Academy of Diagnostic & Osteopathic Medicine
STOMACH
The stomach is located in the upper left quadrant of the abdomen, between the esophagus and the duodenum. It’s divided into four sections: the cardia, fundus, body, and pylorus. Its inner lining has folds called rugae and contains gastric glands that secrete digestive substances. The stomach’s blood supply comes from the left and right gastric arteries, as well as the short gastric arteries, which are all branches of the celiac trunk. Blood is drained through the gastric veins into the portal vein. The primary role of the stomach is to break down food both mechanically, by churning, and chemically, using gastric acid and enzymes like pepsin. Common conditions affecting the stomach include peptic ulcer disease, where excess acid or infection by H. pylori erodes the stomach lining, and gastritis, which is inflammation of the stomach lining caused by infection, alcohol, or certain medications.
PANCREAS
The pancreas is located behind the stomach, stretching from the duodenum on the right to the spleen on the left. It is divided into three parts: the head, the body, and the tail. The pancreas contains endocrine islets, which produce hormones like insulin, and exocrine acini, which produce digestive enzymes. The pancreas gets its blood supply from branches of the celiac trunk, including the splenic artery and pancreaticoduodenal arteries. Blood is drained through the splenic and superior mesenteric veins, which empty into the portal vein. The pancreas has two major roles: it regulates blood sugar by producing insulin and glucagon (the endocrine function) and it produces digestive enzymes like amylase and lipase to help break down food (the exocrine function). Common pancreatic conditions include pancreatitis, an inflammation caused by the activation of digestive enzymes within the pancreas, and pancreatic cancer, which is often aggressive and difficult to detect early.
BILE DUCTS
The bile ducts extend from the liver and gallbladder, joining at the common bile duct, which empties into the duodenum. They consist of intrahepatic bile ducts, the common hepatic duct, the cystic duct, and the common bile duct. Blood supply to the bile ducts comes from the cystic artery and branches of the hepatic artery, while venous blood drains into the portal venous system. Their function is to transport bile, which is produced by the liver and stored in the gallbladder, to the small intestine to aid in fat digestion. Common problems include cholangitis, which is inflammation of the bile ducts due to infection, and bile duct obstruction, often caused by gallstones or tumors, leading to symptoms like jaundice.
TEETH AND GUMS
Teeth & Gums: The Chewing Machines The teeth are calcified structures embedded in the jaw, responsible for chewing and breaking down food. The gums surround and support the teeth, protecting their roots. Teeth receive blood from the maxillary artery, while drainage flows into the facial veins. Their function is to grind, tear, and prepare food for digestion, allowing easier swallowing and enzyme activity. Common problems include cavities (dental caries), gingivitis (gum inflammation), and periodontitis, a severe gum infection that can lead to tooth loss.
TONSILS
Tonsils: The Immune Guards of the Throat The tonsils are small, lymphatic structures located at the back of the throat, forming part of the immune system. They include the palatine tonsils, lingual tonsils, and pharyngeal tonsils (adenoids). Blood supply comes from the tonsillar branch of the facial artery, and venous drainage flows into the pharyngeal venous plexus. Tonsils trap bacteria and viruses, preventing infections in the respiratory and digestive systems. Common issues include tonsillitis, causing sore throat and swelling, and tonsil stones, which form when debris hardens in the crevices of the tonsils.
LIVER
The liver is located in the upper right quadrant of the abdomen, beneath the diaphragm, and to the right of the stomach. Anatomically, the liver is divided into four lobes: the right lobe, the left lobe, the caudate lobe, and the quadrate lobe. The right and left lobes are the largest and are separated by the falciform ligament. The caudate lobe is located on the posterior side, near the inferior vena cava, while the quadrate lobe is positioned near the gallbladder. Inside, the liver contains specialized cells called hepatocytes, along with structures like portal triads and bile ducts. Now, let’s talk about its blood supply. The liver receives oxygen-rich blood through the hepatic artery, which is a branch of the celiac trunk. It also gets nutrient-rich blood from the gastrointestinal tract via the portal vein. Once processed, blood is drained from the liver through the hepatic veins into the inferior vena cava. The liver has several vital functions. It detoxifies blood, synthesizes proteins like albumin, metabolizes nutrients, and produces bile, which is essential for fat digestion. Finally, let’s cover some common liver conditions. One is cirrhosis, which is scarring of the liver caused by things like chronic alcohol use, hepatitis, or nonalcoholic fatty liver disease. Another is hepatitis, which is inflammation of the liver caused by viral infections or toxins. Hepatitis can lead to symptoms like jaundice and liver damage.
GALLBLADDER
The gallbladder is located beneath the liver in the upper right quadrant of the abdomen. It’s a small, pear-shaped organ with three main parts: the neck, the body, and the fundus. The gallbladder connects to the bile ducts through the cystic duct. The cystic artery, a branch of the right hepatic artery, supplies the gallbladder with blood, while the cystic vein drains blood into the portal vein. The gallbladder’s primary job is to store and concentrate bile produced by the liver, releasing it into the small intestine during digestion to help break down fats. Two common gallbladder issues include gallstones, which are solidified bile crystals that can block bile flow and cause pain, and cholecystitis, which is inflammation of the gallbladder often caused by gallstones.
MOUTH AND LIPS
Mouth & Lips: The First Step in Digestion The mouth is the entry point for food, located at the beginning of the digestive tract. The lips help with chewing, swallowing, and speech, while the oral cavity contains teeth, the tongue, and salivary glands. Blood supply comes from the facial and maxillary arteries, and venous drainage flows into the jugular vein. The mouth’s main function is to mechanically break down food with chewing, while enzymes in saliva begin digestion. Common issues include oral infections, dry mouth (xerostomia), and cheilitis, which is inflammation of the lips caused by dehydration or irritation.
ESOPHAGUS
Esophagus: The Food Pipeline The esophagus is a muscular tube that connects the pharynx to the stomach, running behind the trachea. Blood supply comes from the esophageal branches of the thoracic aorta, while venous drainage occurs through the azygos and gastric veins. Its function is to transport food to the stomach through rhythmic contractions called peristalsis. Common conditions include acid reflux (GERD), where stomach acid backs up into the esophagus, and esophageal strictures, which cause narrowing and swallowing difficulty.
SALIVA
Saliva: Nature’s Digestive Lubricant Saliva is produced by the salivary glands—the parotid, submandibular, and sublingual glands—located around the mouth. These glands receive blood from the facial and lingual arteries, and drainage occurs via the jugular veins. Saliva plays a crucial role in digestion, containing enzymes like amylase, which starts breaking down carbohydrates. It also helps with swallowing, taste, and oral health by washing away bacteria. Issues include dry mouth (xerostomia), often caused by dehydration or medications, and salivary gland stones, which can block ducts and cause swelling.
APPENDIX
Appendix: The Forgotten Immune Organ The appendix is a small, finger-like pouch attached to the cecum. Blood is supplied by the appendicular artery, a branch of the ileocolic artery, with drainage into the superior mesenteric vein. Although once thought useless, it’s now known to play a role in gut immunity. The most common issue is appendicitis, a painful inflammation that often requires surgical removal.
JEJUNUM
Jejunum: The Nutrient Absorber The jejunum is the middle part of the small intestine, where most nutrient absorption occurs. Blood is supplied by the jejunal branches of the superior mesenteric artery, and venous drainage flows into the superior mesenteric vein. Its main function is to absorb carbohydrates, proteins, vitamins, and minerals through specialized folds called villi. Common conditions include celiac disease, where gluten damages the intestinal lining, and intestinal obstructions, which prevent proper digestion.
CECUM
Cecum: The Large Intestine’s Entry Point The cecum is the first part of the large intestine, connecting the ileum to the colon. It’s supplied by the ileocolic artery, with venous drainage into the superior mesenteric vein. Its function is to absorb fluids and start stool formation. Common issues include appendicitis, inflammation of the nearby appendix, and cecal volvulus, where the cecum twists, blocking the intestine.
RECTUM
Rectum: The Final Storage The rectum is the last part of the digestive tract, storing stool before elimination. It’s supplied by the rectal arteries, with drainage through the rectal venous plexus. Its role is to control defecation through a system of sphincters. Issues like hemorrhoids, rectal prolapse, and fecal incontinence can cause discomfort and complications.
DUODENUM
Duodenum: The Digestive Control Center The duodenum is the first part of the small intestine, located just after the stomach. It receives digestive enzymes from the pancreas and bile from the gallbladder. Blood supply comes from the superior pancreaticoduodenal and inferior pancreaticoduodenal arteries, with venous drainage into the portal system. Its role is to continue digestion, breaking down fats, proteins, and carbohydrates. Common problems include duodenal ulcers, caused by excess acid, and malabsorption disorders, where nutrients aren’t properly absorbed.
ILEUM
Ileum: The Final Absorption Site The ileum is the last section of the small intestine, connecting to the large intestine at the cecum. It’s responsible for absorbing vitamin B12 and bile salts. Blood is supplied by the ileal branches of the superior mesenteric artery, and venous drainage flows into the portal circulation. Its primary role is to reclaim bile salts for reuse in digestion and absorb nutrients before waste moves into the large intestine. Issues include Crohn’s disease, which causes inflammation and scarring, and short bowel syndrome, where nutrient absorption is impaired.
COLON
Colon: The Water Absorber The colon is the largest part of the large intestine, divided into the ascending, transverse, descending, and sigmoid colon. Blood supply comes from the superior and inferior mesenteric arteries, with venous drainage into the portal system. Its main function is to absorb water, electrolytes, and form solid stool. Conditions like constipation, irritable bowel syndrome (IBS), and colon cancer can affect digestion and elimination.
MICROBIOME
The gut microbiome is a living ecosystem inside you—trillions of bacteria, fungi, and even viruses working together to digest food, produce vitamins, regulate the immune system, and even influence your mood. A balanced microbiome helps prevent disease, while an imbalance—called dysbiosis—is linked to digestive disorders, inflammation, and even neurological conditions. What you eat, how you live, and even the medications you take shape this microscopic world. Your gut isn't just about digestion—it's the command center for whole-body health.