Summary
Summary Grade 9: NS: Revision
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- Natural Sciences
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- 9
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Reproductive system Produces sex cells for the purpose of continuing the species. Reproduction forms
part of the life cycle of any living organism. The main purpose of reproduction is
to ensure the existence of a species. In humans, two people are needed for
reproduction – one male and one female. The reproductive systems of both
genders are well-suited to fulfil this function. During puberty, a child’s body is
prepared to reach maturity when hormones are secreted in to the bloodstream.
Hormones activate the testes in boys and ovaries in girls to secrete sexual
hormones. Testosterone is the male sexual hormone and oestrogen is the female
sexual hormones.
Components:
Testes (the testes are able to produce sperm cells which are the male sex cells)
Uterus (the ovaries produce egg cells which are the female sex cells)
Ovaries (the uterus is where the baby will grow until it’s ready to be born)
Main processes:
Copulation
Ejaculation
Ovulation
Menstruation
Fertilisation
Cell division
Growth
Implantation
Maturation
Health issues:
Infertility (The inability of a male or female to reproduce)
STD’s/ STI’s (Diseases such as Syphilis, HIV, Chlamydia and pubic lice are
transferred during sexual intercourse and close contact)
Foetal alcohol syndrome (The misuse of alcohol during pregnancy can lead to
FAS in the baby. Defects that can occur include stunted growth (before birth),
facial deformities, reduced brain size and abnormal development)
Explanation on main processes:
1. Penis is placed inside the vagina (copulation)
2. Penis releases sperm cells into vagina (ejaculation)
3. Once a month an egg cell is release into the woman’s fallopian tube (ovulation)
Sperm cells swim to fallopian tube
4. One sperm cell fuses with egg cell (fertilisation) OR If fertilisation doesn’t occur,
the lining of the uterus is released into the vagina (menstruation)
5. Fertilised egg divides into more and more cells (cell division)
6. Cell division continues. More and more cells are formed (growth)
7. Fertilised egg moves from fallopian tubes down into the uterus where it attaches
itself to the lining of the uterus (implantation) Woman is pregnant
8. Baby is born after 9 months/ 40 weeks. Baby grows and eventually develops into
an adult. (maturation) The adult can reproduce.
Copulation & ejaculation: Males and females perform sexual intercourse where a
man places his erect penis in to a woman’s vagina. (Also known as coitus) During
sexual intercourse semen containing sperm cells is released by the penis in to the
vagina. Fertilisation: Takes place inside the female. Sperm cells move through the
cervix and enter the fallopian tube where the sperm cell and egg fuse creasing a
zygote. The zygote starts to grow through cell division and moves down the fallopian
, tube to the uterus. The zygote attaches to the endometrium (wall of the uterus)
resulting in pregnancy. The zygote is now known as an embryo. The thickened uterus
wall forms a special tissue, namely the placenta which plays an important role in the
nutrition of the embryo and removal of waste products. Ovulation: Once a month the
ovaries in females release an egg. The ovum (egg) is released in to the fallopian tube.
The lining of the uterus becomes thicker due to the blood vessels increasing in size.
The ovum moves through the fallopian tube towards the uterus. The ovum is ready
for fertilization. Pregnancy: Females are pregnant for approximately 40 weeks/9
months. Pregnancy is the phase between fertilisation and birth. Approximately 8
weeks after fertilization, the embryo starts to look like a human being and is called a
foetus. The foetus is attached to the placenta by an umbilical cord which transports
nutrients and oxygen from the mother. The umbilical cord also transports carbon
dioxide and waste products from the foetus to the mother who then excretes this
through her excretory system.
Menstrual cycle
The menstrual cycle begins on the first day of bleeding (or menstruation). The thick
layer of spongy tissue filled with blood covering the endometrium (uterus wall)
breaks down and passes through the vagina. While menstruation is happening, an
ovum starts to mature in one of the ovaries for the next cycle. (Day 1-5) A new layer
of spongy tissue with blood starts to form on the endometrium in the uterus. The
ovum continues to mature in one of the ovaries. On day 14, the mature ovum is
released from the ovary into the fallopian tube. This is called ovulation. (Day 6-14)
The spongy tissue of the endometrium continues to get thicker. The ovum travels
down the fallopian tube to the uterus. It takes 3–5 days for the ovum to reach the
uterus. When the ovum is in the fallopian tube, the woman can fall pregnant because
the sperm usually fertilises the ovum in the fallopian tube .If the ovum is not
fertilised, it passes through the uterus and out of the vagina .The endometrium also
breaks down and pulls away from the wall of the uterus and menstruation occurs.
The whole menstrual cycle starts again.
Day 6 - 14
What happens during puberty?
Boys become taller. Boys become more muscular and their shoulders become
broader. Their voice becomes deeper. Hair starts to grow on the face, under the arms
and around the genitals. Hair sometimes grows on the chest, stomach and back. Girls
become taller. Hips become wider and rounded. Menstruation starts. Breasts become
enlarged. Hair starts to grow under the arms and around the genitals.
Contraception’s:
The condom:
Stops the sperm from entering the female’s vagina and reaching the egg. Prevents
any fluids mixing between partners. Can prevent people from STD’s – STD’s are
passed on from one person to another when they have sexual contact with an
infected person
IUD (intrauterine device)
A small piece of bendable plastic shaped like a T. A medical doctor must insert
the apparatus in to the uterus as well as remove it.
Sterilisation in females
A surgical procedure in women where the fallopian tubes are removed, clamped
shut, cut off or scorched to prevent sperm cells from reaching the egg cell. A
hysterectomy in women is a procedure which removes the entire uterus.
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