Science chp 17&18

• Puberty

  A time of rapid growth and development that starts at the age of 11 for girls and 12 for boys, triggered by hormones
• Physical changes in boys during puberty

  • Height increases
  • Shoulders become broader
  • Voice gets deeper
  • Hair starts to grow on armpits, legs, and face
  • Skin becomes oily and develops pimples
  • Penis grows longer
  • Testicles become bigger and produce sperm cells
  • Erections happen due to increase in hormones
• Physical changes in girls during puberty

  • Height increases
  • Waist becomes smaller
  • Hips become wider
  • Hair starts to grow on armpits and legs
  • Skin becomes oily and develops pimples
  • Breasts grow bigger and fuller
  • Ovaries start to release egg cells
  • Menstruation
• Emotional changes during puberty

  • Due to physical changes, we could be more aware and sensitive
  • Mood swings due to hormonal changes
• Diet and its effects on growth and development

  • Malnutrition can slow down growth and development
  • Vitamin D deficiency affects bone development
  • Iron deficiency affects developmental delay
  • Protein deficiency affects muscle building and cell repair
  • Lack of carbohydrates and fats affects energy and proper growth
• Diseases that affect human growth

  • Turner syndrome: genetic disorder in females causing stunted growth, short height, undeveloped ovaries and heart
  • Hypothyroidism: body doesn't produce enough hormones, causing stunted growth, delayed puberty, short limbs
  • Down syndrome: genetic disorder causing problems in brain growth and development, and heart not developing properly
• Effects of drugs

  • Caffeine: increases brain activity, causes restlessness, affects pregnancy, makes us more alert
  • Alcohol: affects the brain, ability to make sound decisions, damages the liver
  • Marijuana: causes hallucinations, mood swings, increases heart rate, affects memory
  • Methamphetamine: damages the brain, causes intense excitement/happiness, stresses the heart
  • Cocaine: damages the brain, causes intense excitement/happiness, stresses the heart, may cause restlessness
  • Ecstasy: causes hallucinations, intense happiness, stresses the heart
• Sperm

  • The head contains enzymes to help break the outer coating so it can enter the egg
  • The nucleus contains information that can be transferred during fusion
  • The tail helps it swim faster to the egg
  • Sperm cell is the smallest cell in the body
• Egg cell

  • The largest cell in the body
  • Genetic information is also found in the nucleus
• Male reproductive organs

  • Urinary bladder: holds urine
  • Prostate gland: releases fluid with nutrients for sperm
  • Urethra: tube that allows urine to pass out and release semen
  • Penis: body part that becomes hard and stiff to deposit semen into the female
  • Testes: produce sperm cells and testosterone
  • Scrotum: loose pouch that contains the testes and regulates temperature
  • Sperm duct: muscular tube that carries the sperm
• Female reproductive organs

  • Oviduct (Fallopian tube): connects the ovary to the uterus, wall pushes the egg to the uterus, where fertilisation occurs
  • Ovary: produces estrogen and progesterone, releases eggs
  • Uterus: pear-shaped with thick muscular wall, where the fertilised egg grows
  • Uterine lining: inner layer of the uterus
  • Urinary bladder: contains urine
  • Urethra: allows urine to go out
  • Cervix: ring of muscle at the lower end of the uterus, expands during birth
  • Vagina: muscular tube that connects to the cervix, where semen is deposited and the foetus exits
• Menstrual cycle

  1. Day 1-5: Menstruation - uterus tissues, egg, and blood is discharged through the vagina

  2. Day 6-10: Follicular phase - uterine lining thickens with blood capillaries

  3. Day 11-18: Fertile - a mature egg is released to the Fallopian tube (ovulation), may be fertilised by sperm

  4. Day 19-28: Luteal phase - uterus is ready for the growth and development of the fertilised egg, or it will shed within the next menstrual cycle
• Sexual intercourse

  1. Male's penis erects and enters the female's vagina, ejaculating semen

  2. If intercourse happens during the female's ovulation period, the sperm and egg will meet at the oviduct
• Fertilisation

  Occurs when the nucleus of the sperm and egg combine, creating a new offspring
• Effects of diet and drugs on fertility

  • Unhealthy diet can affect the quality of the egg cell and sperm cell
  • Use of drugs can also affect the quality and quantity of sperm, and may affect ovulation and quantity of the female's eggs
• Foetal development


  1. After fertilisation, the cell known as the embryo will move to the uterus and attach to the uterine lining, developing into a foetus over 40 weeks

  2. Placenta contains blood capillaries and vessels of the embryo, allowing exchange of substances, nutrients and oxygen from the mother to the foetus

  3. Umbilical cord connects the foetus to the placenta, transporting nutrients, oxygen and waste
• Foods to avoid during pregnancy

  • Seafood containing mercury, which is toxic and may affect the foetus's brain
  • Raw foods that may contain bacteria or viruses
  • Alcohol, which may cause facial deformities and affect the foetus
  • Caffeine, which may affect the foetus
• Diseases that affect pregnancy

  • Gonorrhoea: type of bacteria that may cause the foetus to die, be born early, or become blind if it enters the foetus's eyes
  • Syphilis: type of bacteria that may cause death to the foetus, affect the placenta and umbilical cord, and lead to problems with the spleen and liver in babies born with syphilis
• Female produce oestrogen and progesterone hormones. Male produce testosterone hormones.