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Adrenal glands

There are 2 adrenal (= suprarenal) glands, oneat the superior pole of each kidney. Eachgland consists of two parts: an outeradrenal cortex and an inner adrenalmedulla

Adrenal cortex

The adrenal cortex is essential for life. Itsecretes steroid hormones ''

Corticosteroids'' which are derivatives ofcholesterol.

Functional histology

The adrenal cortex is formed of three zones.These zones are:

6. Zona glomerulosa: '' outer zone ' Groups of cells arranged in oval or arched

pattern (glomeruli).

Secretes Mineralocorticoids: Aldosteronemainly and deoxycorticosterone.

Mineralocorticoids hormones control Na+

,K+ and H2O metabolism.

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Adrenal glands - Continued

1. Zona Fasciculata: '' Middle zone ''

Large cells arranged in columns orcords (fascicles), widest zones richin lipid and Vitamin C.

Secretes Glucocorticoids hormones:Cortisol mainly and Corticosterone.

Glucocorticoids control

carbohydrates, proteins and fatmetabolism.

3. Zona reticularis '' Inner zone ''.

Columns of cells arranged in areticular manner.

Secretes sex hormones: Mainlyandrogens (hormones producemusculinizing ''male'' effects e.g.dihydroepiandrosterone = DHEA) &very small amount of estrogen andprogesterone.


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II. GlucocorticoidsGlucocorticoids include Cortisol (hydrocortisone) and corticosterone

hormones secreted from Zona fasciculata of adrenal cortex.

Action of Glucocorticoids:

1- Metabolic effects:

A. Protein metabolism:

o In extra hepatic tissues; Cortisol stimulates protein catabolism

(i.e. mobilization of amino acids from extra-hepatic tissues (mainlyskeletal muscles).

B.Carbohydrate metabolism:

Cortisol increases blood glucose level (hyperglycemic effect).

Cortisol stimulates liver glycogenesis.

C.Fat metabolism:

Cortisol causes lipolysis (breakdown of fat molecules), ketogenesis(formation of ketone bodies) and deposition of fat in face, cervical andtrunk regions.


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Action of Glucocorticoids- Continued

2. Water and electrolyte balance:

Cortisol increases the excretion of water in urine by accelerating

the inactivation of ADH in the liver and inhibiting its secretion.

Cortisol has a weak Mineralocorticoids activity. They help Na+

retention and K+ secretion (excretion) in urine.

3. Blood cells and lymphatic tissues: Cortisol resulted in:

* Polycythaemia, neutrophillia and thrombocytosis.

* Decease the output of T- lymphocytes and antibodies.

* Decrease the size of lymph glands, spleen and thymus gland by

inhibiting mitotic division of lymphocytes and increase their

destruction.

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Action of Glucocorticoids - Continued

4. Anti inflammatory effect: Cortisol in large pharmacologicaldoseInhibitinflammatory reaction because it:

Stabilizes lysozymes membrane. Inhibit the release of vasodilator substances e.g. Kinins. Decreases capillary permeability and edema formation.

Suppresses immune system especially the T lymphocytes.5. Anti-allergic effect: Cortisol in pharmacological doses:o Inhibit histamine release from mast cells.o Decreases the Eosinophile and lymphocytes.

6. Resistance to stress: Cortisol increases the body resistance to

stress through: Increasing vascular reactivity to circulating Catecholamine. Mobilization of fatty acids as a source of energy during stress. Maintenance of plasma volume.

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Disorders of adrenal cortexA) Hypo function of adrenal cortex -''''ADDISION' DISEASE

Addison's disease is an autoimmune disease in which antibodies are formedagainst adrenal cortex causing its damage and atrophy.

Manifestations:

Hypotension:Due to Aldosterone deficiency Na+ and water loss inurine Hypovolemia decreased arterial blood pressure.

Hypoglycemia. (i.e. decreased blood glucose level) due to Cortisol deficiency

Hyperkalemia (i.e. increased Blood K+ level) due to Aldosterone deficiencydiminished K+ excretion in urine.

Hyper pigmentation:Bronze skin pigmentation especially occurs in the face,groins, axilla, nipples, and exposed area to sun light and scars as umbilicus.

Asthenia(i.e. generalized muscle weakness) due to tissue hypoxia,Hyperkalemia and hypoglycemia.

Loss of appetite(anorexia), vomiting and diarrhea. Resistance to stressis decreased.

Sexual disturbances; e.g. amenorrhea in females.

Treatment: Adrenocortical hormones: Aldosterone and Cortisol are given. Diet rich in NaCl and glucose but poor in K+.

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B- Hyper function of adrenal cortex

''Cushing's syndrome''

It is due to excessive secretion or

administration of Glucocorticoids(Cortisol and corticosterone)

Manifestations:

1- Increased protein catabolism; this leads to: Muscle wasting and weakness. Thin skin, hair and subcutaneous tissues.

Osteoporosis; loss of bone mass due todecreased protein content with bonedemineralization leading to:

o Deformity and fractures of boneo Collapse of vertebrae leading to Kyphosis

(i.e. arching of the back).

2-Abnormal fat distribution; fat is depositedin:

Face becomes rounded (moon face) Supra-clavicle region and back of the

neck and inter-scapular region. Trunk and abdominal wall (trunk obesity);

while extremities are thin (Buffalo hump

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.Manifestations of Cushing- Cont3- Hyperglycemia,glucosuria

(i.e. presence of glucose inurine).

4- Hypertension:Due to Na+and H

2O retention.

5- Androgenic manifestations;as acne, Hairsutism(abnormal appearance ofhairs).

6- Increased basal metabolicrate(BMR).

7- Mental abnormalitiesasinsomnia, euphoria andpsychosis.


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Adrenal medulla

a) The adrenal medulla secretes

Catecholamines: Adrenaline or

Epinphrine (80%) and

noradrenaline or

Norepinephrine (20%)hormones.

b) The gland is not essential for

life.

c) Adreno-medullary hormones

help the activity of sympathetic

system when generalized

sympathetic stimulation occurs

(stress response orflight andflight and

fight response)fight response)


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Action of Catecholamines

Catecholamine act on:

Metabolism:Adrenaline stimulates basal metabolic rate, liverglycogenolysis, muscle glycogenolysis and lipolysis.

The heart: Catecholamine stimulates all cardiac properties and dilatescoronary vessels. So, it produces:

Increased heart rate (tachycardia), increased force of contraction, increasedexcitability & enhanced conductivity, increased metabolism and O2consumption and coronary vasodilatation.

III- On blood vessels & blood pressure:

o Noradrenalin causes generalized vasoconstriction increase inthe peripheral resistance increase of blood pressure withconcomitant decrease in cardiac output.

o Adrenaline causes vasoconstriction of skin, renal and splanchnic blood

vessels whilst vasodilatation occurs in skeletal muscles blood vessels.Cardiac output is increased.

IV-Central nervous system:Catecholamine increases the excitabilities of CNS andshortens the response time. Adrenaline increases the alertness, awarenessand mental activity.

V- Respiration:Catecholamine increases the rate and depth of respiration.

VII- Skin:adrenaline causes pallor of the skin due to cutaneous vasoconstriction


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