Human Adrenal Glands (part of the Endocrine System)
Here is a simple summary of information about the adrenal glands. Information on this page is likely to be appropriate for first-level courses such as AS and A-Level Human Biology, ITEC Anatomy and Physiology, and other courses in Health Sciences.
The location(s) of the Adrenal Glands:
The human body normally* includes two adrenal glands.
They are located immediately anterior to the kidneys, and are encased in a connective tissue capsule that is usually partially buried in an island of fat. The adrenal glands lie beneath the peritoneum. That is, they are retroperitoneal.
The Structure of the Adrenal Glands:
The most obvious aspect of the structure of the adrenal glands is their partitioning into two distinctive components: the paler medulla (centre), and the darker cortex (surround). Both of these tissues contain many blood vessels, hence they may be described as "richly vascularized".
The medulla consists of many large columnar cells called chromaffin cells. These synthesize and secrete catecholamines.
There are also some ganglion cells. Blood from throughout the adrenal gland collects into large medullary veins to exit the gland.
The adrenal cortex consists of three concentric zones of steroid-synthesizing cells called the:
- fasiculata, and
Although the boundaries between these zones are indistinct, each of these zones has a characteristic arrangement of cells.
Simple Diagram representing the Adrenal Medulla (centre) and the Adrenal Cortex (surround):
Hormones secreted by the Adrenal Glands:
Prepares the body for 'fright, fight or flight' ('FFF') and has many effects:
Similar effects to adrenalin:
Glucocorticoids (e.g. cortisol, cortisone, corticosterone)
Mineralocorticoids (e.g. aldosterone)
See also an introduction to the endocrine system and information about aspects of it such the locations of and hormones secreted by the main endocrine glands and conditions that affect the endocrine system including diabetes.
- Introduction to the Endocrine System
- What is a hormone ?
- Water Soluble Hormones vs Fat Soluble Hormones
- Triggers for Hormone Release
- Hormone Regulation Feedback Mechanism
- Major Glands of the Endocrine System
- The Pituitary Gland
- Non-endocrine tissues that release hormones
- Conditions of the Endocrine System