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Gestation
Maria Paula Ramirez and Jaime
Andres Gonzales
10 o
What is gestation?
• The term gestation is used in zoology to describe
he time between conception and birth, during
which the embryo or fetus is developing in the
uterus. In other words when a female viviparous
animal carries and supports a breeding
embryonic or fetal in its belly till the time of
delivery. Among mammals, there are species with
multiple gestations who are born in more than
one brood each end of gestation. The durationcalled gestational period, is the duration of the
breeding intrauterine development and varies
from species
Structural stuff
Components
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Uterine epithelium: lining in the uterus made of blood and nutrients, here the fertilized egg implants.
Epiblast: differentiates from the cell mass, becomes a bilaminar disc, the ectoderm, and finally the
amnion.
Hypoblast: differentiates from the cell mass, becomes a bilaminar disc, the endoderm, and finally the yolk
sac and the digestive track.
Thropoblast: divides from the fertilized ovule, becomes the choroid and the villi that attaches to the
epithelium.
Mesoderm: differentiates from the hypoblast and Thropoblast in the bilaminar disc, becomes the embryo
and the umbilical cord.
Uterine wall: found under the lining, filled with capillaries, comes in contact with the villi so close that
blood and nutrients pass through diffusion.
Chorion: sac that surrounds the placenta, is the outer membrane and bonds the villi.
Amnion: sac that holds the embryo/foetus, contains amniotic fluid and is inside the choroid.
Umbilical cord: tube that passes arteries and veins that connect to the villi, connects the baby to its
mother.
Placenta: organ formed in pregnancy that comprehends the permeated uterine lining, the choroid and the
villi.
Amniotic fluid: aqueous substance that holds the embryo/foetus, works as air to develop the lungs,
digestive track and vascular system.
Gestation in humans
• Gestation: period of forty-week, which takes place on the development of
the embryo to complete their training which takes place during the
formation of all organs.
Human pregnancy can be divided into three trimesters. The third
trimester begins at approximately 28 weeks after fertilization. It is
considered viable when a human fetus have passed 23 weeks gestation.
Before this gestational age, the main events of embryonic development is
not yet allowing fetal survival outside the womb. This limit is often
arbitrary for the reason that some children born before this point have
survived, althoug with considerable medical support.
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The human birth occurs between 37 and 42 weeks gestational age. Labor
that occurs before 37 weeks is considered premature and is considered
viable after 25 weeks.
Development of the mother and baby
during gestation
• After fertilization, many changes occur in the body of the pregnant
woman because the baby's development in utero produces large
biochemical changes. For this reason, moms are beginning to see
many signs associated with pregnancy.
The first is the lack of menstruation, but as not all women have
regular periods is important to note other signs such as enlarged
breasts, nausea, heartburn, fatigue or tiredness or frequent
urination. However, it is important for women to confirm the
diagnosis with a pregnancy test, although present all the symptoms,
and see your doctor.
Pregnancy tests can detect the presence of a hormone called
human chorionic gonadotropin, which is produced by the placenta
and is present in the blood and urine of pregnant women.
Beginning of the gestation of the baby
• The life of your baby begins when a sperm
fertilizes one of your eggs. After half an hour, the
fertilized egg is dividing into numerous cells while
traveling down the fallopian tube toward the
uterus to implant in the uterine wall where it will
continue its development. At three weeks, the
embryo has a tiny heart begins to beat. At the
end of the fourth week, the head is easily
recognizable, which has a rudimentary brain and
begin to recognize also the arms and legs.
1-4 weeks
• Ovulation occurs: the egg needs to be fertilizated
• Conception Occurs: the uterus will increase its capacity by 1000 times
• Gender is determined: immediately after fertilization the fetus is set as a
boy or a girl. The sperm determines the gender of the baby, because it
carries a X for girls chromosome or a Y for boys chromosome +. The
gender will be visible in the second trimester via the ultrasound.
• Implantation: some implantation bleeding may occur about 10-14 days
after conception. It’s not menstruation; generally this bleeding is
extremely light and lasts one day or so.
• Neural tube forms: in this period of pregnancy, it will develop into the
nervous system: brain, spinal cord, hair and skin. And the baby has already
the foundation for thought, senses, feeling and more.
• Also in this period, heart and primitive circulatory system is rapidly
formed, this is the support system that would carry the baby through his
or her life.
Week 5
• The first heartbeats begin.
• The umbilical cords develops this is the baby’s lifeline in the uterus. Its
bears the responsibility of pumping oxygen, removing waste, and
supplying the necessary nutrients for the rest of the pregnancy.
• In week five of pregnancy, blood is know pumping. The four heart
chambers are functioning, for that the body of the baby will receive all its
needs , through the remaining of the pregnancy and life.
• Most of others organs begin to develop. The lungs start to appear along
with the brain.
• Arms and leg buds appear at 5 weeks of pregnancy.
Week 6
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The arms and legs continue to develop. These limbs are stretching out more and more.
Brain is growing well, during the remaining months the babys brain will develop over 100
billion neurons
The lenses of the eyes appear in this time
Nostrils are formed
The intestines grow at the 6 week of pregnancy; at the beginning these are located outside
the baby’s body within the umbilical cord
Pancreas. Know the baby is equipped to deal with digestive enzymes and take on processing
the insulin and glucagons the body needs to function.
Week 7
• Elbows form
• Fingers start to develop; these digits often become the baby’s first toy
• Feet start to appear with tiny notches for the toes
• Ears, eyes and nose start to appear
• Intestines start to form in the umbilical cord, initially the intestines are
not form inside the baby’s body
• Teeth begin to develop under the gums
Week 8
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Cartilage and bones begin to form, at the end of the week the baby have already
completed 1/5 of the journey till de birth day.
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They basic structure of the eye is wll underway
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The tong begins to develop
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Intestines move out of the umbilical cord into the abdomen
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Body grows and makes room
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The fingers and toes have appeared but are short and webbed
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The baby’s height is about 0.61 inch, 1.6 cm and weight is about 0.04 ounce, 1
gm.
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Week 9
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Baby has begun movement. But pregnant women can’t feel that moment
Most joints are formed know, the baby is practicing bending and flexing
The fetus will curve its fingers an object placed in the palm of its hand.
Fingerprints are already evident in the skin
The length of the baby is about 0.9 inch that is 2.3 cm and 0.07 ounce that is 2gm
Week 10
• Baby is now called a fetus in “medical terms”
• The most critical part of your infants developments is complete,
now a period of rapid growth is coming
• The head of the baby is now about half its length. The rest of the
body growth will catch up but this area is prepared to keep up with
the brain development
• Eyelids uses shuts and irises begin to develop, eye color is also
determine in this time
• Placenta begins to function during this week or next. The placenta
is the organ responsible for the provision of nutrients and the
removal of waste to keep the baby grow strong
• The baby will be about 1.22 inch long that is 3.1 cm and weight
about 4 grams that are 0.14 ounce .
Week 11
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Nearly all the structures and organs are formed and they start to function
Fingers and toes have separated
Hair and nails begin to grow
The genitals begin to take on the proper gender characteristics, in some few weeks the
ultrasound can show the gender of the baby
Amniotic fluid begins to accumulate as the kidneys begin to function. This fluid that is
formed mostly by water helps to provide a cushion for your baby while he or she is within the
womb
The muscles in the intestinal walls begin to contract digesting food
The baby is about 1.61 inches that are 4.1 cm long and it weighs 0.25 ounces that are 7 gm
Week 12
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Vocal cords begin to form
The eyes begin to move closer together
Ears shift to their normal place on the side of the head
Intestines move further into the child’s body
His or her liver begins to function, that is responsible for cleansing the blood,
storing nutrients and it provides some fundamental chemicals
The pancreas begins to produce insulin
The baby’s length is about 2.13 inches that are 5.4 cm long and it weights 0.49
ounce that is 14 gm
Week 13
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The baby is about 2.91 inches long that is 7.4 cm and it weights around 0.81 ounce
that is about 23 mg
The baby begins practicing inhaling and exhaling movements
Eyes and ears continue developing
Baby’s neck is getting longer so the chin is no longer resting in his chest
His hands are becoming more functional
Baby’s receive all nourishment from the placenta
The mother should hear the heartbeat of the baby with a Doppler
Week 14
• The thyroid gland has matured and the baby begins producing hormones
that would be used during his or her life
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• In the boys the prostate glands develops
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• In the girls the ovaries move from the abdomen to the pelvis
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• The bones are getting harder stronger and harder
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• Lanugo that is a very fine hair covers the baby’s body and will continue
growing for 11 weeks more, it protects the baby skin
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• Your baby is 3.42 inches (8.7cm) long and weighs about 1.52 ounces (43
grams)
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Week 15
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The mother can start to feel some fluttering movements as baby kicks, flails, twists and turn.
The legs of the baby have grown longer than the arms and the body is now longer than the head
The baby is moving the arms and legs continuously
The skin of the baby is very weak, so thin blood vessels are visible. Its covered by a layer called
lanugo that helps to insulate the child.
The three bones in the middle ear have begun to harden, but the auditory center in the brain
haven’t develop yet
Fingernails and toenails are growing
Eyebrows are beginning to grow
The baby is about 3.98 inches and 2.47 ounces
Week 16
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Fat begins to form underneath skin, providing the baby with insulation for the next months
The baby and the placenta are know about the same size
The baby is about 4.57 inches and 3.53 ounces
His head and neck are held straighter now
The mother can hear the heartbeats with a external monitor know
The genitals are developed sufficiently that an experienced sonographer migth be able to
determine the gender of your baby
The heart of the baby is pumping about 6 gallons of blood a day
The baby starts to develop more its reflexes such as sucking, swallowing and blinking n
The baby has learned to breathe. This is from the regular movements of his chest. The baby inhals
and exhals small amounts of amniotic fluid that helps the lungs to develop
Week 17
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The baby weights about 4.97 ounces and it is 5.12 inches long
Pads are forming on his fingerprints and toes
Her or his eyes are looking forward know, but they are still closed
Meconioum that is composed of products of cell loss, digestive secretion and
swallowed amniotic fluid, accumulates in the bowel. This will become the baby’s
first poop
The umbilical cord is growing thicker and stronger and it continues providing blood
and nutrients to the growing baby
If the child is a male, the prostate begins to develop
Her or his skeleton is transforming from cartilage to bone, but the bones remain
flexible to make the journey through the birth canal easier.
Week 18
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Vernix is formed in the baby’s skin with the lanugo, they both protect the skin of
the baby
The placenta continues growing and nourishing the baby
Some tiny air sacs called alveoli begin to form in the lungs
Her or his vocal chords are formed, he or she cries but without air he or she
doesn’t make any sound
Ventricles and chambers should be visible during ultrasound
The baby would measure about 5.59 inches and weight about 6.7 ounces
Week 19
• The baby can now hear sounds and make
more movements while the mother can feel
fluttering in her abdomen. The intestines are
now fully developed to absorbed small
amounts of sugar from the digestive system of
the mother.
Week 20
• The different senses are now slowly
developing. The baby’s sense of taste has
started to develop and brain’s nerve endings
are fully developed that the baby can sense
touch. The entire body will be covered by
lanugo. Nails will grow as well as the eyebrows
and lashes. Heartbeat can now be heard
through a stethoscope and fetus will become
more active as muscles continue to develop.
12-23 weeks
• Low chances of abortion
• The gender is not highly differentiated, genitals are simple identical
bulbs, but in different angles (this becomes the penis or the clitoris)
• The hands develop first as the fingers separate and the bone begins
to strengthen
• The central nervous system has spread throw-out the body and the
first prehensile reflex is evident
• The baby becomes very active, as it has a working digestive
apparatus, and the mother begins to feel the foetus's movements.
24 week
• The foetus is viable to born, with medical aid, since
the 22 week, but this might have future effects on
mental development
• The mother has no longer morning sickness, is
energetic and its abdomen grows
• Senses begin to develop, specially hearing, taste and
smell, as the mothers food taste might reach the baby
through the ingestion of the amniotic fluid.
25 week
• The baby's motor functions begin to develop,
as they shall for the rest of its life
• Eye colour begins to be formed, as some
pigments require light to finish, most will look
clear and pallid, but will darken with time.
26 week
• The baby's heart can be heard at this time,
which beats at twice the speed of its mother
• The foetus is only awake 10% of the time
• The last organ to develop is the lungs which
are not used until child birth
28-37 week
• Brain cortex matures enough to retain memories
• The foetus position changes to have the head
down against the cervix
• The organs are all functional, and the liver begins
to process waste products while self body
regulations begin
38-40 weeks
• Birth is likely to occur
• When the foetus lungs are fully developed, a protein is released,
that lowers the hormone progesterone, but increases oxytocin, that
produces contractions and is known to block memories of pain
• Birth is the most stressful moment of gestation
• Birth:
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The cervix dilates 10 cm
Contractions push the baby through the birth canal
The placenta is expelled.
Bibliography
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http://www.babyzone.com/pregnancy/week/
http://en.wikipedia.org/wiki/Pregnancy
http://en.wikipedia.org/wiki/Gestation
http://en.wikipedia.org/wiki/Fetus
http://en.wikipedia.org/wiki/Placenta
Bibliografy
• http://www.americanpregnancy.org/duringpregnancy/calculatingdates.ht
ml
• http://www.britannica.com/EBchecked/topic/232124/gestation
• http://emedicine.medscape.com/article/259269-overview
• http://www.goatbiology.com/animations/gestcalculator.html
• http://www.thefreedictionary.com/gestation
• http://www.medterms.com/script/main/art.asp?articlekey=3589