PITUITARY GLAND
Definition
Small pea-sized endocrine gland controlling major body hormones
Located in sella turcica of sphenoid bone
Attached to hypothalamus by infundibulum
Location
In hypophyseal fossa
Covered by diaphragma sellae
Below optic chiasma
Parts
Anterior pituitary (adenohypophysis)
Posterior pituitary (neurohypophysis)
Morphology
Oval, reddish-grey gland
Weighs about 0.5 g
Supplied by hypophyseal arteries
Drains to cavernous sinus venous system
Anterior Pituitary (Adenohypophysis)
Glandular epithelium
Produces 6 hormones
GH → growth
TSH → thyroid stimulation
ACTH → adrenal cortex stimulation
FSH, LH → gonadal function
Prolactin → milk secretion
Posterior Pituitary (Neurohypophysis)
Neural tissue
Stores and releases hypothalamic hormones
ADH → water balance
Oxytocin → uterine contraction, milk ejection
Blood Supply
Superior hypophyseal artery
Inferior hypophyseal artery
Hypophyseal portal system (important for hormone transport)
Nerve Supply
Hypothalamic axons via infundibulum (posterior lobe)
No direct nerve supply to anterior lobe
Developmental Process:
- Development of Pituitary Gland: The pituitary gland develops from two distinct sources - the anterior pituitary gland develops from an ectodermal pouch, while the posterior pituitary gland develops from a neural fold.
- Neurohypophyseal Tract: The posterior pituitary gland is connected to the hypothalamus by the neurohypophyseal tract, which allows the hypothalamus to regulate the secretion of oxytocin and ADH.
Muscle Action Sequence:
- Pituitary Gland Function: The pituitary gland functions as a master gland, regulating the secretion of hormones from other endocrine glands.
Clinical Importance
Pituitary adenoma
• Compresses optic chiasma → bitemporal hemianopia
• Causes hormone excess or deficiency
Gigantism & acromegaly
• Excess GH in children → gigantism
• Excess GH in adults → acromegaly
Cushing disease
• Excess ACTH production
Diabetes insipidus
• ADH deficiency → excess urine output
Sheehan syndrome
• Postpartum pituitary necrosis
Transsphenoidal surgery
• Pituitary commonly operated through sphenoid sinus