General Knowledge Flashcards
What are the 4 layers of the GI tract?
Mucosa, Submucosa, Muscularis externa, Serosa/adventitia
What does the mucosa layer contain?
- Epithelium
- Lamina propria - loose, well vascularized connective tissue that contains scattered lymphocytes, plasma cells, and macrophages
- Muscularis mucosae - thin smooth muscle layer for local motility
What does the submucosa layer contain?
Connective tissue containing larger blood vessels, nerve plexes, glands, and lymphatic nodules, along with lymphiod cells scattered about
What does the muscularis externa layer contain?
Inner circular and outer longitudinal layers of smooth muscle and nerve plexes - main function is peristalsis and churning of lumenal contents
What does the serosa/adventitia layer contain?
Outer covering of squamous epithelial cells separated from the underlying muscle by a thin layer of connective tissue. Called the adventitia in the esophagus.
Type of epithelium in esophagus?
Lined with non-cornified squamous epithelium
Muscle in esophagus?
Inner circular and outer longitudinal arrangement. Upper 1/3 is purely skeletal muscle, bottom 1/3 purely smooth muscle, middle 1/3 mixed
Glands in esophagus?
Mucous glands present in mucosa and submucosa
Regions of the stomach?
Cardia, fundus/body, antrum/pyloris
Muscle in stomach?
3 layers - outer longitudinal, inner circular, and inner oblique
Which special
cells are present in the stomach?
Stem cells, surface mucous cells, chief cells, parietal cells, and enteroendocrine cells
Surface mucous cells
Contain large vesicles of mucins and bicarbonate. Directly covering these cells is the glycocalyx
Chief cells
Contain apical vesicles and elaborate basal ER. Secrete pepsinogen
Pepsinogen
Converted to pepsin, an active protease, in the presence of acid. Pepsin needs a low pH to operate as well.
Parietal cells
Have massive canaliculi for acid production, and contain a large number of mitochondria. Stimulated to secrete H+ by gastrin and histamine. Also secrete intrinsic factor.
Zollinger-Ellison syndrome
Excessive secretion of gastrin leads to overproduction of acid by parietal cells. Leads to duodenal ulcers and complications.
Enteroendocrine cells
Many types widely distributed around GI tract
G cells
Secrete gastrin
Stomach and small intestine
A cells
Secrete glucagon
Stomach and small intestine
EC cells
Secrete serotonin
Stomach, small and large intestines
D cells
Secrete somatostatin
Stomach (except middle), small and large intestines
Plicae circulares
Permanent transverse oriented folds in the small intestine. Project ~1cm, and covered in villi.
Paneth cells
Contain large eosinophilic granules which contain defensins, lysozyme, and phospholipase
Brunner’s glands
Only found in duodenum, secrete large quantities of bicarbonate, and mucins.
