[HISTO] Male Repro

• germ cells are haploid
• zygote is diploid
• embryo - from implantation up to the end of 8th week after fertilization
• fetus - from the end of 8th week after fertilization until birth
• spermatogenesis is the production of male gamete
• oogenesis is the production of female gamete
• primordial germ cells are the earliest recognizable stem cells of the male gametes and appear in 2nd week of intrauterine life
• spermatogonia is an immediate differentiation of primordial germ cells upon reaching the developing gonads by the 5th week of intrauterine life
• spermatogonia is the precursor cell of spermatozoa
• spermatogonia has 3 types: type Ad, type Ab, and type B
• spermatogenesis is the differentiation of spermatogonia to spermatozoa
• spermatogenesis occurs in seminiferous tubules of the testis
• spermatogenesis has 3 stages, spermatocytogenesis, meiosis, and spermiogenesis
• type Ad is considered as reserve stem cells and does NOT enter spermatogenic cycle
• type Ap is in spermatogenic cycle and actively replenish or produce type B spermatogonium
• in type Ap, cytokinesis in telophase is not completed since it occurs in subsequent cell divisions before they are released in the lumen of the seminiferous tubules as sperm cells
• the daughter cells in type Ap are connected to each other by cytoplasmic bridges
• type B spermatogonia divide actively to produce primary spermatocytes
• 1st stage of spermatogenesis

  primordial germ cell -> type Ad -> type Ap -> type B -> primary spermatocyte (spermatogenesis)
• 2nd stage of spermatogenesis

  primary spermatocyte (spermatogenesis) -> secondary spermatocyte (meiosis 1) -> spermatid (meiosis 2)
• secondary spermatocyte are the rarest because they rapidly undergo through meiosis
• 3rd stage of spermiogenesis

  spermatid -> spermatozoon
• interphase - chromosomes replicate and give rise to 2 sister chromatids
• prophase 1 takes about 22 days to complete
• leptotene - chromosome condenses and forms threads in the nucleus
• zygotene - chromatin condenses further and homologous chromosomes pair up to make 23 pairs
• pachytene - sister chromatids are now recognizable and crossing over or exchange of chromosome happens
• diplotene - homologous chromosomes begin to separate
• diakinesis - nuclear membrane starts to disintegrate and the homologous chromosomes move a little further away from each other
• metaphase 1 - homologosomatic and sex chromosomes align at the equatorial plate
• anaphase 1 - sister chromatids separate and move to opposite poles of the cell
• telophase 1 - each of the two groups of chromosomes that migrated to the opposite poles acquires a nuclear envelope
• spermiogenesis - the haploid spermatids will undergo transformation and are no longer capable of mitosis, hence maturation
• the spermatids will transform to spermatozoa
• 3 stages of spermiogenesis: golgi phase, acrosomal phase, and maturation phase
• (1) during the golgi phase, the golgi complex produces proacrosomal granules that will coalesce to form the acrosomal vesicle that migrates to one pole of the cell
• (2) during the golgi phase, the nucleus will start to condense and elongate. simultaneously, the centrioles will begin to move toward the pole of the cell opposite of the acrosomal vesicle
• (3) during the golgi phase, they align to the long axis of the nucleus and one centriole starts to elongate to form the flagellum or tail
• (4) in acrosomal phase, the acrosomal vesicle transforms into a cap that covers a big part of the nuclear surface called acrosome. the nucleus elongates and condenses further and the tail continues to lengthen
• (5) during acrosomal phase, the cytoplasm migrates and takes all the mitochondria to the first part of the tail to surround it and form a thick segment called middle piece