parathyroid gland - niu.edu.inniu.edu.in/son/online-classes/parathyroid-presentation.pdf ·...
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BY: DR RAJ SHARMA
NOIDA INTERNATIONAL UNIVERSITY
PARATHYROID GLAND
OVERVIEW OF THYROID GLAND
Thyroid Essentials:
regulates your metabolism
Butterfly-shaped gland wrapped around trachea
The two main thyroid hormones are T3 and T4.
Appear on front of the neck
Thyroid disorders are common, and
they include goiters, hyperthyroidism,
and hypothyroidism.
PARATHYROID GLAND
Human being have four parathyroid glands
Situated at back surface of the thyroid gland
Located in neck
Very small in size
Measures- •6mm long •3mm wide & •2mm thick
Dark brown in colour
DIAGRAMATIC VIEW :
FUNCTIONS OF PARATHYROID GLAND
main function : produce and
secrete a hormone called PTH
(parathyroid hormone)
raises blood calcium level
HISTOLOGY (microscopic study)
made up of chief cells and oxyphil cells
1.CHIEF CELLS: secretes PTH (parathyroid hormone)
2.OXYPHIL CELLS: •degenerates chief cells
•may secrete PTH during
pathological condition
called parathyroid adonema (a small tumour of PT gland)
gland inc. In size due to production of PTH in excess.
SOURCE OF SECRETION
secreted by the
chief cells of the
parathyroid gland
PARATHYROID HORMONE
regulates calcium, magnesium,
phosphorus levels in blood.
Main function is to increase Calcium
levels when they are low
ROLE OF ‘Ca’ IN OUR BODY
Bone&teeeth formation
Neuronal activity
Skeletal muscle activity
Cardiac activity
Smooth muscle activity
Secretory activity
Cell division & growth
Coagulation of blood
CHEMISTRY
Parathyroid hormone is protein in nature
Having 84amino acids
Having molecular weight :- 9,500 Da
SYNTHESIS
Synthesised from precursor called pre-pro-PTH containing 115 amino acids.
PRE-PARATHYROID HORMONE
⬇
PRO-PARATHYROID HORMONE
⬇
PARATHYROID HORMONE
PROCESS OF SYNTHESIS OF PTH
1. pre-PTH hormone (115 amino acids) enters the endoplasmic reticulum of the chief cells of PT gland.
2. Then there,it is converted into a Pro-hormone called pro-PT hormone .
3. Lastly, pro-PTH enters the golgi apparatus,and converted into PARATHYROID HORMONE.
ACTIONS OF PTH ON BLOOD ‘CA’ LEVEL
Primary action of parathyroid hormone is to maintain the blood calcium level.
PTH maintains blood CA level by :-
Resorption of Ca from bones
Reabsorption of Ca from the renal tubules (kidney)
Absorption of Ca from intestine
ROLE OF PTH IN THE ACTIVATION OF VITAMIN D
Vitamin D is very essential for calcium absorption from the intestine.
But vitamin D itself is not an active substance.
So, PTH is the one who is enabling the kidney to produce Vitamin D which inturn goes to intestine and stimulates more absorption of
Calcium.
BLOOD LEVEL OF CALCIUM
PTH secretion is inversely proportional to blood calcium level.
⬆ in blood calcium level ⬇ PTH secretion.
CONDITIONS WHEN PTH SECRETION DECREASES:-
⭐ excess quantities of calcium in diet.
⭐ increase vitamin D in diet.
⭐ increased releasing of calcium from the bones,
caused by factor such as bone diseases.
PARATHYROID DISORDERS
HYPERPARATHYROIDISM
: increased PTH levels in blood
🔹 results to :- HYPERCALCEMIA i.e
too much calcium in the blood.
HYPOPARATHYROIDISM
: decreased secretion of PARATHYROID
HORMONE.
: results to HYPOCALCEMIA i.e
too little calcium in the blood.