ANHB1101 Lecture Notes - Lecture 30: Zygote, Cumulus Oophorus, Motility
3 Jun 2018
School
Course
Professor
Lecture 30
Monday, 23 May 2016
8:50 am
Gametogenesis and Fertilization:
Spermatogenesis:
• Mitotic proliferation
• Meiotic division - major component
• Cell remodelling (spermiogenesis)
• Spermatogonium
o Undergo rounds and rounds of mitosis that starts at puberty
o Type A always remain close to the basement membrane and continue to
go through mitosis
o Type B undergo further stages/mechanisms to form sperm
• Primary spermatocyte
o First cell that will enter the process of meiosis
o Contains 23 pairs of chromosomes
• Secondary spermatocyte
o After first meiotic division
o Cells become haploid - 23 chromosomes
• Spermatids
o After second meiotic division
o Full meiosis procedure that occurs in males
• Spermatozoa
o Cellular remodelling (spermiogenesis)
o Significant amount required to differentiate into a sperm
• Cycle of the seminiferous epithelium
o Stem cells enter into spermatogenesis approx. every 16 days
o Takes ~74 days to complete
• Spermatogenic wave
o Adjacent tubules at different stages of the seminiferous cycle
o Always starts at a given point in the tube and moves along
• Sertoli cells 'organise' spermatogenesis
• Sertoli cell function requires FSH and testosterone
• Developing cells always in contact with sertoli cell - receive nutrients/signals
• Sertoli cells connect to one another via gap junction - mechanism in which they
can communicate with one another to coordinate spermatogenic wave
Spermiogenesis:
• Different organelles within cell go on to form important parts of the mature
sperm
• Golgi apparatus has glycoprotein rich granules
• Differentiate into acrosomal granule - slowly migrates and covers nucleus of
cell
• Matures to form head cap (acrosomal cap)
• Components within nucleus - one migrates to end of the nucleus
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Document Summary
Sperm in the male tract: emission, smooth muscle contraction of prostate, vas, seminal vesicles, contents into urethra, seminal fluid transported to the base of the urethra, relies on parasympathetic nervous system, ejaculation. Important to get through barriers to fertilization: barriers to union of sperm and oocyte, cumulus oophorus, granulosa cells from follicle, capication breaks this barrier, zona pellucida, acrosomal reaction enables sperm to get through this barrier. Acrosome reaction: acrosomal cap - inner and outer layer, special proteins attach to receptors on zona pellucida, once that binds, sperm can fuse and enter the oocyte. Fertilization: outer membranes fuse, stimulates completion of second meiotic division of oocyte, ovum formed, block to polyspermy - impenetrable to other sperm, sperm nucleus decondenses and forms male pronucleus. Results of fertilization: dna replication occurs in male and female pronuclei, pronuclei fuse - diploid number of chromosomes restored, new individual - zygote, primary sex determination (xx or xy)
