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The jejunum continues from the [[Duodenum - Anatomy & Physiology|duodenum]] and leads into the [[Ileum - Anatomy & Physiology|ileum]]. It is the longest part of the small intestine and is highly coiled. It has digestive and absorptive functions.

The jejunum continues from the [[Duodenum - Anatomy & Physiology|duodenum]] and leads into the [[Ileum - Anatomy & Physiology|ileum]]. It is the longest part of the small intestine and is highly coiled. It has digestive and absorptive functions.

==Structure==

==Structure==

[[Image:jejunumphoto.jpg|thumb|right|150px|Jejunum(Dog) - © RVC 2008]]

[[Image:jejunumphoto.jpg|thumb|right|250px|Jejunum(Dog) - © RVC 2008]]

*It occupies the ventral part of the abdominal cavity, filling those parts that are not occupied by other viscera. This produces species variation (see [[#Species Differences|species differences]]).

 

*It lies on the abdominal floor, separated from the parietal [[Peritoneum - Anatomy & Physiology|peritoneum]] by the greater omentum.

Jejunum occupies the ventral part of the abdominal cavity, filling those parts that are not occupied by other viscera. This produces species variation (see [[#Species Differences|species differences]]). It lies on the abdominal floor, separated from the parietal [[Peritoneal Cavity - Anatomy & Physiology|peritoneum]] by the greater omentum. It is suspended by the mesentery (mesojejunum). This conveys the blood vessels and nerves and houses lymph nodes. The mesentery converges to its root. This is where the cranial mesenteric artery branches off from the aorta.

*It is suspended by the mesentry (mesojejunum). This conveys the blood vessels and nerves and houses lymph nodes.  

**The mesentry converges to its root. This is where the cranial mesenteric artery branches off from the aorta.

==Vasculature==

==Vasculature==

*The cranial mesenteric artery, a branch of the abdominal aorta, supplies blood to the jejunum, [[Ileum - Anatomy & Physiology|ileum]], [[Caecum - Anatomy & Physiology|caecum]], [[Colon - Anatomy & Physiology|ascending colon]] and part of the [[Colon - Anatomy & Physiology|transverse colon]].

The cranial mesenteric artery, a branch of the abdominal aorta, supplies blood to the jejunum, [[Ileum - Anatomy & Physiology|ileum]], [[Caecum - Anatomy & Physiology|caecum]], [[Colon - Anatomy & Physiology|ascending colon]] and part of the [[Colon - Anatomy & Physiology|transverse colon]]. It branches greatly within the mesentery of the jejunum. There are many anastomoses within the mesentery, which ensure that the intestine can survive even if a major division of the cranial mesenteric artery is damaged. The cranial mesenteric vein drains blood from the jejunum and enters the portal vein. It is rich in the products of digestion following a meal. The portal vein enters the [[Liver - Anatomy & Physiology|liver]].

*It branches greatly within the mesenty of the jejunum.

**There are many anastomoses within the mesentry, which ensure that the intestine can survive even if a major division of the cranial mesenteric is damaged.

*The cranial mesenteric vein drains blood from the jejunum and enters the portal vein.

**It is rich in the products of digestion following a meal.

**The portal vein enters the [[Liver - Anatomy & Physiology|liver]].

==Species Differences==

==Species Differences==

===Canine===

===Canine===

*Jejunum lies roughly symmetrically about the midline. It contacts the [[Liver - Anatomy & Physiology|liver]], [[Forestomach - Anatomy & Physiology|stomach]] and [[Spleen - Anatomy & Physiology|spleen]] cranially and [[Bladder - Anatomy & Physiology|urinary bladder]] ventrally.  

The jejunum lies roughly symmetrically about the midline. It contacts the [[Liver - Anatomy & Physiology|liver]], [[Monogastric Stomach - Anatomy & Physiology|stomach]] and [[Spleen - Anatomy & Physiology|spleen]] cranially and [[Urinary Bladder - Anatomy & Physiology|urinary bladder]] ventrally.  

===Equine===

===Equine===

*Jejunum is confined to the left dorsal part of the abdomen.

The jejunum is confined to the left dorsal part of the abdomen. It is restricted to this position by the large [[Caecum - Anatomy & Physiology|caecum]] on the right, and ascending [[Colon - Anatomy & Physiology|colon]] ventrally on both sides.

*It is restricted to this position by the large [[Caecum - Anatomy & Physiology|caecum]] on the right, and ascending [[Colon - Anatomy & Physiology|colon]] ventrally on both sides.

===Ruminant===

===Ruminant===

*Jejunum is pushed entirely to the right side of the abdomen by the [[The Rumen|rumen]] which is on the left.  

The jejunum is pushed entirely to the right side of the abdomen by the [[Rumen - Anatomy & Physiology|rumen]] which is on the left. Coils of the jejunum usually lie within the supraomental recess; although this can vary between individuals depending on fullness of the [[Rumen - Anatomy & Physiology|rumen]] and size of the [[Uterus - Anatomy & Physiology|uterus]].

*Coils of the jejunum usually lie within the supraomental recess; although this can vary between individuals depending on fullness of the [[The Rumen|rumen]] and size of the [[Female Reproductive Tract -The Uterus - Anatomy & Physiology|uterus]].

===Porcine===

===Porcine===

*Jejunum lies in the caudoventral aspect of the abdominal cavity, mainly to the right of the midline.

The jejunum lies in the caudoventral aspect of the abdominal cavity, mainly to the right of the midline. This is due to the presence of the [[Colon - Anatomy & Physiology|ascending colon]] on the left.

*This is due to the presence of the [[Colon - Anatomy & Physiology|ascending colon]] on the left.

==Links==

==Links==

*[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0048.mp4 Pot 48 The Small and Large intestine of the Ruminant]

'''Click here for information on [[Intestines, Small and Large - Pathology|pathology of the Small and Large Intestines]]'''

*[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Pot 52 Lateral view of the Abdomen of a young Ruminant]

*[http://stream2.rvc.ac.uk/Frean/sheep/LargeSmallIntestine.mp4 Small and Large intestine of the Sheep]

*[http://stream2.rvc.ac.uk/Anatomy/swine/Pig_abdomen.mp4 The Porcine Abdomen]

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