DR. AHAD HUSSAIN PT

Adrenal Glands

• The adrenal (suprarenal) glands consist of a cortex (secretes mineralocorticoids, glucocorticoids, and androgens) and a medulla (secretes adrenalin).
• The adrenal glands lie at the T12 vertebral level
• They are about 4 cm long and 3 cm thick.

• on the superior pole of each kidney
• and are separated from the kidneys by the renal capsule
• The left adrenal gland is positioned more medially than the right adrenal gland

• The glands are composed of two parts which have different structures and functions.
• The outer part is the cortex and the inner part the medulla.
• The adrenal cortex is essential to life but the medulla is not.

Adrenal cortex

• The adrenal cortex produces three groups of steroid hormones from cholesterol.
• They are collectively called adrenocorticocoids (corticosteroids).
• glucocorticoids
• mineralocorticoids
• sex hormones (androgens).

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Glucocorticoids

• Cortisol (hydrocortisone) is the main glucocorticoid but small amounts of corticosterone and cortisone are also produced
• They are essential for life, regulating metabolism and responses to stress
• Secretion is controlled through a negative feedback system involving the hypothalamus and anterior pituitary.
• It is stimulated by ACTH from the anterior pituitary and by stress
• The highest level of hormone secretion occurs between 4 a.m. and 8 a.m., and the lowest between midnight and 3 a.m
• When the sleeping and waking pattern is changed it takes several days for adjustment of the ACTH/cortisol secretion to take place

• Glucocorticoids have widespread metabolic effects
• gluconeogenesis (formation of new sugar from, for example, protein) and hyperglycaemia (raised blood glucose levels)
• lipolysis (breakdown of triglycerides into fatty acids and glycerol for energy production)
• In pathological and pharmacological quantities glucocorticoids (commonly referred to as ‘steroids’) also have other effects including:
• anti-inflammatory actions
• suppression of immune responses delayed
• wound healing.

Mineralocorticoids (aldosterone)

• Aldosterone is the main mineralocorticoid. Its functions are associated with the maintenance of water and electrolyte balance in the body
• Through a negative feedback system it stimulates the reabsorption of sodium (Na+) by the renal tubules and excretion of potassium (K+) in the urine
• Sodium reabsorption is also accompanied by retention of water and therefore aldosterone is involved in the regulation of blood volume and blood pressure too.
• When blood potassium levels rise, more aldosterone is secreted

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Sex hormones

• Sex hormones secreted by the adrenal cortex are mainly androgens (male sex hormones) and
• the amounts produced are insignificant compared with those secreted by the testes and ovaries in late puberty and adulthood

2. Adrenal Medulla

• The medulla is completely surrounded by the adrenal cortex.
• It is stimulated by its extensive sympathetic nerve supply to produce the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine).

Adrenaline and Non-Adrenaline

• Adrenaline and some noradrenaline are released into the blood from the adrenal medulla during stimulation of the sympathetic nervous system
• Together they potentiate the fight or flight response by:
• increasing heart rate
• increasing blood pressure diverting blood to essential organs,
• including the heart,
• brain and
• skeletal muscles, by
• dilating their blood vessels and
• constricting those of less essential organs,
• such as the skin increasing metabolic rate dilating the pupils.

Response to stress

• When the body is under stress homeostasis is disturbed
• The immediate response is sometimes described as preparing for ‘fight or flight’

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Blood Supply Arterial and Venous

• Each gland receives an arterial supply from three arteries:
• superior adrenal artery (branch of the inferior phrenic artery),
• middle adrenal artery (branch of the aorta), and
• inferior adrenal artery (branch of the renal artery).
• Venous drainage of the right adrenal gland empties directly into the inferior vena cava, whereas that of the left adrenal gland empties into the left renal vein

Nerve Supply

• Sympathetic nerves innervate the adrenal medulla.
• The least splanchnic nerve, through the aorticorenal ganglion, provides innervation. However, unlike other organs innervated by the sympathetic nerves, only preganglionic neurons enter the adrenal medulla.

• The adrenalin (epinephrine) hormones released into the blood stream act like a systemic postganglionic neuron to stimulate tissues around the body that have receptors for adrenalin.
• The adrenal cortex is primarily regulated within the endocrine system by hormones from the pituitary gland (e.g., adrenocorticotropic hormone).

Histology

• On Gross inspection of a freshly cut supra renal gland, two concentric region can be distinguished
• CORTEX: yellowish outer region that constitutes about 90% of the mass of the gland, derived from mesoderm (embryo origin )
• Medulla: smaller inner (central) region that appears reddish to the naked eye, neural crest cells (embryo origin )

1.Adrenal Cortex

• Streoidogenic cells of adrenal cortex shows following characteristics
• Abundant Fat Droplets
• Exceptionally large amount of SER
• Abundant Mitochondri, many of which have tubular cisternae
• Due to abundance of SER and mitochondria, the cytoplasm of steroidogenic cells takes and eosinophilic stains

• The Adrenal cortex divided into three zones on the basis of arrangement of cells
• Zona glomerulosa
• Zona fasciculata
• Zona Reticularis

1.Zona Glomerulosa

• Outermost zone and lies just beneath the capsule
• About 15% of cortical volume
• Composed of columnar or pyramidal cells which contain darkly staining, spherical nuclei
• They stain eosinophilic and due to SER, Mitochondria and Golgi-Apparatus
• Cells secrete mineralcorticoids, chiefly aldosterone

2. Zona Fasiculata

• Thickest zone and count about 70-80% of the cortical volume
• These cells are larger than zona glomerulosa
• Each cell contains a single, spherical, light staining nucleus, but binucleate cells are also commonly seen
• It also contains Golgi appartus, RER
• Cytoplasm contains general eosinophillic stain but some regions contains basophillic stains due to RER.
• The cells of zone produce glucocorticoids, mainly cortisol

3. Zona Reticularis

• About 10% of Cortex lies adjacent to medulla
• Zone consists polyhedral or rounded cells in branches and anastomosing cords.
• Cells are smaller than both other two zones
• Nuclei in this zone is appear to be closely packed
• Cells secrete weak androgens, mainly dehydroepiandrosterone
• Produce small quantities of estrogen progestrone and cortisol

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Clinical Application

• Adrenal Cortical Insufficiency
• Also called addisons disease, is a disorder in which cells of adrenal cortex are destroyed
• Mostly this has an autoimmune basis, but tuberculosis of adrenal glands can also be the underlying reason.
• Symptoms
• Severe fatigue
• Loss of appetite
• Unintentional weight loss
• Increased thirst
• Craving for salty foods

2. Adrenal Medulla

• They have the affinity for chromium salts, medullary cells are also called chromaffin cells.
• They Secrete mainly two catecholamines products, Epinephrine and Norepinephrine (sympathetic activity)
• Epinephrine consists 80% of catecholamine output of adrenal medulla
• The secretory granules of epinephrine producing cells are homogenous and less dense
• The secretory granules of norepinephrine producing cells contain electron-dense core surrounded by an outer zone of lower density

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