The pylorus ( or ), or pyloric part, connects the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

to the

duodenum The duodenum is the first 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 anterior intestine or proximal intestine ...

. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pyloric canal'' ends as the ''pyloric orifice'', which marks the junction between the stomach and the duodenum. The orifice is surrounded by a

sphincter A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the hu ...

, a band of muscle, called the ''pyloric sphincter''. The word ''pylorus'' comes from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

πυλωρός, via

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

. The word ''pylorus'' in Greek means "gatekeeper", related to "gate" ( el, pyle) and is thus linguistically related to the word " pylon".

Structure

The pylorus is the furthest part of the stomach that connects to the

. It is divided into two parts, the ''antrum'', which connects to the body of the stomach, and the ''pyloric canal'', which connects to the duodenum.

Antrum

The ''pyloric antrum'' is the initial portion of the pylorus. It is near the bottom of the stomach, proximal to the pyloric sphincter, which separates the stomach and the duodenum. It may temporarily become partially or completely shut off from the remainder of the stomach during

digestion Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...

by peristaltic contraction of the prepyloric

; it is

demarcated {{Refimprove, date=January 2008 A political demarcation line is a geopolitical border, often agreed upon as part of an armistice or ceasefire. Africa * Moroccan Wall, delimiting the Moroccan-controlled part of Western Sahara from the Sahrawi- ...

, sometimes, from the pyloric canal by a slight groove.

Canal

The ''canal'' ( la, canalis pyloricus) is the opening between the stomach and the duodenum. The wall thickness of the pyloric canal is up to 3 millimeters (mm) in infants younger than 30 days, and up to 8 mm in adults.

Sphincter

The ''pyloric sphincter'', or

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

, is a strong ring of smooth muscle at the end of the pyloric canal which lets food pass from the stomach to the duodenum. It controls the outflow of gastric contents into the duodenum. It receives sympathetic innervation from the

celiac ganglion The celiac ganglia or coeliac ganglia are two large irregularly shaped masses of nerve tissue in the upper abdomen. Part of the sympathetic subdivision of the autonomic nervous system (ANS), the two celiac ganglia are the largest ganglia in th ...

Histology

Under

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of mi ...

, the pylorus contains numerous

gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream ( endocrine gland) or into cavities inside the body or its outer surface ( exocrine gland). Structure ...

s, including gastric pits, which constitute about half the depth of the pyloric mucosa. They consist of two or three short closed tubes opening into a common duct or mouth. These tubes are wavy, and are about one-half the length of the duct. The duct is lined by columnar cells, continuous with the epithelium lining the surface of the

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

of the stomach, the tubes by shorter and more cubical cell which are finely granular. The glands contain mucus cells and G cells that secrete gastrin. The pylorus also contains scattered

parietal cell Parietal cells (also known as oxyntic cells) are epithelial cells in the stomach that secrete hydrochloric acid (HCl) and intrinsic factor. These cells are located in the gastric glands found in the lining of the fundus and body regions of ...

s and

neuroendocrine cell Neuroendocrine cells are cells that receive neuronal input (through neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release messenger molecules ( hormones) into the blood. In this way they br ...

s. These

endocrine The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the ...

cells including D cells, which release

somatostatin Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-co ...

, responsible for shutting off acid secretion. (There is a second hormone-sensitive population near the

fundus ''Fundus'' (Latin for "bottom") is an anatomical term referring to that part of a concavity in any organ, which is at the far end from its opening. It may refer to: Anatomy * Fundus (brain), the deepest part of any sulcus of the cerebral cortex * ...

.) Unstriated muscles, which are entirely involuntary, are located at the pylorus.

Function

The pylorus is one component of the gastrointestinal system. Food from the

, as chyme, passes through the pylorus to the

. The pylorus, through the pyloric sphincter, regulates entry of food from the stomach into the duodenum.

Clinical significance

In such conditions as

stomach cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the Gastric mucosa, lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenoca ...

, tumours may partly block the pyloric canal. A special tube can be implanted surgically to connect the stomach to the duodenum so as to facilitate the passage of food from one to the other. The surgery to place this tube is called a gastroduodenostomy.

Stenosis

Pyloric stenosis Pyloric stenosis is a narrowing of the opening from the stomach to the first part of the small intestine (the pylorus). Symptoms include projectile vomiting without the presence of bile. This most often occurs after the baby is fed. The typical ...

refers to a pylorus that is narrow. This is due to congenital

hypertrophy Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J ...

of the pyloric sphincter. The lumen of the pylorus is narrower, and less food is able to pass through. This problem is often detected in the early weeks of life. When it is present, a newborn baby may projectile vomit after eating, but despite vomiting remain hungry. Pyloric stenosis may be managed by the insertion of a stent, or through surgical cutting of the pyloric sphincter, a ''pyloromyotomy''.

Other

*Pyloric tumors **Pyloric gland adenoma

Additional images

Image:Stomach2.gif, Stomach File:Stomach dissection highlighting pyloric antrum.jpg,

Dissection Dissection (from Latin ' "to cut to pieces"; also called anatomization) is the dismembering of the body of a deceased animal or plant to study its anatomical structure. Autopsy is used in pathology and forensic medicine to determine the cause ...

showing the stomach and pylorus in a cadaver. The antrum of the pylorus is shown in green.

References

External links

*
Pylorus
, Stedman's Online Medical Dictionary at Lippincott Williams and Wilkins * - "Abdominal Cavity: The Stomach" * - "Stomach, Spleen and Liver: The Pylorus" * {{Authority control Digestive system Stomach