diencephallon

What are the components of the diencephalon?

Thalamus,

Hypothalamus,

Epithalamus,

Subthalamus,

Metathalamus

General description of the diencephalon

Part of the nervous system,

complex structure,

composed of multiple elements (thalamus, hypothalamus, etc.)

Shape and structure of the thalamus

Two ovoid masses of grey substance,

long axis converges anteriorly

What is adhesio interthalamica?

Junction where the two thalami may join medially

Anterior end of thalamus

→ Thalamic tubercle

Posterior end of thalamus

Pulvinar (more voluminous, “cushion”)

What is located supero-laterally on the thalamus?

Caudate nucleus

Structures between caudate nucleus and thalamus

Thalamostriate vein,

Stria terminalis (white matter band)

What covers the superior surface laterally and medially?

Laterally: lateral ventricle,

Medially: third ventricle

What is the zonal layer?

Strip of white substance,

extends between thalamic striae,

covers lateral part of superior surface

What is lamina affixa?

Ventricular ependyma over zonal layer

What is stria medullaris?

White matter band running anteroposteriorly on medial side

What is thalamic taenia?

Condensation formed by ependyma of ventricle III on stria medullaris

Supero-lateral relation of thalamus

Caudate nucleus

Superior relation of thalamus

Lateral ventricle

Supero-medial relation

Body of fornix

Medial relation

Third ventricle

Lateral relations of thalamus

External lamina medullaris,

Reticular thalamic nucleus,

Internal capsule (posterior limb),

Lenticular nucleus

Anterior relation

Interventricular foramen (Monroe)

Infero-anterior relation

Hypothalamus

Infero-posterior relation

Subthalamic area → continues to midbrain

Function of intralaminar nucleus

Divides thalamus into: Anterior, Medial, Lateral nuclei

white matter

Definition of hypothalamus

Mass of grey matter,

surrounds lower 1/3 of third ventricle,

inferior to hypothalamic groove

Location of hypothalamus (interpeduncular fossa)

Between: Optic chiasm,

plane posterior to mammillary bodies (posterior perforated substance, PCA branches)

Boundaries around infundibulum root

Anterior: median eminence,

Lateral: lateral eminence,

Posterior: postinfundibular eminence

Layers of hypothalamic nuclei (frontal section)

Periventricular,

Medial,

Lateral

Structures separating hypothalamic layers

Fornix columns,

Mammillothalamic tract,

Retroflex beam

Preoptic area location

Anterior hypothalamus,

posterior to lamina terminalis,

between anterior commissure and optic chiasm

Nuclei of preoptic area

Preoptic periventricular,

Medial preoptic,

Lateral preoptic

General description of epithalamus

Rudimentary structure, linked to olfactory reflex pathways

Location of epithalamus

Posteroinferior roof of third ventricle, posterior and superior to thalamus

Components of epithalamus

Habenular nuclei,

Stria medullaris,

Posterior commissure,

Interstitial nuclei,

Pineal gland (epiphysis)

Location of subthalamus

Between thalamus and midbrain

Components of subthalamus

Subthalamic nucleus (Luys),

Zona incerta,

Prerubral nuclei,

Lenticular loop nuclei

Location of metathalamus

Posteroinferior to thalamus, border of diencephalon and midbrain

Components of metathalamus

Lateral geniculate body → optic pathway,

Medial geniculate body → acoustic pathway (4th neuron)

What is the third ventricle?

Cavity inside diencephalon,

dilation of Sylvian canal

Lateral wall of third ventricle

Superior 2/3: medial surface of thalamus,

Inferior 1/3: medial surface of hypothalamus,

Inferior angle: infundibulum

Communication of third ventricle

Interventricular foramen (Monroe) → lateral ventricles,

Opening of Sylvian canal