//Fetal development

Fetal development

Life begins with a new conception, 23 + 23 = 46 chromosomes

Cleavage, mitosis cell division

Implantation of the early embryo or blastocyst occurs at about 7 days, a few hundred cells

Development at 4 Weeks

https://www.webmd.com/baby/ss/slideshow-fetal-development

All tissues are present, connective, epithelial, neural tube which will become CNS

Developing the structures that will form face and neck.

The heart and blood vessels continue to develop.

Lungs, stomach, and liver start to develop.

A home pregnancy test would show positive.

Slide 4, 5th week post ovulation

An opened oviduct with an ectopic pregnancy

Anatomic features, including tail, limb buds, heart (which actually protrudes from the chest), eye cups, cornea/lens, brain,

Blood cells now being produced

Cardiac contractions began at 3 weeks

Neural tube is closed

8 weeks

Final week of the embryonic period

Organogenesis in now complete

Fetal period begins start of week 9

Eyelids and ears are forming, and you can see the tip of the nose. The arms and legs are well formed.

The fingers and toes grow longer and more distinct.

External genitals differentiate

Heart has 4 contracting chambers

Umbilical cord has one vein and two arteries

Development at 12 Weeks

Starts to make its own spontaneous movements. Top of the uterus can be felt above pubic bone.

Elbows and knees have been bending since week 10

Heart beat may be heard on examination

The sex organs of should start to become clear

Development at 16 Weeks

Mum can feel the top of the uterus about 3 inches below your belly button.

The baby’s eyes can blink and the heart and blood vessels are fully formed.

The baby’s fingers and toes have fingerprints.

Development at 20 Weeks

Between 17 and 20 weeks gestation, thalamo-cortical relays penetrate the cortex.

20 weeks gestation, pain receptors are present and linked.

By 20 weeks gestation, the baby will respond to sound and move, wince, and recoil from sharp objects and incisions.

Big stress hormone response since 18 weeks

Uterus the level of the belly button.

The baby can suck a thumb, yawn, stretch, and make faces.

"quickening."

Slide 14, 24 weeks

Baby now and responds to sounds by moving or increasing their pulse.

Mum may notice jerking motions if they hiccup.

With the inner ear fully developed, the baby may be able to sense being upside down in the womb.

Slide 15, Development at 28 Weeks

Sleeps most of the time, clear sleep wake cycle by about 30 weeks

Activity rapid eye movement sleep

and the quiet resting state of non-REM sleep.

Baby’s First Dreams: Sleep Cycles Of The Fetus

https://www.sciencedaily.com/releases/2009/04/090413185734.htm

Evidence for early dreaming

Slide 16, Development at 36 Weeks

The brain has been developing rapidly.

Lungs are nearly fully developed.

The head is usually positioned down into the pelvis by now.

Early term baby if born between 37-39 weeks

Term, born at 39-40 weeks

Late term 41-42 weeks