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Questions and Answers
What is the type of epithelium found in the mucosa of the esophagus?
What is the type of epithelium found in the mucosa of the esophagus?
- Pseudostratified columnar epithelium
- Stratified squamous non-keratinized epithelium (correct)
- Stratified columnar epithelium
- Simple cuboidal epithelium
What type of fibers are found in the upper one-third of the muscularis externa of the esophagus?
What type of fibers are found in the upper one-third of the muscularis externa of the esophagus?
- Skeletal muscle fibers (correct)
- Cardiac muscle fibers
- Smooth muscle fibers
- Mixed muscle fibers
What is the name of the plexus found in the submucosa of the esophagus?
What is the name of the plexus found in the submucosa of the esophagus?
- Myenteric plexus
- Plexus of Henle
- Plexus of Auerbach
- Plexus of Meissner (correct)
What is the type of epithelium found in the mucosa of the stomach?
What is the type of epithelium found in the mucosa of the stomach?
What are the three histological regions of the stomach?
What are the three histological regions of the stomach?
What is the type of epithelium found in the serosa of the stomach?
What is the type of epithelium found in the serosa of the stomach?
What is the primary function of the small intestine?
What is the primary function of the small intestine?
What percentage of nutrient absorption occurs in the small intestine?
What percentage of nutrient absorption occurs in the small intestine?
Which segment of the small intestine is responsible for most chemical digestion and nutrient absorption?
Which segment of the small intestine is responsible for most chemical digestion and nutrient absorption?
What is the name of the deep transverse folds in the intestinal lining?
What is the name of the deep transverse folds in the intestinal lining?
What is the function of goblet cells in the small intestine?
What is the function of goblet cells in the small intestine?
What is the name of the central lymph capillary in each villus?
What is the name of the central lymph capillary in each villus?
What is the primary function of enteroendocrine cells in the small intestine?
What is the primary function of enteroendocrine cells in the small intestine?
What is the name of the areas of lymphoid tissue in the submucosa?
What is the name of the areas of lymphoid tissue in the submucosa?
What is the function of villi in the small intestine?
What is the function of villi in the small intestine?
What is the main function of the large intestine?
What is the main function of the large intestine?
What is the name of the first portion of the large intestine?
What is the name of the first portion of the large intestine?
What is the name of the muscle bands that run along the outer surfaces of the colon?
What is the name of the muscle bands that run along the outer surfaces of the colon?
What is the purpose of the haustra in the colon?
What is the purpose of the haustra in the colon?
What is the main difference between the small intestine and the large intestine?
What is the main difference between the small intestine and the large intestine?
What is the function of the muscularis externa in the small intestine?
What is the function of the muscularis externa in the small intestine?
What is the name of the glands found in the submucosa of the duodenum?
What is the name of the glands found in the submucosa of the duodenum?
What type of cells are mostly found in the proximal portions of gastric glands?
What type of cells are mostly found in the proximal portions of gastric glands?
Which of the following cells secrete pepsinogen?
Which of the following cells secrete pepsinogen?
What is the function of enteroendocrine cells in the gastric gland?
What is the function of enteroendocrine cells in the gastric gland?
What is the main component of the muscularis externa in the pyloric region of the stomach?
What is the main component of the muscularis externa in the pyloric region of the stomach?
What is the main function of the gastric glands in the fundus and body of the stomach?
What is the main function of the gastric glands in the fundus and body of the stomach?
Which of the following layers of the stomach contains blood vessels, lymphatics, and Meissner's plexus?
Which of the following layers of the stomach contains blood vessels, lymphatics, and Meissner's plexus?
What is the enzyme converted from pepsinogen in the gastric lumen?
What is the enzyme converted from pepsinogen in the gastric lumen?
What is the main characteristic of the pyloric glands in the lamina propria of the pyloric region?
What is the main characteristic of the pyloric glands in the lamina propria of the pyloric region?
What is characteristic of the mucosa of the large intestine?
What is characteristic of the mucosa of the large intestine?
What is the function of the mucosa in the large intestine?
What is the function of the mucosa in the large intestine?
What is characteristic of the Crypts of Lieberkuhn in the large intestine?
What is characteristic of the Crypts of Lieberkuhn in the large intestine?
What is characteristic of the muscularis externa in the large intestine?
What is characteristic of the muscularis externa in the large intestine?
What is characteristic of the vermiform appendix?
What is characteristic of the vermiform appendix?
What is characteristic of the rectum?
What is characteristic of the rectum?
What is characteristic of the anal canal?
What is characteristic of the anal canal?
What is characteristic of the mucosa in the anal canal?
What is characteristic of the mucosa in the anal canal?
Study Notes
Basic Histological Layers of the Digestive System
- The digestive system consists of four main layers: Mucosa, Submucosa, Muscularis, and Serosa
- Mucosa: composed of Epithelium, Lamina Propria, and Muscularis Mucosae
- Submucosa: contains Submucosal plexus (“Plexus of Meissner”)
- Muscularis: contains Myenteric plexus
- Serosa: outermost layer, composed of a thin layer of connective tissue and epithelium
Esophagus
- Mucosa: Stratified squamous non-keratinized epithelium
- Submucosa: contains Meissner's plexus and oesophageal glands
- Muscularis externa: composed of skeletal fibers (upper one-third), mixed fibers (middle one-third), and smooth fibers (lower one-third)
- Adventitia: loose connective tissue
Stomach
- Divided into three histological regions: Cardiac, Fundic, and Pyloric
- Mucosa: simple columnar epithelium with gastric pits
- Gastric glands:
- Found in fundus and body of stomach
- Secrete gastric juice, mucus, and gastrin
- Each gastric pit communicates with several gastric glands
- Two types of secretory cells: parietal cells and chief cells
- Cells of fundic region:
- Mucous neck cells
- Parietal (oxyntic) cells
- Chief (peptic/zymogen) cells
- Enteroendocrine cells
- Undifferentiated cells
- Parietal cells:
- Secrete intrinsic factor and hydrochloric acid (HCl)
- Mostly found in proximal portions of glands
- Chief cells:
- Secrete pepsinogen (inactive proenzyme)
- Most abundant near base of gastric gland
- Pepsinogen is converted by HCl in the gastric lumen to pepsin (active proteolytic enzyme)
Small Intestine
- Divided into three segments: Duodenum, Jejunum, and Ileum
- Mucosa:
- Characterized by Plicae circularis (valves of Kerkring)
- Villi and Microvilli
- Goblet cells (few)
- Crypts of Lieberkuhn (intestinal glands)
- Glands are lined by columnar cells, goblet cells, Paneth cells, and enteroendocrine cells
- Plays key role in digestion and absorption of nutrients
- 90% of nutrient absorption occurs in the small intestine
- Segments of the S.I.:
- Duodenum: 25 cm long, receives chyme from stomach, digestive secretions from pancreas and liver
- Jejunum: 2.5 meter long, middle segment, location of most chemical digestion and nutrient absorption
- Ileum: 3.5 meter long, final segment, joins large intestine at ileocecal valve
Intestinal Folds and Projections
- Structural modifications of the small intestine wall increase surface area
- Plicae: largest, deep transverse (circular) folds in intestinal lining, permanent features
- Intestinal Villi: series of fingerlike projections of mucosa, covered with simple columnar epithelium, which have many plasma membrane projections called microvilli
- All serve to increase surface area for absorption (altogether by 600x)
Large Intestine
- Also called large bowel
- Horseshoe-shaped, about 1.5 meters long and 7.5 cm wide
- Extends from end of ileum to anus
- Lies inferior to stomach and liver
- Functions:
- Reabsorption of water (the last 15-20%)
- Compaction of intestinal contents into feces
- Absorption of important vitamins produced by bacteria
- Storage of fecal material prior to defecation
- Parts of the Large Intestine:
- Cecum: pouchlike first portion, has wormlike appendix projecting from it
- Colon: largest portion
- Rectum: last 15 cm of digestive tract
- Anal canal
- Mucosa:
- Absence of Plicae circulares and villi
- Presence of Microvilli
- Presence of Crypts of Lieberkuhn
- Presence of Goblet cells in large number
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Description
This quiz covers the basic histological layers of the digestive system, including the esophagus, mucosa, submucosa, muscularis, and serosa.
