The digestive system part 4

the act of swallowing.  It is facilitated by the secretion of saliva and mucus and involves the mouth, pharynx and esophagus.  It occurs in three stages.

starts when the bolus is forced to the back of the mouth and into the oropharynx by movement of the tongue upwards and backwards along the palate.

passage of the bolus into the oropharynx.  Involuntary part of swallowing.

the bolus stimulates receptors in the oropharynx which sends impulses here in the medulla oblongata and lower pons of the brain stem.  It sends signals to epiglottis to close and raise the palate and uvula to close off nasal cavity

begins once the bolus enters the esophagus.

a progression of coordinated contractions and relaxations of the circular and longitudinal layers of the muscularis, pushes the bolus onward.

a J-shaped enlargement of the GI tract directly inferior to the diaphragm.  It connects the esophagus to the first part of the small intestine and serves as a mixing chamber and holding reservoir. Digestion of starch continues and that of protein and triglycerides begins

surrounds the superior opening of the stomach.

the rounded portion superior to and left of the cardia

inferior to the fundus is the large central portion of the stomach

the region of the stomach that connects to the duodenum. it has two parts.

connects to the body of the stomach

which leads into the duodenum

when the stomach is empty, the mucosa lies in large folds called this.

the pylorus communicates with the duodenum of the small intestine via a smooth muscle sphincter called this.

the concave medial border of the stomach

the convex lateral border of the stomach

the surface of this layer has a layer of simple columnar epithelial calls called surface mucous cells.  it also contains a lamina propria (areolar connective tissue) and a muscularis mucosae (smooth muscle)

epithelial cells extend down into the lamina propria, where they form columns of secretory cells called these.

secretions from several gastric glands flow into each one of these and then into the lumen of the stomach.

exocrine gland cells that secrete mucous

exocrine gland cells that produce intrinsic factor and hydrochloric acid

needed for absorption of vitamin B12

exocrine gland cells that secrete pepsinogen and gastric lipase

the secretions of mucous, parietal and chief cells form this.

gastric glands include a type of enteroendocrine cells which is located mainly in the pyloric antrum and secretes the hormone gastrin in the blood stream.

a layer of areolar connective tissue

three layers of smooth muscle and outer longitudinal layer, a middle circular layer and an inner oblique layer

the portion of the serosa covering the stomach is part of the visceral peritoneum.