BIOLOGY

• • Sex cells called gametes.
• • Gametes are produced from germline cells.
• • Germline cells first divide by mitosis.
• • Gametes are later produced by meiosis in the testis or ovary.
• • Sperm are produced in the seminiferous tubules of the testis.
• • Testosterone is released from the interstitial cells of the testis.
• • The prostate gland and the seminal vesicles secrete fluids collectively called seminal fluid.
• • Seminal fluids maintains the mobility and viability of the sperm.
• • The ovaries contain many immature ova in various stages of development.
• • The ova are contained within follicles.
• • The follicles protect the ovum and secrete hormones.
• • The release of an ovum from the ovary is called ovulation.
• • From puberty to the menopause, ovulation takes place every 28 days on average.
• • After ovulation, the follicle develops into the corpus luteum.
• • The corpus luteum secretes hormones.
• • After ovulation, the ovum travels down the oviduct where it may be fertilised to form a zygote.
• • Fertilisation takes place when a single sperm fuses with an ovum and its nuclear material joins with that of the ovum.
• • The zygote undergoes a series of divisions as it passes down the oviduct into the uterus.
• • At ovulation, the ovum is released into the oviduct.
•  Sperm are produced in the seminiferous tubules of the testes and ova within the follicles
• label the diagram:

  A) immature ovum in developing follicle

  B) maturing follicle, releasing hormone/oestrogen

  C) follicle ruptures at surface of ovary; ovulation/ovum r

  D) corpus luteum

  
• • The hypothalamus triggers the onset of puberty by passing a releaser hormone to the pituitary gland.
• • The pituitary responds to this releaser hormone by, in turn, releasing follicle stimulating hormone (FSH), luteinising hormone (LH) and interstitial cell stimulating hormone (ICSH).
• • FSH and LH control the production of gametes throughout the reproductive life of the individual.
• • FSH and LH production form part of a negative feedback cycle.
• • FSH stimulates the cells lining the seminiferous tubules to produce sperm.
• • ICSH stimulates the interstitial cells to release testosterone.
• • Testosterone stimulates the production of sperm by the seminiferous tubules.
• • Testosterone activates the prostate gland and the seminal vesicles.
• • High levels of testosterone inhibit the production and release of FSH and ICSH. this is an example of negative feedback control
• • The first day of menstruation marks the start of the menstrual cycle.
• • Aa menstrual cycle lasts 28 days on average.
• • The part of the menstrual cycle up to the point of ovulation is called the follicular phase.
• • The part of the menstrual cycle after ovulation is called the luteal phase.
• • In the first few days of the cycle, the pituitary releases relatively high levels of FSH.
• • FSH stimulates the development of follicles in the ovary.
• • FSH stimulates the release of oestrogen by the follicle.
• • Oestrogen stimulates the proliferation of the endomentrium in preparation for implantation.
• • High oestrogen levels around the time of ovulation cause the production of cervical mucus, which is more watery and more easily penetrated by sperm.
• • The high oestrogen levels of the late follicular phase cause the pituitary to release a surge of LH into the blood.