Human Anatomy - Kotsan I. Y. 2009

Brain
Hypothalamus

The Hypothalamus forms the lower sections of the Diencephalon and participates in The formation of the floor of the Third ventricle. The hypothalamus includes the optic chiasm, optic tract, tuber cinereum with the infundibulum and Pituitary Gland, as well as the mamillary bodies (Fig. 247).

The optic chiasm (chiasma opticum) is located posterior to the terminal lamina of the cerebral hemispheres. It appears as a transversely oriented ridge formed by the fibers of the optic nerves (cranial nerve II), which partially cross to the opposite side (forming the decussation). On each side, laterally and posteriorly, this ridge continues into the optic tract.

The optic tract (tractus opticus) lies medially and posteriorly to the anterior perforated substance, curves around the cerebral peduncle laterally, and terminates with two roots in the subcortical visual centers. The lateral ROOT approaches the lateral geniculate body, while the medial root extends to the superior colliculus of the Midbrain tectum.

The tuber cinereum is situated behind the optic chiasm. The optic tracts are located on the sides of the tuber cinereum, and the mamillary bodies lie posteriorly. Inferiorly, the tuber cinereum extends into the infundibulum, which connects to the pituitary gland (see "Endocrine glands"). The walls of the tuber cinereum are formed by a thin lamina of Gray matter containing the tuberal nuclei (nuclei tuberales).

The mamillary bodies (corpora mamillaria) are located between the tuber cinereum anteriorly and the posterior perforated substance posteriorly. They appear as two small spherical white structures, each 0.5 cm in diameter. White matter is located on the outside of the mamillary body, while gray matter is contained within, featuring the medial and lateral mamillary nuclei (nuclei corporis mamillaris mediales et laterales). The columns of the fornix terminate in the mamillary bodies.

The hypothalamus features three main regions containing clusters of nerve Cell groups that vary in shape and size: the anterior region (regio hypothalamica anterior), the intermediate region (regio hypothalamica intermedia), and the posterior region (regio hypothalamica posterior). The clusters of Nerve Cells in these regions form more than 30 hypothalamic nuclei.

The nerve Cells of the hypothalamic nuclei have The ability to produce a secretion (neurosecretion) that can be transported along the processes of these same nerve cells to the region of the pituitary gland. Such nuclei are termed neurosecretory nuclei of the hypothalamus. The anterior region of the hypothalamus contains the supraoptic Nucleus (nucleus supraopticus) and the paraventricular nuclei (nuclei paraventriculares). The Cell processes of these nuclei form the hypothalamo-hypophysial tract, which terminates in the posterior lobe of the pituitary gland. Among the group in the posterior region of the hypothalamus, the largest are the medial and lateral mamillary nuclei (nuclei corporis mamillaris mediales et laterales) and the posterior hypothalamic nucleus (nucleus hypothalamicus posterior). The group of nuclei in the intermediate hypothalamic region includes: the arcuate nucleus (nucleus arcuatus); the ventromedial and dorsomedial hypothalamic nuclei (nuclei hypothalamicus ventromedialis et dorsomedialis); the dorsal hypothalamic nucleus (nucleus hypothalamicus dorsalis); the infundibular nucleus (nucleus infundibularis); the tuberal nuclei (nuclei tuberales), and others.

The hypothalamic nuclei are connected by a rather complexly structured system of afferent and efferent pathways. Consequently, the hypothalamus exerts a regulatory influence on numerous autonomic Functions of the body. The neurosecretion of the hypothalamic nuclei can influence the function of the glandular cells of the pituitary gland by enhancing or inhibiting the secretion of A number of Hormones, which in turn regulate The activity of other endocrine glands.

The presence of neural and humoral connections between the hypothalamic nuclei and the pituitary gland makes it possible to combine them into the hypothalamo-hypophysial system.