1) Single celled creatures -> divide into two
2) Multi cellular -> produce offspring by breaking away a part
of their bodies.
•Fission In binary fission the parent organism is
replaced by two daughter organisms, because it literally
divides in two
•Budding Some cells split, resulting in a 'mother' and
'daughter‘ cell. The offspring organism is smaller than the
•Spore formation These spores grow into multicellular
individuals without a fertilization event
•Fragmentation a new organism grows from a fragment
of the parent.
the process of producing
▪ Two sexes: each produce reproductive cells called gametes
▪ Male: produces sperms (spermatozoa). Male always produce a
large number of them.
▪ Female: ova (many ovum) or eggs. They are produced in a smaller
and limited number.
*in larger quantities to increase the chance of
*Sperms feed on nutrients in the semen fluid
* have long tails which helps them swim
*has a large number of mitochondria
*it stores nutrients.
*one egg at a time.
*Eggs can’t move
The Reproductive System
* We need a
so the human race
This system is designed to
*produce, nourish, and transport either
the egg or sperm.
*look after a developing baby until birth.
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▪ the fusion of two gametes, such as a sperm and an egg, that form a
zygote which is capable of maturing into an adult individual of that species.
▪ Only one of the approximately 300 million sperm released into a
female‘ s vagina during intercourse can fertilize the single female egg cell
To produce a new individual, a
sperm has to reach an ovum and
fuse with it. (the nuclei)
They form a zygote. It will
grow by cell division to produce
an embryo and then a fully
*The sperms swim through the cervix and into the uterus, enter the oviduct. If there is an ovum in the oviduct, one of the
sperms may enter
*It passes through the thick coating surrounding the egg the zona pellucida
( sugars and proteins)
*The tip of the head of the sperm cell contains enzymes which break through the zona pellucida and aid the
penetration of the sperm
into the egg
*It enters the cytoplasm of the ovum
male nucleus of the sperm fuses with
the female nucleus.
•Once the head of the sperm is inside
the egg, the tail of the sperm falls off
*The perimeter of the egg thickens
to prevent another perm fromentering.
*The released ovum survives for
about 24 hs. Fertilization is able
to happen for about 2 or 3 days (middle life od a sperm)
•The eggs are produced from the female reproductive organs called the ovaries.
•3-4 cm long, the ovaries lie on each side of the uterus.
•Close to the ova is the opening of the oviduct, the tube down which the ova pass when released from the ovary.
(Sometimes called the Fallopian tube).
• The oviducts are narrow tubes that open into the uterus, or womb, lower down in the abdomen.
• The uterus leads to the outside through a muscular tube, the vagina.
• The cervix is a ring of muscle closing the lower end of the uterus where it joins the vagina.
• The urethra, from the bladder, opens into the vulva just in front of the vagina.
The ova are present in the ovary from the time of birth. No more are formed during the lifetime.
Between the ages of 10 and 14 some of the ova are released, one at a time from alterntate ovaries
about every 4 weeks. As each ovum matures, the cells round it divide rapidly and produce a fluid-filled
sac, called follicule. When mature, it projects from the surface of the ovary and finally it
bursts and releases the ovum into the funnel of the oviduct.
The released ovum is enclosed in a jelly-like coat called the zona pellucida and is still surrounded
by a layer of follicle cells. For fertilization to take place, the sperm has to get through this layer and
penetrate the zona.
In humans, usually only one egg is fertilized at a time; two eggs being fertilized produces (non-identical)
The ovaries release an ovum about every 4 weeks.
The oestrogens act on the uterus and cause its lining to become thicker and
develop more blood vessels.
Two hormones, the follicle-stimulating and the luteinizing, produced by the
pituitary gland at the base of the brain promote ovulation.
Once the ovum has been released, the follicle which produced it develops into a
solid body called the corpus luteum. This produces a hormone called
progesterone, which affects the uterus lining in the same way as the oestrogens.
If the ovum is fertilized the corpus luteum continues to release progesterone and
so keeps the uterus in a state suitable for implantation.
If the ovum is not fertilized, the corpus luteum stops producing progesterone. As
a result, the thickened lining of the uterus breaks down and loses blood which
escapes through the cervix and the vagina (menstrual period).
1- Follicular phase (1-14)
• ovarian follicles mature, getting ready to
release an egg
• a rise in Follicle Stimulating Hormone (FSH)
• follicle that reaches maturity Graafian
•Lining of OVULATION the uterus thickens
• Ovulation a mature egg is released
•levels of ESTRADIOL reach a threshold,
estrogen stimulates the production of a large
amount of LUTEINIZING HORMONE (LH)
2- Luteal phase (14-28)
•FSH and LH remaining parts of the
follicle transform into the CORPUS
LUTEUM, which produces
PROGESTERONE BUT suppress
production of the FSH and LH
•the corpus luteum atrophies Falling
levels of PROGESTERONE trigger
Male Reproductive System
The purpose of the organs of the Male Reproductive System is to perform the
* To produce, maintain, and transport SPERM(the male reproductive cells) and
protective fluid (semen)
•To discharge sperm within the female reproductive tract during sex as close to the
uterus as possible
•To produce and secrete male sex hormones responsible for maintaining the male
• Sperms are produced in the male
reproductive organs called testes .
• They lie outside the abdominal cavity in a
special sac called scrotum, so as to keep a
lower temperature for sperm production.
• They consist of a mass of sperm-producing
tubes. These join to form ducts leading to
the epididymis (coiled tube about 6m long
on each side of the testis storage of
sperms). This leads into a muscular sperm
The two sperm ducts open into the
top of the urethra just after it leaves
The seminal vesicle is a short coiled
tube which branches from each
sperm duct just after entering the
prostate gland .
The urethra passes through the
penis . It consists of connective tissue
with many blood spaces in it. This is
called erectile tissue .
1 testis/ 2 testes
The function of the scrotum is to produce sperm and keep the
testis at a temperature slightly lower than that of the rest of
the body as the sperm dies when it is kept too warm.
How does the Scrotum work
When the whether is cool, the scrotum tightens to bring the
testicles closer to the body, and when the weather gets warmer the
scrotum loosen to hang the testicles further away from the body.
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The lining of the
tubules of the testis
consists of rapidly
After a series of cell
divisions, the cells
grow long tails and
become sperms which
pass into the
THE HEAD: has two important features:
*The acrosome contains lytic enzymes which are released
when the sperm reaches an ovum. These enzymes digest the
outer membrane of the egg, allowing penetration of the
* The NUCLEUS (genetic material)
THE MIDDLE SECTION:immediately
behind the head, contains numerous mitochondria . These
respire sugars in the semen to generate ATP to provide the
energy for movement of the tail.
THE TAIL contains microfilaments running the length of the
tail .Rhythmic contraction of the filaments causes the tail to
wave and move against the fluid environment, providing
Parts of the
• Sexual arousal in the male results in an erection.
The penis becomes firm and erect as a result of
blood flowing into the erectile tissue.
• During copulation, the male inserts the penis into
the female’s vagina. This causes a reflex in the
male which results in the ejaculation of semen.
• The epididymis and sperm ducts contract and
force sperms out of urethra.
• The prostate gland and seminal vesicle add fluid
to the sperms. This fluid added to the sperms is
Anti coagulant factors
The fertilized ovum divides into 2 cells, then 4, they continue dividing producing a solid ball of cells, an early stage in the
development of the embryo.
The embryo travels down the oviduct to the uterus, where is implanted to the walls of the uterus.
After 8 weeks, when all the organs are formed, the
embryo is called a fetus.
One of the first organs to form is the heart.
Inside the uterus the embryo becomes enclosed in a
fluid-filled sac called the amnion sac, which protects
it from damage and prevents unequal pressures
from acting on it.
Some cells, instead of forming the organs of the embryo, grow into a disc-like structure called the
1- Provides the oxygen and food needed to keep the embryo alive and growing are obtained from the mother's blood
It is attached to the * lining of the uterus
*embryo by a tube called the umbilical cord.
The blood vessels in the placenta are very close to the blood vessels in the uterus so that oxygen, glucose, amino
acids and salts can pass from the mother's blood to the embryo's blood.
The carbon dioxide and urea in the embryo's blood escape from the vessels in the placenta and are carried away by
the mother's blood in the uterus.
2- It can prevent some harmful substances in the mother's blood from reaching the embryo.
3- Placenta produces hormones(OESTROGENS/PROGESTERONE) that play an important part in maintaining the
pregnancy and preparing for birth.
There is NO DIRECT COMMUNICATION BETWEEN THE MOTHER’S
BLOOD AND THE EMBRYO’S
It is the way a woman should look after herself during pregnancy, so that the
birth will be safe and her baby healthy.
She must take more iron and folic acid than usually, so as to prevent anemia.
SMOKE Pregnant women who drink or smoke are more likely to have babies
with low birth weight or miscarriages
ALCOHOL Heavy drinking is suspected of damaging the developing brain of
the fetus and babies with low birth weight
If a women catches RUBELLA during the first 4 months of pregnancy, there is
a danger that the virus may affect the fetus and cause abortion/ still-birth or
defects in the eyes/ears or nervous system
A woman can release two ova when she ovulates. If both are fertilized,
they may form twin embryos, each with its own placenta and amnion.
Twins formed in this way are called fraternal twins. As they are fertilized
by different sperms, they can be a boy and a girl and are not more alike
than other brothers and sisters.
Another cause of twining is when a single fertilized egg forms two
separate embryos. Sometimes this may share a placent and amnion. This
type of twins must be the same sex, because only one sperm fertilized the
ovum. These ‘one-egg’ twins are sometimes called identical twins.
The baby is an embryo consisting of two layers of
cells from which all her organs and body parts
The baby is now about the size of a bean
and is constantly moving. He has distinct,
slightly webbed fingers.
By now the baby is about 7.52cm long and
weighs nearly 28g. Her tiny, unique
fingerprints are now in place.
The baby is now about 12.7cm long and
weighs 141g. His skeleton is starting to
harden from rubbery cartilage to bone.
Eyebrows and eyelids are now in place.
The baby would now be more than
25.4cm long if you stretched out her
The baby weighs more than 600g. His
wrinkled skin is starting to smooth out as
he puts on baby fat
By now, the baby weighs about 1.5kg and
is more than 38cm long. She can open
and close her eyes and follow a light.
The baby now weighs about 2kg.
His layers of fat are filling him
out, making him rounder, and his
lungs are well developed.
The average baby is more than
48.26cm long and weighs
nearly 3.100kg now, but babies
vary widely in size at this stage
The gestation period is from fertilization to birth, and it takes about 38 weeks.
A few weeks before the birth, the fetus has come to
lie head downwards in the uterus.
When birth starts, the uterus begins to contract rhythmically
(labour). These contractions become stronger and more frequent.
The opening of the cervix widens enough to let the baby's head pass through and the contractions are assisted by muscular
contractions of the abdomen.
WATER SAC breaks and fluid escapes through the vagina
The muscular contractions of the uterus and abdomen push the baby head-first through the cervix and vagina.
The umbilical cord, which still connects the child to the placenta, is tied and cut.
The placenta breaks away from the uterus and is pushed out.
•When the water sac breaks, there’s a sudden fall in
• the temperature
Stimulates the baby to take the first breath and CRY
* When the remains of the umbilical cord falls
There is a scar in the abdominal wall NAVEL
▪ If the pregnancy lasted more than 38 weeks or the placenta doesn’t cope with
the demands of the fetus
The birth is INDUCED (started artificially)
by Breaking the
membrane of the amniotic sac
Taking a sample of amniotic fluid to know if the baby has got Down’s
syndrome or other conditions/ to find out the sex
* During pregnancy mammary glands enlarge increase in the number of
milk-secreting cells but breasts are stimulated to release milk when the baby
* Liquid (with more proteins and antibodies) produced during the first days
* WEANING process by which the baby starts eating solid food
Mother’s milk Cows’ milk
Free from bacteria
Emotional / psychological
Vitamins A and C
Ova start to be released when the female reaches an age of about
Sex hormones are released into the bloodstream, called
oestrogens. They bring the development of secondary sexual
In girls, there is an increased growth of breasts, widening of hips
and growth of hair in pubic regions and armpits. Also an
enlargement of the uterus and vagina.
In boys, testosterona is released by testes into the bloodstream.
Testes and penis are enlarged, voice is deepen, growth of hair in
pubic parts, armpits, chest and face.
There are also emotional and
Between 40 and 55, the ovaries cease to release ova or
As a consequence, menstrual periods cease, the woman can no
longer have children, and sexual desire is gradually reduced.
Usually caused by a failure to ovulate or a blockage or distortion
of the oviducts. The latter can often be corrected by surgery, if
not the couple may use ‘in vitro’ fertilization. Failure to produce
ova can be treated with fertility drugs. They are similar to
hormones and act by increasing the levels of FSH and LH. Their
administration is aimed to promote ovulation to coincide with
▪ Caused by an inadequate quantity of sperms in the
semen or by sperms which are insufficiently mobile to
reach the oviducts.
▪ Artificial Insemination involves injecting semen
through a tube into the top of the uterus.
• The woman may be give fertility drugs to release several mature ova
• The ova are collected by laparoscopy and sucked up in a fine tube
inserted through the abdominal wall.
• Then the ova are mixed with the husband’s seminal fluid and watched
under the microscope to see if cell division take place.
• One or more of the dividing zygotes are introduced to the woman’s
uterus through the cervix by an inserted tube.
• Usually one or none zygote develops though, occasionally, there are