4. Histology of the Esophagus and Stomach Flashcards
What are the four general consistent layers to the G.I. tract?
1: Mucosa
2: Submucosa
3: Muscularis Externa
4: Serosa / Adventitia
What determines the difference between serosa and adventitia?
Serosa is covered by peritoneum, adventitia is retroperitoneal.
What is the lamina propria?
Vascularized loose connective tissue
What is the function and location of the muscularis mucosae?
It is located in the mucosal layer of the G.I. tract, and is a thin layer of smooth muscle which squeezes mucosal glands.
What is the submucosal layer comprised of?
Where do we see glands in the submucosal layer?
Dense irregular connective tissue with neurovasculature and lymphatics
in the esophagus and duodenum
In which layer are the muscles which aid in gastrointestinal peristalsis located?
In the muscularis externa.
Of the two layers to the muscularis externa – a circumferential and a longitudinal layer – which is the outer layer, and which is the inner layer?
The inner layer of the muscularis externa is circumferential
The outer layer of the muscularis externa is longitudinal
Where are the neurovascular plexes located in the muscularis externa?
Between the inner circular and outer longitudinal layers of muscle.
What nerves make up the parasympathetic portion of the extrinsic nervous system of the G.I.?
The vagus nerve – up to the splenic flexure
The pelvic splanchnics – after the splenic flexure
Are the fibers from the vagus nerve and pelvic splanchnics presynaptic or postsynaptic?
They are presynaptic
What nerves provide sympathetic autonomic innervation to the G.I.?
Branches from the greater, lesser, least, and lumbar splanchnic nerves.
Where do the sympathetic nerves for the G.I. synapse?
The celiac, superior mesenteric, inferior mesenteric, and aorticorenal ganglia.
What is the location and function of the plexus of Meissner?
The (submucosal) plexus of Meissner is located in the submucosa, and controls glandular secretion via control of the muscularis mucosae.
What is the location and function of the myenteric plexus of Auerbach?
The myenteric plexus of Auerbach is located in between the layers of the muscularis externa and controls peristalsis.
In terms of motility of the G.I., what would be the function of a presynaptic axon?
Preganglionic axons (of the parasympathetics) increase motility.