Reproductive system

• The follicle-stimulating hormone from the pituitary gland targets

  • targets the seminiferous tubules of testes to produce sperm
  • targets the follicles in the ovaries for the maturation of ovarian follicles.
• Luteinising hormone from pituitary gland

  • Targets the interstitial cells of testes to stimulate the secretion of testosterone
  • Targets the cells of the ovaries to stimulate the secretion of oestrogens and progesterone.
• Oestrogen from the ovarian follicle and corpus luteum targets various organs to develop the female reproductive system and secondary sexual characteristics.
• Progesterone from the corpus luteum targets the uterus and placenta in order to maintain the endometrium and develop and maintain the placenta.
• Testosterone from cells in the testis target various organs in order to develop the male reproductive system and the secondary sexual characteristics.
• 1. Cells forming the wall of the primary follicle begin to enlarge and divide, creating a layer of cells around the developing oocyte.
  2. Secretions from these cells create a fluid-filled space that gradually forces the oocyte to the edge of the follicle and becomes a secondary follicle.
  3. As more fluid accumulates within the follicle, it continues to enlarge and gradually moves towards the surface of the ovary.
  4. On reaching the surface, it produces a mature follicle.


  Stages of the Ovarian Cycle
• Menstruation


  1-4 days. Uterine bleeding, accompanied by shedding of the endometrium.
• Preovulation


  Day 5-12. Endometrial repair begins; development of ovarian follicle; uterine lining gradually thickens.
• Ovulation


  Day 13-15. Rupture of mature follicle, releasing egg
• Secretion


  Day 16-20. Secretion of watery mucus by glands of endometrium, cervix and uterine tubes; movement and breakdown of unfertilised egg; development of corpus luteum.
• Premenstruation


  Day 21-28. Degeneration of corpus luteum; deterioration of endometrium.
• At mid-cycle, LH triggers ovulation - the release of the mature egg cell from the follicle. After ovulation, the empty follicle develops into a structure called the corpus luteum. It releases progesterone which maintains the thickness of the endometrium until the next period.
• The menstrual cycle is controlled by hormones produced by the pituitary gland (FSH) and the ovaries (oestrogen).
• If fertilisation does not occur, the corpus luteum degenerates at the end of the secretory phase and levels of progesterone fall rapidly. This causes the endometrium to break down and bleed during menstruation.
• Where does spermatogenesis occur?

  Inside the seminiferous tubules of each testis
• What are the immature cells called that line the seminiferous tubules?

  Spermatogonia
• How many chromosomes do spermatogonia contain?

  46 chromosomes
• What process do spermatogonia undergo at puberty?

  Mitosis
• What do the daughter cells from spermatogonia provide for sperm production?

  A continuous source of new cells
• What are the enlarged cells called that are formed from spermatogonia?

  Primary spermatocytes
• What type of cells are primary spermatocytes?

  Diploid cells
• What do primary spermatocytes undergo to produce secondary spermatocytes?

  The first stage of meiosis
• How many chromosomes do secondary spermatocytes contain?

  23 chromosomes
• What does the second meiotic division produce from each secondary spermatocyte?

  Two spermatids
• How many haploid spermatids are formed from one diploid spermatogonium?

  Four haploid spermatids
• What happens during the final stage of spermatogenesis?

  Spermatids mature into spermatozoa
• How long does the process of spermatogenesis take?

  72 days
• What nourishes the maturing spermatozoa during their development?

  Special cells that extend from the outer portion of the seminiferous tubule
• What is the process of producing ova called?

  Oogenesis
• What type of cells develop in the ovaries before a female baby is born?

  Oogonia
• How many chromosomes do oogonia contain?

  46 chromosomes
• What happens to primary oocytes at birth?

  They begin prophase of the first meiotic division but stop at this point
• What surrounds each primary oocyte at birth?

  A single layer of cells forming a primary follicle
• What initiates the process of follicle growth and maturation at puberty?

  The increase in gonadotropic hormones
• What does the primary oocyte complete during the first half of the ovarian cycle?

  The stages of the first meiotic division
• What does the secondary oocyte receive during the first meiotic division?

  Half the chromosomes and nearly all the cytoplasm
• What does the first polar body receive during the first meiotic division?

  Other half of the chromosomes but very little cytoplasm
• What happens to the secondary oocyte during the second meiotic division?

  It stops at metaphase
• What occurs during ovulation?

  The follicle ruptures, expelling the secondary oocyte along with its polar body
• What happens to the secondary oocyte if it is penetrated by a spermatozoon?

  Meiosis is quickly completed