Embryology Timeline

Sperm fertilizes secondary ooctye

Week 1

Through cleavage mature ovum becomes a blastocyst

Week 1

Week 2

Blastocyst implants into the endometrium of the uterus and turns into a three layered structure called a gastrula. A gastrula forms the embryo.

Week 3

Neural tube starts to form. (brain, spinal cord, and other neural tissue)

Heart starts forming.

Week four

Tiny buds that become arms and legs develop. Blood cells form and circulation starts. Ear, eye, and mouth structures start to develop

Bones start to form where soft cartilage once was. Embryos head is the largest part of the embryo's body. Heartbeat can be picked up.

Week 5

Major organs start developing. The fetus develops web-like hands and feet.

Eyes take shape and the ears form. Umbilical cord is fully developed.

Week 6

Beginnings of teeth and tastebuds start to form. The muscles form and cause the embryo to have a more human appearance.

Week 7

Arms, hands, fingers feet and toes take full formation. Fingernails and toenails start to form and external ears start to form. Gentitals also begin to form.

Week 8

The fetus is starting to explore a bit by opening and closing its mouth and hands. The knees and elbows can operate, but the mother won't feel any kicks yet. The skin of the fetus is see-through and the bones are hardening.

Week 9

The baby's hair starts appearing

Week 10

Because the baby's body will grow signifigantly in the coming weeks it will need more nutrients. The placenta will grow its red blood cell count will go up.

Week 11

All muscles, organs, bones are in place this at point. The circulaltory system and urinary systems are working. The liver starts producing bile. The fetus' can drink and can pee amniontic fluid

Week 12

Vocal cords form. The head of fetus starts to grow in proportion to it's body.

Week 13

The fetus's skin starts to thicken. The fetus can bring it's fingers to it's mouth and turn it's head. External genitals are fully formed at this point

Week 14

Organs like the intestines and ears settle to their permanent location. The lungs begin to develop and the fetus starts doing more purposeful actions such as sucking it's thumb and smiling

Week 15

The baby's lips have formed and its ears are developed enough that it can hear. Even though the fetus' eyes are shut it can react to light by turning away from it

Week 16

The baby will start putting on fat. A substance called vernix covers baby which protects it from exposure of amniontic fluid

Week 17

The baby is covered in a peach-fuzz like hair called Langou. Langou helps keep the baby warm and provides another layer of protection. The baby can develop a sleep-wake cycle now

Week 18

Baby forms unquie fingertips and can hiccup.

Kicks can now be felt by mother.

Week 19

The baby's nails start to grow toward it's finger tips. The cerebrum of the brain starts forming.

Week 20

Limb movements of the baby become more deliberate and more frequent. The baby starts responding to sound by moving. Bone marrow has also formed which helps produce bone marrow.

Week 21

The baby's grasping ability is getting stronger. It can touch it's ears and umbilical cord

Week 22

The baby starts increasing its fat count in preparation. A baby born week 23 could survive with intensive care.

Week 23

Though the lungs won't work well enough to be outside the uterus, they are now fully developed.

Week 24

Fat keeps developing on the baby making the skin plumber and less wrinkled. The nervous system is maturing quickly.

Week 25

Due to the new production of melanin the baby's skin and eyelashes get their colour. The baby's lungs start to make a substance called surfactant which helps the baby after birth.

Week 26

The baby can open it's eyes and blink.

Week 27

The baby might rotate to head down posistion in the uterus in prepartion for birth.

Week 28

Week 38

The baby is increasing it's fat count by 0.5 per week in prepartion for birth.

Baby is now full term. The mothers body and baby decide when to come out unless doctors do.

Week 39

Out? What is out?

Its week 40 the baby can come out anytime!

Week 40

The baby's kicks and jabs are getting more powerful and it may seem like more of poke to the mother. This is due the baby being cramped in the amnionic sac.

Week 29

The baby can control its own body heat and the brain is maturing quickly.

Week 30

The baby is able to process more stimuli and infomation. The pattern in which the baby is asleep or awake is more distinct.

Week 31

The skin the baby is no longer translucent since the melanin has taken full affect. All the organs of baby are fully developed and for birth, except the brain and lungs.

Week 32

Melanin molecule

Week 33

The baby's bones are hardening. The only bone not hardening is the skull because it needs to be soft in order to go through the birth canal.

The vernix that coats the baby becomes thicker

Week 34

Baby covered in vernix

The baby's brain continues to grow, but it weighs 2/3 of what it should at birth.

Week 35

The baby loses its Languo. Some hair may stay on it's back after birth and hair will stay on its head.

Week 36

Languo hair

The toenails of the baby have grown to reach the end of it's toes. The baby might drop into pelvis.

Week 37