Naziha Sultan Ahmed, BVMS, MSc Scientific degree (Prof. Assis.), Department of Anatomy College of Veterinary Medicine, University of Mosul, Mosul, Iraq https://orcid.org/0000-0002-2856-8277 https://www.researchgate.net/profile/Naziha_Ahmed Anatomy | Part 13| 2nd year 2019 Digestive System The jejunum: Is the largest part of small intestine. It called jejunum because, when we open it it's almost empty or has little liquid ingesta. Jejunum start from the duodeno-jejunal flexure, it form from loops. The mesentery of the jejunum called mesojejunum. Mesojejunum is very long in the animals lead to wide range of motility (movement) In dog and horse, but this motility is little in ruminants, because jejunum tightly coiled along the edge of mesentery around coiled ascending colon. Jejunal loops large and little (6-8 loops) in dog, lie between stomach and pelvic inlet. It covers from both sides by the greater omentum. The jejunum of horse is very long lies at the left dorsal part of the abdominal cavity mingled with the large coils of descending colon. The great length of horse jejunum and mesojejunum give them wide free movement, so its coils may reach the abdominal floor or pelvic cavity or even scrotum through the inguinal canal lead to hernia. Sometimes cause torsion or intussusception lead to spasms or colic. The ileum: A short terminal part of small intestine suspended by mesoileum. Ileum attached to cecum by the ileocecal fold , the end of this fold detect the jejunoileal junction. In horse: the opening of the ileum surrounded by an elevation called the ileal papilla which contain venous plexus due to partially telescope of ileum into cecum, this opening lies at the medial face of cecal base . Ileal orifice of horse lie about 5cm. away of cecocolic opening which lie caudo- laterally, while the ileal orifice lie medially on the lesser curvature of the cecum. CouAnatomy | Digestive system | Prof. Assis. Naziha Sultan Ahmed Page | 1 The large intestine: Consists of cecum, colon, and rectum. The cecum: Initial blind sac of large intestine. The cecum of rabbit have appendix .The cecum of cat is very short. The cecum of dog is longer, with screw-like shape. The cecum is larger in ruminants, with cylindrical (tubular) shape. The cecum is very large in horse, with comma-like shape. Species variation of cecum CouAnatomy | Digestive system | Prof. Assis. Naziha Sultan Ahmed Page | 2 Point of Horse Ruminants Dog comparison Shape of Comma-shaped sacculated organ. Cylindrical (tubular) with Irregularly twisted tube cecum It has rounded base and pointed apex rounded free extremity. (screw-like). connected by body. Length Average 1 meter 75 cm in ox and 25 cm in 12-15 cm. sheep. Capacity Average 30 liter 5 liter in ox and 1 liter in 60 cm. sheep Position Base: at right flank region. Extend along the right On the right, a short Body: follows the contour of flank from near the distance ventral to the abdominal floor and directed ventral end of the last rib transverse processes of nd th ventrocranially. to the pelvic inlet. 2 -4 lumbar Apex: about 20 cm. caudal to vertebrae. xyphoid cartilage of the sternum. Openings Ileo-cecal opening: lie medially on Ileo-ceco-colic opening. Ileo-ceco-colic lessor curvature of cecum base. opening. Ceco-colic opening: lie 5cm. caudo- lateral to first opening. Ligaments Ileo-cecal ligament. Ileo-cecal fold. Ileo-cecal fold. Ceco-colic ligament. Cecum firmly attached to Ceco-colic ligament. The base attached to: right kidney, the root of mesentery. Cecum attached to the pancreas, descending duodenum and root of mesentery root of mesentery. Taenia and Has 4 taenia (longitudinal muscular No taenia. No taenia. sacculation band) which cause sacculation No sacculation. No sacculation. CouAnatomy | Digestive system | Prof. Assis. Naziha Sultan Ahmed Page | 3 .