The jejunum, ileum & mesentery

The jejunum, ileum & mesentery

1. The Jejunum , Ileum & Mesentry

2. SMALL INTESTINE The small intestine extends from: The pylorus to the ileocaecal junction It is about 6 meters long The length is greater in males than in females It is divided into : An upper, fixed part, called the duodenum , 25 cm in length A lower, mobile part, forming many convoluted tube. The upper two-fifths of the mobile intestine are known as the jejunum , and the lower three-fifths are known as the ileum .

3. RELEVANT FEATURES Large Surface Area a. The great length of the intestine. The presence of circular folds of mucous membrane, villi and microvilli . The circular folds of mucous membrane :- Plicae circularis or valve of Kerkring form complete or incomplete circles begin in the 2 nd part of the duodenum continue to proximal half of the jejunum diminish progressively in size and number in:- distal half of the jejunum and the proximal half of the ileum. They are almost absent in the distal half of the ileum

4. . Intestinal Glands or crypts of Lieberkuhn These are simple tubular glands distributed over the entire mucous membrane of the jejunum and ileum The duodenal glands or Brunner’s glands lie in the submucosa. Lymphatic Follicles Solitary lymphatic follicles Aggregated lymphatic follicles or Peyer’s patches .

5. JEJUNUM AND ILEUM The jejunum and ileum:- Suspended from the posterior abdominal wall by the mesentery and The jejunum and ileum are the greatly coiled parts of the small intestine Have considerable mobility The jejunum: upper 2/5 th of the small intestine Jejunum lies between duodenum and the ileum The ileum: lower 3/5 th of the small intestine The jejunum begins at the duodenojejunal flexure The ileum terminates at the ileocaecal junction .

6. Suspensory muscle of the duodenum

7. Arterial Supply The arterial supply to jejunum and ileum is derived from the jejunal and ileal branches of the superior mesenteric artery & drained by corresponding veins These branches anastomose to form loops, called arcades . From the arcades, long and straight arteries arise, called vasa recta

8. Lymphatics Lymph from lacteals (lymphatic capillary) drains into plexuses in the wall of gut . From here it passes into lymphatic vessels in the mesentry It ultimately drains in nodes present in front of the aorta at the origin of superior mesentric artery.

9. Nerve Supply The sympathetic nerves are from T9 - T11 segments Parasympathetic is from Vagus

10. MECKEL’S DIVERTICULUM (Diverticulum Ilei) A remnant of the vitello-intestinal duct which normally disappears during 6 th week of intra uterine life congenital anomaly the diverticulum usually appears as a finger-like pouch It may cause intestinal obstruction

11. MECKEL’S DIVERTICULUM 1. It occurs in 2% subjects 2. Usually it is 5 cm long 3. It is situated about 60 cm proximal to the ileocaecal valve , attached to antimesenteric border of the ileum. Its calibre is equal to that of the ileum Its apex may be free or may be attached to the umbilicus or to any other abdominal structure by a fibrous band

12. Mesentry Fold of peritoneum Broad, fan shaped that suspends the coils of jejunum & ileum from the posterior abdominal wall Border The attached border or root of mesentry is 15 cm long Its directed obliquely downwards & to the right Extends from the duodenojejunal flexure (left) to the upper part of right sacroiliac joint

13. Between these two points ( duodenojejunal flexure (left) to the upper part of right sacroiliac joint ) the root of the mesentery crosses: , The horizontal (3 rd ) part of the duodenum Abdominal Aorta Inferior vena cava Right ureter Right Psoas major The breadth of mesentry is maximum in the central part & gradually diminishes towards both ends

14. Contents of the mesentery Jejunal & ileal branches of the superior mesentric artery Accompanying vein Autonomic nerve plexuses Lymphatics or lacteals 100-200 lymph nodes Connective tissue with fat