Pituitary gland: Histology

Summary

The pituitary gland is a small but crucial structure in the brain, located in the cella turcica. It is divided into the anterior and posterior pituitary, each with distinct embryological origins and functions. The anterior pituitary contains glandular tissue, responsible for secreting hormones like growth hormone and prolactin, while the posterior pituitary mainly consists of neural tissue, releasing oxytocin and ADH. The two parts are differentiated through staining techniques, with the anterior showing rich blood vessels and chromophilic cells, and the posterior showing unmyelinated axons and Herring bodies that release hormones into the bloodstream.

Takeaways

• 😀 The pituitary gland is a small, about 1 cm in diameter, located in the sella turcica at the base of the brain.
• 😀 The pituitary gland is divided into two main parts: the anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis).
• 😀 The anterior pituitary consists of glandular epithelial tissue, while the posterior pituitary is made up primarily of neural secretory tissue.
• 😀 The anterior pituitary (adenohypophysis) has two main types of cells: chromophils (which stain strongly) and chromophobes (which stain weakly).
• 😀 Chromophil cells are further divided into acidophils (which stain red and secrete growth hormone and prolactin) and basophils (which stain blue and secrete ACTH, TSH, FSH, and LH).
• 😀 The posterior pituitary is composed mostly of unmyelinated axons that transport hormones like oxytocin and ADH from the hypothalamus to Herring bodies.
• 😀 The Herring bodies are dilated nerve terminals in the posterior pituitary that release oxytocin or ADH into nearby capillaries.
• 😀 The pars intermedia, located between the anterior and posterior pituitary, contains cystic remnants of Rathke’s pouch, which is the embryological precursor of the anterior pituitary.
• 😀 Staining techniques such as Mason's Tri Chrome and H&E (Hematoxylin and Eosin) are used to differentiate the structures of the pituitary gland under a microscope.
• 😀 The anterior pituitary has a rich blood supply, while the posterior pituitary has a lighter appearance due to its neural tissue and lack of significant blood vessels.

Q & A

What is the size and location of the pituitary gland?

The pituitary gland is a small gland, approximately 1 cm in diameter, located within a saddle-shaped bone cavity at the base of the brain called the cell turcica.

What are the two main parts of the pituitary gland?

The pituitary gland is divided into two main parts: the anterior pituitary (also known as the adeno hypothesis) and the posterior pituitary (also known as the neuro hypothesis).

How do the anterior and posterior pituitary differ in structure and function?

The anterior pituitary consists primarily of glandular epithelial tissue, whereas the posterior pituitary is made up mostly of neural secretory tissue. The anterior pituitary secretes a variety of hormones, while the posterior pituitary stores and releases hormones produced in the hypothalamus.

What is the significance of the embryological origin of the pituitary gland?

The anterior and posterior pituitary have different embryological origins. The anterior pituitary develops from glandular tissue, while the posterior pituitary arises from a bud of nervous tissue from the hypothalamus.

Why does the posterior pituitary stain lighter compared to the anterior pituitary?

The posterior pituitary is composed mostly of unmyelinated axons, which lack nuclei and collagen. As a result, it stains lighter compared to the anterior pituitary, whether stained with Mason's tri-chrome or hematoxylin and eosin.

What is the pars intermedia, and what role does it play?

The pars intermedia is a thin strip of cystic tissue between the anterior and posterior pituitary. It is part of the anterior pituitary and consists of remnants of Rathke's pouch, an embryological structure that develops into the anterior pituitary.

What types of cells are found in the anterior pituitary, and how are they classified?

The anterior pituitary contains chromophils and chromophobes. Chromophils are further divided into acidophils (which stain red and produce growth hormone and prolactin) and basophils (which stain blue and secrete hormones like ACTH, LH, FSH, and TSH). Chromophobes have weakly staining cytoplasm.

How does the posterior pituitary function in hormone release?

The posterior pituitary stores and releases two hormones—oxytocin and ADH (antidiuretic hormone). These hormones are produced in the hypothalamus, travel down unmyelinated axons, and are stored in the dilated nerve terminals called Herring bodies, from where they are released into the bloodstream.

What is the role of the supporting glial cells in the posterior pituitary?

In the posterior pituitary, supporting glial cells, known as pituicytes, help maintain the structure of the tissue and provide support to the unmyelinated axons that carry oxytocin and ADH.

What is the significance of the rich blood supply to the anterior pituitary?

The anterior pituitary has a much richer blood supply compared to the posterior pituitary, with numerous small blood vessels throughout. This is essential for the secretion and regulation of various hormones produced by the anterior pituitary.