Sex Education

• Testis (plural: testes) produces sperms and male sex hormone.
• Scrotum holds the testes outside the abdominal activity. It also allows the testesto be at about 2 - 3 lower than the body temperature, which is optimal for sperm development.
• The epididymis stores sperms temporarily and it is also where sperms become mature.
• The sperm duct transports sperms from the epididymis to the urethra.
• The uretha discharges semen and urine out of the body at different times
• The penis contains erectile tissues and many blood vessels. It transfers semen to the female body by ejaculation.
• The sex glands produce seminal fluid. It:

  • provides nutrients to activate sperm
  • provides a medium for sperms to swim
  • seminal fluid is alkaline so it can neutralize the acidity of the female's vagina
• there are 2 ovaries which produces ova and female sex hormones
• Oivduct is a tube which transport ova or embryos to the uterus. Each of them has a funnel-shaped opening near each ovary and is also a site of fertilization.
• The uterus allows the implantation of embryos into the uterine lining. It provides protection and a stable environment for the development of the embryo and foetus. The muscular wall contracts to push out the foetus during childbirth
• The cervix dilates to allow the foetus to pass through during childbirth.
• The vagina holds the penis during copulation and the environment is acidic to reduce bacterial growth. It also acts as a birth canal for the foetus.
• A sperm is very small and looks like a tadpole. It can swim by itself.
• The structure of a sperm consists of a head, midpiece and tail:

  • head: contains a nucleus which carries genetic information from the father. It also contains acrosome which contains enzymes for penetration into the ovum.
  • midpiece: contains many mitochondria which is the main site of respiration which releases energy from food for swimming
  • tail allows the sperm to swim
• Sperm is continuously produced by the testes starting at puberty throughout lifetime. Millions of them are ejaculated each time.
• A ovum is much larger than the sperm and is spherical-shaped. Unlike sperm, it cannot move by itself.
• Structure of an ovum includes nucleus, cytoplasm and cell membrane

  • nucleus: carries genetic materials from the mother
  • cytoplasm: contains food reserve for the the early development of the embryo
  • cell membrane: is surrounded by jelly coat
• A fixed number of ovum is produced by the ovaries during foetal development (i.e. before baby is born). It starts to develop and become mature during puberty and one mature ovum is released every 28 days until menopause,
• Secondary sexual characteristics are eternal features that tell the two sexes apart. They are not a part of the reproductive system (sex organs) but indirectly related to reproduction.
• Male SSC:

  1. Bear grows on face.
  2. Hair grows around armpits and around genital area
  3. The larynx enlarges and voice deepens
  4. The shoulders broaden and body become more muscular
• Female SSC:

  1. Hair grows in the armpits and around the genital area.
  2. More fat is deposited under the skin
  3. Hips broaden, giving the characteristic figure of female body
  4. Breasts develop
• The development of secondary sexual characteristics begins at puberty:

  1. more sex hormones are secreted by sex organs
  2. usually begins at 10-14 in girls and 11-15 in boys
• During puberty, males produces sperms in testes and the testes & penis enlarges.
• During puberty, females produce ova in the ovaries and there is a periodic change in the thickness of uterine lining
• Menstruation begins at puberty and gradually stops at menopause.
• Menstruation cycle lasts about 28 days but varies
• Day 1-5 of menstruation:

  • if no fertilization, the thickened uterine lining breaks down
  • blood, mucus and the unfertilized ovum are passed out of the body through the vagina as menstrual blood.
  • lasts for about 5 days
• Day 6-13 of menstruation cycle:

  • after menstruation, the uterine lining starts to repair and thicken, preparing the uterine lining for receiving an embryo
• Day 14 of cycle:

  • 1 ovum is released from the ovary, aka ovulation
  • ovum enters oviduct and is transported to uterus
  • ovum only lives for 24 HOURS !!!
• Day 15-28 of cycle:

  • uterine lining becomes VERY thick and is ready to receive an embryo
  • if no fertilization, the uterine lining breaks down and new cycle begins...
• IF FERTILIZATION OCCURS:

  1. uterine lining does not break down and its thickness increases further
  2. mestruation will not occur
• day of ovulation = 14th day after the onset of mentruation
• on the day of ovulation, there is a sudden, slight rise in body temperature
• the best day to get pregnant is ovulation day (14th) as the ovum only lives for 24 hours.
• During sexual intercourse, the penis erects and is out into the vagina. Semen containing millions of sperm is ejaculated into the vagina. The sperm swims up the vagina, cervix and uteris to the oviduct and finally meets the ovum, most of whom die on the way.
• If there is ovum in the oviduct, one sperm may fuse with the ovum, i.e. fertilization.
• If there is no ova in the oviduct, the sperm will die in two to three days.
• The sperm enters the ovum first-come-first-served. Once a sperm has entered, the jelly coat of the ova changes to prevent others from entering.
• Reasons why sperm might die before entering ova:

  1. flows out of vagina
  2. dies due to acidic environment in vagina
  3. goes to the wrong ovary
  4. caught in the oviduct
  5. immune system mistakes it as intruders and destroy it