UNIT 3 – REPRODUCTION
THE FEMALE REPRODUCTIVE SYSTEM
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Sexual characteristics
Sexual characteristics are physical
diferences between men and women.
Primary sexual characteristics are the differences between male and
female reproductive organs. Secondary
sexual characteristics are other differences like men have more hair or women
have wider hips.
·
The female reproductive organs
-
Ovaries: produce reproductive cells called
ova. One ovum matures each month.
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Fallopian tubes connect the ovaries to the
uterus.
-
The uterus is an organ with muscular walls.
Babies develop here. The part of the uterus that is connected to the vagina is
called cervix.
-
The vagina is a muscular organ that connects the
uterus with the exterior. The vulva covers the opening vagina.
·
Puberty in girls
Changes in girls happen during th
puberty (between 10 and 16 years old): breasts develop, pubic hair grows, they
grow and menstruation starts.
·
The menstrual cycle
Ovaries starts to release ova. An ovum
is released from the ovaries to the fallopian tubes about every 28 days, this
is ovulation. The walls of the uterus
get thicker with extra blood and tissue to prepare it for fertilisation. When
fertilisation doesn´t happen the ovum dries and levaes the body with blood,
this is menstruation. It lasts about 3 -5 days. About 50 women don´t produce
more ova and menopause starts.
THE MALE REPRODUCTIVE SYSTEM
·
Sperm
The male reproductive system produces sperm. It has an oval shape and a tail that allows
them to move up the fallopian tubes and fertilise the ovum.
·
The male reproductive organs
The testicles produce
and store sperm. They are covered by a
bag of skin called scrotum and it regulates
the temperature of the testicles. They need to be a Little bit cooler
than the rest of the body.
Sperm travels through
two tubes called vasa deferentia to the seminal vesicles. They produce a liquid that forms part of the
semen. The prostate produces a liquid
that also forms part of the semen.
The penis contains the
urethra. The semens travels through the urethra to the outside of the body. The
urethra also expels urine.
·
Puberty in boys
During
th epuberty testicles activate and produce testosterone, whihc produces
difeerent physical changes: penis get larger and thicker and boys become
fertile, pubic hair grows, boys grow and become heavier, the voice changes,
etc.
·
Genes
Parents
pass their characteristics to their offspring thorugh genes.
PREGNANCY AND
BIRTH
Human reproduction involves two
cells: a female ovum and a male sperm.
It has different steps:
1. Felisitation
happens when the ovum is realised into the fallopian tubes. The man´s penis is
inserted into the woman´s vagina and the sperm is expelled there. One sperm fertilised one ovum. The fertilised
ovum is called zygote.
2. Development
of the embryo. After fertilisation the zygote travels to the uterus where its
divides and becomes an embryo. It fixes onto the walls of the uterus where it
will continue to grow.
3. Development
of the foetus. Afert about nine months, all the organs are formed and the embryo
transforms into a foetus. It is floating in a sac of amiotic fluid. The foetus
recives nutrients and oxygen through the placenta. Waste products and carbón
dioxide are also transmited to the mother through the placenta and it is
connected to the baby by the umbilical cord.
4. Birth.
Preganancy lasts about 280 days. When the foetus is ready to be born it pushes
against the cérvix, whihc starts to open and widen. The amniotic fluid is expeled and the uterus
starts to contract. The cérvix opens until the baby can pass. The baby pushed
against the cérvix with the head. When the baby is born the umbilical cord is
cut and th scar is our navel. The placenta is expeled too after the baby.