Difference Between Adrenal Cortex and Adrenal Medulla

Main Difference – Adrenal Cortex vs Adrenal Medulla

Adrenal glands are situated on top of the kidney. The adrenal gland consists of distinct zones or layers of cells. The outermost layer of the adrenal gland is called the adrenal cortex, and the innermost layer of the adrenal gland is called adrenal medulla. Both adrenal cortex and adrenal medulla produce and secrete hormones. The adrenal cortex secretes glucocorticoids, mineralocorticoids, and androgens. The adrenal medulla secretes epinephrine and norepinephrine. The main difference between adrenal cortex and adrenal medulla is that adrenal cortex helps to release energy from proteins and fats for chronic responses whereas adrenal medulla helps to mediate acute responses.

Key Areas Covered

1. What is Adrenal Cortex
     – Definition, Anatomy, Physiology
2. What is Adrenal Medulla
     – Definition, Anatomy, Physiology
3. What are the Similarities Between Adrenal Cortex and Adrenal Medulla
     – Outline of Common Features
4. What is the Difference Between Adrenal Cortex and Adrenal Medulla
     – Comparison of Key Differences

Key Terms: ACTH, Adrenal Cortex, Adrenal Gland, Adrenal Medulla, Adrenaline, Aldosterone, Cortisol, Noradrenaline, Sympathetic Nervous System

What is Adrenal Cortex

The adrenal cortex is the outer part of the adrenal gland. It produces two major groups of hormones: glucocorticoids and mineralocorticoids. The release of the glucocorticoids is mediated by pituitary gland and hypothalamus. The release of mineralocorticoids is mediated by signals of the kidney. The corticotrophin-releasing hormone (CRH), produced by the hypothalamus stimulates the pituitary gland to release the adrenal corticotrophic hormone (ACTH). The ACTH stimulates the adrenal cortex to produce and secrete glucocorticoid hormones. The two types of glucocorticoid hormones secreted by the adrenal cortex are hydrocortisone (cortisol) and corticosterone. Cortisol regulates the metabolism of the body in response to the stress. It also controls blood pressure and the cardiovascular system. The corticosterone regulates the immune responses of the body along with the cortisol.

The location of the adrenal gland is shown in figure 1.

Figure 1: Adrenal Gland

Aldosterone is a major type of mineralocorticoid. Aldosterone regulates the water and salt balance of the body, controlling the blood pressure. Sex hormones are also secreted by the adrenal cortex. These sex hormones have a less impact than the major sex hormones.  

What is Adrenal Medulla

The adrenal medulla is the inner part of the adrenal gland. The function of the adrenal medulla is not essential for the survival. Adrenal medulla helps to regulate physical and emotional stress. The release of the hormones from the adrenal medulla is mediated by the sympathetic nervous system. The fight-or-flight response of the body is mediated by hormones secreted by the adrenal medulla.

Adrenal cortex and medulla are shown in figure 2.

Figure 2: Adrenal Cortex and Adrenal Medulla

The two hormones called epinephrine (adrenaline), and norepinephrine (noradrenaline) are the hormones secreted by the adrenal medulla. Adrenaline increases the blood glucose levels and heart rate, supplying more glucose and oxygen to the brain and muscles. Norepinephrine constricts the blood vessels to increase the blood pressure.  

Similarities Between Adrenal Cortex and Adrenal Medulla

• Adrenal cortex and adrenal medulla are two zones of the adrenal gland.
• Both adrenal cortex and adrenal medulla secrete hormones that help to regulate the functions of the body.

Difference Between Adrenal Cortex and Adrenal Medulla

Definition

Adrenal Cortex: Adrenal cortex is the outer portion of the adrenal gland, which secretes steroid hormones to regulate protein, fat metabolism and salt and water balance in the body.

Adrenal Medulla: Adrenal medulla is the inner surface of the adrenal gland, which secretes epinephrine and epinephrine in response to acute stress.

Location

Adrenal Cortex: Adrenal cortex is the firm, outer layer of the adrenal gland.

Adrenal Medulla: Adrenal medulla is the softer inner part of the adrenal gland.

Composition

Adrenal Cortex: Adrenal cortex forms 75% of the adrenal gland.

Adrenal Medulla: Adrenal medulla forms 25% of the adrenal gland.

Fibrous Capsule

Adrenal Cortex: Adrenal cortex is enclosed by a fibrous capsule.

Adrenal Medulla: Adrenal medulla is not enclosed by a fibrous capsule.

Origin

Adrenal Cortex: Adrenal cortex originates from the mesoderm.

Adrenal Medulla: Adrenal medulla originates from the ectoderm.

Anatomy

Adrenal Cortex: Adrenal cortex consists of three regions: zona glomerulosa, zona fasciculata, and zona reticularis.

Adrenal Medulla: Adrenal medulla consists of chromaffin cells.

Hormones

Adrenal Cortex: Adrenal cortex releases glucocorticoids, mineralocorticoids, and androgens.

Adrenal Medulla: Adrenal medulla releases epinephrine and norepinephrine.

Role

Adrenal Cortex: Adrenal cortex mediates chronic responses.

Adrenal Medulla: Adrenal medulla mediates acute responses.

Significance

Adrenal Cortex: The hormones secreted by the adrenal cortex are essential for the survival.

Adrenal Medulla: The hormones secreted by the adrenal medulla are not essential for the survival.

Conclusion

Adrenal cortex and adrenal medulla are two major cell layers of the adrenal gland. The adrenal gland is located on the top of the kidney. Both adrenal cortex and adrenal medulla secrete hormones to regulate the functions of the body. The adrenal cortex secretes enzymes, which regulate the metabolism of the body. The adrenal medulla secretes hormones, which mediate the fight-or-flight response. The main difference between adrenal cortex and adrenal medulla is the functions that are mediated by the hormones secreted by each layer of the adrenal gland.

Reference:

1. “An Overview of the Adrenal Glands.” EndocrineWeb, www.endocrineweb.com/endocrinology/overview-adrenal-glands. Accessed 13 Sept. 2017.

Image Courtesy:

1. “Kidney and adrenal gland” By Alan Hoofring (Illustrator) – released by the National Cancer Institute, an agency part of the National Institutes of Health (Public Domain) via Commons Wikimedia
2. “Adrenal cortex labelled” By Jpogi – (CC0) via Commons Wikimedia