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

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

Cells – 2 types

stromal cells – secretary

glial cells

Gland contains highly permeable capillaries

Size – infants >adults

Calcification – importance

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

ML-1 high affinity with two sub types mel 1a

,1b

ML -2 low affinity

Both are G protein coupled receptor

Shows diurnal variation

Secreted more during dark period of the day

Correlates to various internal activities

Role of hypothalamus in circadian rhythm

Role in circadian rhythm

Effects on gonads

Effects on MSH and ACTH

Induction of sleep

Inhibition of puberty

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

Cortex – actively multiplying lymphocytes

Medulla – reticular epithelial cells and some

lymphocytes in Hassall's corpuscles

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

Thymosin

Thymin – inhibits Ach release in NMJ

relation to myasthenia gravis