38 Questions
What is the type of epithelium found in the mucosa of the esophagus?
Stratified squamous non-keratinized epithelium
What type of fibers are found in the upper one-third of the muscularis externa of the esophagus?
Skeletal muscle fibers
What is the name of the plexus found in the submucosa of the esophagus?
Plexus of Meissner
What is the type of epithelium found in the mucosa of the stomach?
Simple columnar epithelium
What are the three histological regions of the stomach?
Cardiac, fundic, and pyloric regions
What is the type of epithelium found in the serosa of the stomach?
Simple squamous epithelium
What is the primary function of the small intestine?
Absorption of nutrients
What percentage of nutrient absorption occurs in the small intestine?
90%
Which segment of the small intestine is responsible for most chemical digestion and nutrient absorption?
Jejunum
What is the name of the deep transverse folds in the intestinal lining?
Plicae circularis
What is the function of goblet cells in the small intestine?
Production of mucins
What is the name of the central lymph capillary in each villus?
Lacteal
What is the primary function of enteroendocrine cells in the small intestine?
Production of intestinal hormones
What is the name of the areas of lymphoid tissue in the submucosa?
Peyer's patches
What is the function of villi in the small intestine?
To absorb large particles into the body
What is the main function of the large intestine?
To reabsorb water and compact intestinal contents
What is the name of the first portion of the large intestine?
Cecum
What is the name of the muscle bands that run along the outer surfaces of the colon?
Taeniae coli
What is the purpose of the haustra in the colon?
To permit expansion and elongation of the colon
What is the main difference between the small intestine and the large intestine?
The large intestine has a larger diameter and thinner wall than the small intestine
What is the function of the muscularis externa in the small intestine?
To facilitate absorption and lymph movement
What is the name of the glands found in the submucosa of the duodenum?
Brunner's glands
What type of cells are mostly found in the proximal portions of gastric glands?
Parietal cells
Which of the following cells secrete pepsinogen?
Chief cells
What is the function of enteroendocrine cells in the gastric gland?
Secrete serotonin, histamine and gastrin
What is the main component of the muscularis externa in the pyloric region of the stomach?
Inner circular and outer longitudinal layer
What is the main function of the gastric glands in the fundus and body of the stomach?
To secrete gastric juice, mucus, and gastrin
Which of the following layers of the stomach contains blood vessels, lymphatics, and Meissner's plexus?
Submucosa
What is the enzyme converted from pepsinogen in the gastric lumen?
Pepsin
What is the main characteristic of the pyloric glands in the lamina propria of the pyloric region?
They extend half the thickness of the mucosa
What is characteristic of the mucosa of the large intestine?
Abundance of goblet cells
What is the function of the mucosa in the large intestine?
Provides lubrication for fecal material
What is characteristic of the Crypts of Lieberkuhn in the large intestine?
They are dominated by goblet cells
What is characteristic of the muscularis externa in the large intestine?
It forms taenia coli
What is characteristic of the vermiform appendix?
It has a large accumulation of lymphoid tissue
What is characteristic of the rectum?
It has a continuous coat of longitudinal muscle
What is characteristic of the anal canal?
It has a stratified squamous non-keratinized epithelium
What is characteristic of the mucosa in the anal canal?
It has characteristic longitudinal folds
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
This quiz covers the basic histological layers of the digestive system, including the esophagus, mucosa, submucosa, muscularis, and serosa.
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