Flashcards in Lecture 15: Introduction to G.I. Tract Physiology Deck (144)
List the layers of the gut tract wall from outer to inner.
> longitudinal smooth muscle layer
> myenteric plexus (of Auerbach)
> circular smooth muscle layer
> Meissner's plexus (submucosal plexus)
Which of the two layers of the gut tract wall is composed of contractile tissue?
- Longitudinal smooth muscle layer
- Circular smooth muscle layer
Contractile tissue of the G.I. tract is almost entirely smooth muscle except in which two places?
- upper third of esophagus (skeletal muscle)
- anal sphincter (skeletal muscle)
Is the serosa layer continuous with the mesentery?
Yes - is the pathway for blood vessels to the gut tube.
What kind of tissue is the serosa layer replaced with in some missing parts (i.e., esophagus)?
Replaced with advetitia connecting to abdominal wall.
What is the serosa layer?
Outer layer of connective tissue and simple squamous epithelium.
What is the submucosa layer similar to, but thinker?
Similar to lamina propria (q.v.), but thicker.
What does the submucosa layer incorporate?
Incorporates blood vessels and submucosal plexus.
What does the mucosa layer form?
Forms a continuous sheet lining entire G.I. tract.
Does the mucosa layer of the G.I. tract include the lamina propria?
Yes - loose CT with sensory nerves, blood vessels, and some glands.
You know that the lamina propria is included in the mucosa layer, but what is found in the lamina propria?
Loose CT with sensory nerves, blood vessels, and some glands.
Is the muscularis mucosa included in the mucosa layer?
What is the muscularis mucosa?
- This layer of smooth muscle.
- Creates mucosal ridges and folds.
What does the muscularis mucosa of the mucosa layer create?
Creates mucosal ridges and folds.
What does the mucosa layer of the G.I. tract support?
Supports simple columnar epithelium with goblet cells which lines entire gut tract.
Which two plexuses collectively form the enteric nervous system of the gut tract?
- Myenteric plexus
- Meissner's plexus
True or False:
The enteric nervous system of the gut tract can operate autonomously via intrinsic regulation and sensory reflexes.
You know that the enteric nervous system of the gut tract works with sympathetic and parasympathetic (mostly vagus nerve) systems. What does the parasympathetic and sympathetic system generally cause with respect to G.I. tract activity?
Parasympathetic system -> increases GI tract activity
Sympathetic system -> decreases GI tract activity
What cell type supports neurons of the enteric nervous system?
Neurons are supported by intrinsic glial cells.
Where is the Myenteric (Auerbach's) plexus located?
Located between longitudinal and smooth muscle layers.
What does the Myenteric (Auerbach's) plexus primarily control?
Intestinal smooth muscle.
What does the Myenteric (Auerbach's) plexus participate in?
Participates in tonic and rhythmic contractions.
What type of interconnecting neurons does the Myenteric (Auerbach's) plexus consist of?
Linear chain of interconnecting neurons.
Does the Myenteric (Auerbach's) plexus extend the entire length of the G.I. tract?
True or False:
Myenteric (Auerbach's) plexus is mostly excitatory (Ach/NO).
What neurotransmitters are used by the Myenteic (Auerbach's) plexus?
- Acetylcholine (Ach)
- Nitric Oxide (NO)
True or False:
Some inhibitory signals may inhibit intestinal sphincter muscles (VIP?).
What are the effects from stimulation of the Myenteric (Auerbach's) plexus?
- Increased tonic contraction of gut wall.
- Increased intensity of rhythmical contractions.
- Slightly increased rate of thythmical contraction.
- Increased velocity of excitatory waves.
What does the Meissner's (submucosal) plexus mainly control?
- Controls mainly G.I. secretion, absorption, and local blood flow.
- Mainly concerned with controlling function within inner wall of each minute segment of the intestine.
- Helps in control of local secretion, local absorption, and local contraction of submucosal muscle.