(pleks′ŭs )

[L., plexus, a braid]
An interwoven network of nerves, blood vessels, or lymphatics.
SEE: rete

arterial plexus

A plexus of anastomosing arteries.

Auerbach plexus

SEE: Auerbach plexus

autonomic plexus

Any of the nerve plexuses of sympathetic or parasympathetic axons, often containing autonomic neurons or ganglia and visceral afferent fibers. The plexuses typically travel on the arteries for which they are named. The large autonomic nerve plexuses are the cardiac, pulmonary, celiac, superior hypogastric, and inferior hypogastric.

basilar plexus

A venous plexus filled with anastomosing vascular channels and located in the dura that covers the clivus of the skull, under the brainstem. Rostrally, the basilar plexus connects with the cavernous sinuses, laterally with the superior and inferior petrosal sinuses, and caudally with the occipital and marginal sinuses and the vertebral venous plexuses, which continue outside the foramen magnum.

brachial plexus

A nerve plexus formed of anterior rami from spinal nerves C5-T1. Branches include: dorsal scapular, suprascapular, long thoracic, lateral pectoral, medial pectoral, thoracodorsal, subscapular (upper and lower), musculocutaneous, axillary, medial (brachial and antebrachial) cutaneous, radial, median, and ulnar. In the rearranging segments, the fibers merge to form three trunk nerves (upper, middle, and lower), and the trunks divide and merge to form divisions (anterior and posterior) and then three nerve cords (lateral, posterior, and medial).

capillary plexus

An anastomosing plexus of blood capillaries or of lymphatic capillaries (lymphatics).

cardiac plexus

The autonomic nerve plexus at the base of the heart. It is composed of parasympathetic axons from the vagus nerves, visceral afferents, and sympathetic fibers from the sympathetic trunks, and cells of the cardiac ganglion. The cardiac plexus provides both afferent and efferent axons to the heart and the great vessels.
SYN: SEE: plexus cardiacus

plexus cardiacus

SEE: Cardiac plexus.

carotid plexus

1. Any of the autonomic nerve plexuses that invest the carotid arteries. All carotid plexuses receive postganglionic sympathetic axons from the superior cervical ganglia. The external carotid plexus sends axons to the smooth muscles of the face and upper neck along branches of the external carotid artery. The internal carotid plexus sends axons to the trigeminal and ciliary ganglia, and the oculomotor, trochlear, ophthalmic, abducens, and glossopharyngeal nerves. Some axons leave the internal carotid artery at the foramen lacerum, inside the skull, to form the deep petrosal nerve, which runs to the pterygopalatine ganglion. Other carotid plexus axons continue along the anterior and middle cerebral arteries to provide sympathetic innervation to arteries of the brain.
2. A venous plexus that exits the skull through the carotid canal and interconnects the cavernous sinus inside the skull with the internal jugular vein outside the skull.

cavernous plexus

A plexus of a cavernous part of the body, including a venous plexus in the mucosa covering the superior and middle conchae of the nasal cavity, an autonomic nerve plexus at the base of the penis giving rise to large and small cavernous nerves, an autonomic nerve plexus at the base of the clitoris, and an autonomic plexus of the cavernous sinus in the skull.

celiac plexus

A dense nerve plexus along the celiac artery and the trunk of the superior mesenteric artery. The plexus interconnects the two large celiac ganglia. Its parasympathetic axons come from the vagus; the sympathetic axons come from the greater and lesser splanchnic nerves. The celiac plexus gives rise to a number of secondary autonomic plexuses including the phrenic, hepatic, left gastric, splenic, suprarenal, renal, testicular, ovarian, superior mesenteric, and inferior mesenteric plexuses.
SYN: SEE: solar plexus

cervical plexus

A nerve plexus in the cervical region, in which axons from cervical spinal nerves C1-C4 rearrange to form nerves to the neck muscles, to the diaphragm, and to the skin of parts of the head, neck, and chest. These nerves include the lesser occipital, great auricular, transverse cutaneous, supraclavicular, and phrenic nerves.

choroid plexus

A plexus of small, tufted projections into the ventricles of the brain that are made of evaginations of pia mater and their underlying blood vessels covered by a thin coat of ependymal cells. They are made of evaginations of pia mater and their underlying blood vessels covered by a thin coat of ependymal cells. These projections secrete cerebrospinal fluid.

coronary plexus

A plexus of autonomic nerve fibers that lies close to the base of the heart.

dental plexus

A plexus of sensory nerve fibers that are distributed to the teeth. The inferior alveolar nerve is distributed to the mandibular teeth; the anterior, middle, and posterior superior alveolar nerves contribute fibers to innervate the maxillary teeth.

dermal plexus

Any of the nerve plexuses containing autonomic axons and cutaneous sensory axons and found throughout the dermis of the skin.

enteric plexus

A complex autonomic nerve plexus inside the walls of the gastrointestinal tract, from esophagus to anus. The plexus contains intrinsic sensory and motor axons connected through local ganglionic interneurons. It is also joined by postganglionic sympathetic axons from external autonomic ganglia and preganglionic parasympathetic axons from the vagus nerve. This intrinsic neural network controls peristalsis, vasodilation, vasoconstriction, and secretion and absorption of substances from the intestinal lumen. The ganglion cells and axons of the enteric plexus that are found between the circular and longitudinal layers of muscles in the lamina externa are collectively called the myenteric division of the enteric plexus; the ganglion cells and axons found in the submucosa are called the submucosal division of the enteric plexus.
SEE: enteric nervous system

esophageal plexus

A nerve plexus investing the inferior aspect of the esophagus. The plexus is formed by the vagus nerves: the left vagus nerve spreads around the anterior surface of the esophagus; the right vagus nerve spreads around the posterior surface. The plexus is joined by sympathetic axons from the thoracic sympathetic trunk.

gastric plexus

Any of the secondary autonomic nerve plexuses that are derived from the celiac plexus and follow the gastric arteries to the stomach.

hemorrhoidal plexus

SEE: Rectal plexus.

inferior hypogastric plexus

ABBR: IHP A long, thin plexus descending from the superior hypogastric plexus on the right and the left sides. The inferior hypogastric plexus, which feeds into the pelvic, middle rectal, vesical, prostatic, and uterovaginal plexuses, contains sympathetic axons from the superior hypogastric plexus and the lowest lumbar splanchnic nerves and parasympathetic axons from the pelvic splanchnic nerves. The inferior hypogastric plexus (or a portion of it) is also called the hypogastric nerve or the pelvic plexus.

inferior mesenteric plexus

A secondary nerve plexus found along the inferior mesenteric artery and its branches. It is connected to the celiac plexus, and it also receives axons from the lumbar splanchnic (sympathetic) nerves. The inferior mesenteric plexus contains one or more inferior mesenteric ganglia found near the trunk of the inferior mesenteric artery.

Leber plexus

SEE: Leber, Theodor

lumbar plexus

A nerve plexus lying within and posterior to the psoas major muscle, along the posterior abdominal wall. In this plexus, axons from spinal nerves L1-L4 rearrange to form nerves to muscles of the thigh and to the skin of the lower limb. These nerves include the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, and accessory obturator nerves.

lumbosacral plexus

SEE: lumbar plexus; SEE: sacral plexus

lymphatic plexus

An anastomosing network of lymphatics.

Meissner plexus

SEE: Meissner, Georg

mucosal plexus

An autonomic nerve plexus that contains no ganglia, is found in the lamina propria in the wall of the gastrointestinal tract, and is part of the enteric nervous system.

myenteric plexus

The division of the enteric plexus found in the external muscular layer (muscularis externa) of the walls of the gastrointestinal tract.
SYN: SEE: Auerbach plexus

nerve plexus

nervous plexus A plexus of axons, fascicles of axons, or nerves outside the central nervous system.

ovarian plexus

A secondary autonomic nerve plexus that follows the ovarian artery to the ovary and the fallopian tube. This plexus is connected to the celiac plexus; it receives additional sympathetic axons from the lowest thoracic spinal segments and parasympathetic axons from the inferior hypogastric plexus.

pampiniform plexus

1. In females, a venous plexus located in the broad ligament. It intervenes between the veins draining the ovary and the final ovarian veins, which empty blood back into the systemic circulation. It is homologous to the male plexus.
2. In males, a venous plexus that surrounds the testicular artery inside the distal segment of the spermatic cord. The pampiniform plexus drains the spermatic veins. Before the spermatic cord enters the inguinal canal from the scrotum, the pampiniform plexus empties intothree or four parallel veins. After exiting the inguinal canal, these veins merge to form two testicular veins. It is homologous to the female plexus.

papillary plexus

A nerve plexus that ramifies throughout the junction between the reticular and papillary layers of the dermis of the skin. The plexus contains autonomic axons and cutaneous sensory axons.

pelvic plexus

SEE: inferior hypogastric plexus

perivascular plexus

An autonomic nerve plexus coating an artery.

pharyngeal plexus

1. A nerve plexus along the posterior surface of the middle pharyngeal constrictor muscle. The plexus contains sympathetic, parasympathetic, and somatic (branchial) axons from the pharyngeal branch of the vagus nerve, the glossopharyngeal and external laryngeal nerves, and the sympathetic trunk. Axons from the pharyngeal plexus innervate the muscles and mucosa of the pharynx and soft palate.
2. A venous plexus that interconnects with the pterygoid plexus, drains the pharynx, and empties into the internal jugular and facial veins.

prevertebral plexus

One of the plexuses of the autonomic nervous system that lie in body cavities. The plexuses are the cardiac, celiac, and hypogastric (pelvic) plexuses.

prostatic plexus

1. In males, an autonomic nerve plexus that is an extension of the inferior hypogastric plexus. It sends axons to the prostate gland, the erectile tissue of the penis, and the seminal vesicles.
2. In males, a venous plexus anterior to the bladder and prostate gland. It connects with the vesical plexus and the internal pudendal vein, and it empties into the vesical veins and internal iliac vein. Its tributaries include the deep dorsal vein of the penis.

pterygoid plexus

A venous plexus lying between the temporalis, lateral pterygoid, and medial pterygoid muscles. Many of the deeper veins of the front of the head (such as the deep temporal, sphenopalatine, inferior ophthalmic, dental veins) connect with this plexus. The plexus empties into the deep facial vein and is in communication with the cavernous sinus.

pulmonary plexus

An autonomic nerve plexus extending from the cardiac plexus into the lungs along the right and left pulmonary arteries. Parasympathetic axons come from the vagus nerves, and sympathetic axons from the sympathetic trunk. Axons from the pulmonary plexus follow the bronchi and the bronchial vessels and provide the autonomic innervation inside the lungs.

rectal plexus

1. Any of three autonomic nerve plexuses (superior plexus, middle plexus, inferior plexus) innervating the rectum. These plexuses are subplexuses of the inferior hypogastric plexus and follow the three corresponding rectal arteries.
2. Any of three venous plexuses (external plexus, internal plexus, superior plexus) in and around the rectum. The external rectal plexus empties via the internal rectal vein into the internal pudendal vein; the internal and the superior rectal plexuses empty into the superior rectal vein. The varices that form in the veins in the internal rectal plexus are called hemorrhoids.
SYN: SEE: hemorrhoidal plexus

renal plexus

A dense autonomic nerve plexus running along the renal artery, containing small ganglia whose axons follow the branches of the renal artery into the kidney.

sacral plexus

1. A nerve plexus lying along the posterior wall of the pelvis, deep to the internal iliac blood vessels and anterior to the piriformis muscle. In this plexus, axons from spinal nerves L4-S4 rearrange to form sensory and motor nerves to the thigh, leg, and foot. These nerves include the superior gluteal, inferior gluteal, posterior femoral cutaneous, sciatic, and pudendal nerves. The lower portion of the sacral plexus also gives rise to the preganglionic parasympathetic axons of the pelvic splanchnic nerves.
2. A venous plexus on the pelvic surface of the sacrum that interconnects the lateral sacral veins.

solar plexus

SEE: Celiac plexus.

subdermal plexus

A nerve plexus found in the deep dermis and between the dermis and the subcutaneous tissue, containing autonomic axons and cutaneous sensory axons.

submucosal plexus

submucous plexus The division of the enteric plexus found in the submucosal layer of the walls of the gastrointestinal tract. The most superficial layer of the submucosal plexus is also called the Meissner plexus.
SEE: Meissner plexus under SEE: Meissner, Georg

superior mesenteric plexus

A continuation of the celiac nerve plexus. It runs along the superior mesenteric artery and provides autonomic innervation to the same intestinal segments supplied by the artery.

sympathetic plexus

An autonomic plexus composed of sympathetic axons. Large sympathetic plexuses surround the midline (prevertebral) sympathetic ganglia, which are found near major midline arteries such as the celiac trunk.

thoracic aortic plexus

A nerve plexus that invests the thoracic aorta. It is composed of axons from the superior ganglia of the sympathetic trunk and with axons from the greater splanchnic nerve, the vagus nerve, and visceral afferents. This plexus is continuous with the celiac plexus caudally.

tympanic plexus

A nerve plexus along the medial wall of the tympanic cavity. The axons of this plexus come from the glossopharyngeal nerve and the caroticotympanic nerves.

vaginal plexus

1. The autonomic nerve plexus that supplies axons to the walls of the vagina.
2. A venous plexus that surrounds the vagina and empties via the internal pudendal vein into the internal iliac vein.

venous plexus

A plexus of interconnecting veins.

vertebral plexus

1. An autonomic nerve plexus that runs along each vertebral artery and carries sympathetic axons to arteries inside the skull.
2. Any of the anastomosing plexuses of valveless veins draining the vertebral column and spinal cord. Outside the spinal canal, anterior vertebral plexuses lie in front of the vertebral bodies; posterior plexuses surround the vertebral spines and other vertebral processes. Inside the spinal canal, dense vertebral plexuses run between the bone and the dura; at the top of the cord, the internal vertebral plexuses communicate with intracranial sinuses.

vesical plexus

1. An autonomic nerve plexus that is an extension of the inferior hypogastric plexus and supplies nerves to the bladder muscles and, in males, to the seminal vesicles and the ductus deferens.
2. A venous plexus surrounding and draining blood from the upper part of the urethra and the neck of the bladder. It empties via vesical veins into the internal iliac vein. In males, it connects to the prostatic plexus; in females, to the vaginal plexus.

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