Welcome to the World, Little One
The birds and the bees - a timeline
First Trimester - Initial Stages - Emotional Rollercoaster
The Moment - Fertilization - Week Three, Day One
As shown, the egg is around 30 times wider then the sperm, and has 500 times the volume.
Location and Enlarged View
This whole process happens as the egg is in the uterine tube on its way to the uterus.
Having to penetrate many layers, the sperm uses enzymes in its head to eat through the layers and deposit the nucleus for fusion with the egg's alleles.
Location and Enlarged View
First Divisions - The Morula - Week Four, Day Two-Five
#It's Official - Implantation/Gastrulation - Week Four-Five
hCG (or human chorionic gonadotrophin) deactivate the two genes located on chromosomes nine and six which are responsible for menstruation. This makes sure the growing blastocyst isn't ejected from the uterus, because that would be terribly anti-climactic.
Towards the end of week two, the baby has formed into a mass of cells called a gastrula, with three distinct layers (ectoderm/mesoderm/endoderm) which evolve to form every bodily system we have. This is also where the baby gets the cushioning amniotic sac, and the nourishing/blood cell producing yolk sac - both characteristic of nearly all growing vertebrates.
- Ectoderm == nervous system/skin/hair/mammary&sweat glands/tooth enamel
- Mesoderm == circulatory system/muscles/bones/cartilage
- Endoderm == digestive tract/respiratory system/thyroid/pancreas/urinary tract
Drumroll - First Heartbeats/Physical Developments - Six Weeks
Putting On the Leash - Umbilical Cord Forms - Seven Weeks
Power Button Green - First Neural Connections - Eight Weeks
Awakening - Structure/Movement/Reflexes - Ten-Twelve Weeks
At ten weeks, the baby can bend their limbs and kick. The heart is formed in all its' glory, and other features such as teeth and gums have arrived. Also, the internal sex organs begin to form
The SOX9 gene from Hox1 gene pool produces transcription factors which activate mesenchyme multipotent stem cells in face and limbs to differentiate into chondrocytes, or cartilage tissue. After differentiation, the chondrocytes divide to form model for bones - after which they stop dividing and increase their volume drastically, which allows for calcification of the bones (or ossification). This more volumetric cartilage is called hypertrophic chondrocytes.
This scaffolding of cartilaginous bones holds the baby together until the cartilage can be ossified. This allows for the full range of movement in the baby.
The baby can move spontaneously and will react to outside stimuli by squirming. By this point, the baby is unmistakably human. At two inches long, the baby is fully formed and growing incredibly fast.
Second Trimester - 14 Weeks - Emotional Peace and Huge Development
Promiscuousness and Strengthening - Gender Revealed/Ossification Begins - Fifteen Weeks
The CBFA1 gene in the HoxA master gene web begins to produce transcription factors which cause mesenchyme multipotent stem cells and existing chondrocytes to differentiate and become osteoblasts - which are the builders of bone tissue. As well as the osteoblast creation, blood vessels begin invading the hypertrophic chondroblasts and kill them, making a blood-rich space which will then mature into bone marrow.
This is the activation of ossification - when the cartilage bone structure of the baby is now using ingested calcium from the mother to build real bones with working osteocytes. Around 250 milligrams a day is applied to the bone network.
Morning Alarm - Hearing Achieved - Seventeen Weeks
Bookeeping - Formation of Myelin - Eighteen Weeks
Definitely Shaggy - First Hairs - Nineteen Weeks
Waking Up - Eyes Open - 20 Weeks
Third Trimester - 28 Weeks - Emotions Return and Rapid Weight Gain
Trash Bags - First Bowel Movement - 36 Weeks
At this time, the "early-term" baby may begin feeling the pressure of external cephalic version - which is a process used by doctors to urge the baby into a head-down position.
Ready to Go, but Preferably Not - "Full Term" - 39 Weeks
Welcome - Beginning of Labor/Birth - 40-41 Weeks
During labor, contractions of the female uterus force the baby out through the heavily stretched cervix and vagina. To allow this to happen, the baby's skull bones are soft and can shift around, sometimes causing a "coneheaded look" immediately after delivery.
Although labor is unimaginably painful, every mother makes the journey through it to have a baby in her arms. Occasionally, a painkiller called an epidural is injected into the mother if she cannot bear it naturally.
BabyCenter LLC. (2015). Inside Your Womb. Retrieved September 22-24, 2015, from http://www.babycenter.com/fetal-development-inside-your-womb
CBR Systems Inc. (2015). Ossification by Pregnancy Weekly. Retrieved September 23, 2015, from http://www.parentingweekly.com/pregnancy/fetal-development/ossification.htm
CK-12 Foundation. (2015). Human Egg Cells. Retrieved September 24, 2015, from http://www.ck12.org/life-science/Human-Egg-Cells-in-Life-Science/lesson/Human-Egg-Cells-Basic/
Gilbert, S. F. (2000). Osteogenesis: The Development of Bones. Retrieved September 23, 2015, from http://www.ncbi.nlm.nih.gov/books/NBK10056/
What to Expect Foundation. (2015, August 15). What to expect. Retrieved September 22-23, 2015, from http://www.whattoexpect.com/pregnancy/baby-bone-development/
Zimmermann, G., Ackermann, W., & Alexander, H. (2012, March 30). Result Filters. Retrieved September 22, 2015, from http://www.ncbi.nlm.nih.gov/pubmed/21832169