physiology of Thymus and pineal gland

2.  Considered as Seat of soul by Rene
Descartes in 17th century
 Third eye
 Secretes melatonin
 Helps in functioning of biological clock
 Helps maintaining circadian rhythm
 Role in reproduction

4.  Aka – epiphysis
 5 * 7 mm -150 mg
 Situated between superior colliculi in
diencephalon
 Forms posterior boundary of third ventricle
under corpus callosum
 Above the hypothalamus

5.  Cells – 2 types
stromal cells – secretary
glial cells
 Gland contains highly permeable capillaries
 Size – infants >adults
 Calcification – importance

6.  N-acetyl -5 methoxy tryptamine
 Precussor – tryptophan
 Plasma Levels
 Higher in night
 Higher in children than adults
1-3 yrs -- 250pg/ml
8-15yrs – 120 pg
20-27 yrs – 70pg
67-84 yrs – 30pg
Metabolized in the liver by 6 hydroxylation and
conjugation

7.  ML-1 high affinity with two sub types mel 1a
,1b
 ML -2 low affinity
 Both are G protein coupled receptor

8.  Shows diurnal variation
 Secreted more during dark period of the day
 Correlates to various internal activities
 Role of hypothalamus in circadian rhythm

11.  Role in circadian rhythm
 Effects on gonads
 Effects on MSH and ACTH
 Induction of sleep
 Inhibition of puberty

12.  Lymphoid structure of lower neck in front of
trachea below thyroid
 10-12g at birth and gradually enlarges till
puberty to reach 20 -30g
 reduces in size with age 3-6g
 Castration – effects on thymus

13.  Cortex – actively multiplying lymphocytes
 Medulla – reticular epithelial cells and some
lymphocytes in Hassall's corpuscles

14.  Immunological ; maturation of T lymphocytes
 Thymosin ; reticulo epithelial cells , lymphopoiesis
in the period of 3months before and 3
months after birth
 Thymectomy and its effects
1) lymphopenia and lymphoid atrophy
2) failure to produce Ab
3) reduced delayed hypersensitivity
4)failure to produce graft rejection

15.  Thymosin
 Thymin – inhibits Ach release in NMJ
relation to myasthenia gravis