Adrenal Gland

What do you think happens in your body when you are scared or preparing yourself to face some kind of imminent danger? Do you feel stress? Do you feel your hands shaking? This is all because of adrenal glands – small, triangular glands, situated on the top of both your kidneys. This adrenal gland is also known as suprarenal gland.

When you think of these glands, stress, fear and panic might automatically come to your mind. And you’re probably right; the adrenal glands are known for releasing adrenaline, arguably one of the best-known hormones out there. Therefore, the adrenal hormones help prepare one’s body to go into fight or flight mode, when faced with a dire situation.

Let’s take a deeper look into the adrenal gland what does it do.

Adrenal Gland Location

Also called the suprarenal glands, these glands are found at the top of both kidneys. The name "adrenal" translates to " near kidneys" in Latin. The inferior vena cava flank anterior part of right adrenal gland, whereas right crus of diaphragm surround its posterior side. Likewise, the posterior side of left adrenal is surrounded by the left crus of diaphragm.

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Figure : Location of the Adrenal Glands

Do it yourself – Now that you know where the adrenal glands lie, test yourself and write down the adrenal gland definition in your notebook. 

Adrenal Gland Anatomy

The adrenal gland consists of two main regions.

1. First, the adrenal cortex, which is the largest and outermost part of a gland. Further, it consists of three separate zones, namely, zona glomerulosa, zona reticularis and zona fasciculata. Each of these zones produces specific hormones for different parts of one’s body.

2. Second, the adrenal medulla, situated inside the adrenal cortex, at the centre of the adrenal gland. This part releases stress hormones.

Together with the adrenal cortex, the adrenal medulla is encased in a protective layer called the adipose capsule, that surrounds the adrenal gland. 

Also, among these two glands, the right is pyramidal in shape and comparatively smaller than the left. The left is almost semilunar in form, and the two glands are generally 5x3 centimetres in size. A pair of healthy adrenal glands usually weigh anything between 7-10 grams and are yellow in colour.

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Figure : Anatomy of Adrenal Glands

Pop Quiz 1

1. Which of the Following are Parts of Adrenal Glands?

1. Medulla oblongata.

2. Adrenal medulla.

3. Adrenal cortex.

4. Both (b) and (c).

Adrenal Gland Function

As mentioned above, the adrenal gland plays a key role in helping the body to spring into action when faced with a stressful situation. Moreover, it forms a very intricate part of the hypothalamus, pituitary and adrenal axis. In effect, this axis forms the cornerstone of a physiological relationship, that is very crucial to the body’s wellbeing.

• Significantly, cortisol released by adrenal glands helps to increase the levels of glucose in the nervous system, by breaking down all available proteins and fats to glucose in the liver.

• Furthermore, cortisol has potent anti-inflammatory and anti-allergic properties. 

• The most essential function of the adrenal, however, is launching the fight or flight mode. When you are scared or stressed or angry, and feel your heart beating fast, it's the adrenal glands working.

Pop Quiz 2

1. How Does the Adrenal Gland Respond to Stress?

1. By releasing adrenaline

2. By releasing TSH

3. By releasing growth-stimulating hormone

4. None of the above

Adrenal Gland Hormones

The role of adrenal glands is to secrete specific hormones that dictate how one’s body responds to stress-inducing situations. These are vital to our survival and help us overcome obstacles and potential harm or danger.

Each part of the adrenal glands releases specific hormones. These are – 

1. Cortisol

It is a glucocorticoid hormone that the zona fasciculata secretes to help regulate the sleep/wake cycle, handle emergencies, and monitor the body's use of fats among a host of other functions.

2. Aldosterone

Aldosterone is a mineralocorticoid hormone that the zona glomerulosa secretes to regulate blood pressure and control the levels of electrolytes like sodium in the body.

3. Androgenic Steroids and DHEA

These are some weak male hormones secreted by the zona reticularis. They are the precursors of the male (androgens) hormones and female (oestrogens) hormones.

4. Adrenaline (epinephrine) and Noradrenaline (norepinephrine)

As the names suggest, these are the most important hormones secreted by adrenal glands. The adrenal medulla plays a vital role in regulating these hormones and inducing a flight or fight response. They are capable of increasing our metabolism, heart rate and as well as maintaining our blood pressure.

Altogether, hormones secreted by the adrenal glands are all activated in times of stress, fear or panic and help the body to cope by providing resources and energy to endure stress.

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Figure : Adrenal Gland Diagram

This was all about what is adrenal gland. For more on other glands and their functions, keep an eye out for our expertly-curated study notes, sample papers and live demo classes. Don’t forget to install Vedantu’s app as well to take your notes with you!