QS Study

The pituitary gland is a small endocrine gland situated in the hypophyseal fossa in relation to the base of the brain. It is a part of our endocrine system. Its major purpose is to emit hormones into your bloodstream. It secretes hormones that control the actions of other endocrine organs and various tissues around the body.

Shape: Oval.

Size: Anteroposteriorly – 8min and Transversely – 12min.

Weight: 500 mg.

Subdivision: These two divisions or lobes of the pituitary produce different types of hormones that are vital for normal functions of other endocrine organs and other body organs as well. It has two main parts:

(A) Adenohypophysis –

  • Anterior lobe or pars anterior.
  • Intermediate lobe or pars intermedia.
  • Tuberal lobe or pars tuberalis.

(B) Neuro hypophysis –

  • Posterior lobe (pars posterior).
  • Infundibular stem.
  • Median eminence.

Anterior lobe: The anterior lobe of the pituitary receives hypothalamic-releasing hormones from the hypothalamus that bind with receptors on endocrine cells in the anterior pituitary that regulate the release of adrenal hormones into the circulatory system.

(A) Chromophilic cells:

(a) Acidophils –

  • Somatotrophs: Secrete growth hormone.
  • Mammotrophs: Secrete lactogenic hormone.
  • Corticotrophs: Secrete ACTH.

(b) Basophils –

  • Thyrotrophs: Secrete TSH.
  • Gonadotrophs: Secrete FSH.
  • Luteotrophs: Secrete LH.

(B) Chromophobic Cells: Represent the non-secretory phase of the other cell types or their precursors.

Intermediate lobe: Made up of numerous basophil cells and chromophobe cells surrounding masses of colloid material. It secretes the melanocyte stimulating hormone (MSH).

Posterior lobe: The posterior lobe of the pituitary gland develops as an extension of the hypothalamus. As such, it is not capable of producing its own hormones; instead, it stores hypothalamic hormones for later release into the systemic circulation. Composed of –

  1. Large numbers of non-myelinated fibers &
  2. Modified neurological cells, called pituicytes.

Sub Division of Pituitary Gland 1

Fig: Sub Division of Pituitary Gland

Hormones:

  1. vasopressin (ADH),
  2. Oxytocin.

Development of pituitary gland:

(a) Adenohypophysis: Develops from the Rathke’s pouch, which is formed by the ectodermal out pocketing from the stomodeum in front of the buccopharyngeal membrane.

(b) Neurohypophysis: Develops from the down growth of the floor of the diencephalon. It is neuroectodermal.

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