ADRENAL GLAND The adrenal gland made up of two words...

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C.N. Saxena B.sc. IV th Sem. Assistant Professor, Unit - iii Department of Zoology Sri J.N.M. P.G. collage (KKC), Luclnow ADRENAL GLAND The adrenal gland made up of two words, AD – means - upon , RENAL- means – kidney. Thus meaning thereby - upon kidney. This gland is situated over the kidney, hence called Adrenal or supra renal gland. The weight of adrenal gland is about 4 to 6 gram. The adrenal glands have a rich blood supply. They are served by several arteries branching off the aorta, including the suprarenal and renal arteries. Blood flows to each adrenal gland at the adrenal cortex and then drains into the adrenal medulla. Adrenal hormones are released into the circulation via the left and right suprarenal veins. The gland has three parts. 1. Capsule 2. Cortex 3. Medulla Major division of adrenal gland

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C.N. Saxena B.sc. IVth Sem. Assistant Professor,

Unit - iii Department of Zoology Sri J.N.M. P.G. collage (KKC),

Luclnow

ADRENAL GLAND

The adrenal gland made up of two words, AD – means - upon , RENAL- means

– kidney. Thus meaning thereby - upon kidney. This gland is situated over the

kidney, hence called Adrenal or supra renal gland.

The weight of adrenal gland is about 4 to 6 gram. The adrenal glands have a

rich blood supply. They are served by several arteries branching off the aorta, including the

suprarenal and renal arteries. Blood flows to each adrenal gland at the adrenal cortex and then

drains into the adrenal medulla. Adrenal hormones are released into the circulation via the

left and right suprarenal veins.

The gland has three parts.

1. Capsule

2. Cortex

3. Medulla

Major division of adrenal gland

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The adrenal gland consists of an outer cortex of glandular tissue and an inner medulla of nervous tissue. The cortex itself is divided into three zones: the zona glomerulosa,

the zona fasciculata, and the zona reticularis. Each region secretes its own set of hormones.

Adrenal cortex

1. Zona glomerulosa –

The outermost, zona glomerulosa, is a thin layer of cells, which makes up about 15%

of the total cortical mass. The cells in this zone are capable of producing the steroid

aldosterone. This characteristic is given by the presence of the enzyme aldosterone synthase,

an enzyme essential for the synthesis of this hormone. Aldosterone is mainly responsible for

regulation of electrolyte balance and its production is stimulated by the circulatory

concentration of angiotensin II and potassium.

Aldosterone is the major mineralocorticoid. It is important in the regulation of the

concentration of sodium and potassium ions in urine, sweat, and saliva. For example, it is

released in response to elevated blood K+, low blood Na+, low blood pressure, or low blood

volume. In response, aldosterone increases the excretion of K+ and the retention of Na+,

which in turn increases blood volume and blood pressure. Its secretion is prompted when

CRH from the hypothalamus triggers ACTH release from the anterior pituitary.

Aldosterone is a key component of the renin-angiotensin-aldosterone system (RAAS) in

which specialized cells of the kidneys secrete the enzyme renin in response to low blood

volume or low blood pressure. Renin then catalyzes the conversion of the blood protein

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angiotensinogen, produced by the liver, to the hormone angiotensin I. Angiotensin I is

converted in the lungs to angiotensin II by angiotensin-converting enzyme (ACE).

Angiotensin II has three major functions:

1. Initiating vasoconstriction of the arterioles, decreasing blood flow

2. Stimulating kidney tubules to reabsorb NaCl and water, increasing blood volume

3. Signaling the adrenal cortex to secrete aldosterone, the effects of which further

contribute to fluid retention, restoring blood pressure and blood volume

Once the corticosteroids are secreted, they are transported in circulation by

carrier proteins. This increases their water solubility, serves as a temporary storage,

and increases the half-life of the steroid. Glucocorticoids are carried mainly by a

corticosteroid binding globulin (CBG) that is produced in the liver and secreted into

circulation. A smaller proportion is carried by albumin and about 10% is circulating

freely. On the other hand, 40% of mineralocorticoids are circulating freely, 50% are

bound to albumin and only 10% use CBG.

2. Zona fasciculata –

The central and largest zone of the adrenal cortex is the zona fasciculata, making up

about 75% of the cortex mass. Its main role is the secretion of glucocorticoids, in particular

cortisol and corticosterone. It also has the capability of secreting small amounts of androgens

and estrogens. the zona fasciculata, named as such because the cells form small fascicles

(bundles) separated by tiny blood vessels. The cells of the zona fasciculata produce hormones

called glucocorticoids because of their role in glucose metabolism. The most important of

these is cortisol, some of which the liver converts to cortisone. A glucocorticoid produced in

much smaller amounts is corticosterone. In response to long-term stressors, the hypothalamus

secretes CRH, which in turn triggers the release of ACTH by the anterior pituitary. ACTH

triggers the release of the glucocorticoids. Their overall effect is to inhibit tissue building

while stimulating the breakdown of stored nutrients to maintain adequate fuel supplies. In

conditions of long-term stress, for example, cortisol promotes the catabolism of glycogen to

glucose, the catabolism of stored triglycerides into fatty acids and glycerol, and the

catabolism of muscle proteins into amino acids. These raw materials can then be used to

synthesize additional glucose and ketones for use as body fuels. The hippocampus, part of

the temporal lobe of the cerebral cortices and important in memory formation, is highly

sensitive to stress levels because of its many glucocorticoid receptors.

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3. Zona reticularis - The deepest region of the adrenal cortex is the zona reticularis, which produces small

amounts of a class of steroid sex hormones called androgens. During puberty and most of

adulthood, androgens are produced in the gonads. The androgens produced in the zona

reticularis supplement the gonadal androgens. They are produced in response to ACTH from

the anterior pituitary and are converted in the tissues to testosterone or estrogens. In adult

women, they may contribute to the sex drive, but their function in adult men is not well

understood. In post-menopausal women, as the functions of the ovaries decline, the main

source of estrogens becomes the androgens produced by the zona reticularis.

Adrenal medulla

The medullary tissue is composed of unique postganglionic SNS neurons

called chromaffin cells, which are large and irregularly shaped, and produce the

neurotransmitters epinephrine (also called adrenaline) and norepinephrine (or noradrenaline). Epinephrine is produced in greater quantities—approximately a 4 to 1 ratio

with norepinephrine—and is the more powerful hormone. Because the chromaffin cells

release epinephrine and norepinephrine into the systemic circulation, where they travel

widely and exert effects on distant cells, they are considered hormones. Derived from the

amino acid tyrosine, they are chemically classified as catecholamines.

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Catecholamines are neurotransmitters, as well as hormones. In their role as

neurotransmitters they are synthesized all through the organism. In their role as hormones

they are produced by the adrenal medulla in response to sympathetic stimulation. The most

common are epinephrine and norepinephrine.

Catecholamines may bind at least 4 types of receptors. Alpha receptors are more

potently stimulated by norepinephrine (α1 and α2), although norepinephrine can weakly

stimulate beta (β1 and β2) receptors. The final response of a tissue depends on the types of its

available receptors. For example, heart tissue has mainly β1 while smooth muscle has mainly

β2 receptors. Therefore, these tissues respond more to epinephrine.

Function of adrenaline hormone

1) Pupillary dilation

2) It constricts erecter pilli muscle of hair known as(piloerection)

3) Increase sweating

4) Increase heartbeat

5) Stimulate trachea and bronchi muscle to relax (due to this

adrenaline also used in the cure of asthma)

6) Constrict blood vessels of the skin

7) Increase the concentration of glucose in blood break down

glycogen

8) Produce contraction of spleen so that it releases its stored blood

9) Clotting period of blood reduced.

Endocrine

Gland

Hormone Exercise

effect

Target organ Major function

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HYPO AND HYPER FUNCTION OF ADRENAL GLAND;

Addison's disease:-

Addison's disease, also called adrenal insufficiency, is an uncommon disorder that occurs

when body doesn't produce enough of certain hormones. In Addison's disease, adrenal

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glands, located just above kidneys, produce too little cortisol and, often, too little

aldosterone.

Addison's disease occurs in all age groups and both sexes, and can be life-threatening.

Treatment involves taking hormones to replace those that are missing.

Symptoms

Addison's disease symptoms usually develop slowly, often over several months. Often, the

disease progresses so slowly that symptoms are ignored until a stress, such as illness or

injury, occurs and makes symptoms worse. Signs and symptoms may include:

Extreme fatigue

Weight loss and decreased appetite

Darkening of your skin (hyperpigmentation)

Low blood pressure, even fainting

Salt craving

Low blood sugar (hypoglycemia)

Nausea, diarrhea or vomiting (gastrointestinal symptoms)

Abdominal pain

Muscle or joint pains

Irritability

Depression or other behavioral symptoms

Body hair loss or sexual dysfunction in women

Acute adrenal failure (addisonian crisis)

Sometimes the signs and symptoms of Addison's disease may appear suddenly. Acute adrenal

failure (addisonian crisis) can lead to life-threatening shock. Seek emergency medical

treatment if you experience the following signs and symptoms:

Severe weakness

Confusion

Pain in your lower back or legs

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Severe abdominal pain, vomiting and diarrhea, leading to dehydration

Reduced consciousness or delirium

In an addisonian crisis you will also have:

Low blood pressure

High potassium (hyperkalemia) and low sodium (hyponatremia)

Cushing syndrome:-

Cushing syndrome occurs when body is exposed to high levels of the hormone

cortisol for a long time. Cushing syndrome, sometimes called hypercortisolism, may

be caused by the use of oral corticosteroid medication. The condition can also occur

when body makes too much cortisol on its own.

Too much cortisol can produce some of the hallmark signs of Cushing syndrome —

a fatty hump between your shoulders, a rounded face, and pink or purple stretch

marks on your skin. Cushing syndrome can also result in high blood pressure, bone

loss and, on occasion, type 2 diabetes.

Treatments for Cushing syndrome can return body's cortisol production to normal

and noticeably improve your symptoms. The earlier treatment begins, the better your

chances for recovery.

Symptoms

The signs and symptoms of Cushing syndrome can vary depending on the levels of

excess cortisol.

Common signs and symptoms of Cushing syndrome

Weight gain and fatty tissue deposits, particularly around the midsection and

upper back, in the face (moon face), and between the shoulders (buffalo hump)

Pink or purple stretch marks (striae) on the skin of the abdomen, thighs, breasts

and arms

Thinning, fragile skin that bruises easily

Slow healing of cuts, insect bites and infections

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Acne

Signs and symptoms women with Cushing syndrome may experience

Thicker or more visible body and facial hair (hirsutism)

Irregular or absent menstrual periods

Signs and symptoms men with Cushing syndrome may experience

Decreased libido

Decreased fertility

Erectile dysfunction

Other signs and symptoms that may occur with Cushing syndrome

Severe fatigue

Muscle weakness

Depression, anxiety and irritability

Loss of emotional control

Cognitive difficulties

New or worsened high blood pressure

Headache

Increased pigmentation of the skin

Bone loss, leading to fractures over time

In children, impaired growth

Cushing syndrome

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