Gastrointestinal Tract Overview

Study Notes

The GIT is a complex system for processing food, including digestion and absorption.
The GIT is composed of multiple organs and structures including the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
Accessory organs like the liver, gallbladder, and pancreas also play critical roles in digestion.
The GIT includes three main parts: foregut, midgut, and hindgut.
Each region is supplied by specific artery systems (Celiac trunk, superior mesenteric artery, inferior mesenteric artery).

The oral cavity includes the hard palate, soft palate, mouth cavity proper, vestibule of the mouth, tongue and epiglottis.
The tongue is a musculomembranous structure with anatomical parts (anterior 2/3, posterior 1/3, tip, dorsal and ventral surface, and root).
The hard palate consists of anterior 2/3 and soft palate posterior 1/3.
Saliva, produced by salivary glands (parotid, sublingual, and submandibular), aids in digestion. Salivary glands help in digestion by making food more liquid and easy to swallow.

The pharynx is a tube-shaped passageway situated posterior to the nasal and oral cavities.
The pharynx has three major parts: nasopharynx, oropharynx, and laryngopharynx.
The nasopharynx is the part of the pharynx that lies superior to the oral cavity, and above the soft palate.
The oropharynx is located between the soft palate and the epiglottis.
The laryngopharynx is inferior to the oropharynx.

The esophagus is a muscular tube connecting the pharynx to the stomach.
The esophagus runs from the level of C6 to T10, penetrating the diaphragm.
The esophagus is a muscular tube approximately 10 inches/25 cm long, transporting substances from the pharynx to the stomach.

The stomach is a j-shaped organ situated in the upper left quadrant of the abdominal cavity.
The stomach is mainly on the left side of the abdomen.
Common sites of stomach are left hypochondrium, epigastrium and umbilical regions.
The stomach has four major parts: fundus, body, pylorus, and cardiac.
Pyloric opening is situated between the stomach and duodenum.
Major anatomical landmarks of the stomach include the lesser curvature, angular incisure, greater curvature, cardiac notch, and fundus.

The small intestine is a long, convoluted tube extending from the stomach to the large intestine.
It includes duodenum, jejunum and ileum.
The duodenum is a C-shaped part of the small intestine attached to the stomach.
The jejunum and ileum comprise the rest of the small intestine, connecting to the large intestine at the ileocecal junction.
The small intestine is important for the absorption of nutrients.

The large intestine is a wider tube extending from the ileum to the anus.
It includes the cecum, appendix, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, and rectum.
The ileocecal junction is the connection point between the small and large intestines.
The large intestine is responsible for water absorption and the formation of feces.

The liver is a vital organ located in the upper right quadrant of the abdomen, underneath the diaphragm.
The liver is divided into four lobes: right, left, caudate, and quadrate.
The liver has multiple functions, including filtering blood, producing bile, and metabolizing nutrients.
The porta hepatis is an important anatomical structure in the liver, containing blood vessels and biliary ducts.

The biliary system includes the gallbladder and biliary ducts for bile storage and transport.
The gallbladder, a pear-shaped sac, stores and concentrates bile from the liver.
The biliary ducts (cystic, common hepatic, and common bile ducts) transport and deliver the bile into the duodenum.

The pancreas is a gland situated behind the stomach, having a horizontal position on the posterior abdominal wall.
The pancreas has a head, neck, body, and tail.
The pancreas produces enzymes for digestion and hormones regulating blood sugar levels.
The pancreatic ducts transport pancreatic enzymes into the duodenum.