MedCourseFinder

Structure

Pituitary gland

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The pituitary gland (hypophysis) is a pea-sized endocrine gland at the base of the brain that controls several other endocrine glands. It has two functionally distinct parts, the anterior (adenohypophysis) and posterior (neurohypophysis) lobes.

Terminologia Anatomica (Latin): Hypophysis; Glandula pituitaria · Open in the 3D atlas

Location

It lies in the hypophyseal fossa (sella turcica) of the sphenoid bone, below the hypothalamus and connected to it by the infundibulum (pituitary stalk). The optic chiasm lies just above and in front, the cavernous sinuses (with CN III, IV, V1, V2, VI and the internal carotid artery) lie on either side, and the sphenoid sinus lies below.

Structure

The anterior lobe (derived from Rathke pouch, an ectodermal outgrowth of the oral cavity) contains somatotrophs, lactotrophs, corticotrophs, thyrotrophs and gonadotrophs. The posterior lobe (neural ectoderm) comprises axons of hypothalamic neurones from the supraoptic and paraventricular nuclei with their terminals, and pituicytes.

Blood supply

The superior hypophyseal arteries (from the internal carotid) feed the primary capillary plexus in the median eminence, which drains through the hypophyseal portal veins to a secondary plexus in the anterior lobe, carrying hypothalamic releasing and inhibiting hormones. The inferior hypophyseal arteries mainly supply the posterior lobe. Venous blood drains to the cavernous sinuses.

Innervation

The anterior lobe has no direct neural connection with the hypothalamus; control is by the portal vascular link. The posterior lobe is innervated by the hypothalamo-hypophyseal tract, whose axons release antidiuretic hormone (ADH, vasopressin) and oxytocin. Sympathetic fibres from the carotid plexus innervate the gland vasculature.

Function

The anterior lobe secretes GH, prolactin, ACTH, TSH, FSH and LH under hypothalamic releasing and inhibiting hormones with negative feedback from target glands. The posterior lobe stores and releases ADH (water reabsorption) and oxytocin (uterine contraction, milk ejection).

Clinical correlations

Pituitary adenomas (prolactinoma is the most common functioning type) may cause hormone excess (acromegaly, Cushing disease, hyperprolactinaemia) or hypopituitarism; suprasellar extension compresses the optic chiasm, producing classical bitemporal hemianopia. Posterior lobe dysfunction causes diabetes insipidus or SIADH. Pituitary surgery often uses a transsphenoidal approach.

Common exam points

  • Lies in the sella turcica below the optic chiasm; adenoma gives bitemporal hemianopia.
  • Anterior lobe from Rathke pouch; posterior lobe from neural ectoderm (infundibulum).
  • Hypophyseal portal system links the median eminence to the anterior lobe.
  • Posterior lobe stores ADH and oxytocin made in the supraoptic and paraventricular nuclei.
  • Cavernous sinus relations: CN III, IV, V1, V2, VI and internal carotid artery.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Williams Textbook of Endocrinology. Elsevier, 14th edition (2019) — Tier 3 (textbook)

References are listed only where the article cites them. See the sources page for the full policy. How sources are chosen and credited

Back to the index