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22.5B: Submucosa

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  • Page ID
    8038
  • The submucosa is a dense, irregular layer of connective tissue with large blood vessels, lymphatics, and nerves that supports the mucosa.

     

    LEARNING OBJECTIVES

     

    Describe the submucosa of the GI tract

     

    KEY TAKEAWAYS

    Key Points

     

    • The absorbed elements that pass through the mucosa are picked up from the blood vessels of the submucosa.
    • In the gastrointestinal tract, the submucosa is the layer of dense, irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle (fibers that run circularly within a layer of longitudinal muscle).
    • Tiny parasympathetic ganglia are scattered around to form the submucosal plexus (or Meissner’s plexus) where preganglionic parasympathetic neurons create synapses with postganglionic nerve fibers that supply the muscularis mucosae.

     

    Key Terms

     

    • parasympathetic ganglia: The autonomic ganglia of the parasympathetic nervous system; they lie near or within (respectively) the organs they innervate.
    • lymphatic: The system that carries a clear fluid called lymph that is formed from interstitial fluid collected through the capillaries.
    • nerve: A bundle of neurons with their connective tissue sheaths, blood vessels, and lymphatics.

     

    The Layers of the GI tract

     

    The GI tract is composed of four layers. Each layer has different tissues and functions. From the inside out they are called:

    1. Mucosa
    2. Submucosa
    3. Muscularis
    4. Serosa

     

    The Submucosa

     

    The submucosa is relatively thick, highly vascular, and serves the mucosa. The absorbed elements that pass through the mucosa are picked up from the blood vessels of the submucosa.

    The submucosa also has glands and nerve plexuses. The submucosa lies under the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer, the muscularis externa.

    The stomach is illustrated, with a closeup view of the layers of stomach lining: the mucosa, submucosa, muscularis, and serosa.

    Layers of stomach lining: Stomach. The serosa is labeled at far right, and is colored yellow.

    The Muscularis

    The muscularis in the stomach differs from that of other GI organs in that it has three layers of muscle instead of two. Under these muscle layers is the adventitia—layers of connective tissue that are continuous with the omenta.

    The general structure of the gut wall is illustrated.

    General structure of the gut wall: The general structure of the gut wall is illustrated.

    The submucosa consists of a dense irregular layer of connective tissue with large blood vessels, lymphatics, and nerves that branch into the mucosa and muscularis externa. It contains Meissner’s plexus, an enteric nervous plexus, situated on the inner surface of the muscularis externa.

    In the gastrointestinal tract, the submucosa is the layer of dense irregular connective tissue or loose connective tissue that supports the mucosa. It also joins the mucosa to the bulk of underlying smooth muscle (fibers running circularly within layer of longitudinal muscle).

    Blood vessels, lymphatic vessels, and nerves (all supplying the mucosa) will run through here. Tiny parasympathetic ganglia are scattered around forming the submucosal plexus (or Meissner’s plexus) where preganglionic parasympathetic neurons create synapses with the postganglionic nerve fibers that supply the muscularis mucosae.