Origin and Development of germ cells in male and female Flashcards
What are the earliest germ cells called?
Primordial germ cells
Where are Primordial germ cells originated from?
Yolk sac
Where do Primordial migrate to from the yolk sac?
through hind gut to genital ridge
What tissue does primordial cells migrate through?
Mesentary tissue
Where do gonads develop?
Genital ridge
Where does the kidney develop from?
Mesonephros
What cells do primordial cells associate with at the genital ridge?
Pre-sertoli cells (somatic cells)
In the male genital ridge how do the somatic cells align themselves?
Align in cords and develop into semineferous hoops to tubules as they grow
What cells settle on the tubule wall first?
PGC primordial germ cells then somatic cells
What are the male and female processes called?
Spermatogenesis
Ovagenesis
Where are the Spermatogonia developed in males?
Outside the blood testes barrier BTB
In females what is different in the associate with somatic cells?
Stop in cortical region from the ridge and form a layer around each germ cell
What is BTB?
Blood testes barrier - tight junctions that hold the cell together, it is impermeable so cells have to go through cells
Why is BTB important?
The immune system develops very early, so post puberty cells express new proteins that immune would think are foreign bodies
What does spermatogonia develop in regards to BTB?
develop germ cells behind the barrier
How do PGC’s proliferate and what in to?
Mitosis and into gonocytes
What happens to gonocytes?
Proliferate by mitosis and develop into pro-spermatogonia (end of foetal stage)
What happens to early spermatogonia and what do they acquire?
Become stem cells and acquire self-renewal capacity
What effects can Gonocytes not proliferating cause?
if stuck in cell cycle arrest then remain in situ, can randomly activate and proliferate to form tumours
What happens to the spermatogonia sitting on tubule wall?
Embeds into sertoli cells with tight junctions forming BTB
Where and what does spermatogonia develop into?
change to spermatocytes from cytoplasm to the lumen where they develop
Why is a large stem cell pool good in primates?
develops same number as germ cells and so greater human resilience
What division produces spermatocytes?
Peri-natal spermatogonial division (2nd mitotic division)
Where do spermatocytes arrest in?
Prophase of 1st meiotic division
What is the role of preleptotene spermatocytes and what phase does it occur?
Duplicate DNA shape in S-phase
What do Leptotene and zygotenes do?
Chromatin remodelling
What is the role of Pachytene spermatocytes?
Transcription and translation , increases in size
What is the role of diplotene?
Enters meiosis , prepare proteins for after meiosis
What happens at the first meiotic division?
chr seperate and cells become haploid - activate after meiosis
What happens at the 2nd meiotic division?
homologous chromatids seperated leads to spermatid phase
What happens at the spermatid phase?
The haploid cells produce 4 gametes (sperm cells)
What is the term for the development of spermatids?
Spermiogenesis
What are the 3 types of spermatids?
Round, elongation, maturation
What happens during the round phase?
Nucleus still does transcription, but nuclear histones are replaced by transition proteins, flagellum develops
What happens to at the elongation phase to spermatids?
Transition proteins are replaced by protamines, nuclear size decreases and flagellum full develops, cytoplasm shrinks to droplet
What happens to spermatids at the maturation phase?
shed into lumen of tubule at spermiation and cytoplasmic droplet phagocytosed by sertoli cell
What cell phagocytes the cytoplasm?
Sertoli cell
What happens at spermiation?
Mature spermatoza shed into lumen of tubule
What is the female primordial germ cell called?
Oogonium
What is important at oogenesis?
2 cell cycles occurm, 1st at meiosis phase 1, second at m phase
What cells in arrested in prophase 1 of females?
Diplotene
What does oogonium turn into after mitosis?
Primary oocyte
What core does the primary oocyte form?
Primordial follicle
how is the primordial follicle formed?
Thin covered spindle somatic cells form around oocyte form the follicle at germinal vesicle
How do Primary follicles grow?
After puberty , 1 or a few primordial follicles are randomly selected to further develop into a primary follicle
When does final oogensis occur?
Has zuna pallucida so doesnt rupture, but when implanted with sperm
What is the zona pallucida?
A packet of dna covering the oocyte - secrete glycoproteins
How many germ cells to an oocyte?
1, The rest form a polar body - only at fertilization
What happens at the dictyate stage after 2nd cell cycle arrest?
Large numbers of dicytate germ cells die by apoptosis in the last trimester
What is the pre-antral follicle?
Division of granulosa cells that has gap junctions and is avascular
Where cells surround the internal and external follicle?
Ovarian stroma cells
What is the antral follicle?
When the gran cells proliferate and increase in size they secrete follicular fluid called antrum
What is antrum consisted of?
Mucopolysaccharides and serum
What is the thick gran cell that is connected to oocytes as a stalk?
Cumulus oophorous - continues storage of mRNA
