File:Nelsen1953 fig022.jpg

Fig. 22. Chart showing the effects of the hypophyseal anterior lobe upon the developing gametes

It also suggests the various factors influencing pituitary secretion of the gonadotrophic hormones. FSH and LH. Observe that the primitive gamete in the cortex of the ovary is subjected to the cortical environment and develops into an oocyte, whereas in the medullary or testicular environment it develops into a spermatocyte. Experiments upon sex reversal have demonstrated that the medullary and cortical portions of the gonad determine the fate of the germ cell. In the male area or medulla, the germ cell differentiates in the male direction, while in the cortex, the differentiation is in the direction of the female gamete or oocyte, regardless of the innate sex-chromosome constitution of the primitive germ cell.

The fate of the germ cell thus is influenced by four main sets of factors:

1. Internal and external environmental factors, controlling the secretions of the pituitary body,
2. Environment of the testicular tissue (medulla) and possible humoral substances produced in this tissue,
3. Environment of the ovarian tissue (cortex) and possible humoral substances elaborated there, and
4. Secretions of the anterior lobe of the pituitary body.

Reference

Nelsen OE. Comparative embryology of the vertebrates (1953) Mcgraw-Hill Book Company, New York.

Cite this page: Hill, M.A. (2024, April 26) Embryology Nelsen1953 fig022.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Nelsen1953_fig022.jpg

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