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Pituitary Gland

Hypophysis

For medical students2 min readUpdated 2026-10-10

The pituitary gland (hypophysis) is an exceptionally small yet critically vital endocrine organ located at the base of the brain. It has a complex dual embryonic origin and is functionally divided into two main parts: the adenohypophysis and the neurohypophysis.

TopographyHypophysial fossa of the sella turcica of the sphenoid bone
CapsuleCapsule of dense fibrous connective tissue
WeightAbout 0.5 g in adults
HormonesADH and oxytocin (in secretory granules)

Topography and Macroscopic Structure

The pituitary gland (hypophysis) is an organ that, despite weighing only about 0.5 g in humans, plays a crucial role in regulating body functions.

Anatomically, this gland is located in a specialized bony depression — the hypophysial fossa of the sella turcica (sella turcica) of the sphenoid bone. For protection, the entire organ is enclosed externally by a tough capsule formed of dense fibrous connective tissue.

In relation to the brain, the pituitary is situated on its inferior surface. Directly superior to the organ lies the tuber cinereum (tuber cinereum). The connection between them is maintained via the pituitary stalk, inside of which runs the infundibulum (infundibulum). The infundibulum has a tapering cavity that is a direct topographical continuation of the third ventricle of the brain.

Structurally and embryologically, the pituitary is divided into two main parts:

Microscopic Connection with the Hypothalamus

At the microscopic level, the function of the organ is inextricably linked to the hypothalamus. This functional connection is realized through neurosecretion and axonal transport.

In the cytoplasm of specialized neurosecretory cells of the hypothalamus (for example, cells of the supraoptic nucleus), secretory granules are formed and accumulated. These granules contain hormones — vasopressin (antidiuretic hormone, or ADH) and oxytocin.

Processes (axons) extending from the cell bodies of these neurosecretory cells project directly into the tissues of the posterior pituitary lobe — the neurohypophysis. It is via these axons that neurohormones are transported, ensuring reliable functional integration of the hypothalamus and the pituitary gland.

Embryogenesis (Development)

The pituitary gland is distinguished by its unique dual origin during embryonic development. The organ forms from two completely different primordia growing toward each other:

  1. Ectodermal primordium (grows upward). It forms as an invagination of the ectoderm of the developing embryo's oral cavity (stomodeum). This epithelial pouch forms the hypophysial pouch, or Rathke's pouch. Later, the entire adenohypophysis develops from its structures.
  2. Neural primordium (grows downward). This primordium descends from the diencephalon and gives rise to the cellular and fibrous structures of the neurohypophysis.

Mnemonic

Rathke's pouch reaches up from the oral ectoderm like hands to the light (Adenohypophysis). The neural tube grows down from the brain to form the Neurohypophysis.

Frequently asked questions

What subdivisions are distinguished within the adenohypophysis upon histological examination?

The adenohypophysis comprises three structural components:

  • Anterior lobe (pars anterior) — the largest part of the pituitary gland.
  • Intermediate lobe (pars intermedia) — a narrow strip of tissue containing follicles, separated from the anterior lobe by the hypophysial cleft.
  • Tuberal part (pars tuberalis) — a poorly developed extension of the anterior lobe closely applied to the pituitary stalk.

All these parts develop from the epithelial tissue of the embryonic oral cavity.

What cells form the glial framework of the neurohypophysis parenchyma?

The glial framework of the neurohypophysis parenchyma is formed by pituicytes. These are small, branched glial cells (a type of specialized astrocyte) comprising up to 30% of the volume of the posterior lobe. They form a supporting framework (stroma) for the lobe, weaving into three-dimensional networks. Pituicyte processes envelop the axons and terminals of neurosecretory cells. Their main functions include structural support, trophic support, and direct participation in regulating the release of neurosecretions (ADH and oxytocin) into the blood.

What are Herring bodies and in which part of the pituitary gland are they located?

Herring bodies are neurosecretory accumulations representing large dilations of the axons of hypothalamic neurosecretory cells. They are located in the posterior lobe of the pituitary gland (neurohypophysis), in the region of axon terminals and axovasal synapses. In these structures, neurohormones synthesized in the supraoptic and paraventricular nuclei of the anterior hypothalamus — vasopressin (antidiuretic hormone) and oxytocin — are stored and depoted before being released into the bloodstream.

How is the portal (hypophyseal portal) blood supply system of the pituitary organized?

The hypophyseal portal system is a venous portal system:

  1. The superior hypophysial artery enters the median eminence and breaks up into a primary capillary network.
  2. Hypothalamic neurons terminate on these capillaries with axovasal synapses, releasing releasing hormones (releasing factors) and release-inhibiting hormones.
  3. The capillaries converge into 10–12 portal veins that run down the pituitary stalk and reach the anterior lobe of the pituitary.
  4. There, they break up into a secondary sinusoidal capillary network, delivering hormones to adenocytes.
  5. Capillaries of the secondary network drain into the efferent anterior hypophysial veins.
What hormones are produced by basophilic endocrinocytes of the adenohypophysis?

Basophilic adenocytes of the anterior pituitary secrete tropic hormones that regulate the functions of other glands:

  • Thyrotrophs — produce thyroid-stimulating hormone (TSH), which stimulates thyroid hormone production by the thyroid gland.
  • Gonadotrophs (FSH cells) — secrete follicle-stimulating hormone (FSH). In females, it stimulates oogenesis and estrogen synthesis; in males, it activates spermatogenesis.
  • Gonadotrophs (LH cells) — produce luteinizing hormone (LH), which stimulates corpus luteum development and progesterone secretion in females.
What hormones are secreted by acidophilic cells of the anterior pituitary lobe?

Acidophilic (oxyphilic) cells of the anterior pituitary secrete two main hormones depending on their functional population:

  • Somatotrophs — produce growth hormone (somatotropin). These cells are characterized by small granules. Growth hormone stimulates cell division and somatic growth.
  • Lactotrophs (mammotrophs) — secrete prolactin (mammotropin). These cells are characterized by very large granules. This hormone enhances mammary gland growth and milk secretion during and after pregnancy, and also supports corpus luteum function and progesterone production in some species.
Where exactly are granules containing vasopressin and oxytocin synthesized and located?

Granules containing these hormones are located in the cytoplasm of hypothalamic neurosecretory cells (e.g., in the supraoptic nucleus), from where they are transported via axons to the neurohypophysis.

What type of tissue makes up the capsule of the pituitary gland?

Externally, the pituitary gland is securely covered by a capsule consisting of dense fibrous connective tissue.

From which embryonic primordium does the adenohypophysis develop?

The adenohypophysis originates from the ectodermal primordium — an invagination of the oral ectoderm that forms Rathke's pouch (hypophysial pouch).

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