Human Digestive System Fall 2017 Anatomy and Physiology Lab II Dr. Santos

Alimentary canal (gastrointestinal tract)- A passage extending from the mouth to the anus through which food travels as it is digested; it includes the pharynx, esophagus, stomach, and intestines. Accessory organ- Organs that assist in mechanical or chemical digestion, including the teeth, tongue, salivary glands, pancreas, and the liver. Peritoneal cavity- A cavity located between a double-layered serous membrane that secretes serous fluid, allowing organs to slide over each other without friction; much of the alimentary canal and many accessory organs reside here.

Oral cavity (mouth)- The oral cavity includes the lips, the inside lining of the lips and cheeks (buccal mucosa), the teeth, the gums, the front two-thirds of the tongue (mixes food in the mouth), the floor of the mouth below the tongue, and the bony roof of the mouth (hard palate). Hard palate- bony roof of the mouth, anterosuperior boundary of the oral cavity, supported by bone. Soft palate- the back of the roof of the mouth. The Uvula hangs from its posterior edge. Vestibule- area between the teeth and lips/cheeks

Stomach Organ where protein digestion begins Rugae-Folds of the stomach mucosa Muscular organ that receives food from the esophagus (links back of mouth to the stomach). Secretes acid And enzymes to break down food. Empties food into the small Intestine.

Esophageal sphincter- muscular valve that regulates the movement of food from esophagus to stomach. Pyloric sphincter- controls the movement of food from the stomach into the duodenum.

Small intestine Receives pancreatic juice and bile (emulsification of fat) Organ in which stomach empties Most food digestion, absorption and water absorption Folds in the small intestinal walls are called Plicae circulares. Duodenum- First part of the small intestine Jejunum- Middle part of the small intestine; between the duodenum and the ileum Ileum- Last part of the small intestine; between the jejunum of the small intestine and the cecum of the large intestine

Villi- fingerlike extensions of the internal mucosa that increase surface area. Microvilli- projections of the plasma membrane of a cell that increase the cell’s surface area.

The Large intestine From the small intestine, the material goes into the large intestine. The ileocecal valve prevents material from moving back into the small intestine once it has entered the large intestine. The large intestine (colon or large bowel) is about 5 feet long and about 3 inches in diameter. The colon absorbs water from wastes, creating stool. As stool enters the rectum, nerves there create the urge to defecate. The ascending colon including the cecum and appendix. The transverse colon including the colic flexures and transverse mesocolon. The descending colon. The sigmoid colon – the s-shaped region of the large intestine. Haustra- sac like outpocketing of the large intestinal walls.

Rectum and anus Rectum- is the last stop before the feces is eliminated through the anal canal.  Anus- the opening where the gastrointestinal tract ends and exits the body.

Accessory glands Salivary glands- Accessory organs around the mouth that secrete saliva, which contains substances such as water, salivary amylase, antibodies, and lysozyme. Three pairs; parotid, sublingual and submandibular) Pancreas- Exocrine and endocrine gland that sits posterior and inferior to the stomach; its exocrine functions are digestive whereas its endocrine functions are metabolic.

Liver- Organ located on the right side of the abdominal cavity consisting of four lobes; produces bile for digestion; detoxifies, processes, and eliminates toxins in blood before the blood enters the general circulation in the body Gallbladder- Sac-like organ located under the liver’s right lobe that stores the liver’s bile; when stimulated by certain hormones, it will contract and eject bile into the cystic duct to aid in digestion. Common bile duct- carries bile from the gallbladder and empty it into the upper part of the small intestine (the duodenum).

Common hepatic duct- is the duct formed by the convergence of the right hepatic duct (which drains bile from the right functional lobe of the liver) and the left hepatic duct (which drains bile from the left functional lobe of the liver). This joins a duct from the gallbladder (cystic duct) to form the common bile duct and carry bile to the small intestine.

Peritoneum The peritoneum is a membrane made up of two layers. One layer lines the cavity and the other layer lines the organs. The peritoneum helps support the organs in the abdominal cavity and also allows nerves, blood vessels, and lymph vessels to pass through to the organs. The outer layer, called the parietal peritoneum, is attached to the abdominal wall (serosa of the abdominal wall). The inner layer, the visceral peritoneum, is wrapped around the internal organs that are located inside the intraperitoneal cavity.

Three extensions/modifications are; greater omentum- connects the stomach to the posterior abdominal wall lesser omentum- membrane attached to the lesser curvature of the stomach. Mesentery- structure that suspends the small intestine from the posterior body wall.