Congenital Anomalies Re- lated to the Development of Pituitary Gland

Congenital Anomalies Related to the Development of Pituitary GlandPharyngeal Hypophysis. Rarely, a small part of the stalk of the Rathke’s pouch fails to disappear. Such a remnant may give rise to pituitary tissue in 

the roof of the oropharynx. When present,· this abnormally located tissue is called pharyngeal hypophysis. Craniophanyngiomas. These are
tumours that may arise from a remnant of Rathke’s pouch. They may develop in the roof of the pharynx or in the basisphenoid bone, but their most com-
mon location is above the sella turcica.Craniophanyngiomas may damage the healthy pituitary tissue and cause pituitary dysfunction. They may also pro-
duce symptoms by pressure on neighboring structures, eg, optic atrophy or hydrocephalus.


The telencephalon consists of a median portion and two lateral out- pouchings called cerebral vesicles. The median portion forms the anterior end
of the third ventricle and is closed by the lamina terminalis. The cerebral vesicles are primordia of the cerebral hemispheres. The cavity within each
-primitive cerebral hemisphere is .known as lateral ventricle. The lateral ventricles communicate with the cavity of the third ventricle through the interventricu lar foramina.
Initially each developing cerebral hemisphere consists mainly of – two parts: (i) a thick basal part, which, gives rise to the corpus striatum, and (ii) a
thin part, called pallium, which forms rest of the wall of the cerebral hemisphere. The pallium is the future cerebral cortex.

The neuroblasts in the mantle layer of the basal part of each cerebral vesicle proliferate and give rise to a large mass of gray matter that bulges into the lateral ventricle. The nerve fibers going to and coming from the cerebral cortex pas through the corpus striatum and ffe~and of white matter called internal capsule. The internal capsule divides the corpus striatum into two parts: (i) a dorsomedial portion called caudate nucleus, and (ii) a ventrolateral part called lentiform nucleus. The lentiform nucleus becomes subdivides further into a _ lateral part called putamen and a medial part known as globus pallidus. As each 

cerebral hemisphere expands, its me dial wall approaches the lateral wall of the diencephalon, so that the caudate nucleus and thalamus come in close
contact with each other.
Initially the roof plate of the telencephalon forms dorsal part of each cerebral hemisphere. However, as a result of disproportionate growth of different parts of the hemisphere, the roof plate is displaced medially, so that it becomes attached to the roof of the dienaphalon. This part of the medial wall of the developing hemisphere consists of a layer of ependymal cells covered by vascular pia mater. This becomes folded into each lateral ventricle along the choroidal fissure and gives rise to’ the choroid plexus of the lateral ventricle.
As the development proceeds, the cerebral hemispheres grow rapidly and expand in various directions, so that ultimately four lobes can be distin-
guished in each hemisphere. The hemisphere expands anteriorly to form the frontal lobe, then laterally and superiorly to form the parietal lobe and
finally posteriorly and inferiorly to for the occipital and temporal lobes. The lateral ventricles follow the development of the cerebral hemispheres and,
eventually, a part of the ventricle lies in each lobe of the hemisphere. The body of the lateral ventricle lies within the parietal lobe of the hemisphere,
whereas the anterior, posterior and inferior horns extend into the frontal, occipital and temporal lobes, respectively.
Initially the surface of the cerebral hemispheres is smooth. However, as the hemispheres grow, the cerebral cortex folds into an increasingly com- plex pattern of gyri (elevated convolutions) separated by sulci (grooves). These gyri and sulci allow a substantial increase in the surface area of the cortex without requiring a great increase in the size of the cranium. The cerebral cortex covering the external surface of the corpus striatum grows relatively more slowly than rest of the cortex. This area, therefore, soon becomes depressed and is called insula. Later, the insula is overgrown by the neighboring frontal, parietal and temporallobes. By the time of birth, the insula is completely hidden from view and lies in the depth of the lateral sulcus.

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