Mesentery
Encyclopedia
In anatomy
, the mesentery is the double layer of peritoneum
that suspends the jejunum
and ileum
from the posterior wall of the abdomen
. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.
and ileum
(parts of the small intestine
) to the back wall of the abdomen. Between the two sheets of peritoneum are blood vessels, lymph vessels, and nerve
s. This allows these parts of the small intestine to move relatively freely within the abdominopelvic cavity. The brain, however, cannot map sensation accurately, so sensation is usually referred to the midline, an example of referred pain
.
The root of proper mesentery extends 15 cm from duodenojejunal flexure
at the level of left side of L2 obliquely (toward inferior right) to the ileocecal junction in the right iliac fossa
at the level of right sacroiliac joint
. The root of mesentery crosses the second and third parts of duodenum
, abdominal aorta
, Inferior vena cava
, right ureter
, right psoas major muscle
, and right gonadal artery
.
. The dorsal mesentery is larger than the ventral mesentery
, which gradually becomes other parts of the peritoneum. Most parts of the ventral mesentery are associated with the liver.
Mesenteries in the body:
s, the term mesentery is used for any tissue that divides the body cavity (coelom
) into partitions.
, veal crow is typically blanched then cooked in stock, and sometimes subsequently fried.
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
, the mesentery is the double layer of peritoneum
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
that suspends the jejunum
Jejunum
The jejunum is the middle 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 middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
and ileum
Ileum
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.The ileum follows the duodenum...
from the posterior wall of the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.
Mesentery (proper)
The mesentery proper (i.e. the original definition) refers to the peritoneum responsible for connecting the jejunumJejunum
The jejunum is the middle 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 middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
and ileum
Ileum
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.The ileum follows the duodenum...
(parts of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
) to the back wall of the abdomen. Between the two sheets of peritoneum are blood vessels, lymph vessels, and nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s. This allows these parts of the small intestine to move relatively freely within the abdominopelvic cavity. The brain, however, cannot map sensation accurately, so sensation is usually referred to the midline, an example of referred pain
Referred pain
Referred pain is pain perceived at a location other than the site of the painful stimulus. An example is the case of ischemia brought on by a myocardial infarction , where pain is often felt in the neck, shoulders, and back rather than in the chest, the site of the injury...
.
The root of proper mesentery extends 15 cm from duodenojejunal flexure
Duodenojejunal flexure
The duodenojejunal flexure or duodenojejunal junction is the border between the duodenum and the jejunum.The ascending portion of the duodenum ascends on the left side of the aorta, as far as the level of the upper border of the second lumbar vertebra, where it turns abruptly forward to become the...
at the level of left side of L2 obliquely (toward inferior right) to the ileocecal junction in the right iliac fossa
Iliac fossa
The iliac fossa is a large, smooth, concave surface located on the internal surface of the ilium...
at the level of right sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...
. The root of mesentery crosses the second and third parts of duodenum
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 may be used instead of duodenum...
, abdominal aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
, Inferior vena cava
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
, right ureter
Ureter
In human anatomy, the ureters are muscular tubes that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually long and ~3-4 mm in diameter....
, right psoas major muscle
Psoas major muscle
-External links: - "Posterior Abdominal Wall: Muscles of the Posterior Abdominal Wall"* *...
, and right gonadal artery
Gonadal artery
The term gonadal artery is a generic term for a paired artery, with one arising from the abdominal aorta for each gonad. Specifically, it can refer to:* the testicular artery in males* the ovarian artery in females...
.
Development
The mesentery is derived from what is known in the embryo as the dorsal mesenteryDorsal mesentery
The portion of mesentery attached to the greater curvature of the stomach is named the dorsal mesentery , and the part which suspends the colon is termed the mesocolon....
. The dorsal mesentery is larger than the ventral mesentery
Ventral mesentery
-Development:The cephalic portion of the septum transversum takes part in the formation of the diaphragm, while the caudal portion into which the liver grows forms the ventral mesentery ....
, which gradually becomes other parts of the peritoneum. Most parts of the ventral mesentery are associated with the liver.
Mesentery (general)
Mesenteries are composed of two layers of peritoneum. The peritoneum that lies on the walls of the abdominopelvic cavity (parietal peritoneum) invaginates at certain parts, with an organ inside this invagination. This invaginated peritoneum (visceral peritoneum) will often surround all but a part of the organ ("bare area"), through which the organ transmits blood vessels and nerves. If this organ is invaginated far enough into the peritoneum, the visceral peritoneum will come in contact with itself, forming the organ's mesentery.Mesenteries in the body:
- Mesentery (proper) - surrounds parts of the small intestineSmall intestineThe small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
(the jejunumJejunumThe jejunum is the middle 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 middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
and the ileumIleumThe 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.The ileum follows the duodenum...
) - Mesocolon - surrounds parts of the colonColon (anatomy)The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
- Meso-appendix - peritoneum of the vermiform appendixVermiform appendixThe appendix is a blind-ended tube connected to the cecum , from which it develops embryologically. The cecum is a pouchlike structure of the colon...
- Transverse mesocolonTransverse mesocolonThe transverse mesocolon is a broad, meso-fold of peritoneum, which connects the transverse colon to the posterior wall of the abdomen.It is continuous with the two posterior layers of the greater omentum, which, after separating to surround the transverse colon, join behind it, and are continued...
- peritoneum of the transverse colonTransverse colonThe transverse colon, the longest and most movable part of the colon, passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath... - Sigmoid mesocolonSigmoid mesocolonThe sigmoid mesocolon is the fold of peritoneum which retains the sigmoid colon in connection with the pelvic wall.Its line of attachment forms a V-shaped curve, the apex of the curve being placed about the point of division of the left common iliac artery....
- peritoneum of the sigmoid colonSigmoid colonThe sigmoid colon is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about 40 cm...
- Meso-appendix - peritoneum of the vermiform appendix
- Broad ligament of the uterusBroad ligament of the uterusThe broad ligament of the uterus is the wide fold of peritoneum that connects the sides of the uterus to the walls and floor of the pelvis.-Subdivisions:The broad ligament may be divided into three subcomponents:...
- peritoneum of the uterusUterusThe uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, uterine tubes, and ovaries
Invertebrate anatomy
In invertebrateInvertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, the term mesentery is used for any tissue that divides the body cavity (coelom
Coelom
The coelom is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size...
) into partitions.
Cookery
Among cooks, the mesentery is known as the crow. In classical French cuisineFrench cuisine
French cuisine is a style of food preparation originating from France that has developed from centuries of social change. In the Middle Ages, Guillaume Tirel , a court chef, authored Le Viandier, one of the earliest recipe collections of Medieval France...
, veal crow is typically blanched then cooked in stock, and sometimes subsequently fried.