Adrenal Gland |Introduction, Structure, Location & Function
Adrenal Gland Definition
What is the adrenal gland? The adrenal gland or suprarenal gland is an endocrine organ that produces a variety of hormones, among them epinephrine (adrenaline) and norepinephrine (noradrenaline). These play important roles in the sympathetic nervous system’s flight-or-fight response. The adrenals also secrete steroid hormones like cortisol which regulates glucose metabolism. It lies at the top of the kidneys. These two tiny glands, which have a total weight of about 1.25 grams, produce more than 50 hormones and chemical substances to maintain blood glucose levels, control salt concentrations, form red blood cells, and muscle movement. In addition, adrenaline is also released from the adrenal gland, the “fight or flight” hormone.
Location of Adrenal Gland
Where is the adrenal gland located? It is at the superior pole of each kidney in most animals; however, it arises from the 3rd to 6th week of embryonic life in humans. Because this embryological association disappears after birth, many texts do not recognize its presence until later. Each gland has two separate glands joined together by the rate mirabilis that consists of blood capillaries and nerve fibers.
Structure of Adrenal Glands
The complex anatomy of these glands is composed of an outer cortex and inner medulla, which are connected by a thin capsule. It was not until 1784 that these organs were discovered by Italian anatomist Mattia Pacchioni (1740-1821). The discovery was made during his research into the anatomy of sheep, in which he removed the medulla and left a space. He then discovered that the cortex still functioned normally. This led him to believe that this was instead a single organ. Only when he cut it open after death did he discover his mistake.
An adventitia lined by a hypodermis surrounds the adrenal gland. This is the major component of the adrenal gland, and it contains several structures arranged irregularly. The most important are:
The outer layer, or cortex, comprises three layers called zona glomerulosa, zona fasciculata, and zona reticularis.
The medulla is composed of chromaffin cells, and the zonas glomerulosa and zona fasciculata surround it.
Blood vessels: adrenal arteries and veins that carry blood to and from the gland.
The three layers of the cortex are separated by unmyelinated nerve fibers, which handle the exchange of information between cells. How the glands give instructions to each other and secrete hormones is still a mystery. But what we know is that this communication mechanism involves the release of adrenaline from nerve terminals, which then stimulate specific receptors within cell nuclei.
Adrenal Glands Functions
The functions of this gland is described below:
Adrenal Glands Hormones
What hormones does the adrenal gland produce? The adrenal gland produces many different substances, all with their functions: the sex hormones cortisol and aldosterone.
Steroid Hormones are made by the adrenal gland. Steroid compounds such as glucocorticoids (cortisol) and mineralocorticoids (aldosterone). These regulate blood glucose levels and help retain salt in the body.
Corticosteroids are steroid compounds, mainly hormones, produced in the cortex of the adrenal glands. The primary corticosteroid is cortisol (hydrocortisone). Its secondary metabolite, 11-desoxycortisol (compound S), is also essential. Cortisol is critical to homeostasis and stress response because it modulates immune, metabolic, and neural activity through its interaction with glucocorticoid receptors. It binds to mineralocorticoid receptors to regulate salt/water balance in the body via its effects on the kidneys.
Corticosteroids, which control metabolism and inflammation, are made in small amounts by other tissues in the body; these include deoxycorticosterone produced by the inner layer (endodermis) of the kidney (the primary organ that helps regulate blood pressure) and aldosterone produced by cells within the adrenal cortex itself. The enzyme P450scc is involved in the production of aldosterone and cortisol.
Dexamethasone is another corticosteroid that has a potent anti-inflammatory activity. Cortisol, 11-deoxycortisol, and dexamethasone are secreted by cells lining the zona fasciculata of each adrenal gland. The corticosterone hormones are not found in humans because they are metabolized to cortisol before being released into circulation.
Glucagon is a hormone that increases blood sugar during fasting or starvation. The alpha cells in the pancreas secrete glucagon when stimulated by the pancreatic polypeptide. Glucagon’s primary role is to increase blood sugar levels when they fall too low, such as fasting or diabetes mellitus. Glucagon and cortisol secretion and glucocorticoids and catecholamines must be tightly regulated because of their implications for stress response, metabolism, and immunity. Glucose homeostasis is maintained by pancreatic beta-cells, which produce insulin, liver cells that secrete glucagon, and alpha cells within the pancreatic islets of Langerhans.
Androgens are steroid hormones, which control the development of characteristics of men and women during puberty, stimulate the growth of smooth muscles in bones and help regulate red blood cell production.
Enzymes of the cytochrome P450 family synthesize from cholesterol in the adrenal cortex of humans and other vertebrates androgens. In humans, these include CYP11A1, CYP17A1, and CYP19A1.
In mammals, there are five significant classes of androgen: (1) the androstane (including testosterone), (2) the androstenediol (including DHT), (3) the estranes (e.g., estradiol; E 2 ), (4) the pregnanes, and (5) the gonane steroids, such as chorionic gonadotropin.
The primary and most crucial androgen in humans is testosterone (T), which is synthesized by the testes, adrenal glands, and pituitary glands. It promotes the formation of male reproductive tissues, such as the penis, scrotum, and prostate development. Testosterone also regulates the production of seminal fluid and sperm quality and quantity. The primary function of androgens in women is regulating libido and maintaining female reproductive tissues, such as the development of external genitalia.
Several anabolic steroids are also derived from testosterone. Androgens can be divided into two categories: corticosteroid or gonadal. The first category includes primarily glucocorticoids (cortisol) and mineralocorticoids (aldosterone). The second category comprises androgens, estrogens, and progestogens.
Catecholamine hormones, such as adrenaline. These are released into the bloodstream to prepare us for action to “fight or flee” when we face danger or experience high emotion. We will then respond with increased powers of awareness, perception, judgment, and physical strength. The body’s immediate response includes
- increasing our heart rate,
- expanding blood vessels to increase cardiac output,
- dilating air passages to allow more oxygen intake, and
- converting glycogen to sugar for instant energy.
If the danger persists, the adrenal gland releases another catecholamine hormone called noradrenaline (norepinephrine), which triggers an even greater by protecting the brain and other organs in case of an emergency; slowing digestion and metabolism, which conserves energy for the emergency response; increasing muscle tension to improve our strength if we have to fight or have a physical struggle with an attacker.
Epinephrine (also called adrenaline) is a hormone that occurs naturally to help stimulate the nervous system. It also stimulates heart muscle, speeds up breathing, and raises metabolism. This can be helpful if you need to increase your energy level because of physical exertion or emotional stress. Epinephrine is sometimes used as a medication to treat specific heart problems: asthma, hay fever (allergic rhinitis), blood vessel problems in the lungs, bleeding into the adrenal gland, or tumors found in the adrenal glands.
The adrenal medulla releases catecholamine hormones to respond to stress coming from either external or internal stimuli. These hormones work rapidly in a cascade effect to prepare the body to deal with stressful circumstances by “fight or flight.” They are called catecholamines because they are derived from L-DOPA, synthesized in many tissues of the human body.
The primary symptoms of low adrenaline and noradrenaline are tiredness, depression, and lethargy. Emotions can significantly affect the adrenal glands because they stimulate the release of catecholamines. This causes an increase in heart rate, blood pressure, and oxygen consumption. Catecholamine hormones are released during moments of great feelings such as elation, anger, or fear. The release of catecholamines due to such high emotions can cause the receiver to shake and tremble.
Norepinephrine (Noradrenaline) is a hormone and neurotransmitter. It affects blood vessel diameter, blood pressure, heart rate, pupil dilation, memory, attention, and motivation. The nerve cells that use norepinephrine are located in the brain, where norepinephrine is involved in arousal and stimulation. Norepinephrine is also responsible for “fight or flight” responses to danger or stress, supporting survival behaviors important for adaptation. It is released in response to various physical conditions such as pain, anxiety, fear, and anger.
The sympathetic nervous system releases noradrenaline, which prepares the body by accelerating heart rate and constricting blood vessels. This, along with increased oxygen consumption and sugar breakdown, ensures that muscles are supplied with large amounts of energy and oxygenated blood.
Adrenal Gland Disorders
Adrenal gland tumors are most often benign, but once they have been diagnosed, it is essential to follow their growth with regular medical examinations so their development can be monitored at intervals. In cases where they become large enough, adrenal gland tumor surgery may be necessary.
Adrenal tumors can be benign or malignant and may produce hormones such as cortisol, aldosterone, and estrogen. When it is time for surgery, the adrenal glands are removed so that cancer cells will not spread to other parts of the body. Adrenal gland tumors rarely spread to other areas of the body. Cancer rarely comes back after treatment.
Treatment options include:
Surgery — Surgery removes the tumor and some normal tissue around it.
Radioactive iodine therapy — Radioactive iodine (RAI) destroys cancer cells by giving off radiation that damages their DNA and kills them. This treatment is used only if the tumor makes too much cortisol or aldosterone hormone.