Three swellings develop in the lateral walls of the third ventricle, later becoming the epithalamus, thalamus and hypothalamus. The roof of diencephalon gives rise to the plexus choroideus and epiphysis. The downward extension of the diencephalon forms the infundibulum (future stalk and the pars nervosa of the hypophysis). Lateral evagination of diencephalon participates in the formation of the eye.

1. Lateral ventricle
2. Choroid plexus
3. Foramen of Monro
4. 3rd ventricle
5. Ependymal roof of the 3rd ventricle
6. Corpus striatum
7. Hypothalamus
8. Neopallium
9. Hippocampus

The hypophysis or pituitary gland develops entirely from the ectoderm derived from two sources: ectodermal outpocketing of the stomodeum, known as Rathke's pouch and a downward extension of the diencephalon, the infundibulum.
Rathke's pouch appears during the fourth week and loses its connection with the oral cavity by the end of the 8th week.
The cells of the Rathke's pouch increase rapidly in number and give rise to the adenohypophysis (the anterior lobe), pars tuberalis and pars intermedia. The infundibulum gives rise to the stalk, and the neurohypophysis (the posterior lobe).

1. Oral cavity
2. Infundibulum
3. Rathke's pouch
4. Notochord
5. Diencephalon













1. Anterior lobe
2. Lumen of diencephalon
3. Pars nervosa
4. Sphenoid bone
5. Pars intermedia