The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus.
It consists of axonal fibres that run between the cerebral cortex and the pyramids of the medulla.
The internal capsule is V-shaped when cut both coronally (on the same plane as the face) and horizontally/transversely (the same plane as the brim of a top hat).
When cut horizontally:
- the bend in the V is called the "genu".
- the part in front of the genu is the "anterior limb". or crus anterius.
- the part behind the genu is called the "posterior limb" or crus posterius.
There is also a retrolenticular and a sublenticular part to the internal capsule.
- The posterior limb of the internal capsule contains corticospinal fibers and sensory fibers from the body.
- The anterior limb of the internal capsule contains:
Blood supply is similar to the other structures of the region. Striate arteries, which come off the middle cerebral artery, enter through the anterior perforated substance in the base of the brain.
Infarctions to the internal capsule tend to be small, punctate lesions.
They can affect sensory and motor systems on the opposite side of the body, and possibly eyesight (to the contralateral visual field).
Hearing should not be affected in a single capsule lesion, as this information crosses over to both sides of the brain while in the brainstem.
Deep dissection of brain-stem. Lateral view.
Superficial dissection of brain-stem. Ventral view.
Coronal section of brain immediately in front of pons.
Coronal section of brain through intermediate mass of third ventricle.
Section of brain showing upper surface of temporal lobe.
Coronal section through anterior cornua of lateral ventricles.
Coronal section of brain through anterior commissure.
Dissection showing the course of the cerebrospinal fibers.
|Brain: telencephalon (cerebrum, cerebral cortex, cerebral hemispheres)|
|Frontal lobe||Precentral gyrus (Primary motor cortex, 4)
Superior frontal gyrus/Frontal eye fields (6, 8, 9), Middle frontal gyrus (46), Inferior frontal gyrus/Broca's area (44-Pars opercularis, 45-Pars triangularis)
Orbitofrontal cortex (10, 11, 12, 47)
Prefrontal cortex, Premotor cortex
Precentral sulcus - Superior frontal sulcus - Inferior frontal sulcus - Olfactory sulcus
|Parietal lobe||Somatosensory cortex (Primary (1, 2, 3, 43), Secondary (5)), Precuneus (7m) - Parietal operculum
Parietal lobules (Superior (7l), Inferior (40)), Angular gyrus (39)
Intraparietal sulcus, Marginal sulcus
|Occipital lobe||Primary visual cortex (17), (Cuneus, Lingual gyrus, Lateral occipital gyrus (18, 19))|
|Temporal lobe||Primary auditory cortex (41, 42), Superior temporal gyrus (38, 22/Wernicke's area), Middle temporal gyrus (21), Inferior temporal gyrus (20)|
Fusiform gyrus (37) Medial temporal lobe (Amygdala, Parahippocampal gyrus (27, 28, 34, 35, 36)
|Cingulate cortex/gyrus||Subgenual area (25), Anterior cingulate (24, 32, 33), Posterior cingulate (23, 31), Retrosplenial cortex (26, 29, 30)|
|Interlobar sulci/fissures||lateral: Central (frontal+parietal), Lateral (frontal+parietal+temporal), Parietoöccipital|
medial: Medial longitudinal, Cingulate (frontal+cingulate), Collateral (temporal+occipital)
|White matter tracts||Commissural fibers - Association fibers
Internal capsule (Anterior limb, Genu, Posterior limb), Corona radiata, External capsule, Lamina terminalis, Extreme capsule, Semioval center
Olfactory tract, Terminal stria
gray: Olfactory bulb, Anterior olfactory nucleus, Basal optic nucleus of Meynert, Substantia innominata, Anterior perforated substance
Corpus striatum - Limbic lobe
|Some categorizations are approximations, and some Brodmann areas span gyri.|