in different directions. The roots of adjacent molars sometimes cross. Often the upper molars (especially the second) have additional chewing tubercles. The third molar (wisdom tooth) may not erupt or appear after 30 years. Often there are additional teeth located on the side of the gum. There are different possible bite options.

Tongue. Rarely absent (aglossia). The blind opening is absent in 7% of cases. The tongue may be split at the end, forming two or three lobes. Additional muscles may appear, including the corneal-glossal muscle, which extends into the thickness of the tongue from the wheat cartilage of the larynx. Possible presence of muscle bundles in the form of the median longitudinal muscle of the tongue, the additional oroglossal muscle, and the auriculoglossal muscle.

Cheeks. The expression of the cheek fat pad varies sharply. The configuration of the cheek, the thickness of the buccinator muscle, and the area of its origin are variable.

Major salivary glands. At the anterior edge of the masseter muscle, there is an additional parotid salivary gland of various sizes and shapes. Its excretory duct can open independently. More often, it connects with the excretory duct of the parotid salivary gland. Near the submandibular gland, at the lateral edge of the geniohyoid muscle, there are additional glandular lobules. Additional sublingual glands are possible. The number of small sublingual ducts varies from 18 to 30.

Pharynx. Very rarely, there is an absence of the pharynx, narrowing in one or another part of it. There may be communications between the pharynx and the skin (branchial fistulas), corresponding to unclosed gill slits. Fistulas open at the posterior edge of the sternocleidomastoid muscle, above the sternoclavicular joint, near the mastoid process of the temporal bone. The muscles of the pharynx are variable.

The inferior pharyngeal constrictor may have additional bundles coming from the trachea. In 4% of cases, the ligament-pharyngeal muscle is found. It starts on the surface of the lateral thyrohyoid ligament and is woven into the middle or inferior pharyngeal constrictors. In 60% of cases, the cricopharyngeal muscle is found. Sometimes muscle bundles go from it to the right or left lobes of the thyroid gland (the muscle that lifts the thyroid gland). Muscle bundles often go from the middle pharyngeal constrictor to the intermediate tendon of the digastric muscle.

The pharyngeal-basal fascia is sometimes replaced, partially or completely, by the unpaired pharyngeal muscle, which connects the pharynx to the skull. The stylopharyngeal muscle is sometimes doubled at different lengths. Additional bundles often intertwine with it, originating on the mastoid process of the temporal bone (mastoid-pharyngeal muscle) or on the surface of the occipital bone (occipital-pharyngeal muscle). In the area of the vault of the pharynx, one or more pockets (cavities) in the mucous membrane are possible, measuring 1.5 cm in length and 0.5 cm in width (pharyngeal bursa). The pharyngeal bursa may be connected to the pharyngeocranial canal.

Esophagus. Possible (rare) is the absence of the esophagus, its overgrowth at different lengths (atresia), the presence of congenital diverticula. Doubling of the esophagus, the presence of fistulas - connections with the trachea are extremely rare. Sometimes there are fistulas connecting the esophagus with the skin of the lower part of the neck, at the anterior edge of the sternocleidomastoid muscle. The expression of the muscular membrane of the esophagus varies. The striated muscles of the muscular membrane are replaced by smooth ones in different parts of the esophagus. The expression of the bronchoesophageal and pleuroesophageal muscles varies, they are often absent. In 30% of cases, in the lower part of the posterior mediastinum behind and to the right of the esophagus, there is a blindly closed serous paraesophageal sac 1.5-4 cm long (Sachs's bursa). In 10% of cases, the aorta and esophagus pass through the diaphragm through one aortic opening. The direction and bends of the esophagus, the number, length and size of its narrowings vary considerably.

Stomach. Very rarely absent or doubled. Complete or partial transverse constrictions of the lumen of the stomach of various shapes and sizes are possible. They are most often located near the pylorus. The thickness of the muscular layer of the stomach, the number and especially the area of location (length) of the gastric glands vary.

Small intestine. The shape and relationship with neighboring organs of the duodenum are variable. In addition to the typical horseshoe shape, an incomplete or complete ring-shaped duodenum is often observed. Sometimes the horizontal part of the intestine is absent and the descending part directly passes into the upper. The absence of the descending part of the duodenum is possible. Then the upper part of the duodenum passes directly into the horizontal part.

The absence of the small intestine is rare, more often - one of its sections - the duodenum, jejunum or ileum. The diameter and length of the small intestine often vary. Elongation (dolicocholy) or shortening (brachycholy) of the intestine is possible. Sometimes there are cases of atresia of various sections of the intestine, the presence of transverse constrictions, diverticula. The appearance of a Meckel's diverticulum (2% of cases), which is a remnant of the yolk-intestinal duct of the fetus, is possible. A distinction is made between free, open and closed forms of Meckel's diverticulum. In the most common free form, a protrusion of the ileum is determined on the side opposite the mesenteric edge. The diverticulum is located at a distance of 60-70 cm (rarely further) from the level of the ileocecal junction. The length of the diverticulum varies from a few millimeters to 5-8 cm. A diverticulum 26 cm long has been described. In the open form of Meckel's diverticulum, it is a tube connecting the navel with the intestine with an opening in the navel and in the intestine (congenital intestinal fistula). In some cases, Meckel's diverticulum is a canal closed at the ends, connected on one side with the navel, on the other - with the intestine (incomplete closure of the yolk-intestinal duct). Rare cases of the location of a saccular remnant of the yolk-intestinal duct, not directly connected with the intestine in the navel or near it have been described. Sometimes there is a congenital umbilical hernia, which appears as a result of non-return to the abdominal cavity of the physiological protrusion of the embryonic intestine outward through the umbilical ring.

Sometimes the mesentery of the small intestine contains muscle bundles extending from the anterior surface of the spine. Rarely, a common mesentery of the ileum and cecum is observed.

Large intestine. The intestine is extremely rare, if absent or partially duplicated. More common are narrowings of the lumen of the large intestine (in different parts, at different lengths). Various anomalies of intestinal rotation often occur during its development. Quite common are cases of rectal atresia (absence of the anus), combined with fistulas into adjacent organs (or without fistulas). There are variants of congenital expansion and duplication of part or all of the colon, below which there is a narrowing zone (aganglionic megacolon, or Hirschsprung's disease). Variants of various relationships of the colon sections with the peritoneum are common. In cases of total dolichomegacolon (11%), the entire large intestine has a mesentery and an intraperitoneal position. In this case, the intestine increases in length and width. In 2.25% of cases, general ptosis (prolapse) of the colon (colonoptosis) is observed, in which the intestine, having a mesentery along its entire length, descends almost to the level of the small pelvis. Partial elongation and/or ptosis of different parts of the colon are possible.

The presence of a third (upper) sphincter, located at the level of the transverse fold of the rectum, is described for the rectum. When the anal membrane is broken, closure (atresia) of the anus is possible, manifested to varying degrees.

Liver. The size and shape of the right and left lobes (especially the left) vary. Often, areas of liver tissue in the form of a bridge are thrown over the inferior vena cava or the round ligament of the liver. Sometimes there are additional lobes of the liver (up to 5-6). Near the visceral surface of the liver, at its posterior or anterior edge, there may be an independent additional liver of small size. Blindly ending bile ducts are not uncommon in the ligament of the inferior vena cava.

Gallbladder. Sometimes the bladder is completely covered by the peritoneum, has a short mesentery. Very rarely the gallbladder is absent or doubled. The cystic duct occasionally flows into the right or left hepatic duct. The relationship between the common bile duct and the pancreatic duct is extremely variable, especially in their distal parts - before entering the duodenum (more than 15 different variants).

Pancreas. The lower part of the head of the pancreas is occasionally elongated and encircles the superior mesenteric vein in a ring-shaped manner. Very rarely, there is an accessory pancreas (about 3 cm in diameter) located in the wall of the stomach, sometimes in the wall of the duodenum or in the wall of the jejunum, in the mesentery of the small intestine. Sometimes there are several accessory pancreas. Their length reaches several centimeters. The position of the main pancreatic duct is extremely variable. The accessory pancreatic duct may anastomose with the main duct, may be absent or may be overgrown before the place where it enters the minor papilla of the duodenum. Rarely, there is an annular pancreas encircling the duodenum in the form of a ring. Cases of shortening and bifurcation of the tail of the pancreas have been described.

Rarely, a complete or partial reverse arrangement of the internal organs (situs viscerus inversus) occurs. The liver is on the left, the heart is mostly on the right, the spleen is on the right, etc. A complete reverse arrangement of the internal organs occurs in 1 case per 10 million births.