Description
Learning Objectives
– Explain information related to indifferent gonad
– Interpret scenarios on testis and ovary
– Answer questions about meiosis
– Interpret scenarios on spermatogenesis
– Solve problems concerning oogenesis
INDIFFERENT GONAD
Although sex is determined at fertilization, the gonads initially go through an indifferent stage between weeks 4 and 7 when there are no specific ovarian or testicular characteristics.
The indifferent gonads develop in a longitudinal elevation or ridge of intermediate mesoderm called the urogenital ridge.
Primordial Germ Cells
Primordial germ cells arise from the lining cells in the wall of the yolk sac. At week 4, primordial germ cells migrate into the indifferent gonad.
Components of the Indifferent Gonad
- Primordial germ cells migrate into the gonad from the yolk sac and provide a critical inductive influence on gonad development.
- Primary sex cords are fingerlike extensions of the surface epithelium that grow into the gonad that are populated by the migrating primordial germ cells.
- Mesonephric (Wolffian) and the paramesonephric (Mullerian) ducts of the indifferent gonad contribute to the male and female genital tracts, respectively.