In pars dorsaIis there is formatio reticularis pontis which is continuation of a retikulyarny formation of a medulla, and over a retikulyarny formation — the bottom of a diamond-shaped pole covered ependimy with the kernels of cranial nerves lying under it.
The external pyramidal layer strongly varies on width, the sizes of neurons, consists of pyramidal neurons. The sizes of neurons increase in depth, settling down in the form of the columns divided by radial bunches of fibers. Especially well this layer is developed in a pretsentralny crinkle.
In ventralny departments of the bridge ahead of longitudinal pyramidal bunches cross going surface fibers of the bridge which in total form the top bunch of the bridge settle down. More dorsalno between pyramidal bunches there are cross fibers of the bridge, fibrae pontis transcersae going to back departments of pedunculus cerebellaris medius; they form the lower bunch of the bridge.
All space between gray substance of brain bark and bazalny kernels is occupied with white substance. It consists of a large amount of the nervous fibers going in various directions and forming the carrying-out ways of a final brain: it connects bark of one crinkle with bark of other crinkles of the and opposite hemispheres, and also with underlying educations. Nervous fibers can be divided into three systems: associative, komissuralny and projective fibers.
Back median and back lateral furrows limit back, funiculus posterior which is continuation of the bunch of the same name of a spinal cord. The intermediate furrow divides back into two bunches. One bunch lies between it and a back median furrow, a thin bunch, fasciculus gracilis passing above into a thickening, a hillock of a thin kernel, tuberculum nuclei gracilis, another — also between an intermediate furrow and a back lateral furrow, a wedge-shaped bunch, fasciculus cuneatus which is also passing above into less expressed wedge-shaped hillock, tuberculum nuclei cuneati.
The external molecular layer – light, contains few cellular elements, strongly varies on width. Consists generally of apikalny dendrites of pyramidal layers and neurons of a spindle-shaped form scattered between them.
Outside hillocks (as well as all plate) are roofed by a thin layer of white substance. In the thickness of hillocks the congestion of gray substance which in top is called as a gray layer of the top hillock, of stratum griseum colliculi superioris, and in the lower hillock — a kernel of the lower hillock, nucleus colliculi inferioris lies.
Nicleus olivaris, olive kernel, has an appearance of an izvity plate of gray substance open medially, and causes outside protrusion of an olive. It is connected with a gear kernel of a cerebellum and is the intermediate kernel of balance which is the most expressed at the person which vertical situation needs the perfect device of gravitation.
The roof of a midbrain, tectum mesencephali is hidden under the back end of a calloused body and is subdivided by means of two flutes going cross-wise — longitudinal and cross — into four hillocks. It: two top hillocks, colliculi superiores, right and left, larger, and on lower dvukholmy which two lower hillocks, colliculi inferiores, also right and left, but the smaller sizes, than top enter. The top hillocks, colliculi superiores, are the subcrustal centers of sight, lower, colliculi inferiores — the subcrustal centers of hearing.
In both of these thickenings congestions of gray substance lie: in a hillock of a thin kernel — a thin kernel, nucleus gracilis, in a wedge-shaped hillock — a wedge-shaped kernel, nucleus cuneatus. In cages of these kernels fibers of the corresponding bunches of a back kanatik come to an end. Immediately at the top end of a back lateral furrow, over backs of a yazyko-pharyngeal nerve, in the form of continuation of back and lateral kanatik the thickening, the lower cerebellar leg, pedunculus cerebellaris inferior settles down a semicircular form. The lower cerebellar legs limit dorsalno and lateralno a diamond-shaped pole, fossa rhomboidea.
The medulla, medulla oblongata, is derivative a back brain bubble or a diamond-shaped brain, rhombencephalon which at a further stage of five bubbles becomes a medulla, myelencephalon.