TNPSC Free Notes Biology- Pineal gland

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான  முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Pineal gland

 In human, the pineal gland or epiphysis cerebri or conarium is located
behind the third ventricle of brain and is formed of parenchymal cells and
interstitial cells.
 It secretes the hormone, melatonin, which plays a central role in the
regulation of circadian rhythm of our body and maintains the normal
sleep wake cycle.
 It also regulates the timing of sexual maturation of gonads.
 In addition melatonin also influences metabolism, pigmentation, menstrual
cycle and defence mechanism of our body.
Thyroid gland
 Edward C. Kendal in 1914 first crystallized thyroxine hormone.
 Charles Harrington and George Barger identified the molecular structure of
thyroxine in 1927.
 Thyroid gland requires “120 μg” of iodine every day for the production of
thyroxine.
 The butterfly shaped thyroid gland is a bilobed gland located below the
larynx on each side of upper trachea.
 It is the largest endocrine gland in the body.
 Its two lateral lobes are connected by a median tissue mass called isthmus.
 Each lobe is made up of many lobules. The lobules consist of follicles
called acini (acinus in singular).
 The lumen of acinus is filled with colloid, a thick glycoprotein mixture
consisting of thyroglobulin molecules.
 An amino acid tyrosine and iodine are involved in the formation of thyroid
hormone.
The hormones secreted by the thyroid gland are
1. Tri-iodothyronine (T3)
2. Tetraiodothyronine or Thyroxine (T4)
Functions of thyroid hormones

1. Production of energy by maintaining the Basal Metabolic Rate (BMR) of
the body.
2. Helps to maintain normal body temperature.
3. Influences the activity of central nervous system.
4. Controls growth of the body and bone formation.
5. Essential for normal physical, mental and personality development.
6. It is also known as personality hormone.
7. Regulates cell metabolism.
Thyroid Dysfunction
 When the thyroid gland fails to secrete the normal level of hormones, the
condition is called thyroid dysfunction.
 It leads to the following conditions
Hypothyroidism
 It is caused due to the decreased secretion of the thyroid hormones.
 The abnormal conditions are simple goitre, cretinism and myxoedema.
Goiter
 It is caused due to the inadequate supply of iodine in our diet.
 It leads to the enlargement of thyroid gland which protrudes as a marked
swelling in the neck and is called as goiter.
Cretinism
 It is caused due to decreased secretion of the thyroid hormones in children.
 The conditions are stunted growth, mental defect, lack of skeletal
development and deformed bones.
 They are called as cretins.
Myxedema
 It is caused by deficiency of thyroid hormones in adults.
 They are mentally sluggish, increase in body weight, puffiness of the face
and hand, oedematous appearance.
Hyperthyroidism

 It is caused due to the excess secretion of the thyroid hormones which leads
to Grave’s disease.
 The symptoms are protrusion of the eyeballs (Exophthalmia), increased
metabolic rate, high body temperature, profuse sweating, loss of body
weight and nervousness.

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