Digestive System Anatomy Lab

• Lab Exercise # 10 is on the Digestive System Anatomy.

Digestive System

• Involves digestion and absorption of food.
• Gastrointestinal Tract contains the:
  • Oral cavity
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
• Accessory Organs contain the:
  • Salivary gland
  • Liver
  • Gall bladder
  • Pancreas

Oral Cavity

• Contains the mucus membrane, tongue, teeth, and gingivae.
• Anterior portion of the roof in oral cavity is the hard palate.
• It is hard because the palatine bones and palatine processes of maxillae underlie it.
• Forms upper portion of anterior opening into oral cavity in the superior lip.
• The superior labial frenulum attaches the upper lip to gums.
• Posterior portion of the roof is the soft palate in the oral cavity.
• It is muscular and no bone underlies it.
• It rises to close off nasopharynx when swallowing.
• The uvula is a projection off the soft palate.
• Forms lateral walls of the oral cavity is the cheek.
• Composed of skeletal muscle and lies in floor of oral cavity is the tongue.
• Movements help to mix food, swallow, and produce speech and has the location of the majority of taste buds.
• Lingual frenulum attaches body of tongue to the floor of the mouth.
• Commonly called the gums, a mucous membrane surrounding base of teeth is the Gingiva.
• Attaches lower lip to gums is the inferior labial frenulum.
• Space found between lips and cheeks and teeth is the vestibule.
• Forms lower portion of anterior opening into oral cavity in the inferior lip.

Teeth

• Teeth reside in the upper and lower jaw.
• Types and Number of Teeth vary.
• The structure of a tooth varies.
• The Gingiva is similar.
• Incisor teeth have a narrow edge, like a knife blade and are designed for cutting and biting.
• The cuspid tooth is also called the eye tooth or canine tooth, has a single point, and is designed for biting.
• Bicuspid teeth have two flat cusps and are designed for grinding.
• Molar teeth are larger teeth with multiple rounded cusps and are designed for grinding.
• The crown is the portion of a tooth visible above the gum line.
• While the root is the portion of a tooth not visible and below the gum line.
• Enamel covers the crown and harder than bone.
• The dentin underlies enamel and forms bulk of root, made of calcified connective tissue.
• Pulp cavity is a chamber within tooth housing blood vessels and nerves.
• Cementum covers the root.
• Periodontal ligament anchors tooth in socket.
• Root canal is the section of pulp cavity in each root, continuous with pulp cavity, containing nerves and blood vessels.
• The neck is the junction between crown and root.

Pharynx

• Consists of the nasopharynx, oropharynx, laryngopharynx, and tonsils.

Structure of GI Tract

• Contains the Sphincter, Peristalsis, Muscularis interna, Circular muscles, Longitudinal muscles, and Serosa.
• Contains the Epithelium, Lamina propria, Muscularis mucosae, and Myenteric plexus.
• Deepest layer that lines lumen of GI tract is the mucosa.
• It is also known as mucous membrane.
• It's made of epithelium, lamina propria, and muscularis mucosae.
• Dense irregular connective tissue is the submucosa.
• Inner layer of circular fibers and outer layer of longitudinal fibers are the muscularis externa.
• Stratified squamous in esophagus, simple columnar in stomach, small and large intestines, and keratinized stratified squamous in anus is the epithelium.
• Loose connective tissue, contains mucosal glands in stomach and large intestine, contains lymphatic nodules (MALT) is the lamina propria.
• A thin layer of smooth muscle is the muscularis mucosae.
• A network of nerves within muscularis externa is the Myenteric plexus.
• Outermost layer and serous membrane is the serosa.
• Finger-like extensions of mucosa found in the small intestine and increase surface area for absorption of nutrients are the villi.

Esophagus

• Has a mucosa, submucosa, and histology of wall of esophagus.

Stomach

• Has gastric pits and glands, chyme and enzymes, and rugae.
• Cardia, fundus and pyloric antrum are all part of the stomach.
• Muscle layers are also part of the stomach.
• The stomach affects the role in digestion.
• The cardia receives food from the esophagus.
• The fundus is the dome-shaped superior region and holds food.
• The body is the largest region and mixes food with gastric juices.
• The pyloric canal opens through the pyloric sphincter.
• The pyloric antrum is the tapering distal stomach leading to the duodenum.
• Rugae are folds in the gastric mucosa that flatten out to allow the stomach to expand.

Small Intestine

• The Duodenum, Jejunum, and Ileum are parts of the small intestine.
• Affects the role in digestion and absorption

Large Intestine

• The Cecum, Ascending colon, Transverse colon, Descending colon, Sigmoid colon, Rectum and Anus are all parts of the large intestine.
• Duodenum is the first section of small intestine receiving chyme from stomach and digestive enzymes from pancreas and bile from liver and gallbladder.
• Jejunum is the second section of small intestine with the bulk of chemical digestion and nutrient absorption in this section.
• Ileum is the third section of small intestine which delivers remaining material to cecum of large intestine.
• Cecum is an expanded pouch that collects material from ileum and begins compaction.
• The appendix is a slender, hollow attachment off the distal cecum and contains lymphoid nodules.
• The rectum stores feces prior to defecation.
• Anus is the distal opening of GI tract.

Salivary Glands

• Parotid glands, Submandibular glands and Sublingual glands all make up the salivary glands.
• Salivary amylase, mucin and lysozyme are all secreted here.
• Parotid gland is the largest salivary gland, lying on the surface of masseter muscle just distal to ear.
• Sublingual gland lies in floor of mouth under the tongue.
• Submandibular gland lies in floor of mouth along inner surface of mandible.

Liver

• Includes right, left, quadrate and caudate lobes.
• Also the right and left hepatic duct.
• Containing the common hepatic duct.
• The bile and gall bladder also contribute.
• Includes the hepatic lobules and hepatocytes.
• The right lobe of the liver has additional liver lobes, caudate lobe and quadrate lobe, are visible only from posterior.
• The left lobe of the liver performs multiple functions, one is to produce bile, bile emulsifies lipids and fats making digestion easier.
• Gallbladder is a hollow, sac-like organ, storing bile produced by liver.
• Hepatopancreatic ampulla is a point at which common bile duct and pancreatic duct connect to duodenum.

Pancreas

• Exocrine pancreas - acini.
• Endocrine pancreas – islets of Langerhans.
• Secretes, pancreatic secretions and Pancreatic hormones