34 - GI System II Flashcards
(69 cards)
What are the 4 main layers of the gastrointestinal tube?
1 - Mucosa
2 - Submucosa
3 - Muscularis externa
4 - Serosa/adventitia
Describe the serosa/adventitia
- The outermost layer of the GI tube can be either serosa or adventitia
- Most of the GI is serosa
- Both have connective tissue
Serosa has an additional component. What is it?
Mesothelium - it is found external to the muscularis externa and includues visceral peritoneum
Note that the adventitia does NOT hav a mesothelium, just an outer connective tissue component
What are the three main components of the mucosa of the GI tract?
1 - Epithelium + basal lamina
2 - Lamina propria (with glands)
3 - Muscularis mucosae
What type of epithelium would you find in the mucosa of the GI tract?
The epithelium rests on the basal lamina
- Mostly simple columnar
- The esophagus and anus have stratified squamous epithelium
What is the lamina propria of the GI mucosa?
A connective tissue layer found external to the epithelium
What type of tissue and glands are found in the lamina propria of the GI mucosa?
Lymphoid tissue and glands
Where is the muscularis mucosae found?
External to the lamina propria in the mucosa of the GI tract
Note that this muscular layer in the mucosa is separate from the muscle in the muscularis externa layer (one of the main 4 layers of the GI tract)
What type of muscle layers are found in the muscularis mucosae?
Two layers of smooth muscle
- Inner CIRCULAR layer
- Outer LONGITUDINAL layer
What are the three main components of the submucosa?
1 - Dense irregular connective tissue
2 - Glands in the esophagus and duodenum (all other glands are found in the mucosa within the lamina propria)
3 - Submucosal (Meissner’s) nerve plexus
What are the main components of the muscularis externa of the GI tract?
Muscularis externa
- Inner CIRCULAR layer
- Outer LONGITUDINAL layer
Note that most area of the GI tract will have smooth muscle
Skeletal muscle is also found in some areas of the GI tract… What areas are these?
Proximal esophagus and distal portion of the GI tube
What part of the GI tract can have three muscle layers in the muscularis externa instead of just two?
The stomach
What are the two nerve plexuses found in the GI tube?
Submucosal plexus (Meissner's) Myenteric plexus (Auerbach's)
Where is the submucosal (Meissner’s) plexus found?
Between the circular muscle layer and the muscularis mucosae
What is the function of the submucosal (Meissner’s) plexus?
- Regulate secretory cells
- Regulate blood flow within the walls of the GI tube
- Innervate the muscularis mucosae
Where is the myenteric (Auerbach’s) plexus located?
Between the longitudinal and circular muscle layers
What is the function of the myenteric (Auerbach’s) plexus?
Regulate peristalsis
What type of neurons does the submucosal (M) plexus contain? What type does the myenteric (A) plexus contain?
Both plexuses contain autonomic neurons
- Parasympathetic postganglionic neurons and processes
- Sympathetic postganglionic fibers (from outside the GI tube)
What type of epithelium is found in the esophagus?
Stratified squamous, non-keratinized epithelium
What is the function of the epithelium of the esophagus
Protects the course texture of a food bolus as it passes through the lumen of the esophagus
Where in the esophageal tissue are glands found?
- Esophageal gland proper with ducts are found in the submucosa
Are there any exceptions to where esophageal glands are located?
Yes, toward to distal and proximal ends of the esophagus, you may also find glands in the lamina propria
What would you call esophageal glands found in the lamina propria?
Cardiac esophageal glands
NOT esophageal gland proper