Which layer controls motility of the digestive tract?

RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Applied Physiology

Easy

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

The muscle layer, or muscularis externa, is the primary layer responsible for motility in the digestive tract.
It consists of an inner circular and an outer longitudinal layer of smooth muscle.
The coordinated contractions of these muscle layers, known as peristalsis and segmentation, propel and mix the contents of the GI tract.
This motor activity is controlled by the myenteric (Auerbach's) plexus, which is located between the two muscle layers.

Option A: The lamina propria is a layer of connective tissue within the mucosa. It supports the epithelium and contains capillaries and immune cells but does not control the main propulsive movements of the GI tract.
Option B: The submucosa contains the submucosal (Meissner's) plexus, which primarily controls glandular secretions and local blood flow, not the large-scale motility of the entire tract.
Option D: The serosa is the outermost protective layer of the GI tract within the abdominal cavity. Its main function is to reduce friction between organs, not to generate movement.

Visual 1: Diagram: A cross-section of the intestinal wall, clearly labeling the four main layers (Mucosa, Submucosa, Muscularis Externa, and Serosa) and the nerve plexuses (Meissner's and Auerbach's). This helps visualize the location of the muscle layer and its controlling plexus.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of the layers of the gastrointestinal (GI) tract wall as background academic context rather than a clinical decision trigger.
Understanding the function of the muscle layer is crucial for comprehending motility disorders like gastroparesis (delayed gastric emptying) or paralytic ileus (cessation of intestinal peristalsis), often seen post-operatively.
Many medications, such as anticholinergics or opioids, can significantly affect the myenteric plexus, leading to decreased GI motility and constipation, a common nursing concern.
What if? If a patient has Hirschsprung's disease, there is a congenital absence of ganglion cells (including the myenteric plexus) in a segment of the colon. In this case, the affected segment cannot relax and perform peristalsis, leading to a functional obstruction.

How to Approach the Question

First, identify the key term in the question: 'motility'.
Recall the four main layers of the GI tract wall: Mucosa, Submucosa, Muscularis Externa (Muscle layer), and Serosa.
Systematically review the primary function of each layer.
Associate 'motility' (movement, peristalsis) with the muscle layer (Muscularis Externa).
Differentiate the function of the two nerve plexuses: Meissner's (submucosal) for secretion and Auerbach's (myenteric) for motility.
Select the option that directly corresponds to the function of large-scale movement.

Concept Tested & Keywords

Concept Tested: Functions of the layers of the gastrointestinal (GI) tract wall.
Stem keywords: motility, digestive tract, layer
Lead-in keywords: Which

QAwSgKEvnprVq8l8mf9phw