Architectonics and structural elements
Anatomically, intramural nerve plexuses form a dense three-dimensional network inside the organ wall. This network is characterized by a high degree of branching and the formation of loops of various diameters.
The structure includes the following basic elements:
- Wide-meshed and narrow-meshed nerve fibers, which permeate the layers of the organ and ensure the transmission of impulses to effector tissues.
- Clusters of nerve cells, varying in shape and size depending on the specific region of the plexus.
- Isolated intraorgan nodes — intramural ganglia (ganglia intramuralia), which act as critical integrative centers at the local level.
Functional role of intramural ganglia
Intraorgan nodes (ganglia intramuralia) are fundamentally important for the functioning of the parasympathetic division of the autonomic nervous system. It is here that the cell bodies of the second (effector) neurons of the parasympathetic pathway are located.
Two key processes take place within the nodes of intramural plexuses:
- Termination of preganglionic parasympathetic fibers arriving from central nuclei.
- Synaptic transmission of the nerve impulse to postganglionic neurons, whose processes directly contact the smooth muscle or glands of the organ.
Sources of plexus formation
Intramural networks are not isolated; they are formed through the influx of fibers from various divisions of the nervous system. Three types of nerve fibers participate in the formation of these intraorgan structures:
- Parasympathetic preganglionic fibers — they reach the organ without interruption and terminate in local nodes. This parasympathetic component is leading within the intramural plexuses.
- Sympathetic postganglionic fibers — these fibers have already undergone relay in the paravertebral or prevertebral ganglia of the sympathetic trunk and enter the plexus ready for innervation.
- Sensory fibers (afferent) — provide reception and transmission of information regarding the state of the organ wall back to the central nervous system.
Localization in the human body
Intraorgan plexuses are unevenly developed. They are most clearly expressed in organs requiring complex autonomic regulation of tone and motility.
Main localization zones of well-developed intramural plexuses:
| Organ system | Specific organs with prominent plexuses |
|---|---|
| Cardiovascular | Walls of the heart |
| Respiratory | Trachea and bronchial tree |
| Digestive | Esophagus, stomach, small and large intestine |
| Genitourinary | Urinary bladder, uterus, vagina |
Briefly: answers to topical questions
What are the main intramural plexuses of the digestive tube wall called?
The main intramural plexuses of the digestive tube wall are the myenteric plexus (Auerbach's plexus) and the submucosal plexus (Meissner's plexus). They are formed by networks of nerve fibers, clusters of nerve cells, and individual intramural ganglia.
Which neurotransmitter is released by preganglionic fibers in intramural ganglia?
Acetylcholine is released by preganglionic fibers in intramural ganglia.
Intramural nodes are localized within the innervated organs and belong to the parasympathetic nervous system. Synaptic transmission at this level has the following features:
- Acetylcholine — the main neurotransmitter ensuring the transmission of excitation from the preganglionic to the effector neuron.
- N-cholinergic receptors — nicotinic-sensitive receptors with which the neurotransmitter interacts in the ganglia.
This mechanism of excitation transmission is identical for all autonomic ganglia.
For quick memorization of the fiber composition in the plexus, use the rule "PSC": Parasympathetic (preganglionic, also the leading ones), Sympathetic (postganglionic), Sensory.
Class and exam questions
Which nerve component is the main one in intramural plexuses?
The leading component within intraorgan plexuses is the parasympathetic one.
Where exactly do parasympathetic preganglionic fibers terminate?
They reach the organ and terminate directly in the nodes of the intramural plexuses (intramural ganglia), where they synapse onto postganglionic neurons.
In what form do sympathetic fibers enter the intramural plexus?
Unlike parasympathetic fibers, sympathetic fibers enter the intramural plexuses already as postganglionic fibers (after synapsing in other ganglia).
In which organs of the digestive system are these plexuses best developed?
They are exceptionally well developed in the walls of the esophagus, stomach, and throughout the small and large intestines.
What else to study on this topic
- Topography of intramural ganglia (ganglia intramuralia)
- Morphological differences between wide-meshed and narrow-meshed networks
- Mechanism of synaptic transmission to postganglionic neurons
- Features of sympathetic postganglionic fibers in organ walls
- Function of sensory fibers within intramural plexuses
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