Life Sciences Glossary: Parathyroid Glands, Tetanic and Osteoporosis

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Parathyroid Glands

Parathyroid are two pairs, partially or completely embedded in the dorsal surface of thyroid gland. They are present in all vertebrates except fishes. Parathyroid contains two kinds of cells, chief cells and oxyphil cells. Chief cells are the major synthesizer of parathormone or parathyroid hormone (PTH) or Culp՚s hormone) . PTH regulates the amount of calcium and phosphate in ECF. It promotes the absorption of calcium from food in intestine, it accelerates elimination of phosphates in urine. PTH decreases blood phosphates level and increases blood calcium level. Parathormone is responsible for regulation of calcium and phosphate metabolism. Parathormone induces increase in serum calcium level.

Tetanic

Hypo parathyroidism result in hypocalcaemia. Skeletal muscles fail to relax causing titan.

Osteoporosis

Hyper parathyroidism results in osteoporosis, i.e.. dissolution of bone and hyperkalemia.

Otitis Fibrosis Cystic

Hyper parathyroidism also result in Otitis fibrosis cystic (normal bone is replaced by cysts and fibrous tissue) .

Adrenal Glands

Adrenal glands are paired endocrine glands, located superior to kidneys, hence called ‘Suprarenal՚s’ . Adrenal gland is structurally and functionally divided into outer adrenal cortex and inner adrenal medulla. Adrenal gland is also known as 4S gland.

  • Sugar metabolism
  • Salt retaining
  • Sex hormone
  • Source of energy

Adrenal Cortex

Adrenal cortex is derived from mesoderm, it is bright yellow in colour constituting 80 - 90 % of gland. Adrenal cortex is sub divided into 3 zones namely outer zone glomerulus, middle zone fasciculate and inner zone reticular is. The zone glomerulus secrete mineral corticoids, zone fasciculate secrete glucose corticoids and zone reticular is synthesize gonad corticoids. The principal mineral corticoid is aldosterone commonly called ‘salt retaining hormone’ two basic functions of aldosterone are conservation of sodium and water and elimination of potassium. Low blood pressure stimulates the Renin- angiotensin pathway. Glucocorticoids are a group of hormones concerned with normal metabolism. Low level of glucocorticoids in the blood stimulates the secretion of ACTH from anterior pituitary, Adrenal cortex secretes both male and female sex hormones, (gonad corticoids) estrogens and androgens. Concentration of sex hormones secreted by normal adult adrenals is usually so low that their effects are insignificant. All hormones secreted by adrenal cortex are steroids derived from cholesterol.

Addison՚s Disease (Hypoadrenalism)

Hypo secretion of glucocorticoids results in Addison՚s disease.

Cushing՚s Syndrome (Hypoadrenalism)

Hyper secretion of glucocorticoids results in Cushing ′ s syndrome. Clinical symptoms are ′ Red Moon face ′ and Buffalo hump ′ .

Aldosterones

Hyper secretion of aldosterone results a decrease in body՚s potassium.

Adrenogenital Syndrome

The tumors of adrenal cortex result in an excess of adrenal sex hormones.

  • Nihilism: Development of male characters like growth of beard, deep voice and baldness in a female due to excessive secretion of androgen by adrenal tumors.
  • Gynecomastia: Development of mammary glands in a male due to excessive secretion of estrogens by adrenal tumors.

Adrenal Medulla

  • Adrenal medulla is derived from ectoderm, it is reddish brown in colour constituting 10 - 20 % of the gland. Adrenal medulla contains chromaffin cells secreting two hormones: epinephrine (adrenaline) and norepinephrine (noradrenaline) . Adrenaline is the methylated noradrenaline. Both are derived from the amino acid tyrosine. Catecholamines refer to dopamine, adrenaline and noradrenaline. The secretion of adrenaline is in direct response to nervous activity (others are pineal and neurohypphysis) . The secretion of adrenaline is directly controlled by the autonomic nervous system, but not under the control of pituitary.
  • Adrenal medulla contributes the ‘fright, fight or figreactionoccurs in ia-saving hormones are secreted by adrenals. Adrenaline is also called emergency hormone’ . The secretion of adrenaline increases in emotional disturbances. Adrenaline accelerates the rate of respiration, dilates irater, decreases the rate of digestion, increases blood sugar level and stimulates cellular metabolism. Adrenaline increases both the heartbeat and blood pressure. When a person suffers from marked fall in blood pressure, it is helpful to give adrenaline to him.

Pheochromocytomas

It is due to tumors of chromaffin cells of adrenal medulla. hyper secretion of adrenaline causes high blood pressure, high levels of sugar in the blood and urine, high metabolic rate, nervousness and sweating.

Pineal Gland

Pineal gland is an endocrine organ, it is located on the roof of diencephalon, pineal gland is ectodermal in origin, and is absent in crocodiles. Pineal gland is composed of modified nerve cells called pinealocytes. Pineal gland in man starts to degenerate at about the age of 7 years, in adult it is largely fibrous tissue. Pineal gland secretes hormones in direct response to nervous activity. Pineal gland secretes three hormones namely melatonin, serotonin and adrenoglomerulotropin.

Melatonin

Is a derivate of the amino acid tryptophan and its target cells are melanophores of skin. It is antagonistic to that of melanocyte stimulating hormone (MSH) secreted by pars intermediate of pituitary. Darkness stimulates pineal secretion of melatonin, whereas exposure to light inhibits melatonin secretion.

Serotonin (5HT)

Acts as a vasoconstrictor, increasing blood pressure.

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