CNUR 303 Study Material Latest Update 2025/2026
with 100% Correct Solutions
FETAL DEVELOPMENT
Preembryonic stage
fertilization to the 2nd week (HcG levels become detectable in the blood several days after
implantation
- and detectable in the urine about 1-2 weeks later)
steps of preembryonic stage
Begins with fertilization of the ovum around 2 weeks after the last normal period (28 day cycle)
Fertilization occurs in the outer third of the ampulla of fallopian tube - mitosis begins
immediately
The zygote reaches the uterine cavity within 72 hours, and then implantation occurs - where the
zygote attaches itself to the surface of the endometrium
embryonic stage
and of the 2nd week through the 8th week
-Embryonic membranes begin to form at the time of implantation (chorion and amnion)
-These 2 fetal membranes form the amniotic sac that protects the floating embryo
-Amniotic fluid fills this sac and increases in volume throughout the pregnancy
,-During the embryonic stage the basic structures of all major body organs and main external
features form
embryonic development week 3
beginning of brain, spinal cord, heart development - neural tube forms, GI tract starts to form, leg
and arm buds appear
embryonic development week 4
limb buds continue grow and develop, brain differentiates
embryonic development week 5
heart now beats at a regular rhythm, eyes and ears begin to form, some cranial nerves evident,
muscles innervated
embryonic development week 6
lungs begin to form, circulation established, liver produces RBCs, further development of brain,
primitive skeleton & CNS form, brain waves detectable
embryonic development week 7
trunk straightens, nipples and hair follicles form, elbows and toes visible, arms and legs move,
diaphragm formed, mouth with lips and tooth buds
embryonic development week 8
rotation of intestines, facial features continue development, heart development complete,
resembles human being
,Fetal stage
end of the 8th week through to birth
-All major systems are present in their basic form, but undergo major growth and refinement
-This is the longest stage of development during the pregnancy
-On average, this stage lasts 7 months
fetal development week 9-12
-Sexual differentiation continues, buds for all 20 baby teeth laid down
-Digestive system shows activity, head makes up half of fetal size, face and neck are well formed
-Urogenital tract completes development, gender can be identified by 12 weeks, urine produces
and excretes
-Limbs are long and thin, digits are well formed
fetal development week 13-16
-Lanugo develops on head, fetal skin almost transparent, bones calcify and become harder
-Fetus makes active movements, sucking motions made with mouth, amniotic fluid is swallowed
-Fingernails and toenails present, weight quadruples, fetal movement can be detected by some
mothers (known as quickening)
, fetal development week 17-20
-Rapid brain growth, fetal heart tones detectable with stethoscope
-vernix caseosa covers the fetus, eyebrows and hair appear, brown fat deposited to maintain
temperature
-Muscles are well developed
fetal development week 21-24
-Eyebrows and eyelashes are well formed
-Fetus has hand grasp and startle reflexes
-Alveoli forming in lungs, surfactant begins to produce
-Skin is translucent and red
fetal development week 25-28
-Fetus reaches length of 15 inches, rapid brain development continues
-Eyelids open and close, nervous system controls some functions
-Fingerprints are set, blood formation shifts from spleen to bone marrow
with 100% Correct Solutions
FETAL DEVELOPMENT
Preembryonic stage
fertilization to the 2nd week (HcG levels become detectable in the blood several days after
implantation
- and detectable in the urine about 1-2 weeks later)
steps of preembryonic stage
Begins with fertilization of the ovum around 2 weeks after the last normal period (28 day cycle)
Fertilization occurs in the outer third of the ampulla of fallopian tube - mitosis begins
immediately
The zygote reaches the uterine cavity within 72 hours, and then implantation occurs - where the
zygote attaches itself to the surface of the endometrium
embryonic stage
and of the 2nd week through the 8th week
-Embryonic membranes begin to form at the time of implantation (chorion and amnion)
-These 2 fetal membranes form the amniotic sac that protects the floating embryo
-Amniotic fluid fills this sac and increases in volume throughout the pregnancy
,-During the embryonic stage the basic structures of all major body organs and main external
features form
embryonic development week 3
beginning of brain, spinal cord, heart development - neural tube forms, GI tract starts to form, leg
and arm buds appear
embryonic development week 4
limb buds continue grow and develop, brain differentiates
embryonic development week 5
heart now beats at a regular rhythm, eyes and ears begin to form, some cranial nerves evident,
muscles innervated
embryonic development week 6
lungs begin to form, circulation established, liver produces RBCs, further development of brain,
primitive skeleton & CNS form, brain waves detectable
embryonic development week 7
trunk straightens, nipples and hair follicles form, elbows and toes visible, arms and legs move,
diaphragm formed, mouth with lips and tooth buds
embryonic development week 8
rotation of intestines, facial features continue development, heart development complete,
resembles human being
,Fetal stage
end of the 8th week through to birth
-All major systems are present in their basic form, but undergo major growth and refinement
-This is the longest stage of development during the pregnancy
-On average, this stage lasts 7 months
fetal development week 9-12
-Sexual differentiation continues, buds for all 20 baby teeth laid down
-Digestive system shows activity, head makes up half of fetal size, face and neck are well formed
-Urogenital tract completes development, gender can be identified by 12 weeks, urine produces
and excretes
-Limbs are long and thin, digits are well formed
fetal development week 13-16
-Lanugo develops on head, fetal skin almost transparent, bones calcify and become harder
-Fetus makes active movements, sucking motions made with mouth, amniotic fluid is swallowed
-Fingernails and toenails present, weight quadruples, fetal movement can be detected by some
mothers (known as quickening)
, fetal development week 17-20
-Rapid brain growth, fetal heart tones detectable with stethoscope
-vernix caseosa covers the fetus, eyebrows and hair appear, brown fat deposited to maintain
temperature
-Muscles are well developed
fetal development week 21-24
-Eyebrows and eyelashes are well formed
-Fetus has hand grasp and startle reflexes
-Alveoli forming in lungs, surfactant begins to produce
-Skin is translucent and red
fetal development week 25-28
-Fetus reaches length of 15 inches, rapid brain development continues
-Eyelids open and close, nervous system controls some functions
-Fingerprints are set, blood formation shifts from spleen to bone marrow
