Anatomy of the Pituitary Gland

Introduction

• Focus on head and neck anatomy, specifically the pituitary gland.
• Emphasis on anatomical aspects rather than endocrinology.
• Understanding the three-dimensional positioning within the cranial cavity is crucial.

Location and Structure

• The pituitary gland is situated in the midline of the head.
• Bone: Lies within the sphenoid bone, specifically in the "sella turcica" (Turkish saddle).
• Position: Near the nasal cavity and in proximity to the internal carotid arteries on either side.
• Protection: Covered by dura mater, which is part of the meningeal layer (other layers include arachnoid mater and pia mater).

Connection to Hypothalamus

• Connected via the pituitary stalk (infundibulum) to the hypothalamus, located below the thalamus.
• The connection remains when the brain is removed during dissection, leaving the pituitary behind.

Blood Supply and Drainage

• Arterial Supply: Internal carotid artery; there is a hypophyseal portal system connecting capillary beds between the hypothalamus and the pituitary gland.
• Venous Drainage: Into the cavernous sinus and then into the internal jugular vein.
• Special Feature: Capillaries are fenestrated (leaky) to allow hormone passage, unlike the typical blood-brain barrier.

Pituitary Gland Parts and Hormones

• Structure: Divided into anterior lobe, intermediate lobe, and posterior lobe.
• Hormones Produced:
  • Anterior Lobe: Produces ACTH, GH, TSH, LH, FSH, and prolactin.
  • Posterior Lobe: Known as neurohypophysis, it stores and releases vasopressin (ADH) and oxytocin.
  • Intermediate Lobe: Produces melanocyte-stimulating hormone (less significant in humans).
• Developmental Origin:
  • Anterior lobe from the roof of the mouth (oral ectoderm).
  • Posterior lobe from brain (neural ectoderm).

Clinical Relevance

• Pituitary Tumors:
  • Adenomas can form from any of the hormone-producing cells, leading to overproduction of hormones such as GH, causing conditions like acromegaly.
  • Tumor growth can affect surrounding structures, including the optic chiasm.
• Impact on Vision: Enlargement of the pituitary gland can press against the optic chiasm, affecting visual fields.

Conclusion

• The pituitary gland plays a key role in endocrine regulation and has significant anatomical and physiological relationships with surrounding structures.
• Understanding its location and connections is critical for interpreting imaging (MRI, CT) and considering clinical implications.

Note:

These notes capture the key anatomical details and physiological connections related to the pituitary gland covered in the lecture. For further details on the physiological functions and clinical implications, additional resources may need to be consulted.