L5D

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Key Terms

Digestive System Structures

Alimentary canal (gastrointestinal tract) _________________________________________________________

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Accessory organ ____________________________________________________________________________________

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Peritoneal cavity ____________________________________________________________________________________

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Gastroesophageal sphincter ________________________________________________________________________

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Pyloric sphincter ____________________________________________________________________________________

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Duodenum ___________________________________________________________________________________________

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Jejunum ______________________________________________________________________________________________

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Ileum ________________________________________________________________________________________________

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Colon ________________________________________________________________________________________________

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Salivary glands _______________________________________________________________________________________

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Pancreas _______________________________________________________________________________________

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Liver _________________________________________________________________________________________________

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Gallbladder ___________________________________________________________________________________________

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Digestive Histology

Mucosa ______________________________________________________________________________________________

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Submucosa ___________________________________________________________________________________________

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Muscularis externa __________________________________________________________________________________

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Serosa _______________________________________________________________________________________________

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Differentiate Between the Digestive Tract and the Accessory Digestive Organs:

List the basic parts of the digestive tract.

List the accessory organs of the mouth.

List the accessory organs of the small intestine.

Anatomy of the Digestive System:

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· Salivary Glands

· Parotid salivary glands and ducts

· Submandibular salivary glands and ducts

· Sublingual salivary glands and ducts

· Pharynx

· Nasopharynx (not part of digestive tract)

· Oropharynx

· Laryngopharynx

· Esophagus

· Stomach

· Cardiac sphincter / lower esophageal sphincter

· Cardia

· Fundus

· Body

· Greater curvature

· Lesser curvature

· Rugae / gastric folds

· Pylorus

· Pyloric sphincter

· Small intestine

· Duodenum

· Major duodenal papilla

· Circular folds (plicae circulares)

· Jejunum

· Ileum

· Large Intestine

· Ileocecal valve

· Cecum

· Appendix

· Ascending colon

· Hepatic flexure (r colic flexure)

· Transverse colon

· Splenic flexure (L colic flexure)

· Descending colon

· Sigmoid colon

· Taeniae coli

· Haustra

· Rectum

· Anus

· Anal sphincter (internal and external)

· Peritoneal extensions

· Greater omentum

· Lesser omentum

· Falciform ligament

· Mesentery

· Mesocolon

Accessory organs of the small intestine

· Liver

· Right lobe

· Left lobe

· Gall bladder

· Pancreas

· Head

· Body

· Tail

· Main pancreatic duct

· Accessory pancreatic duct

· Biliary system

· Right hepatic duct

· Left hepatic duct

· Common hepatic duct

· Cystic duct

· Common bile duct

· Hepatopancreatic duodenal ampulla

Trace the movement of food from mouth to anus.

Histology
of Selected Portions of the Digestive Tract

Esophagus

· Mucosa

· Stratified squamous epithelium

· Lamina propria

· Muscularis mucosae

· Submucosa

· Esophageal glands

· Muscularis externae

· Circular muscle layer

· Longitudinal muscle layer

· Adventitia

The mucosa consists of three layers: the outer, dark-stained stratified squamous epithelium, the lamina propria, and a muscularis mucosae. The thick, pink-stained submucosa contains purple-stained esophageal glands which produce mucus for lubrication. Look for ducts from these glands connecting to the mucosal surface. Two layers of the muscularis muscle layer and the outer longitudinal muscle layer. The thick, outermost layer is the adventitia.

Stomach: Ruga

· Mucosa

· Gastric pits

· Gastric glands

· Submucosa

· Muscularis externae

· Oblique muscle layer

· Circular muscle layer

· Longitudinal muscle layer

· Serosa

· Simple squamous epithelium

On lowest power, note the fold of combined mucosa and submucosa; this is a ruga. On high power, in the mucosa, identify numerous depressions, called gastric pits, and gastric glands, which produce gastric secretions and are located at the base of each gastric pit. Surrounding the individual gastric glands is the lamina propria. Just below the lamina propria’s base, the muscularis mucosae is visible as a distinct layer of smooth muscle, which contracts to help expel gastric gland secretions. In the submucosa, find arteries and veins, note that this layer is thickest in the ruga. Beneath the submucosa, find arteries and veins, note that this layer is thickest in the ruga. Beneath the submucosa look for the oblique, circular, and longitudinal layers of the muscularis externae. Finally, identify the serosa, composed of simple squamous epithelium which is the outermost layer.

Small intestine: Villi

· Mucosa

· Simple columnar epithelium (Note the microvilli forming the brush border and mucus secreting goblet cells)

· Lamina propria

· Submucosa

· Muscularis externae

· Circular muscle layer

· Longitudinal muscle layer

· Serosa

· Simple squamous epithelium

On lowest power, note the villi, which are numerous, deep folds of intestinal mucosa. On low power, observe that each villus has an outer layer of epithelium with a core of connective tissue, the lamina propria. On high power, locate goblet cells in the simple columnar epithelium. The hazy appearance of the top border of the cells is due to the presence of microvilli, forming the brush border. On low power, again, observe that the submucosa blends with the lamina propria of the villi. The muscularis externae consists of circular and longitudinal layers. A thin serosa of simple squamous epithelium forms the outermost layer.

Colon / Large Intestine

· Mucosa

· Simple columnar epithelium (Note the presence of MANY Goblet cells)

· Intestinal glands

· Lamina propria

· Submucosa

· Muscularis externae

· Circular muscle layer

· Longitudinal muscle layer

· Serosa (not always visible)

· Simple squamous epithelium

In the high power view, note the closely packed intestinal glands in the mucosa, which is made of simple columnar epithelium and is filled with many goblet cells which produce mucus to help with the movement of undigested materials through the large intestine. On the low power view, note the submucosa is thin and dense in this section. The circular muscle layer often shows dense streaks where ends of neighboring smooth muscle cells overlap. The longitudinal muscle layer and serosa can also be identified. Occasional lymphoid tissue is seen.

How to identify/distinguish different parts of the GI Tract Using the Microscope

All of the digestive tract is lined with some kind of epithelium.

THIS DIAGRAM ABOVE IS PART OF THE HIGHLIGHTED ASSIGNMENT…COULDN’T HIGHLIGHT