Transcript File - CAPE BIO UNIT I 2012

H2O
Module 3- Reproduction
Janett Noyan
Crystal Sutherland
Olicia Sylvester
Toni-anne Murray
What is the Placenta?
• Mass of tissue that unites foetus to the uterus
• Formed by interlocking of membranes of the
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•
foetus with the lining of the womb.
Is soft, disc-shaped, dark red and has villi which
fit closely in the uterus wall.
Is supplied with a network of blood vessels
though which oxygen and nourishment pass
form the mother’s blood to that of the foetus.
THE PLACENTA
Functions of Placenta
1. The placenta allows for exhange of materials
between the mother and foetus without the two
bloods mixing. This is so since the fetal blood
may be different from the mother due to the
influence of the fathers gene.
2. Oxygen, water, amino acids, glucose, essential
minerals among many others, are transferred
from maternal to fetal blood to nourish the
developing baby (fetus).
Placenta
3. Carbon dioxide and waste materials
diffuse from the foetus and are carried
away in mother’s blood. This to ensure
that no harm comes to the fetus. At birth,
the placenta reduces the secretion of
progesterone which stimulates the
pituitary gland to secrete oxytocin.
Oxytocin stimulates contractions of the
uterus wall.
Placenta
4. The placenta provides some immunity to
the fetus, meaning certain maternal
antibodies pass into the developing baby.
The term for this is passive immunity.
5. Certain pathogens and their toxins are
prevented from entering the amniotic fluid
then the fetus. An exception is the Rubella
(German measles), gonorrhoea, syphilis
etc., virus can also pass over the
[placenta, for example HIV.
PLACENTA
6. The placenta further protects the foetus
by creating a barrier against maternal
hormones, which can cause adverse
effects in the fetal development.
7. Since the two blood systems- the
mother’s and fetus’ blood systems- are not
directly mixed the placenta allow to
operate at different pressures without
causing harm to the mother or child.
Placenta
8. During the pregnancy, the placenta takes
on the role of hormone production. It
produces progesterone, which prevents
ovulation and menstruation. It also
secrete human choriogonadotrophin
(HCG), a hormone whose presence in the
urine of pregnant women is the basis of
most pregnancy test.
Blood flow in the placenta
The Amnion
• This is a strong membrane.
• Inside the amnion is a liquid called
amniotic fluid.
• This fluid helps to support the embryo and
to protect it.
Contraceptive methods
• These methods are carried out to prevent
pregnancy. Knowledge of the human
reproductive anatomy and physiology has
been applied to the development of these
methods. One of such methods is the use
of condoms. The male covers his penis
with this thin rubber sheath when it
becomes erect. Sperms are caught in the
end of the condom when they are
ejaculated, therfore do not reach the egg.
Images
Contraceptives used by
FEMALES
• Females also wear condoms, these are
called diaphram. They are thin sheaths of
rubber or polyurethane with rings at both
ends which are inserted into the vagina.
The female may also take contraceptive
pills which contains hormones similar to
those produced during the menstrual
cycle. These hormones prevent the
release of the egg from the ovary.
Images
Contraceptive methods
• Females may also use a coil, which is a
small spring-shaped stucture made of
plastic or copper and must be inserted by
a doctor inside the uterus. As it fits inside
the uterus, it is called an intra-uterine
device (IUD). The coil interrups the
preparation of the womb for the fertilised
egg and so prevents implantation.
An intra-uterine device (IUD)
Contraceptive methods:
sterilization
• Surgical sterilization is available in the
form of tubal ligation for women
and vasectomy for men.
Possible effects of maternal behavior on
foetal development:
Nutrition
• A balanced, nutritious diet is an important
aspect of a healthy pregnancy. Eating a healthy
diet, balancing carbohydrates, fat, and proteins,
and eating a variety of fruits and vegetables,
usually ensures good nutrition. Adequate
periconceptional folic acid (also called folate or
Vitamin B9) intake has been proven to limit fetal
neural tube defects, preventing spina bifida, a
very serious birth defect.
Possible effects of maternal behavior on
foetal development:
Nutrition
• DHA omega-3 is a major structural fatty acid in
the brain and retina, and is naturally found in
breast milk. It is important for the woman to
consume adequate amounts of DHA during
pregnancy and while nursing to support her
well-being and the health of her infant.
Developing infants cannot produce DHA
efficiently, and must receive this vital nutrient
from the woman through the placenta during
pregnancy and in breast milk after birth.
Possible effects of maternal behavior on
foetal development:
use of drugs
• Drugs used during pregnancy can have temporary or
•
permanent effects on the fetus. Therefore many
physicians would prefer not to prescribe for pregnant
women.
Drugs have been classified into categories A,B,C,D and X
based on the Food and Drug Administration (FDA) rating
system to provide therapeutic guidance based on
potential benefits and foetal risks. Drugs
like multivitamins that have demonstrated no fetal risks
after controlled studies in humans are classified as
Category A. On the other hand drugs
like thalidomide with proven fetal risks that outweigh all
benefits are classified as Category X.
Possible effects of maternal behavior on
foetal development:
alcohol
• Alcohol ingestion during pregnancy may
cause fetal alcohol syndrome, a
permanent and often devastating birthdefect syndrome.
Possible effects of maternal behavior on
foetal development:
cigarette smoking
• Numerous studies show that children
exposed to prenatal cigarette smoke may
experience a wide range of behavioral,
neurological, and physical difficulties.
Possible effects of maternal behavior on
foetal development:
Sexual activity during pregnancy
• Most pregnant women can enjoy sexual
activity during pregnancy throughout
gravidity.
• A significant number of women report
greater sexual satisfaction throughout
their pregnancies.
Summary
• Placenta: provides large suface area for
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exchange of substances between mother’s and
embryo’s/ foetus’ blood.
Wall of placenta: prevents mixing of mother’s
and foetus’ blood, therefore preventing
unwanted substances entering foetus’ blood.
Contraceptive methods: used to prevent
pregnancies, eg. Use of condoms, coil (IUD),
contraceptive pills, the rhythm method, and
sterilisation.
Method
How it works
Effectiveness
Advantages
Disadvantage
Sterilization
Male(vasectomy)- the
vas defrence are cut
and tied off.
Female(tubal ligation)the oviducts are cut
and tied off.
100%
No artificial appliance
is involved. Once the
operation has been
performed there is
not futher cost.
Irreversible in
normal
circumstances.
Prevention of
ovulation
Oral contraceptive99%
contains artificial
oestrogen and
progesterone
Implant
100%
contraceptv- implant
placed under skin which
releases artificial
oestrogen and
progesterone.
Very reliable if taken
regularly
Occasional side
effects: nausea,
breast tenderness
Almost totally reliable.
Each implant lasts 5
years.
Can cause irregular
menstrual
bleeding.
Morning-after Pillblocks the action of
progesterone.
Intra-Uterine
Device- device usually
made of plastic&/or
copper whhich is
inserted into the womb
by a doc. And which
prevents implantation.
Can be used after
rather than before
intercourse.
Once fitted, no
further action is
required except for
annual check-ups.
1.High dose of
oestrogen can
produce sideeffects. Not
suitable for regular
use.
2.Possible
menstrual
discomfort. May be
displaced or
rejected.
Prevention of
implantation
Not widely used
but probably 99100%
98%
Method
Barriers which
prevent sperm
reaching the egg
Natural Method
How it works
Effectivenes
s
Advantage
Disadvantage
Female (Diaphragm,
cap) – A Dome-shaped
sheet of thin rubber, with
a thicker spring rim, which
is inserted into the vagina
over the cervix.Best used
with spermicide.
Female (condom) Sheath of thin rubber with
two springy rings. Smaller
inserted into vagina,
larger remains outside.
Very
reliable if
used with a
spermicide
Reliable. Available
for use by all
women.
Must be inserted prior
to intercourse and
should be removed 824 hours after
intercourse. Initial
fitting must be by a
trained practitioner.
Male (Condom,
Sheath) – A sheath of
thin rubber unrolled onto
the erect penis prior to
intercourse. Seamen is
collected in teat at the tip.
Best used with a
spermicide.
Very
reliable
90% and
up to 98%
if used with
a
spermocide
Rhythm methodrefraining from intercourse
during those times in the
menustral cycle, when
conception is most likely.
Variable-not
very reliable
76% and
up to 98%
with
practice.
Very
reliable
Readily available,
quite easy to fit.
Gives some
protection against
sexually
transmitted
diseases.
Easily available
and easy to use.
Available for use
by all men. Gives
some protection
against sexually
transmitted
disease including
AIDS.
No appliance
required.Only
acceptable
method to some
religious groups.
May reduce enjoyment
of intercourse.
May reduce sensitivity
of the penis and so
interfere with
enjoyment.
Not reliable.Restricts
times when
intercourse can take
place.
Multiple choice questions
1) Which would be referred to as the least
reliable method of birth control?




Use of condom
Intra-uterine device (IUD) or coil
Rhythm method
Sterilisation
Multiple choice questions
2) At birth, what hormone is secreted by the
pitutary gland to stimulate contractions of
the uterus wall?
 Progesterone
 Oxytocin
 Oestrogen
 Testosterone