reproductive systems

• Germ cells are called gametes (spermatozoa and secondary oocytes)
• Gonads produce gametes and secrete sex hormones
• Somatic cells have 46 chromosomes and are produced by mitosis
• Gametes are haploid cells (23 chromosomes) and are produced by meiosis
• Prophase 1: chromosomes become visible, mitotic spindle appears, nuclear membrane and nucleoli disappear, synapsis (copies of homologous chromosomes pair off), and crossing over
• Metaphase 1: homologous pairs of chromosomes line up along metaphase with attached microtubules
• Anaphase 1: each set of homologous chromatid chromosomes are pulled apart
• Result of meiosis 1 is 2 cells with haploid number of chromosomes
• Meiosis 2:

  -              No s phase prior to meiosis 2

  -              No synapsis or crossing over

  -              Sex is determined by presence of SRY (male)
• male Birth- puberty: background levels of testosterone

  Puberty: levels of GnRH from hypothalamus increase: causes anterior pituitary to release FSH and LH
• FSH stimulates spermatogenesis
• LH stimulates testosterone secretion
• Testes (gonads): surrounded by tunica albuginea, each is filled with 2 or 3 seminiferous tubules where sperm are formed (spermatogenesis)
• Spermatogenesis is the formation of sperm cells from spermatogonia (stem cells for sperm)
• Seminiferous tubules contain: spermatogonia (parent cell), primary spermatocyte, secondary spermatocyte (for meiosis 2), spermatid, spermatozoa, nurse (receptors for FSH) and setoli cells
• Leydig cells are in-between tubules and secrete testosterone
• Semen contains spermatozoa and glandular secretions from seminal vesicle and prostate gland
• Bulbourethral gland produces mucous over the head of the penis
• spermatogenesis

  primary spermatocyte undergo meiosis 1, secondary undergo meiosis 2
• spermatogenesis: round to mature sperm shape
• spermination: release into lumen of seminiferous tubules
• spermatozoon morphology:

  -              head contains DNA held together by protamine’s for compactness

  -              midpiece contains many mitochondria to form ATP for flagellum
• Vagina & external genitalia constitute the vulva
• tunica albuginea encapsulates the ovaries (dense CT), ovaries also have an outer lining of peritoneum. the cortex has follicles and the medulla has CT, BV, and lymphatics
• Germinal epithelium is a simple epithelial covering of the ovary (mesothelium)
• female hormones from birth and puberty

  GnRH causes anterior pituitary to release FSH and FSH stimulates recruitment and development of follicles

  LH stimulates oestrogen secretion from the follicles, ovulation, and formation of corpus luteum
• Puberty- menopause: uterine cycle driven by oestrogen and progesterone, fertilisation is required to maintain corpus luteum
• Oestrogen: proliferation and regrowth of endometrium
• Progesterone: from corpus luteum causes endometrium to prepare for implantation
• No fertilisation= no corpus luteum= no progesterone= menses (shedding of outer layer of endometrium)
• folliculogenesis

  Development of follicles within the ovary
• Store of follicles within the ovary: primordial follicles (primary oocyte arrested at prophase 1 and a single layer of flattened follicle cells
• From before birth – menopause: primordial follicles are stimulated to begin development (initial recruitment)
• without FSH, all follicles die (atresia)
• From puberty: FSH captures developing secondary follicles causing one to be ovulated a month (cyclic recruitment)
• Remnant ovulated follicle forms a small endocrine organ (corpus luteum)
• Oogonium only exist before birth, these becomes primary oocytes
• At day 13, there is an LH surge, this causes ovulation and resumption of meiosis (forms secondary oocyte and spits out excess chromosomes into polar body
• The primary oocyte is arrested in prophase 1
• At ovulation, the secondary oocyte is arrested in metaphase 1, and 1st polar body is produced