Pituitary Gland Development

Study Notes

Develops from two ectodermal sources: Rathke's pouch (anterior lobe) and infundibular process (posterior lobe)
Rathke's pouch, an ectodermal pouch, forms the anterior lobe (adenohypophysis)
The pouch diverticulum grows towards the infundibulum during the third week
Forms a vesicle connected to the stomodeal roof by a stalk
The stalk disappears by the second month
Infundibular process, another ectodermal pouch, forms the posterior lobe (neurohypophysis)
Originates from the neuroectoderm of the diencephalon floor
Grows downward
Upper part becomes the pituitary stalk
Lower part develops into the pars nervosa (posterior lobe)
The infundibular recess remains patent in the third ventricle

The anterior wall thickens to form the pars distalis
The posterior wall thins to form the pars intermedia
The cavity of the vesicle becomes the pituitary cleft
The pars tuberalis extends upward from the pars distalis and wraps around the infundibular stalk

Agenesis: Absence of the pituitary gland, often fatal
Hypoplasia: Small pituitary gland size, potentially causing pituitary dwarfism
Absence of the anterior lobe: Development failure of Rathke's diverticulum
Ectopic lobe: Anterior lobe misplaced along Rathke's pouch
Pharyngeal hypophysis: Remnant of Rathke's pouch attached to oropharyngeal roof
Craniopharyngioma: Tumour originating from Rathke's pouch remnants, potentially causing hydrocephalus and pituitary dysfunction

Develops from a small ectodermal diverticulum arising from the posterior third ventricle
During the seventh week of intrauterine life, the ependymal area of the third ventricle thickens and forms a diverticulum
Initially, a hollow mass, it eventually becomes solid
Connects to the thalamus via a stalk divided into superior and inferior laminae
Congenital anomalies:
- Agenesis (absence of the pineal gland): Genetic mutations in the PAX6 gene are associated with fragmented sleep-wake patterns