Lecture 3: Fertilisation And Implantation Flashcards
What are some of the differences between somatic and germ cells?
Somatic Body Cells:
Diploid, 46 chromosomes, 2 sets of 23 chromosomes=2n
Germ Cells:
Haploid, 23 chromosomes, 1 set of 23 chromosomes=1n
Mitosis vs Meiosis (Meiosis 1 and 2)?
Mitosis:
The process of nuclear division in somatic cells (during cell division and multiplication) where each chromosome divides into two
Meiosis:
Cell division that occurs to form gametes, each with a haploid number of chromosomes. Meiosis 1 halves the number of chromosomes. Meiosis 2 halves the DNA content of each chromosome-splitting the sister chromatids
What are primary and secondary spermatocytes?
Primary spermatocytes/oocytes:
Cells that start and end meiosis I
Secondary spermatocytes/oocytes:
Cells that start and end meiosis II
Provide an outline of what happens in spermatogenesis (include where it occurs):
IN THE TESTIS:
Primordial germ cells start undergoing mitosis at around 7 weeks’ gestation. Spermatogonia undergo mitotic arrest until puberty, at which point mitosis resumes and meiosis begins.
The haploid products of meiosis II are round spermatids. These undergo spermiogenesis to become the elongated oval spermatids which are then released as spermatozoa (in a process calmed spermiation)
IN THE EPIDYMIS:
Sperm undergo maturation and become motile. There are also membrane charges in the head of the sperm that allow it to bind to the ZP.
IN THE FEMALE GENITAL TRACT: Capacitation: • Sperm become hypermotile • Able to bind to ZP • Able to undergo acrosome reaction Acrosome reaction: induced by the ZP of the egg • Ability to penetrate ZP • Ability to fuse with the egg membrane (sperm head has acrosome which contains hydrolytic enzymes to break down ZP)
What are the times for the formation of follicles in oogenesis?
Primordial=14-20/40 (fetal life)
Primary and Preantral= 20/40 (fetal life)
Antral= End of pregnancy (fetal life)
Pre-ovulatory= During reproductive life (adult life)
When is meiosis (1 and 2) completed in oogenesis?
Meiosis 1 is complete just before ovulation
Meiosis 2 is complete after fertilization
At which stage are female germ cell numbers the highest? Also, how many germ cells does a female have at birth, and at puberty?
16-20/40= six to seven million Birth= one to two million Puberty= 300,000
What happens during fertilization?
• Sperm penetration of the ZP
• Sperm fusion with egg-plasma membrane
• Egg metabolic activation:
1. Cortical granulation reaction fi block to polyspermy (at ZP and egg oolema)
2. Resumption of meiosis II in egg nucleus
What is a woman’s implantation window assuming a 28 day cycle?
The Window of Endometrial Receptivity= Days 20-24
Apposition, adhesion and implantation are the three stages describing what?
Implantation of the blastocyst.
Why might a woman experience a missed period?
Because implantation takes roughly 14 days, resulting in HCG release etc.
