Origins of Gametes - Male Gamete Flashcards
Where do male germ cells colonise?
The medulla of the gonads
The sex cords
What do the germ cells do after colonising the gonads?
Before birth they proliferate by mitosis, forming spermatogonia
What happens to the male sex cords at puberty?
They hollow out to form seminiferous tubules
Tell me about spermatogonia
They are maintained by mitosis, they haven’t begun meiosis
This raw material of spermatogenesis is available for up to 70 years
They sit around the periphery of seminiferous tubules
Most spermatogonia just maintain their selves like any other cell in the body, but a small proportion divide differently, how?
They divide to produce two different cells
One to continue the line of all the other spermatogonia
But another that goes down a line to produce sperm
These are known as A1 spermatogonia
Describe what an A1 spermatogonia is.
It is a spermatogonia cell that divide mitotically to produce about 64 diploid cells that are all stuck together (not completely separated) all linked by cytoplasm
These are known as primary spermatocytes
When does meiosis begin in male gametes?
After the A1 spermatogonia has divided to produce 64 clones, known as primary spermatocytes
They then divide by meiosis to form 4 haploid cells each
Producing 256 haploid spermatids
Describe Sertoli cells.
They are from testicular origin
They are nurse cells
They help the spermatogonia, by feeding them and stimulating them
And they are the site of action for the hormones that control spermatogenesis
What happens to the spermatids once released, and what is this known as?
They are remodelled as they pass down the tubule through the rete testis, ducti efferentes and epididymis
They form spermatozoa
This is called spermiogenesis
What is semen made up of?
Secretions of seminal vesicle (60%)
Secretions of Prostate (20%)
Sperm (via vas deferens)
Secretions of bulbo-urethral glands
