Plexus (medicine)

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The plexus ( Latin for “braid”; plural “the plexus” with a long u ) describes a network of nerve fibers or blood vessels in anatomy . A nerve plexus or nerve plexus is created when nerve branches protruding from the spine unite before the nerve fibers bundled in a plexus branch again, for example into the internal organs or the extremities .

Nerve plexus

Somatic nerve plexus

Voluntary motor and sensory nerve fibers form one on each side:

  • Cervicobrachial plexus , which can be divided into
    • Cervical plexus for the muscles and sensitivity of the back of the head and neck, formed from the nerve roots C1 to C4
    • Brachial plexus for the muscles and sensitivity of the shoulder and arm , formed from the nerve roots C5 to Th1
  • Lumbosacral plexus , which can be divided into
    • Lumbar plexus for hip and leg , formed from the nerve roots Th12 to L4
    • Sacral plexus formed primarily from the L5 and S1 nerve roots, with motor and sensory fibers for the leg; most of the fibers of the sacral plexus unite to form the sciatic nerve
  • Plexus pudendus with vegetative nerve fibers for the bladder, genital organs and rectum, formed from the nerve roots S2 to S4

In humans, the cervical plexus and brachial plexus have no connection and are therefore not collectively referred to as the cervicobrachial plexus .

Furthermore, the supply of the genitals is regulated by the pudendal nerve , which in humans originates from the sacral plexus. The regulation of stool and urine emptying ( defecation and micturition ) is controlled by the sphincter muscles and the pelvic floor muscles . Apart from the internal anal sphincter and the internal urinary bladder sphincter , which are regulated by the vegetative nervous system, innervation comes from a small coccyx plexus (segments Co1 to Co2 / Co3).

Vegetative nerve plexus

Vegetative plexuses and ganglia of the abdomen.

The largest plexuses of the autonomic nervous system are:

The first two together are also called the solar plexus or plexus solaris . They contain sympathetic fibers for the bowels in the abdomen: stomach, liver, spleen, pancreas, kidneys, adrenal glands, small intestine, initial part of the large intestine

They are located at the branches of the three large arteries, the celiac trunk, superior / cranial mesenteric artery and inferior / caudal mesenteric artery from the abdominal aorta . Smaller plexuses go from them to the individual organs . The sympathetic fibers come from the spinal cord in the chest and lumbar region, the parasympathetic fibers from the vagus nerve and from the cross part of the spinal cord.

Vegetative plexus also arise from interweaving of the vegetative nerve fibers in the immediate vicinity of the end organs:

The intestinal nervous system consists of scattered nerve cells in the wall of the entire trunk intestine and causes peristalsis . This over the entire hull intestines scattered neurons are also called Plexus, however, correspond morphologically not the definition of a vegetative plexus (see above). A distinction is made between a submucosal plexus (Meissner) in the tela submucosa of the trunk intestine and a myenteric plexus (Auerbach) in the tunica muscularis, between the circular stratum and the longitudinal stratum of the smooth intestinal muscles.

Vascular plexus

(see also Rete mirabile )

Venous plexus

Individual evidence

  1. Central nervous system: exit ports of the spinal nerves from the spine
  2. ^ WG Forssmann, Chr. Heym: Neuroanatomie. 3rd edition, Springer, Berlin / Heidelberg / New York 1982, ISBN 3-540-11404-1 , p. 213 f.