The Digestive System (II) - The Alimentary Canal (Esophagus through Large Intestine) Flashcards
What are the four basic layers of the gut wall? What major regions define each layer?
- Serosa/adventitia (outermost)
- Muscularis externa (two or three layers of smooth muscle)
- Submucosa (above muscularis mucosa)
- Mucosa (innermost - epithelium and lamina propria and muscularis mucosa)
What three layers make up the mucosa?
epithelium, lamina propria, muscularis mucosae
What two layers make up the muscularis externa?
inner circular layer and outer longitudinal layer
What two layers make up the serosa?
areolar tissue and mesothelium
List the order of the layers of the alimentary canal.
Mucosa - Epithelium
Mucosa - Lamina Propria
Mucosa - Muscularis Mucosae
Submucosa
Muscularis externa - Inner Circular Layer
Muscularis externa - Outer Longitudinal Layer
Adventitia
Serosa - Areolar Tissue
Serosa - Mesothelium
What is the primary function and composition of the mesentaries?
these translucent serous membranes loosely bind organs to the abdominal wall preventing the small intestine from entanglement
in close association with the serosa and peritoneum (serous membrane lining the abdominal cavity)
What two plexuses compose the enteric nervous system?
submucosal plexus and the myenteric plexus
What is the submucosal plexus responsible for?
regulaton of mucosal tension and folding, and secretion of mucosal glands
What is the myenteric plexus responsible for?
regulation of peristalsis and of the submucosal plexus
What is the name and function of the two sphincters of the esophagus? What is the name of the opening into the stomach?
Upper Esophageal Sphincter - keeps air out of the digestive tract by holding the upper end closed when there is no active swallowing
Lower Esophageal Sphincter - constriction that keeps the churning stomach from pushing contents back upwards into the esophagus
*Cardiac Orifice - the opening where the esophagus empties into the stomach (named for its proximity to the heart on the other side of the diaphragm)
What two glands are present in the walls of the esophagus?
submucosal glands
esophageal (cardiac or mucosal) glands
What three gland types are present in the stomach?
Cardiac Glands, Pyloric Glands, Gastric Glands
What cell types are present in the gastric glands of the stomach? (5)
- Stem Cells
- Mucous Neck Cells
- Parietal (Oxyntic) Cells – egg-like appearance
- Chief (Zymogenic) Cells – between parietal cells, not as distinct in borders
- Enteroendocrine Cells (>8 kinds)
What are the various types of secretions the cells of the stomach are responsible for? (6 Secretions)
Hydrochloric Acid - Parietal Cells
Intrinsic Factor - Parietal Cells
Pepsinogen - Chief Cells
Gastric Lipase & Chymosin - Chief Cells
Hormones and Paracrines - Enteroendocrine Cells
Mucus - Mucous Neck Cells
What is the purpose of Hydrochloric Acid?
- activates pepsin and lingual lipase
- breaks up connective tissue and plant fiber (collagen and cellulose)
- converting Fe 3+ to Fe 2+ (absorbable form)
- Nonspecific disease (antibacterial, antiparasitic) resistance
What is a stomach ulcer?
A wound within the stomach where epithelial cells are corroded and the underlying tissue is damaged by stomach acid - can result in gastric bleeding
Which of the following cells does not have a digestive function?
Parietal Cells
Oxyntic Cells
Chief Cells
Mucus Neck Cells
Mucus Neck Cells - secrete mucous only
What are the divisions of the small intestine?
Starts at the pyloric sphincter
Duodenum, Jejunum, Ileum
Ends at ileocecal valve
Where can you find the submucosal plexus?
within the submucosa, with connective tissue and blood vessels
Where can you find the myenteric plexus?
Within the muscularis externa
Which of the following cells do not have a digestive function?
Parietal Cells
Chief Cells
Mucus Neck Cells
Oxyntic Cells
Mucus Neck Cells - secrete mucous only
What four things contribute to surface area of the inestines?
Length, Circular Folds, Villi and Microvilli (forming brush border)
How much of the small intestine is portioned to each of the three segments?
Duodenum - first 25 cm
Jejunum - first 40% postduodenum
Ileum - last 60% postduodenum
What is the name of the lower spaces between villi? What is a specific cell characteristic of this region?
Intestinal Crypts
Paneth Cells - secrete antibacterial lysozyme
What are the elaborations of the microvilli and what are they made up of?
Glycocalyx - composed of carbohydrates
What are some characteristics of the Duodenum?
circular folds are absent of small, duodenal glands called “Brunner’s” Glands lie directly beneath the villi
What are some characteristics of the Jejunum?
lacking duodenal glands or Peyer patches - not lacking circular folds but rather having abundant folding
What are some characteristics of the Ileum?
circular folds present, shorter villi, greater number of lymphocytes - having Peyer patches with ~10-200 lymphoid nodules each = GALT system on the anti-mesenteric side of the ileum
Describe the differences between the cardiac, fundic, and pyloric stomach(s).
