A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. The thoracic duct usually begins from the upper aspect of the cisterna chyli, passing out of the abdomen through the aortic hiatus into first the posterior mediastinum and then the superior mediastinum, extending as high up as the root of the neck before descending to drain into the systemic (blood) circulation at the venous angle.
In human anatomy, the spinal canal, vertebral canal or spinal cavity is an elongated body cavity enclosed within the dorsal bony arches of the vertebral column, which contains the spinal cord, spinal roots and dorsal root ganglia. It is a process of the dorsal body cavity formed by alignment of the vertebral foramina. Under the vertebral arches, the spinal canal is also covered anteriorly by the posterior longitudinal ligament and posteriorly by the ligamentum flavum. The potential space between these ligaments and the dura mater covering the spinal cord is known as the epidural space. Spinal nerves exit the spinal canal via the intervertebral foramina under the corresponding vertebral pedicles.
The vertebral vein is formed in the suboccipital triangle, from numerous small tributaries which spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas.
The pterygoid plexus is a fine venous plexus upon and within the lateral pterygoid muscle. It drains by a short maxillary vein.
The superficial temporal vein is a vein of the side of the head which collects venous blood from the region of the temple. It arises from an anastomosing venous plexus on the side and top of the head. The superficial temporal vein terminates within the substance of the parotid gland by uniting with the maxillary vein to form the retromandibular vein.
The deep cervical vein is the vena comitans of the deep cervical artery. The vein is formed in the suboccipital region by the convergence of communicating branches of the occipital vein, veins draining the suboccipital muscles, and veins from the venous plexuses that surround cervical nerves. The vein and corresponding artery then pass in between the semispinalis capitis muscle and the semispinalis colli muscle. The vein passes anterior-ward in between the transverse process of the 7th cervical vertebra and the neck of the first rib to terminate in the vertebral vein.
The posterior spinal artery arises from the vertebral artery in 25% of humans or the posterior inferior cerebellar artery in 75% of humans, adjacent to the medulla oblongata. It is usually double, and spans the length of the spinal cord. It supplies the grey and white posterior columns of the spinal cord.
The inferior cervical ganglion is one of the three cervical sympathetic ganglia. It is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib, on the medial side of the costocervical artery.
The lumbar veins are four pairs of veins running along the inside of the posterior abdominal wall, and drain venous blood from parts of the abdominal wall. Each lumbar vein accompanies a single lumbar artery. The lower two pairs of lumbar veins all drain directly into the inferior vena cava, whereas the fate of the upper two pairs is more variable.
The internal vertebral venous plexuses lie within the vertebral canal in the epidural space, embedded within epidural fat. They receive tributaries from bones, red bone marrow, and spinal cord. They are arranged into four interconnected, vertically oriented vessels - two situated anteriorly, and two posteriorly:
The basivertebral veins are large, tortuous veins of the trabecular bone of vertebral bodies that drain into the internal and external vertebral venous plexuses.
The intervertebral veins accompany the spinal nerves through the intervertebral foramina to drain the internal vertebral venous plexuses into the external vertebral venous plexuses. They drain into vertebral vein, intercostal veins, lumbar veins, and lateral sacral veins. Upper posterior intercostal veins may additionally drain via brachiocephalic vens. They may drain to ascending lumbar veins. They may drain into the inferior vena cava directly, reaching it by winding around the surface of the vertebral body.
The spinal veins are situated in the pia mater and form a minute, tortuous, venous plexus.
The prevertebral fascia is the layer of deep cervical fascia that surrounds the vertebral column. It is the deepest layer of deep cervical fascia.
The posterior atlantooccipital membrane is a broad but thin membrane extending between the to the posterior margin of the foramen magnum above, and posterior arch of atlas below. It forms the floor of the suboccipital triangle.
Anterior spinal veins are veins that receive blood from the anterior spinal cord.
The following outline is provided as an overview of and topical guide to human anatomy:
The marginal sinus is a dural venous sinus surrounding the margin of the foramen magnum inside the skull, accommodated by the groove for marginal sinus. It usually drains into either the sigmoid sinus, or the jugular bulb. It communicates with the basilar venous plexus anteriorly, and the occipital sinus posteriorly ; it may form extracranial communications with the internal vertebral venous plexuses, or deep cervical veins.
