Chapter 27: Sperm production Flashcards
Where do primordial cells form?
they form in the yolk sac, a membrane associated with the developing embryo.
What are primordial germ cells?
the first stem cells specifically destined to become sperm
What happens to the primordial germ cell in the fifth to sixth week of development?
they crawl into the embryo itself and colonize the gonadal ridges. This is where they become stem cells called spermatogonia
Where do spermatogonia sit during childhood?
They lay along the periphery of the seminiferous tubule near the basement membrane, outside of the blood testis barrier
they are also dormant through childhood
How do spermatogonia divide?
they divide by mitosis
What is a type A spermatogonium?
Type A spermatogonia serve as a lifetime supply of stem cells, so men normally remain fertile even in old age.
What is a type b spermatogonium?
its the other daughter cell that migrates slightly away from the tubule wall on its way to produce sperm.
What does a type B spermatogonium become?
it enlarges and becomes a primary spermatocyte.
Primary spermatocyte
What happens when the spermatocytes moves forwards and goes through the BTB (blood testis barrier)
Now that the cell is safely isolated from blood born antibodies it undergoes meiosis I. This gives it two equal size haploid and genetically unique secondary spermatocytes.
What happens when each secondary spermatocyte undergoes meiosis II?
it dives into two spermatids for a total of four for each spermatogonium.
What is spermiogenesis?
after a secondary spermatocyte under goes meiosis II it no longer dives. Instead it undergoes spermiogenesis in which it differentiates into a single spermatozoon. The spermatid sprouts a tail (flagellum) and discards most of its cytoplasm making the cell light weight and self propelled
How do spermatozoon move?
via ejaculation
How long does it take for a type B spermatogonium to become a mature spermatozoa?
it takes about 70 days
