Gestation

Maria Paula Ramirez and Jaime Andres Gonzales

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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 duration-called gestational period, is the duration of the breeding intrauterine development and varies from species

Structural stuff

Components• 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.

•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 • 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 • 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.

• They basic structure of the eye is wll underway

• The tong begins to develop • Intestines move out of the umbilical cord into the abdomen

• Body grows and makes room

•  The fingers and toes have appeared but are short and webbed

• The baby’s height is about 0.61 inch, 1.6 cm and weight is about 0.04 ounce, 1 gm. •  

Week 9 • 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 • 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• 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• 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 • • In the boys the prostate glands develops • • In the girls the ovaries move from the abdomen to the pelvis • • The bones are getting harder stronger and harder • • 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 • • Your baby is 3.42 inches (8.7cm) long and weighs about 1.52 ounces (43 grams)•

Week 15 • 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 • 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 • 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 • 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:

1. The cervix dilates 10 cm2. Contractions push the baby through the birth canal3. The placenta is expelled.

Bibliography

• 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