Difference Between Adrenal Cortex and Adrenal Medulla

The key difference between adrenal cortex and adrenal medulla is that adrenal cortex is the outer region of the adrenal gland that secretes steroid hormones while adrenal medulla is the centre of the adrenal gland that secretes epinephrine and norepinephrine.

Adrenal gland is a small triangular organ located just above the kidney. Therefore, there are two adrenal glands in humans. They are endocrine glands, which secrete different hormones. Adrenal gland has two main parts: adrenal cortex and adrenal medulla. Adrenal cortex is the outer region of the adrenal gland while adrenal medulla is the inner region of the adrenal gland. Adrenal cortex produces steroid hormones whereas adrenal medulla produces epinephrine and norepinephrine.

CONTENTS

1. Overview and Key Difference
2. What is Adrenal Cortex 
3. What is Adrenal Medulla
4. Side by Side Comparison – Adrenal Cortex vs Adrenal Medulla in Tabular Form
5. Summary

What is Adrenal Cortex?

Adrenal cortex is the outer region of the adrenal gland. It is triangular in shape. There are three layers in the cortex. Zona glomerulosa is the outermost layer which occupies 10% of the cortex area. Zona fasiculata is the middle layer, and it is the major portion of the adrenal cortex and occupies 80% of the cortex. Zona reticularis is the innermost layer, and it occupies about 10% of the cortex.

Adrenal cortex secretes different types of steroid hormones. Zona glomerulosa secretes aldosterone, which is important in reabsorption of sodium ions in the distal convoluted tubule. Zona fasiculata secretes cortisol, which is important in increasing glucose in the body. Zona reticularis, on the other hand, secretes androgens, especially testosterone, which are male hormones.

What is Adrenal Medulla?

Adrenal medulla is the inner region of the adrenal gland. It is mainly composed of chromaffin cells. In fact, they are the cell bodies of postganglionic sympathetic nervous system neurons. Chromaffin cells of adrenal medulla secrete catecholamines known as epinephrine and norepinephrine, which prepare the body for emergencies, the so-called “fight-or-flight” responses. Catecholamines work as hormones as well as neurotransmitters of the nervous system. Catecholamines are mainly responsible for managing body responses for stress.

Hormones epinephrine and norepinephrine signal the liver and skeletal muscle to convert glycogen into glucose and increase blood glucose level. Moreover, they are important in increasing heart rate, pulse, and blood pressure. Furthermore, these hormones are responsible for dilating airways in order to raise blood oxygen levels.

What are the Similarities Between Adrenal Cortex and Adrenal Medulla?

• Cortex and medulla are two main parts of the adrenal gland.
• Both parts secrete hormones.

What is the Difference Between Adrenal Cortex and Adrenal Medulla?

Adrenal cortex is the outer region of the adrenal gland, and it secretes steroid hormones. On the other hand, adrenal medulla is the inner region of the adrenal gland, and it secretes amine hormones. So, this is the key difference between adrenal cortex and adrenal medulla. Moreover, adrenal cortex occupies 90% of the total adrenal weight while adrenal medulla occupies 10% of the total adrenal weight. Besides, the adrenal cortex secretes aldosteron, cortisol and androgens while adrenal medulla secretes epinephrine and norepinephrine.

The following table summarizes the difference between adrenal cortex and adrenal medulla.

Summary – Adrenal Cortex vs Adrenal Medulla

Adrenal cortex and adrenal medulla are the two main parts of an adrenal gland. Adrenal cortex occupies a major portion of the adrenal gland, bearing 90% of the adrenal weight. It is the outer region of the adrenal gland composed of three different layers. Adrenal medulla is the inner region composed of chromaffin cells. It occupies 10% of the adrenal weight. Adrenal cortex secretes steroid hormones while adrenal medulla secretes amine hormones, especially catecholamines. So, this is the summary of the difference between adrenal cortex and adrenal medulla.

Reference:

1. Utiger, Robert D. “Adrenal Gland.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 4 Oct. 2019, Available here.
2. “The Adrenal Glands .” Anatomy and Physiology, OpenStax, 6 Mar. 2013, Available here.

Image Courtesy:

1. “Adrenal cortex labelled” By Jpogi – Unlabelled here (CC0) via Commons Wikimedia
2. “1818 The Adrenal Glands” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia