Basal ganglia, White Mater and Lateral Ventricle

Exercise 6 Transverse section of the brain Neuroanatomy Basal ganglia, White mater and Lateral ventricle A: Transverse section of the brain (at the level of lat. sulcus & 3rd ventricle) The section is surrounded by cortex of the frontal lobe anteriorly, the temporal and parietal lobes laterally and the occipital lobe posteriorly. On the midline the hemispheres are divided by longitudinal fissure and are connected by genu (ant.) and splenium (post.) of the corpus callosum. The septum pleucidum, fornix, and cavum of the third ventricle are visible between the genu and splenium. On the anterior part of the section the frontal horns of the lateral ventricles are seen (close to the midline), separated by the septum pleucidum. The lateral walls of the frontal horns are formed by head of caudate nucleus, the lentiform nucleus is lens form shaped and the anterior limb of internal capsule (white mater) located between it and caudate nuclei. On the middle part of the section the 3rd ventricle is visible and can be seen at the midline just behind the frontal horn of lateral ventricle. The interventricular foramen (monro) may be seen. The thalami lie on each side of the 3rd ventricle, the posterior limb of internal capsule separates the thalami from globus pallidus, which is situated medially, and putamen lies laterally (of lentiform nucleus). Part of the internal capsule between anterior and posterior limbs is known as the genu. A thin sheet of gray mater, the claustrum can be seen lateral to the putamen. Separated from it by the external capsule and separates from the insula by extreme capsule. The insula is the floor of the lateral sulcus. On the posterior part of the section the posterior part of the temporal lobes and the occipital lobes can be seen. Trigon of the lateral ventricle between the parietal and occipital horns is visible and part of choroid plexus may be seen. B: Basal nuclei (ganglia) Page 1 Basal nuclei (ganglia) are the masses of gray mater situated deep to the cortex (subcortical) near the base of each cerebral hemisphere. It consists of caudate nucleus, lentiform nucleus amygdala and claustrum. Exercise 6 Transverse section of the brain Neuroanatomy Basal ganglia, White mater and Lateral ventricle Caudate nucleus has head and tail, the head is located lateral to the frontal horn of the lateral ventricle. The first part of the tail forms the lateral border of the floor of the central part of the lateral ventricle and ends to the amygdaloid body in temporal lobe (deep to the uncus) Lentiform nucleus is lens shaped and lies lateral to the thalamus. It includes the putamen laterally and globus pallidus medially. lentiform nucleus and caudate nucleus together called corpus striatum. Claustrum, a thin layer of gray mater lies between the putamen and insular cortex. The claustrum is bounded by external and extreme capsule. Amygdaloid body (amygdala) situated in the temporal lobe anterior to hippocampus and deep to the uncus of parahippocampal gyrus. C: White mater of the hemispheres: there are three types as follows: 1) Commissural fibers, which connect corresponding area of the two hemispheres, such as the corpus callosum and anterior commissure. 2) Projecting fibers, which join the cortical areas to subcortical areas such as internal capsule. This capsule has anterior and posterior limbs and genu is between them. 3) Association fibers, which connects different parts of the cortex of same hemisphere. An example is cingulum which are the fibers deep to cingulate gyrus. D: Lateral ventricle Page 2 The lateral ventricle is a C-Shaped cavity found within each hemisphere. Each ventricle consists of four parts: (horns) which is located in four lobes of the brain: the central part (body) located in the parietal lobe, has a flat roof formed by corpus callosum. The floor is formed by dorsal surface of the thalamus, which is covered by choroid plexus, the lateral part of the floor formed by caudate nucleus (part of the striatum). The thalamostriate vein and stria terminalis located between thalamus and caudate Exercise 6 Transverse section of the brain Neuroanatomy Basal ganglia, White mater and Lateral ventricle nucleus (part of striatum) on the floor. The frontal horn (ant.) located anterior to the interventricular foramen which connects lateral and 3rd ventricles. Page 3 The septum pellucidum forms the medial wall, and head of the caudal nucleus forms lateral wall of frontal horn. In the occipital horn (post.) the calcar avis which corresponds to the calcarine sulcus lies on the medial wall of the occipital horn. The temporal horn (inf.) part of the floor is formed by triangular area called collateral trigon which extend backward to occipital horn. The collateral eminence on the trigon is created by collateral sulcus on the inferior surface of the brain. The hippocampus occupies the floor and medial wall along its entire length of temporal horn, the enlarged anterior end is called pes hippocampus. The fimbria lies along its medial border of hippocampus and continues backward as crus of fornix at the posterior end of the hippocampus beneath the splenium. The choroid plexus of the lateral ventricle is U-shaped which is continues in central part and temporal horn. The frontal and occipital horns have no choroid plexus.