The pylorus ( or ) connects the stomach to the duodenum. 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 language πυλωρός, via Latin. The word pylorus in Greek means "gatekeeper", related to "gate" () and is thus linguistically related to the word "pylon".
Structure
The pylorus is the furthest part of the stomach that connects to the
duodenum. 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 antrum also called the
gastric antrum or the
pyloric antrum is the initial portion of the pyloric region. 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 by
peristaltic contraction of the prepyloric
sphincter; it is
demarcated, sometimes, from the pyloric canal by a slight groove.
Canal
The
pyloric canal () is the opening between the stomach and the duodenum.
[ University of Illinois Medical Center:Health Library ] 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, surrounding the
pyloric orifice 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 acts as a
valve, controlling the outflow of gastric contents into the duodenum
and release of
chyme. Its function is modulated by both the central and enteric nervous systems.
It receives sympathetic innervation from the
celiac ganglion.
Histology
Under
microscopy, the pylorus contains numerous
, including
, 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 of the stomach, the tubes by shorter and more cubical cell which are finely granular. The glands contain mucous cells and
G cells that secrete
gastrin.
[Cardiac, fundus and pyloric regions of the stomach, Pyloric region. available from: http://histology.leeds.ac.uk/digestive/cardiac_pyloric.php (Last inspected April 16, 2017)]
The pylorus also contains scattered and neuroendocrine cells. These endocrine cells include D cells, which release somatostatin,
Function
The pylorus is one component of the gastrointestinal tract. Food from the
stomach, as
chyme, passes through the pylorus to the
duodenum. 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
== Additional images ==
showing the stomach and pylorus in a
cadaver. The antrum of the pylorus is shown in green.]]
See also
-
A Confederacy of Dunces#Ignatius J. Reilly
External links
-
" Pylorus", Stedman's Online Medical Dictionary at Lippincott Williams and Wilkins
-
- "Abdominal Cavity: The Stomach"
-
- "Stomach, Spleen and Liver: The Pylorus"
