reproduction in humans

• Hormone


  Chemical messenger secreted by an endocrine gland, secreted into the blood to alter the activity of the target organ
• Examples of hormones


  • FSH (produced from pituitary gland)
  • LH (produced from pituitary gland)
  • Oestrogen (produced from ovary)
  • Progesterone (produced from ovary/placenta)
  • Insulin (produced by the pancreas)
  • Glycagon (produced by the pancreas)
  • Adrenaline (produced from adrenal glands)
• Effect of adrenaline


  • Increase heart rate
  • Increase breathing rate and depth
  • Increase alertness
  • Vasodilation in muscles and vasoconstriction to digestive system
  • Stimulate the break down of glycogen in liver into glucose, to increase blood glucose level for more respiration
  • Eye pupil dilates
• Situations in which adrenaline is released

  • Fight
  • Exam due to stress
  • Running from a predator
  • Predator chasing a prey
  • Exercise
• Testes


  Produce sperm cells and testosterone
• Epididymis


  Storage of sperm cells till time of ejaculation
• Scrotum


  Protect the testes from physical damage, keep the testes at cooler temperature than body temperature by 2 to 3 C to allow development of sperm
• Sperm duct/vas deferens


  Transport the sperm cells from epididymis to the urethra by peristalsis
• Seminal vesicle and prostate gland


  Produce the seminal fluid (provide nutrients for the sperm to stay alive, medium for the sperm to swim, alkaline pH to neutralize the acidity of the vagina) where the seminal fluid+ sperm form semen
• Urethra


  Carry the semen from the sperm duct to tip of the penis, and carry urine out of the body
• Urine and semen never mix as there are rings of muscles close during sexual intercourse to ensure that there is no chance for semen and urine to get mixed, so they never get out of urethra at same time
• Ovary


  Produce egg cell (ovum), site of ovulation and produce oestrogen and progesterone
• Oviduct


  Site of fertilisation, lined with cilia to beat and move the zygote or embryo down the oviduct into the uterus (besides peristalsis)
• Uterus


  Uterus lining which is the site of implantation of the embryo, site of growth and development of the embryo into fetus, uterus muscle contract and birth time to help push the baby out through vagina
• Cervix


  Muscular rings close during pregnancy to help the fetus stay in place and dilates at birth time and open to pass the baby out
• Vagina


  Site of copulation and sperm deposition as well as birth canal
• Puberty in males


  Testosterone released from testes, responsible for the development of secondary sexual characteristics like voice deepening, shoulder widening, testes stimulated to start producing sperm cells, facial hair development
• Puberty in females


  Oestrogen released from the ovary, responsible for the development of secondary sexual characteristics like hips widening, menstruations starting, breast development, ovaries releasing egg cells
• Common changes in puberty for both girls and boys

  • Hair grown in arm pits, and in pubic regions
  • Growth spurt (sudden fast rate of growth)
  • Body smells increase
• Menstrual cycle


  A cycle that lasts for 28 days involving changes in uterus lining and ovary under the control of 4 hormones: oestrogen, progesterone, FSH, LH
• Role of FSH


  1. Produced during early days of menstrual cycle

  2. Produced from pituitary gland

  3. Target the ovary

  4. Stimulate the development of follicle around an egg to allow maturation of egg

  5. Stimulate the release of oestrogen/follicle release the estrogen
• Role of Oestrogen


  1. Stimulate the ovulation, by stimulating the release of egg from ovary into the oviduct to be ready for fertilisation

  2. Change the remaining follicle into corpus luteum to release progesterone

  3. Produced/secreted from pituitary gland (into the blood)
• Role of LH

  Stimulate the release of egg from ovary
• Role of Progesterone


  1. Maintain the thickness of uterus lining to be ready for implantation

  2. Inhibit the release of FSH (prevent maturation of another egg)

  3. Inhibit the release of LH (prevent release of another egg)

  4. First 3 months of pregnancy released from corpus luteum, and last 6 months pregnancy released from placenta
• Steps of Fertilisation


  1. Takes place in the first third of oviduct

  2. Sperm releases enzymes that digest and dissolve the jelly coat around the egg

  3. Male and female nuclei (haploid) fuse and form a zygote

  4. Zygote is diploid

  5. Zygote divide by mitosis forming a ball of cells called embryo

  6. Embryo moves down the oviduct into the uterus by action of cilia

  7. Embryo implanted into the uterus lining
• Adaptation of placenta


  • Has finger like projection (chorionic villi) to provide large surface area for exchange of substances between the fetus and the mother
• Role of placenta in protection


  • Act as barrier to reduce risk of transmission of pathogens from mother to fetus
  • Act as barrier to prevent mixing of different blood groups which might cause blood clotting
  • Protect the delicate blood vessels of the fetus from high blood pressure of mother
  • Allow transfer of antibodies from mother to fetus to provide passive immunity
• Role of placenta in exchange of substances

  • Allow exchange of substances between mother and fetus such as oxygen and glucose from the mother to fetus and waste products as urea and CO2 from fetus to mother
  • Secrete hormones
  • Secrete progesterone to maintain the thickness of the uterus lining and prevent uterine contraction
• Umbilical cord


  Join the fetus with the placenta, contain blood vessels (arteries and veins) to take away CO2 and urea from fetus to mother and deliver oxygen and nutrients (glucose) from mother to fetus
• Amniotic sac


  Secrete amniotic fluid which acts as a mechanical shock absorber, prevents temperature fluctuations, allows baby to practice movement, and provide sterile environment for fetus and collect fetal waste
• Calculating the fertile period

  1. Count 14 days from day 1 of bleeding/period as ovulation day

  2. Sperm survive 3 days, egg survive 2 days

  3. Fertile period is 5 days (2 days before ovulation, day of ovulation, 2 days after ovulation)
• Artificial selection by selective breeding

  Isolate animals to breed or use artificial insemination to allow selective breeding
• Captive breeding programmes


  Use assisted reproduction (AI and IVF) to breed animals and increase genetic diversity of species
• Assisted reproduction - IVF

  1. Treat female with hormones to allow super ovulation

  2. Inject FSH at early days of menstrual cycle to stimulate follicle development and egg maturation

  3. Inject LH to stimulate ovulation

  4. Collect sperm from donor, screen and wash to select healthy sperm

  5. Mix egg and sperm externally in a dish, allow zygote to divide and form embryo

  6. Insert multiple embryos into the uterus
• Reasons for IVF: very expensive, may not treat infertility successfully, may lead to multiple births, allows infertile couples to have children, allows study of embryonic stem cells and genetic screening
• Sexually transmitted disease


  Consists of nucleic acid (DNA or RNA) and protein coat (capsid)
• How HIV affects the immune system

  • HIV destroys T lymphocytes over time
  • Less stimulation of other lymphocytes and phagocytes
  • Less antibodies released
  • Less phagocytosis by phagocytes
  • Weakening of the immune system, leading to AIDS (a group of infectious diseases)
• Methods of transmission of HIV


  • Unprotected sexual intercourse
  • Sharing contaminated needle/syringe
  • Blood transfusion
  • Mother to fetus through placenta or during birth
  • Through breast feeding
• what does the seminal fluid do

  provide nutrients for the sperm to stay alive medium for the sperm to swim alkaline ph