Theca cells synthesize and secrete progesterone.

TLS Online TPP Program

#Id: 7021

#Unit 5. Developmental Biology

The adult stem cell is housed in and controlled by its own adult stem cell niche, which regulates stem cell self-renewal, survival, and differentiation of those progeny that leave the niche.

TLS Online TPP Program

#Id: 7022

#Unit 5. Developmental Biology

Stem cell niches in the testes of male Drosophila illustrate the importance of local signals, cell-to-cell adhesion, and asymmetric cell division.

TLS Online TPP Program

#Id: 7023

#Unit 5. Developmental Biology

The daughter cell attached to the hub is maintained as a stem cell, whereas the cell that is not touching the hub becomes a gonialblast, a committed progenitor cell that will divide to become the precursors of the sperm cells.

TLS Online TPP Program

#Id: 7024

#Unit 5. Developmental Biology

The somatic cells of the hub create asymmetric proliferation by secreting the paracrine factor Unpaired onto the cells attached to them

TLS Online TPP Program

#Id: 7025

#Unit 5. Developmental Biology

Unpaired protein activates the JAK-STAT pathway in the adjacent germ stem cells to specify their self-renewal

TLS Online TPP Program

#Id: 941

#Unit 5. Developmental Biology

 The mode of fertilization in sea urchin being external, the egg and spermatozoa are released into the sea water.