Introduction

• The GI system serves two major functions:

  1. Digestion
  2. Elimination
• Elimination is the process of eliminating waste products from the body through excretion of feces.
• Digestion is a process where food and fluid are broken down into simple chemicals for absorption and transportation throughout the body
• The walls of the GI tract from the esophagus to the large intestine are made up of four basic tissue layers or tunic:

  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Visceral peritoneum
• GI Tract = Alimentary canal
• Accessory GI Organs:

  • Liver
  • Biliary Duct System
  • Pancreas
• Mouth = oral cavity
• Saliva is mixed with food to soften it.
• Lips = labium
• Teeth = odonto
• Cheeks = bucca, buccae
• Hard palate = palatum, palati
• The soft palate, which forms a partition between the mouth and the nasopharynx, is continuous with the hard palate.
• The vestibule is the space between the lips and the cheeks externally and the teeth and gums (gingiva) internally.
• The frenulum, a fold membrane, secures the tongue to the floor of the mouth and limits its posterior movement during mastication.
• Tongue = glossa, lingua
• After food is chewed, it is formed into a round sticky mass called a bolus, which is pushed by the tongue from the mouth into the pharynx or throat. Its downward movement is guided by a soft, fleshy V-shaped tissue called uvula.
• The funnel-shaped pharynx serves as a passageway for air and food. It provides a resonating chamber for speech sounds and has both respiratory and digestive functions.
• The pharynx is divided into (1) nasopharynx, (2) oropharynx and (3) laryngopharynx.
• The alternating contractions of the muscle layers in the pharynx propel food to the esophagus below. This propelling mechanism is called peristalsis
• Windpipe = trachea
• Esophagus = gullet
• The stomach acts as a temporary storage tank for food as well as site for food breakdown or breaking food into smaller fragments and chemical breakdown of protein.
• The stomach acts as a temporary storage tank for food as well as site for food breakdown or breaking food into smaller fragments and chemical breakdown of protein.
• The antrum is the grinder of the stomach.\
• The small intestine also contains intestinal crypts, Peyer’s patches and Brunner’s glands
• Peyer’s patches are collections of lymphatic tissues within the submucosa. Brunner’s glands secrete mucus
• The colon is divided into:

  • Ascending colon - extends from the cecum to the lower border of the liver and turns abruptly to form the hepatic flexure.
  • Transverse - the part of the colon between the right and left flexures.
  • Descending - the part of the colon extending from the left colic flexure to the pelvic brim.
  • Sigmoid - the part of the colon describing an S-shaped curve between the pelvic brim and the third sacral segment. It is continuous with the rectum.
• The pancreas is an elongated, somewhat flattened organ that lies posterior and slightly inferior to the stomach. In the digestive system, it provides digestive juice that passes through the pancreatic duct.