HUMAN MEDICAL BIOLOGY, ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 3. ANATOMICAL AND PHYSIOLOGICAL ASPECTS OF BODY FUNCTION SELF-REGULATION

BRAIN

6. DIENCEPHALON

6.1. Structure OF THE Diencephalon

The diencephalon (diencephalori) is located beneath the corpus callosum. It consists of parts such as the thalamus and Hypothalamus, with the Third ventricle forming its cavity (Fig. 3.20).

Class="center">

Fig. 3.20. The diencephalon and its topographical relations with other PARTS OF THE Brain; sagittal section (semi-schematic)

The thalamus is a paired cluster of grey matter divided into the thalamus proper, metathalamus, and epithalamus. The thalamus proper contains anterior, lateral, and medial nuclear groups. The lateral nuclei serve as Relay stations for all sensory pathways ascending to the Cerebral Cortex. Furthermore, the anterior part of the thalamus is known as the anterior tubercle, while the posterior part forms the pulvinar, which houses subcortical visual centers. The medial surfaces of the thalamus proper form the lateral walls of the third ventricle.

The metathalamus comprises the medial and lateral geniculate bodies, which act as subcortical auditory and visual centers, respectively. The medial geniculate body is connected to the inferior colliculi of the Midbrain tectum via the inferior brachium, whereas the lateral geniculate body is connected to the superior colliculi via the superior brachium.

The epithalamus consists of the Pineal Gland (pineal body), situated between the superior colliculi of the midbrain tectum. Striae medullares extend from the pineal gland, anchoring it in position. As these striae approach the thalamus, they widen to form the trigena of the habenula.

The hypothalamus is located ventral to the thalamus proper and comprises the subthalamic region along with a series of structures on the Base of the brain (Figs. 3.21, 3.22). These include the terminal lamina, optic chiasm, tuber cinereum, infundibulum (which Supports the Pituitary Gland), and mammillary bodies. The subthalamic region contains nuclei with neurosecretory Nerve Cells capable of producing Hormones (neurosecretion). This neurosecretion travels via the axons of these nerve cells into the posterior lobe of the pituitary gland and subsequently enters the bloodstream. The anterior lobe of the pituitary gland is connected to the nuclei of the posterior hypothalamus via a specialized Blood vessel system.

Fig. 3.21. Ventral surface of the frontal lobes of the cerebral hemispheres, diencephalon, midbrain, Pons, and Medulla Oblongata

Fig. 3.22. Brain (sagittal section)

The third ventricle is a narrow cleft whose lateral walls are formed by the medial surfaces of the thalamus proper (Fig. 3.22). The anterior wall of the third ventricle is formed by the columns of the fornix and the anterior commissure, the posterior wall by the epithalamus, the floor by structures of the hypothalamus, and the roof by the choroid plexus, which produces CEREBROSPINAL FLUID. The third ventricle communicates with the Lateral ventricles through the interventricular foramina and with the Fourth ventricle via the cerebral aqueduct.