how long is preembryonic stage
from fertilization to 2 weeks
when is the first critical period
in the preembryonic stage. “all or no effect”
what processes occur in the preembryonic stage
mitosis, entry of zygote into uterus, implantation, germ layer development and embryonic membranes development
how long is the embryonic stage
starts on first day of week 3 (day 15) and lasts until the end of week 8
what processes occur in the embryonic stage
differentiation of cells, organogenesis, and weekly developments begin
when is the second critical period
in the embryonic stage (weeks 3-8). teratogens can cause congenital defects
what are the developments that occur in the 2nd month?
eyes, ears, nose, jaw, neck form. tiny buds become arms, legs, fingers, toes. intestines grow. heart develops separate chambers. liver and spleen produce blood cells.
what month does movement begin
2nd month
how big is embryo in 2nd month
1/2 inch long
what happens to embryo in 2nd week
cells that form part of fetal membranes and placenta develop
what happens to embryo in 3rd week
CNS begins to develop
what happens to embryo at weeks 4-5
brain develops rapidly, heart beats in week5
what happens to embryo in 6th week
head is prominent, facial development begins
what happens to embryo in 7th week
general growth and refinement of all systems
what happens to embryo in 8th week? how long?
definite human form, refinement of systems continue, becomes “fetus”.
over 1/2 inch in size. eyelids and ears are forming, tip of nose forming. arms and legs well formed. fingers and toes longer and more distinct
when are all major systems basically present?
a. fetal stage
b. embryonic stage
c. preembryonic stage
a
when do lungs begin to expand and contract
9-12 wks
when does the brain begin to signal body movement
9-12 wks
when are external genitals well formed
9-12 wks
when are fingers and tooth buds present
9-12 wks
when are RBCs produced by liver
9-12 wks
when is fetus 2 inches
12 weeks
when does fetus start to make its own movements
12 wks
when can the uterus start to be palpated above pubic bone
12 wks
when can the doctor hear baby heartbeat with special instruments
12 wks
when do sex organs start to become clear
12 wks
when does quickening begin
13-16 wks
when is the rapid growth in length period
13-16 wks
when does the fetus measure 4.3-4.6 inches
16 wks
when does the fetus weigh about 3.5 oz
16 wks
when can you feel the top of the uterus about 3 inches below belly button
16 wks
when can baby blink
16 wks
when are heart and blood vessels fully formed
16 wks
when does fetus develop fingerprints and toeprints
16 wks
when does heat retaining brown fat develop
20 wks
when is vernix developing
20 wks
when does fetus get lanugo
20 wks
what does fetus weigh and how long at 20 wks
10 oz, little more than 6 inch long
where is uterus at 20 wks
at level of belly button
what actions can baby do at 20 wks
suck thumb, yawn, stretch, make faces
t/f quickening is occuring at 20 wks
true
what forms at 24 wks
alveoli in lungs
when does vernix cover the baby
24 wks
how much does baby weigh at 24 wks
1.4 lbs
how does baby respond to sounds at 24 wks
weaving or increasing its pulse
what may be noticed at 24 wks if baby has this?
may notice jerking if has hiccups
when can baby sense that its upside down
24 wks. with inner ear fully developed at 24 wks, may sense that its upside down in the womb
when are lungs mature enough to provide gas exchange
25-28 wks
how much does baby weigh at 28 wks
2 lbs 6 oz
when does baby start to make position changes often
28 wks
when is CNS able to direct breathing movement
29-32 wks
when are bones fully developed
29-32 wks
when is the baby gaining weight
33-36 wks
how long and weight of fetus at 36 wks
18.5 inches and close to 6 lbs
when is the brain developing rapidly with the lungs nearly fully developed
33-36 wks
when is the head usually positioned down into the pelvis by
33-36 wks
when is the brain fully developed
38-40 wks