2x2 Week 2 The Digestive Tract ROBERT FREDERICK GABRIEL ONTIVEROS JR AND LITERALLY NOBODY ELSE. ESPECIALLY NOT JACOB.

Stomach is important in the digestion of food. The stomach is located between the esophagus and the duodenum of the small intestine. Four parts of the stomach: Cardia where the contents from the esophagus comes in. Fundus Body (Corpus) this is the main central region (most important part) Pylorus after this the stomach empties into the small intestine Pathway: mouth pharynx esophagus esophageogastric junction stomach (cardia, fundus, body, pyloris), pylorus sphincter duodenum jejunum ileum ascending colon transverse colon descending colon rectum anus

Ascending Colon up Transverse Colon across Descending Colon down Rectum - The folds here are gastric folds (called ruggae) which help in moving things along and are found mostly in the body part of the stomach

Non keratinized stratified squamous epithelium Gastric pits junction ESOPHAGEAL JUNCTION (same as the esophageogastric junction) Right part: Esophagus (non-keratinized stratified squamous epithelium) Left part: Stomach (simple columnar epithelium) Gastric Pits: an indentation in the stomach which denotes the entrance into the gastric glands This junction connects the esophagus to the stomach The space is used to increase surface area for absorption Ratio of pits to gland: 4:1; 4 gastric pits for every 1 gland

Epithelium/mucosa/ submucosa glands Innermost oblique This is a longitudinal section of the Gastric Fundus. The Innermost Oblique turns food to help digestion As you enter the fundus, gastric pits become shorter and shorter. NO GOBLET CELLS IN THE STOMACH!!! Instead, you have pepsin, which helps break down enzymes and is composed of pepsinogen and hydrochloric acid Four types of cells here: Parietal Cells secrete hydrochloric acid (HCL) located in the stomach Mucous Cells secrete mucus into the gastric pits to move things into the stomach for lubrication Enteroendrocine Cells produce hormones in response to the various peptides (hormose) and releases them into the bloodstream (1) to release them to the bloodstream, (2) diffuse them as messengers or (3) transmit them to the nervous system; most numerous endocrine cells of the body and is located in the stomach, intestines, and pancreas Chief Cells secrete pepsinogen and rennin Outer longitudinal muscularis

submucosa villi Plica circularis Brunner’s glands microvilli LONGITUDINAL SECTION OF THE DUODENUM Duodenum Cells no goblet cells; entire inside is Plica circularis Submucosa has Brunner’s Glands, which secrete bicarbonate ions to neutralize chyme, which is from gastric juices Villi increases the surface area for absorption microvilli

Fig 315 LONGITUDINAL SECTION OF THE JEJUNUM Has elongated villi Less Plica Circularis NO Brunner’s Glands NO Peyers Patches A few goblet cells, but not that many, because you are getting close to cecum Goblet cells are only found mostly in the small intestines

Fig 316 Lymphoid nodules Germinal centers Peyer’s Patches LONGITUDINAL SECTION OF THE ILEUM NO Plica Circularis NO Brunner’s Glands There are Peyers Patches loaded with lymphocytes; important in immunity; located in the germinal center

Fig 316 Temporary folds 1 LONGITUDINAL SECTION OF LARGE INTESTINE NO villi NO Brunner’s glands NO Plica circularis Here, getting closer to cecum, so a lot of goblet cells to lubricate the feces as they move down FUNCTION: to absorb water, minerals, and electrolytes

Fig 329 CROSS-SECTION OF VERMIFORM APPENDIX Attached to the cecum CENTER OF THE SCREEN: POOP! Triangular portion white part if the lumen; orange thing is feces Submucosa Lymphoid Nodule a circle of lymphocytes Germinal center Muscularis externa Serosa connective tissue PATHWAY: mucosa submucosa inner circulatory muscles outer longitudinal muscles serosa (going from in to out)