The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep wake cycle.
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.
The spinothalamic tract is a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus.
The intertransversarii are small muscles placed between the transverse processes of the vertebrae.
The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum.
The dorsal root of spinal nerve is one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. Nerve fibres with the ventral root then combine to form a spinal nerve. The dorsal root transmits sensory information, forming the afferent sensory root of a spinal nerve.
The semimembranosus muscle is the most medial of the three hamstring muscles in the thigh. It is so named because it has a flat tendon of origin. It lies posteromedially in the thigh, deep to the semitendinosus muscle. It extends the hip joint and flexes the knee joint.
The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee.
The lesser wings of the sphenoid or orbito-sphenoids are two thin triangular plates, which arise from the upper and anterior parts of the body, and, projecting lateralward, end in sharp points [Fig. 1].
In the spinal cord, the most lateral of the bundles of the ventral nerve roots is generally taken as a dividing line that separates the antero-lateral region into two parts: an anterior funiculus , between the anterior median fissure and the most lateral of the ventral nerve roots; and a lateral funiculus, between the exit of these roots and the posterolateral sulcus.
The anterior grey column is the front column of grey matter in the spinal cord. It is one of the three grey columns. The anterior grey column contains motor neurons that affect the skeletal muscles while the posterior grey column receives information regarding touch and sensation. The anterior grey column is the column where the cell bodies of alpha motor neurons are located.
A funiculus is a small bundle of axons, enclosed by the perineurium. A small nerve may consist of a single funiculus, but a larger nerve will have several funiculi collected together into larger bundles known as fascicles. Fascicles are bound together in a common membrane, the epineurium.
The lateral vestibular nucleus is the continuation upward and lateralward of the principal nucleus, and in it terminate many of the ascending branches of the vestibular nerve.
The rhomboid fossa is a rhombus-shaped depression that is the anterior part of the fourth ventricle. Its anterior wall, formed by the back of the pons and the medulla oblongata, constitutes the floor of the fourth ventricle.
The posterior scrotal branches or posterior labial branches are two in number, medial and lateral. They are branches of the perineal nerve, which is itself a branch of the pudendal nerve. The pudendal nerve arises from spinal roots S2 through S4, travels through the pudendal canal on the fascia of the obturator internus muscle, and gives off the perineal nerve in the perineum. The major branch of the perineal nerve is the posterior scrotal/posterior labial.
The medullary pyramids are paired white matter structures of the brainstem's medulla oblongata that contain motor fibers of the corticospinal and corticobulbar tracts – known together as the pyramidal tracts. The lower limit of the pyramids is marked when the fibers cross (decussate).
The cells of the dorsal nucleus of vagus nerve are spindle-shaped, like those of the posterior column of the spinal cord, and the nucleus is usually considered as representing the base of the posterior column. It measures about 2 cm. in length, and in the lower, closed part of the medulla oblongata is situated behind the dorsal motor nucleus of the vagus; whereas in the upper, open part it lies lateral to that nucleus, and corresponds to an eminence, named the vagal trigone, in the rhomboid fossa.
The spinal root of accessory nerve is firm in texture, and its fibers arise from the motor cells in the lateral part of the anterior column of the gray substance of the medulla spinalis as low as the fifth cervical nerve.
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. It encloses the central canal of the spinal cord, which contains cerebrospinal fluid. The brain and spinal cord together make up the central nervous system (CNS). In humans, the spinal cord begins at the occipital bone, passing through the foramen magnum and entering the spinal canal at the beginning of the cervical vertebrae. The spinal cord extends down to between the first and second lumbar vertebrae, where it ends. The enclosing bony vertebral column protects the relatively shorter spinal cord. It is around 45 cm (18 in) in men and around 43 cm (17 in) long in women. The diameter of the spinal cord ranges from 13 mm in the cervical and lumbar regions to 6.4 mm in the thoracic area.
The proper fasciculi, or spinospinal fasciculi, or propriospinal tracts, are groups of short fibres, ascending and descending, and crossed and uncrossed, within the spinal cord. These fibres are grouped into anterior, posterior, and lateral regions and make up a spinal pathway. Descending dorsal root collaterals are often included in the pathway.
