Understanding the Adrenal Cortex and Medulla: A Key Component of Endocrine Functionality

The adrenal gland, located above the kidneys, plays a vital role in the body's endocrine system. It is comprised of two distinct tissue types - the adrenal cortex and medulla - each with its unique embryological origin and function. In this article, we will delve into the development, structure, and function of the adrenal cortex and medulla, highlighting their characteristics and features that make them unique to mice.

Development of Adrenal Cortex and Medulla

In mice, the adrenal cortex and medulla are fully functional at birth. The medullary cells undergo significant growth and differentiation during embryonic development, with a chromaffin reaction evident by gestation day 16 (Sass, 1996a). By gestation day 15, both cortical and medullary development is nearly complete (Yarrington, 1996).

The cortical anlage and medullary sympathoblasts are in close proximity on gestation day 12, while centrally located medullary cells are surrounded by cortical cells as they undergo further cytoplasmic differentiation on gestation day 14 (Tischler & Sheldon, 1996). The medulla originates from neural crest ectoderm, with two collections of sympathoblasts migrating along the sympathelic nerves toward the cortical anlage around the same gestational age (Sass, 1996a).

Structure and Function of Adrenal Cortex and Medulla

The adrenal cortex is formed on gestation day 11 through the condensation of celomic epithelium into the adrenogonadal primordium between the mesogastrium and urogenital fold. The mouse adrenal gland is comprised of two tissue types with distinct embryological origins - the cortex and medulla.

The adrenal cortex plays a crucial role in life, while the function of the medulla is not essential for survival. The cortex is responsible for producing various hormones, including cortisol, aldosterone, and sex steroids, which regulate metabolism, electrolyte balance, and reproductive functions. In contrast, the medulla produces catecholamines, such as epinephrine and norepinephrine, which play a role in the 'fight or flight' response.

Unique Features of Mouse Adrenal Gland

The mouse adrenal gland exhibits several species-specific histological features that distinguish it from other mammals. Notably, there is no zona reticularis and a prominent x-zone at the cortico-medullary junction, unlike in humans. Additionally, subcapsular proliferation of fusiform cells, frequent occurrence of accessory proliferative cortical nodules, and deposition of cortical lipogenic pigment are characteristic features of mouse adrenal glands.

The adrenal cortex and medulla play crucial roles in maintaining endocrine functionality, with unique embryological origins and functions that make them distinct to mice. Understanding the development, structure, and function of these tissue types provides a sound basis for assessing and interpreting changes associated with exposure to xenobiotic agents and other challenges. In conclusion, the mouse adrenal gland is an essential component of endocrine system functionality, with its unique characteristics making it a valuable model for studying endocrine development and disease.

Adrenal cortex and medulla