Pituitary gland

Pituitary gland is located within the sella turcica of the sphenoid bone.

Anterior and posterior pituitary lobe

Adenohypophysis	Neurohypophysis
75% of the gland Ectodermal origin from roof of the stomodeum Three components: Pars tuberalis includes Portion of the infundibular stalk Median eminence of hypothalamus Pars intermedia Pars distalis: majority of the gland, has no direct arterial supply	25% of the gland Diencephalic origin Three components: Pars nervosa (posterior lobe) Infundibulum Nuclei (supraoptic and paraventricular)

Hypophyseal portal system

• Hypophyseal portal system is formed by the superior hypophyseal arteries (supraclinoid ICA) and the inferior hypophyseal arteries (branch of cavernous ICA meningohypophyseal trunk).
• These arteries join in and around the pituitary stalk and form sinusoids that feed the infundibulum and the anterior pituitary gland.
• The superior hypophyseal artery supplies the infundibulum and the median eminence.
• The inferior hypophyseal artery supplies the posterior pituitary lobe.

Superior hypophyseal artery

• several small arteries arising from the posteromedial portion of the intradural ICA
• They course beneath the optic nerve to supply:
  • Pituitary (anterior pituitary lobe, pituitary stalk) and tuber cinereum
  • Optic nerve and chiasm (inferior surface)

Inferior hypophyseal a.

• ⇒ posterior lobe of pituitary
• postpartum occlusion causes pituitary infarcts (Sheehan's necrosis): however, DI is rare because the stalk is spared