Cross Section of Cerebrum Through Internal Capsule
Here is the cross section/ horizontal section of the cerebrum passing through the internal capsule. The section is taken at the level of interventricular foramen. The interventricular foramen connects the lateral ventricles with the third ventricle.
In this specimen we can identify the following structures:
- Genu of corpus callosum
- Internal capsule
- Lentiform nucleus
- Optic radiation
- Auditory radiation
- Anterior horn of lateral ventricle
- Rostrum of corpus callosum
- Caudate nucleus
The corpus callosum is the largest commissure of the brain connecting the cerebral cortex of the two cerebral hemispheres. The parts of the corpus callosum are rostrum, genu, trunk/body and splenium. The genu and the splenium can be appreciated in the midline in the horizontal section of the cerebrum. The genu is located anteriorly and medial to the frontal lobes while the splenium is located posteriorly and medial to the occipital lobes.
The corpus callosum is mainly responsible for the transfer of interhemispheric information that is essential for bilateral responses and in learning processes.
The internal capsule is a compact bundle of projection fibers (white matter) between the thalamus and caudate nucleus medially and the lentiform nucleus laterally. It connects the cerebral cortex to subcortical structures such as the corpus striatum, thalamus, brain stem and spinal cord. The parts of the internal capsule are anterior limb, genu, posterior limb, retrolentiform form part and sublentiform part.
The ascending (sensory) and descending (motor) fibers of the internal capsule mainly interconnect the cerebral cortex with the brainstem and spinal cord. These fibers are responsible for the sensory and motor innervation of the opposite half of the body.
The caudate nucleus is a large comma shaped mass of grey matter which surrounds the thalamus. Its whole length of convexity projects into the cavity of lateral ventricle. It is made up of three parts, the head, body and tail. It is an intricate part of a system of grey matter nuclei responsible for the regulation and production of movement called the basal ganglia. The basal ganglia include the corpus striatum, claustrum and amygdaloid body. The caudate and lentiform nuclei are the parts of the corpus striatum.
The lentiform nucleus is a large lens-shaped mass of grey matter beneath the insula. It forms the lateral boundary of the internal capsule. In the horizontal section of the cerebrum, it appears wedge-shaped with a broad convex base directed laterally. It consists of two parts, namely the putamen and globus pallidus. The putamen lies lateral to the globus pallidus.
The thalami are a pair of ovoid diencephalic structures located bilaterally, with respect to the third ventricle. Functionally, the thalamus is considered as the great sensory gateway (except olfactory) to the cerebral cortex. The thalami act as a relay station for afferent and efferent fibers communicating between the cortex and subcortical and structures. It is separated from the putamen by the posterior limb of the internal capsule.