This document discusses the pineal gland, also known as the epiphysis. It is located in the brain between the superior colliculi, where it plays roles in circadian rhythm and melatonin secretion. The pineal gland contains two types of cells and highly permeable capillaries. It secretes more melatonin at night and levels vary based on age, being highest in children. Melatonin is synthesized from tryptophan and metabolized in the liver. The pineal gland affects various functions like sleep, reproduction and hormone secretion through circadian rhythms.

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