Alimentary Canal and Abdominal Regions

Alimentary Canal

• Comprises the oral cavity (mouth), pharynx, esophagus, stomach, duodenum, small intestine, large intestine, and anus.
• Accessory organs include the salivary glands, pancreas, liver, and gallbladder.
• Functions include intake and digestion, absorption, and elimination.

Abdominal Regions

• Right Hypochondriac Region contains the liver, gallbladder, right kidney, and small intestine.
• Epigastric Region contains the stomach, liver, pancreas, duodenum, spleen, and adrenal glands.
• Left Hypochondriac Region contains the spleen, colon, left kidney, and pancreas.
• Right Lumbar Region includes the gallbladder, liver, and right colon.
• Umbilical Region contains the umbilicus, parts of the small intestine, and the duodenum.
• Left Lumbar Region includes the descending colon and left kidney.
• Right Iliac Region contains the appendix and cecum.
• Hypogastric Region contains the urinary bladder, sigmoid colon, and female reproductive organs.
• Left Iliac Region contains the descending colon and sigmoid colon.

Esophagus

• It is a straight muscular tube that connects the pharynx to the stomach.
• It is approximately 10 inches or 25 cm long, with an average diameter of 2 cm.
• Extends from the pharynx to the stomach.
• It contains mucous glands for lubrication which originates around C6.
• It propels swallowed food to the stomach.

Esophagogram

• It captures radiographic images at 1, 2, and 5 minutes.
• It involves the patient swallowing barium sulphate (45% weight/volume) in 15-20 seconds, typically about 100-250 mL.

Stomach

• It is a dilated sac-like portion of the digestive tract and is able to hold contents of about 1.5L capacity.
• The stomach is divided into cardia near the gastroesophageal junction, fundus which is the dilated superior part, body that lies between fundus and pyloric antrum and pylorus as a distal part and is divisible into pyloric antrum (wide part) and pyloric canal (narrow part).
• The stomach mixes saliva, food, and gastric juice to form chyme and serves as a reservoir for food before release into the small intestine.
• Secretes gastric juice containing HCl to kill bacteria and denature protein, pepsin to begin protein digestion, intrinsic factor which aids in vitamin B12 absorption along with gastric lipase for the digestion of triglycerides.
• Secretes gastrin into the blood.

Small Intestine

• The divisions are the duodenum, jejunum, and ileum.
• The shortest part of the small intestine is the duodenum and is approxiamtely 10 inches or 25 cm.
• The jejunum is known for its coiled spring and feathery appearance.
• The Ileum is known to be the longest, has a few indentations and is the smallest diameter,

Duodenum

• It is the first and shortest part of the small intestine.
• It is the widest and fixed part of the small intestine.
• It is C-shaped, about 10 inches long (25cm).
• It begins in the pylorus on the right side and ends at the duodeno-jejunal junction on the left side at the L2 vertebra.
• Four portions: superior, descending, horizontal, and ascending.
• The first part is 5cm long and lies anterolateral to the body of L1.
• The descending part is 7 to 10cm long and descends along the right sides of L1 through L3.
• The bile duct and main pancreatic duct unite to form the ampulla that opens on Major Duodenal papillae.
• The horizontal part, 6 to 8cm long, crosses L3 and the superior mesenteric artery.
• The ascending part (5cm) begins at the L of L3 and rises superiorly as far as the superior border of L2.
• The duodenojejunal flexure is held in position by the suspensory ligament of the duodenum / LIGAMENT OF TREITZ, attached to the right crus of the diaphragm.

Jejunum

• The middle portion of the small intestine measures from 7.5-8.5 feet long.
• It has circular folds (valvular conniventes) of mucous membrane, which are larger and thickly set.
• Located in the LUQ

Ileum

• The most distal portion of the small intestine measuring from11.5-12 feet long, having the narrowest cavity.
• The coats are thinner and less vascular.
• There are few circular folds, which are smaller and disappear entirely towards the lower end.

Jejunum compared to Ileum

• The jejunum makes up the proximal 2/5 of the SI and the Ileum, distal 3/5 of the SI.
• Caliber for Jejunum: 2-4 cm vs Ileum which is 2-3 cm.
• The Jejunum occupies the LUQ where as the Ileum occupies the false pelvis in RLQ.
• The wall is thick and heavy in the jejunum, where as the wall is thin and light in Ileum.
• There are numerous large, tall plica in the jejunum whereas there are smaller and widely separated plica in Ileum.
• Jejunum has a deeper red (redder) color and greater vascularity vs the Ileum that are palar pink with less vascularity.
• The Jejunum has longer vasa recta branches that are few and large vs the Ileum with numerous, short vasa recta with many prominent arcades.
• The Jejunum has less fat.
• The Ileum has more fat with many aggregations of lymphoid tissue and positive Peyer patches.

Large Intestine

• Shorter but has larger caliber than the small intestine, at 5-5.5 feet in length while extending from the ileo-caecal junction at the right iliac fossa to the anus.
• Widest at its proximal portion and gradually diminishes in caliber towards the canal.
• The divisions are the cecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal.

Ascending Colon

• It is the continuation of the caecum upwards along the right side of the abdominal cavity, occupying the R iliac, R lumbar, and R hypochondriac regions and typically measures from 5-8 inches in length.

Right Colic/ Hepatic Flexure

• It is acute, bending forward, anteriorly to the left of the large intestine below the right lobe of the liver, marking the transition of the ascending colon into the transverse colon.
• The right colic/ hepatic flexure lies in the right hypochondriac region, at the level of the 9th costal cartilage.

Transverse Colon

• Occupies the umbilical region, crosses from the right colic flexure below the right lobe of the liver, hands downward and ascends to the left colic/ splenic flexure below the spleen and is about 15 inches (38cm) in length.
• It is the longest, largest, and most mobile part of the colon.

Left Colic/ Splenic Flexure

• Acute bending upwards, and backwards to the left of the large intestine below the stomach and the lower part of the spleen.
• Occupies the L hypochondriac region, but at a higher level than the right.

Haustra

• Sacculation in the colon, which give the colon its segmented appearance.

Difference Between Small and Large Intestine

• Small Intestine: Duodenum, jejunum and ileum vs Large Colon: Colon, rectum and anal canal.
• small intestine is narrower being around 1 inch or 2.5 cm where as large intestine is wider and around 3 inches at 7.5 cm.
• large intestine is shorter at around 5 feet or 1.5 meters and small intestine is longer being 10-16 feet at 3-5 meters.
• The ascending and descending colon, rectum are fixed, where as the transverse colon and sigmoid colon are mobile vs all small intestines except duodenum that are mobile.
• The colon has Fatty deposits covered with peritoneum in In the colon (except the rectum).
• They are located on tenia libera and tenia omentalis vs absent for small intestine.
• The colon has The longitudinal (external) muscle layer is arranged in 3 separate bands vs absent for small intestine.
• The colon has Sacculation (except the rectum), which give the colon its segmented appearance vs absent for small intestine.
• Mucosal villi is absent for colon vs present for small intestine.
• The colon's function is principally absorbing absorbs water and electrolytes small intestine’s function is principally absorbing digested nutrients.

Cecum

• A blind-ended pouch situated in the right iliac fossa.

• Around 2 1/2 inches (6cm) long, includes peritoneum, is movable is around 2 1/2 inches (6cm) long, includes peritoneum, is movable and does not have a mesentery but contains an ileocecal valve.

Vermiform Appendix

• Wormlike, blind intestinal diverticulum with short triangular mesentery-mesoappendix that measures 3-5 inches in length (6-10cm).
• The base is attached to the posteromedial of cecum about 1 inch below the ileocecal junction and lies in right iliac fossa.

Appendicitis

• May become inflamed as a result of either an obstruction by a stool (fecalith in adults) or hyperplasia of its lymphatic tissue (common in children)

• Colicky pain is referred over the umbilical region.

• Irritation to the parietal peritoneum may result in pain localized over the base of the appendix at McBurney point.

• The Iliohypogastric nerve may be injured in appendectomy, which can weaken the anterior abdominal wall.

• The whole appendix is not a lymphoid organ but just accumulates aggregated lymphoid tissue.

• Lymphoid organs produce lymphocytes and include the thymus, red bone marrow, spleen, and tonsils.

Descending colon

• The descending colon that descends along the left side of the abdominal cavity, occupying the L hypochondiac, L lumbar and L iliac regions and measures about 10 inches in length at 25cm long.

Sigmoid Colon

• Is an S-shaped loop at Approximately 10-15 inches long (25-38cm) and extends from the iliac fossa to the 3rd sacral vertebra-rectum.

Rectum

• It is five inches long, found in the lower part of large intestine in pelvic cavity beginning in front of the 3rd sacral vertebra, passing downward ends in the front of the tip of coccyx-anal canal.

Salivary Glands

• Exocrine glands in the mouth produce saliva, which has digestive, lubricating, and immunologic functions.

• Three pairs of major salivary glands along with numerous minor salivary glands scattered throughout the oral cavity including the parotid, submandibular (submaxillary), and sublingual glands

Liver

• The largest glandular organ of the body has a normal weight of 1,500 grams, accounting for 2.5% of the body weight shaped like a dome.
• Lies mainly in the RUQ of the abdomen and occupying most of the R hypochondrium, upper epigastrium, and extends into the left hypochondrium.
• Lying deep to the ribs 7-11 on the right side and crosses the midline towards the left nipple.

Liver Segments

• Has a porta hepatis, which is the hilum of the liver in the form of a deep fissure in the inferior surface of the liver.
• It is where all the neurovascular structures (except hepatic veins) and hepatic ducts enter or leave the liver as well as containing the PORTAL TRIAD between and containing the common hepatic duct, hepatic artery and hepatic portal vein:

Functional Segments of Liver

• The caudate lobe is described as giving rise to caudate process which extends to the right between IVC and porta hepatis also called “third liver," described at segment 1.
• The lateral superior is segment 2.
• The lateral inferior is segment 3.
• The medial superior is segment IV A.
• The Medial inferior = IV B – QUADRATE LOBE.
• The anterior inferior = V.
• The posterior inferior = VII.
• The posterior superior equals VII.
• And the anterior superior equals the 7th.

Gall Bladder

• It is a pear-shaped sac lying on the inferior surface of the liver and located at the junction of the 9th costal cartilage with lateral border of the rectus abdominis in the epigastric to right hypochondrium region, having a capacity of 30-50 mL.
• Receives, stores and concentrates bile by absorbing water and salts contracts to expel bile upon release of cholecystokinin from duodenum.
• Parts includes the fundus which is the rounded blind end, body which has direct contact with liver, transverse colon and superior part of duodenum, neck as a narrow part directed toward the porta hepatis which gives rise to the cystic duct and Hartmann pouch as infundibulum of the GB, junction between neck and cystic duct.

Biliary Tree

• Includes intrahepatic ducts composing of ductular and canalicular network from the liver, forming the hepatic ducts and traveling with branches of the portal vein and hepatic artery in portal triads.
• Also includes extrahepatic ducts in which the right and left hepatic ducts fuse at the hilum (porta hepatis), anterior to bifurcation of the portal vein to form the hepatic duct, which is then inserted by cystic duct from the GB and becomes CBD.
• Right hepatic duct drains four segments of the right lobe of the liver:
  • Segment 5 and 8- anterior division.
  • Segment 6 and 7- posterior division.
• Left hepatic duct drains segment 2, 3, and 4 of the left lobe.

Pancreas

• Exocrine and endocrine elongated accessory digestive gland.
• It lies retroperitoneally and transversely across the posterior abdominal wall and has a normal weight of 60 to 100grams.
• Its parts include the head with an expanded par and embraces the C shaped curve of the Duodenum, neck which is the constructed portion of the pancreas and connects the head to the body.
• The neck lies in front of PV.
• It has a body to the left SMA and SMV and tail closely related to the hilum of spleen and left colic flexure.
• Extends through the entire length of pancreas and joins the bile duct to form the hepatopancreatic ampulla and finally empties into the duodenum.
• Accessory pancreatic duct lies in head of pancreas and drains into the main duct.