Three estrogens are present in the plasma of the human female:

1. β-estradiol

2. Estrone

3. Estriol

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#Id: 6577

#Unit 7. System Physiology – Animal

When the embryo has functional testes, Leydig cells of the fetal testis secrete testosterone, and the Sertoli cells secrete MIS (MRF)

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#Id: 6578

#Unit 7. System Physiology – Animal

MIS is a 536-amino-acid homodimer a member of the TGF-β superfamily

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#Id: 6579

#Unit 7. System Physiology – Animal

MIS causes regression of the müllerian ducts

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#Id: 6580

#Unit 7. System Physiology – Animal

The walls of the seminiferous tubules are lined by primitive germ cells and Sertoli cells, large, complex glycogen- containing cells that stretch from the basal lamina of the tubule to the lumen

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#Id: 6581

#Unit 7. System Physiology – Animal

Tight junctions between adjacent Sertoli cells near the basal lamina form a blood–testis barrier

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#Id: 6582

#Unit 7. System Physiology – Animal

Sertoli cells secrete 

Androgenbinding protein (ABP), inhibin, and MIS

The fluid in the lumen of the seminiferous tubules is quite different from plasma; it contains very little protein and glucose but is rich in androgens, estrogens, K+ , inositol, glutamic and aspartic acids.  Maintenance of its composition depends on the blood–testis barrier.