003 Physiology of the GI tract: Overview of function; salivary secretion Flashcards
How long is the GI tract?
5.5m
What are the 3 salivary glands?
Parotid gland (behind the mouth), sublingual gland (below the tongue), submandibular gland (below the jaws)
Name the 6 different parts of the large intestine
Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Anal canal
What are some exocrine glands of the GI tract?
Salivary glands, pancreas, liver
What are the layers of the digestive canal, beginning from inside to outside?
Epithelium Mucosa Muscularis mucosa Submucosa Muscularis externa Serosa
What does the muscularis layer contain?
Circular muscle layer
Longitudinal muscle layer
What is the serosa?
The outer layer of the digestive canal that contains the epithelium and areolar connective tissue. It forms the visceral peritoneum and is continuous with parietal peritoneum.
Where is the myenteric plexus located?
Between the layers of circular muscle and longitudinal muscle in the muscularis.
Where is the submucosal plexus located?
On the submucosa layer
What is the submucosa?
Loose connective tissue of collagen and elasin fibrils that contain blood and lymph vessels, glands, and the submucosal plexus.
Where are submucosal glands found along the GI tract?
Only exist in the duodenum
What is different about the muscularis externa in the digestive canal and the stomach?
In the stomach, it has a 3rd oblique layer that is controlled by the myenteric plexus and hormones.
Which part of the enteric nervous system is mainly responsible for motor function of GI tract?
Myenteric plexus
How would you identify the lining of esophagus on histology slides?
Layer of squamous cells
Alot of smooth muscle
Tough epithelium
How would you identify the lining of stomach on histology slides?
Contains gastric pits that make 50% of surface. Contain glands that secrete acids and enzymes.
How would you identify the lining of small intestine on histology slides?
Villi extensions of mucosa
Villi consists of single layer columnar epithelial cells and have mucosal glands.
Enterocytes are absorptive cells that line the intestine.
How would you identify the lining of a large intestine on histology slides?
Villi are absent
Increased appearance of goblet cells that aid mucus secretion as contents become more solid.
What cells line the villi and what is the brush border membrane?
Absorptive enterocytes line the villi, and on the apical face of the cell lines a brush border membrane that increases surface area.
What is a crypt?
Each villi is associate with a crypt that contains approx 250 cells including stem cells, paneth cells and transit amplifying cells.
What are paneth cells?
Paneth cells are found at the base of the intestinal glands. They are specialized stem cells but unlike other epithelial cell types, they migrate downward from stem cell region and settle adjacent to it. They provide antibacterial substances into the lumen.
What can intestinal stem cells differentiate into?
Secretory cells such as paneth cells, enteroendocrine cells and globlet cells. The majority differentiates into absorptive cells.
What cells secrete mucus?
Goblet cells
What cells secrete peptide hormones?
Enteroendocrine cells
What is intrinsic factor and where is it produced?
It is produced in the stomach, and binds and protects vitamin B12 to allow absorption into the ileum.