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 .
Somatic nerve plexus
- Cervicobrachial plexus , which can be divided into
- Lumbosacral plexus , which can be divided into
- 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
The largest plexuses of the autonomic nervous system are:
- Celiac plexus in the upper abdomen
- Plexus mesentericus superior (in animals it is called cranialis instead of “superior” ) in the middle abdomen
- Inferior / caudal mesenteric plexus in the lower abdomen
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:
- External carotid plexus for the sweat glands, the smooth muscles of the hair follicles, and blood vessels around the head and face
- Internal carotid plexus for Eyes ( dilator muscle of the pupil , muscle orbital , muscle tarsal ) and the lacrimal and salivary glands
- Cardiac plexus on the heart from the terminal branches of the parasympathetic vagus nerve
- Pulmonary plexus in the wall of the bronchi for the bronchi and lungs
- Gastric plexus with parasympathetic fibers for supplying the stomach
- Vesical plexus with parasympathetic fibers for the supply of the urinary bladder and the genital organs
- Plexus pelvinus for the parasympathetic supply of the rectum ( peristalsis ) and the parasympathetic supply of the internal intestinal sphincter, which is not subject to voluntary control (relaxation)
- Plexus hypogastricus superior and plexus hypogastricus inferior for the innervation of the sexual organs ( seminal vesicles , prostate , vas deferens)
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.
(see also Rete mirabile )
- Central nervous system: exit ports of the spinal nerves from the spine
- WG Forssmann, Chr. Heym: Neuroanatomie. 3rd edition, Springer, Berlin / Heidelberg / New York 1982, ISBN 3-540-11404-1 , p. 213 f.