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 band of muscle, called the ''pyloric sphincter''.
The word ''pylorus'' comes from
Greek πυλωρός, via
Latin. 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
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 ...
. 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 intes ...
by
peristaltic contraction of the prepyloric
sphincter; it is
demarcated
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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 the ...
.
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 mic ...
, 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 pit
Gastric pits are indentations in the stomach which denote entrances to 3-5"Secretions from several gastric glands flow into each gastric pit" Principals of Anatomy & Physiology 15th Ed 2017, Gerard Tortora & Bryan Derrickson tubular shaped gastric ...
s, 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
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
, 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 is ...
of the stomach, the tubes by shorter and more cubical cell which are finely granular. The glands contain mucus cells and
G cells
In anatomy, the G cell or gastrin cell, is a type of cell in the stomach and duodenum that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells. G cells are found deep within the pyloric glands of the stomach antr ...
that secrete
gastrin.
The pylorus also contains scattered
parietal cells and
neuroendocrine cells. 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 neur ...
cells including
D cells, which release
somatostatin,
responsible for shutting off acid secretion. (There is a second hormone-sensitive population near the
fundus.)
Unstriated muscles, which are entirely involuntary, are located at the pylorus.
Function
The pylorus is one component of the
gastrointestinal system
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) 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 ...
. Food from 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 ...
, as
chyme
Chyme or chymus (; from Greek χυμός ''khymos'', "juice") is the semi-fluid mass of partly digested food that is expelled by a person's stomach, through the pyloric valve, into the duodenumduodenum
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, through the pyloric sphincter, regulates entry of food from the stomach into the duodenum.
Clinical significance
In such conditions as
stomach cancer, 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 refers to a pylorus that is narrow. This is due to congenital
hypertrophy 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 o ...
showing the stomach and pylorus in a cadaver
A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...
. The antrum of the pylorus is shown in green.
See also
*
Human gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) 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 ...
*
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 ...
*
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 ...
*
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 intes ...
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