| Circular folds | |
|---|---|
 Small intestine (jejunus-ileum) with circular folds. | |
| Details | |
| Location | Small intestine |
| Identifiers | |
| Latin | plicae circulares |
| TA98 | A05.6.01.007 |
| TA2 | 2943 |
| FMA | 15071 |
| Anatomical terminology | |
The circular folds (also known as valves of Kerckring, valves of Kerchkring, plicae circulares, plicae circulae, and valvulae conniventes) are large valvular flaps projecting into the lumen of the small intestine.
The entire small intestine has circular folds of mucous membrane. [1] The majority extend transversely around the cylinder of the small intestine, [2] for about one-half or two-thirds of its circumference. Some form complete circles. Others have a spiral direction. The latter usually extend a little more than once around the bowel, but occasionally two or three times. While the larger folds are about 1 cm in depth at their broadest part, most folds are smaller. There tends to be an alternating pattern between larger and smaller folds. [1]
They are not found at the commencement of the duodenum, but begin to appear about 2.5 or 5 cm beyond the pylorus.
In the lower part of the descending portion, below the point where the bile and pancreatic ducts enter the small intestine, they are very large and closely approximated.
In the horizontal and ascending portions of the duodenum and upper half of the jejunum, they are large and numerous. [3] From this point, down to the middle of the ileum, they diminish considerably in size.
In the lower part of the ileum, they almost entirely disappear; hence the comparative thinness of this portion of the intestine, as compared with the duodenum and jejunum.
Unlike the gastric folds in the stomach, they are permanent, and are not obliterated when the intestine is distended.
The spaces between circular folds are smaller than the haustra of the colon, and, in contrast to haustra, circular folds reach around the whole circumference of the intestine. These differences can assist in distinguishing the small intestine from the colon on an abdominal x-ray.
The circular folds slow the passage of the partly digested food along the intestines, and afford an increased surface for absorption. [4] They are covered with small finger-like projections called villi (singular, villus). Each villus, in turn, is covered with microvilli. The microvilli absorb fats and nutrients from the chyme.
The circular folds are also called the valves of Kerckring, [3] valves of Kerchkring, [5] plicae circulares, [3] [4] plicae circulae, [5] and valvulae conniventes. [3]
The gastrointestinal tract is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines. Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled at the anus as faeces. Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines.
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In mammals it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest part of the small intestine.
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum. Its main function is to absorb vitamin B12, bile salts, and whatever products of digestion that were not absorbed by the jejunum.
The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum.
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about 5.5 metres long and folds many times to fit in the abdomen. Although it is longer than the large intestine, it is called the small intestine because it is narrower in diameter.
Intestinal villi are small, finger-like projections that extend into the lumen of the small intestine. Each villus is approximately 0.5–1.6 mm in length, and has many microvilli projecting from the enterocytes of its epithelium which collectively form the striated or brush border. Each of these microvilli are about 1 µm in length, around 1000 times shorter than a single villus. The intestinal villi are much smaller than any of the circular folds in the intestine.
The nasolacrimal duct carries tears from the lacrimal sac of the eye into the nasal cavity. The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. The opening of the nasolacrimal duct into the inferior nasal meatus of the nasal cavity is partially covered by a mucosal fold.
In human anatomy, the superior mesenteric vein (SMV) is a blood vessel that drains blood from the small intestine. Behind the neck of the pancreas, the superior mesenteric vein combines with the splenic vein to form the portal vein that carries blood to the liver. The superior mesenteric vein lies to the right of the similarly named artery, the superior mesenteric artery, which originates from the abdominal aorta.
The right colic artery is an artery of the abdomen, a branch of the superior mesenteric artery supplying the ascending colon. It divides into two terminal branches - an ascending branch and a descending branch - which form anastomoses with the middle colic artery, and ileocolic artery (respectively).
The greater omentum is a large apron-like fold of visceral peritoneum that hangs down from the stomach. It extends from the greater curvature of the stomach, passing in front of the small intestines and doubles back to ascend to the transverse colon before reaching to the posterior abdominal wall. The greater omentum is larger than the lesser omentum, which hangs down from the liver to the lesser curvature. The common anatomical term "epiploic" derives from "epiploon", from the Greek epipleein, meaning to float or sail on, since the greater omentum appears to float on the surface of the intestines. It is the first structure observed when the abdominal cavity is opened anteriorly.
The duodenojejunal flexure or duodenojejunal junction, also known as the angle of Treitz, is the border between the duodenum and the jejunum.
The superior mesenteric ganglion is a ganglion in the upper part of the superior mesenteric plexus. It lies close to the origin of the superior mesenteric artery.
Intestinal atresia is any congenital malformation of the structure of the intestine that causes bowel obstruction. The malformation can be a narrowing (stenosis), absence or malrotation of a portion of the intestine. These defects can either occur in the small or large intestine.
Holocrine is a term used to classify the mode of secretion in exocrine glands in the study of histology. Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
Enteroendocrine cells are specialized cells of the gastrointestinal tract and pancreas with endocrine function. They produce gastrointestinal hormones or peptides in response to various stimuli and release them into the bloodstream for systemic effect, diffuse them as local messengers, or transmit them to the enteric nervous system to activate nervous responses. Enteroendocrine cells of the intestine are the most numerous endocrine cells of the body. They constitute an enteric endocrine system as a subset of the endocrine system just as the enteric nervous system is a subset of the nervous system. In a sense they are known to act as chemoreceptors, initiating digestive actions and detecting harmful substances and initiating protective responses. Enteroendocrine cells are located in the stomach, in the intestine and in the pancreas. Microbiota play key roles in the intestinal immune and metabolic responses in these enteroendocrine cells via their fermentation product, acetate.
The rectovesical pouch is the pocket that lies between the rectum and the bladder in males in humans and other mammals. It is lined by peritoneum.
Theodor Kerckring or Dirk Kerckring was a Dutch anatomist and chemical physician.
The abdominopelvic cavity is a body cavity that consists of the abdominal cavity and the pelvic cavity. The upper portion is the abdominal cavity, and it contains the stomach, liver, pancreas, spleen, gallbladder, kidneys, small intestine, and most of the large intestine. The lower portion is the pelvic cavity, and it contains the urinary bladder, the rest of the large intestine, and the internal reproductive organs.
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. From the inner cavity of the gut outwards, these are:
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase.
This article incorporates text in the public domain from page 1173 of the 20th edition of Gray's Anatomy (1918)
