What is the structure and function of the 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.
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.
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?
Medulla oblongata.
Adrenal medulla.
Adrenal cortex.
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?
By releasing adrenaline
By releasing TSH
By releasing growth-stimulating hormone
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!
FAQs on Adrenal Gland Anatomy and Hormonal Functions
1. What is the adrenal gland and where is it located?
The adrenal glands are small, triangular-shaped endocrine glands located on top of each kidney. They are part of the endocrine system and release hormones directly into the bloodstream.
- There are two adrenal glands, one above each kidney.
- They are also called suprarenal glands.
- They regulate stress response, metabolism, blood pressure, and electrolyte balance.
2. What are the main parts of the adrenal gland?
The adrenal gland has two main regions: the adrenal cortex and the adrenal medulla. Each region produces different hormones.
- Adrenal cortex (outer layer): Produces steroid hormones.
- Adrenal medulla (inner core): Produces catecholamines like adrenaline.
- The cortex itself has three zones: zona glomerulosa, zona fasciculata, and zona reticularis.
3. What hormones are produced by the adrenal gland?
The adrenal gland produces steroid hormones from the cortex and catecholamines from the medulla. These hormones regulate stress, metabolism, and blood pressure.
- Aldosterone (zona glomerulosa): Controls sodium and potassium balance.
- Cortisol (zona fasciculata): Regulates metabolism and stress response.
- Androgens (zona reticularis): Contribute to secondary sexual characteristics.
- Adrenaline (epinephrine) and noradrenaline (medulla): Trigger fight-or-flight response.
4. What is the function of the adrenal cortex?
The adrenal cortex produces steroid hormones that regulate metabolism, immune response, and electrolyte balance. It plays a major role in long-term stress adaptation.
- Secretes cortisol for glucose metabolism and stress control.
- Releases aldosterone to maintain blood pressure and salt balance.
- Produces small amounts of adrenal androgens.
5. What is the function of the adrenal medulla?
The adrenal medulla secretes catecholamines that prepare the body for immediate stress responses. It is controlled by the sympathetic nervous system.
- Releases adrenaline (epinephrine).
- Releases noradrenaline (norepinephrine).
- Increases heart rate, blood pressure, and blood glucose during the fight-or-flight response.
6. How does the adrenal gland respond to stress?
The adrenal gland responds to stress by releasing cortisol and adrenaline through coordinated nervous and hormonal pathways. This response helps the body adapt quickly and effectively.
- Immediate response: Adrenal medulla releases adrenaline.
- Long-term response: Adrenal cortex releases cortisol.
- Regulated by the hypothalamic–pituitary–adrenal (HPA) axis.
7. What is the difference between the adrenal cortex and adrenal medulla?
The adrenal cortex produces steroid hormones for long-term regulation, while the adrenal medulla produces catecholamines for rapid stress response. They differ in structure, function, and hormone type.
- Cortex: Outer layer; secretes steroid hormones like cortisol and aldosterone.
- Medulla: Inner region; secretes adrenaline and noradrenaline.
- Cortex is controlled by hormones; medulla is controlled by the sympathetic nervous system.
8. What is the role of aldosterone in the body?
Aldosterone is a mineralocorticoid hormone that regulates sodium and potassium levels to control blood pressure. It is produced in the zona glomerulosa of the adrenal cortex.
- Increases sodium reabsorption in the kidneys.
- Promotes potassium excretion.
- Helps maintain blood volume and arterial pressure.
9. What happens if the adrenal gland does not function properly?
Improper adrenal gland function can lead to hormonal imbalances affecting stress response, metabolism, and blood pressure. Disorders may involve hormone deficiency or excess.
- Addison’s disease: Insufficient cortisol and aldosterone production.
- Cushing’s syndrome: Excess cortisol production.
- Symptoms may include fatigue, abnormal blood pressure, and metabolic disturbances.
10. How is the adrenal gland regulated in the endocrine system?
The adrenal gland is regulated by the hypothalamic–pituitary–adrenal (HPA) axis and the sympathetic nervous system. These systems coordinate hormonal release based on body needs.
- The hypothalamus releases CRH (corticotropin-releasing hormone).
- The pituitary gland secretes ACTH (adrenocorticotropic hormone).
- ACTH stimulates the adrenal cortex to produce cortisol.
- The adrenal medulla is directly stimulated by sympathetic nerve impulses.
