Lower Digestive System (Abdomen) PDF

Lower digestive system (Abdomen) prepared by Fatma M. Abdelmaksoud Dept. of Anatomy and Embryology Fac. of Vet. Medicine Assiut University  Abdomen The lower digestive organs include the esophagus ( very short part of it f...

Lower digestive system (Abdomen) prepared by Fatma M. Abdelmaksoud Dept. of Anatomy and Embryology Fac. of Vet. Medicine Assiut University  Abdomen The lower digestive organs include the esophagus ( very short part of it found in the abdomen), stomach, intestine, liver & the pancreas.  Abdominal regions For topographic purposes, the abdomen is divided into 3 regions by 2 transverse planes : 1. The cranial abdominal (Epigastric) region: extends from the diaphragm to a transverse plane at the most caudal point on the costal arch. 2. The middle abdominal (Mesogastric) region: extends from the plane through the most caudal point on the costal arch to the plane through the most cranial point on the tuber coxae. 3. The caudal abdominal (Hypogastric) region: extends to the pelvic inlet.  Each abdominal region is subdivided by 2 longitudinal lines into 3 smaller ones : a. The cranial abdominal region is subdivided into hypochondriac & xiphoid regions. The hypochondriac region is cranial to the costal arch and as the name indicates, is over the costal cartilages. The triangular xiphoid region lies between the costal arches. b. The middle abdominal region consists of flank (lateral abdominal region) & the umbilical region on the ventral midline. In the dorsal part of the flank is the paralumber fossa, which is bounded dorsally by the tips of the lumbar transverse processes c. The caudal abdominal region consists of inguinal region which extends laterally to the fold of the flank and thigh and median pubic region (the area in front of the pubic bones).  Abdominal cavity Boundaries of the abdominal cavity : − Cranially : diaphragm. − Caudally : It is continuous through the pelvic inlet with the pelvic cavity. − Dorsally : lumbar vertebrae & associated musculature. − Ventrally & Laterally : the abdominal muscles. The abdominal cavity consists of the abdominal cavity proper & the intrathoracic part (part of the abdominal cavity extends under cover of the lung and the thoracic wall).  Peritoneum Serous membrane lined the abdominal cavity. Consists of two layers; parietal (lined the wall) and visceral layers (covered the abdominal viscera). - Connecting peritoneum connects the parietal and visceral layers, or the visceral layers of adjacent organs and can form peritoneal folds called ‘mesenteries’, ‘omenta’, or ‘ligaments.’ The greater and lesser omentum are connective tissues associated with the greater and lesser curvatures of the stomach. - Greater peritoneal cavity (between the partial and visceral layers) and lesser peritoneal cavity (Omental bursa). Omentum Horse Ruminant The Digestive Organs 1. Stomach  H The stomach is a musculo-glandular, sac like enlargement of the digestive tube between the esophagus and the duodenum. It varies in shape and size according to the kind of food. Classification of the stomach: I- Monolocular : a stomach composed of one compartment. It is divided according to the lining mucous membranes into : a. monolocular simple stomach (lined wholly with glandular m.m.) b. monolocular compound stomach (lined by glandular & non glandular mucus membrane). II- Multilocular : a stomach composed of more than one compartment, in which only its last part is glandular. = The glandular mucosa of the stomach is divided into three regions based on the type of glands present, the regions are the cardiac, fundic & pyloric. = The nonglandular part is called esophageal or proventricular part Anatomical features : The stomach presents 2 orifices, 2 borders and 2 surfaces. − The cardiac orifice where the oesophagus opens into the stomach − The pyloric orifice (pylorus) : where the ingesta passes from the stomach to the duodenum. It is surrounded by the pyloric sphincter and is marked externally by a circular groove called the pyloric constriction. − The lesser curvature : It is the concave dorsal border of the stomach. It extends between the cardiac & pyloric orifices. In some species it presents the angular notch. − The greater curvature : It is larger ventral border, extends also between the two orifices. - The visceral surface: It is directed caudoventrally, related to the intestine and the greater omentum. − The parietal surface : is related to the diaphragm. The part of the stomach which lies to the left of the angular notch called the body, the part of the body which bulges above the level of the cardia called the fundus and is separated from the cardia by the cardiac notch. The pylorus or pyloric region is divided into a wide pyloric antrum and a narrow pyloric canal which ends at the pyloric sphincter. Fixation of the stomach :. Greater omentum : attaching the greater curvature of the stomach to the dorsal abdominal wall.. Lesser omentum : attaching the lesser curvature to the liver.. Gastrophrenic ligament : attaching the parietal surface to the diaphragm.. Gastrosplenic : attaching the greater curvature to the spleen. Comparative features of the stomach  Dog g − Type: Monolocular simple stomach − Position: situated in the intrathoracic part of the abdominal cavity in the left hypochondriac region. − Shape: The empty stomach resembles the letter "u". The moderate full stomach is "C" shaped. The empty stomach fails to contact the ventral abdominal wall, − The lesser curvature has a deep angular notch, − Relations: The parietal surface is related to the diaphragm and liver while the visceral surface related to the intestine, pancreas and left kidney. − In addition to the cardiac and pyloric sphincters, present also the sphincter of the pyloric antrum.  Pig g − Type: Monolocular compound stomach − Position: situated in the intrathoracic part of the abdominal cavity mainly to the left of the median plane. When the stomach is full, its long axis is transverse, and the greater curvature extends caudally on the abdominal floor till a point situated equally between the xiphoid and the umbilicus. − Shape: The normally filled stomach resembles a sac bearing a blind conical diverticulum called the ventricular (gastric) diverticulum which is marked from the cardiac region by a circular groove. − The pyloric sphincter presents a rounded prominence consisting of fat and muscular fibers and situated dorsally and known as the Torus pyloricus. − The mucosa has a nonglandular region is folded and limited around the cardia.  Horse − Type: Monolocular compound stomach. − Position: It is present in the dorsal part of the intrathoracic part of the abdominal cavity on the left side. The stomach of horse never reaches the abdominal floor. − Shape: The pyloric orifice is marked externally by the pyloric constriction. The fundus bulges dorsally forming a blind sac known as the Saccus caecus. − It presents a deep angular notch which allows the cardia and the pylorus to be close to each other. − The cutaneous (non glandular) part of the mucosa is large and lines the saccus caecus and separated from the glandular mucous membrane by the Margo plicatus. https://forms.gle/YKNaHzDKMBeYLyAv9