4/4/25, 6:09 NR327-Fetal Development DETAILED VERSION |
PM
NR327-FETAL DEVELOPMENT DETAILED VERSION EXAM
QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
LATEST UPDATE
Terms in this set (40)
First Trimester 1-13 weeks
Second Trimester 14-26 weeks
Third Trimester 27-40 weeks
-Amniotic sac forms-Embryo (is not called embryo because sac is formed)
Week 4 -Nervous system (brain and spinal cord start to develop)
-Placenta is attached to uterine wall
-Organs start to form: the brain, spinal cord, nerves, heart, blood vessels, kidneys,
GI tract
Week 5 -Embryo: digestive, circulatory, and nervous system are in early stages of
development
-Placenta: is continuing to develop along with the embryo
-Eyes and ears begin to develop during weeks 6 and 7
Week 6 -Arms and Leg buds start to form
-Bones: spine and other bones are in the early stages of development
-Heart: is beating at a regular rhythm, allowing blood to flow through the early
circulatory system. Average 90-110bpm, can likely be detected by ultrasound
Week 7 -Kidneys: during approx. the first 10 weeks 3 sets of kidneys form - the
metanephros kidneys turn into adult kidneys
-Umbilical cord: now fully formed
-Arms and Legs: Arms and legs lengthen and the embryonic tail becomes less
noticeable
Week 8 -Organs: Brain becomes larger and lungs begin to form
-Genitalia: during approx. weeks 7-14 the reproductive organs and external
genitalia develop. During week 8, testes or ovaries have formed
-Embryo: continues to grow in size and may start to move around
-Heart: during approx. weeks 6-9, thin walls called septa form between the four
heart chambers to create the upper atria and lower ventricles. Valves also
Week 9
begin to form
Limbs: Upper and lower limbs continue to lengthen, and individual fingers
and toes are distinguishable.
-Fetus: at week 10 the embryo is considered a fetus. Notably during week 10, the
intestines rotate
-Umbilical cord and placenta continue to grow, the umbilical cord may be
Week 10 detectable with US
-Head: the features are more distinguishable, particularly the outer ears, nose,
and eyelids
-Placenta and Umbilical cord: continue to grow, the cord appears thicker due to
increased size and number of blood vessels
-Face: features become more defined and move into place. Ears move further
Week 11 along the side of the head. The eyelids, nose, and nasal passages become more
developed
Genitalia: weeks 7-14 the reproductive and external genitalia develop. The penis or
clitoris and labia majora have started to form
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, 4/4/25, 6:09 NR327-Fetal Development DETAILED VERSION |
PM
-Face: features are more defined. Vocal cords and nasal passages become more
developed.
Week 12
-Nails: fingernails and toenails start to appear
-Kidneys: kidneys begin to function
Head: continues to develop. 1/3 the total length of the fetus
Week 13 -Fetus: large enough to fill the amniotic sac and uterus
-Lanugo: soft, fine hair starts to appear
-Head: position of the head starts to lift and straighten. Eyes are still wide-set but
Week 14 they start to move toward the front of the face.
-Genitalia: external continue to develop
-Hair: hair growth may start to become more apparent during week 15
and upcoming weeks
-Ears: External become more defined. Inner ear structures including the tympanic
Week 15
membrane and small bones (ossicles) continue to develop
-Bones: Musculoskeletal tissues in the fetus continue to develop rapidly. Bones
lengthen and become more solid, while muscles strengthen.
-Head: lifted into an upright position and the neck is more defined
-Mouth: Inside the mouth, taste buds have started to form on the tongue
Week 16
-Toes: fingernails and toenails continue to strengthen. Toenails may lengthen and
become more noticable during approx week 18
-Organs: The liver, pancreas, and spleen are developed and produce secretions
Week 17 -Musculoskeletal system: continue to develop and bones steadily harden. Fetus
may become increasingly active in the coming weeks
Eyes: At this stage, most structures of the eye including the cornea, iris, lens,
retina, and ciliary body have formed but are not fully refined yet.
The eyelids remain closed. The eyes, eyelashes, eyebrows, and eyelids will
Week 18
continue developing until the final trimester.
-Ears: The structures of the inner and outer ear are nearly fully
developed. As a result, the fetus starts to hear sounds.
-Vernix caseosa: A waxy, cream-colored coating called the vernix caseosa
appears around week 19.
The vernix caseosa protects the growing fetus from abrasions and chafing from
Week 19
the amniotic fluid and immediately after birth.
-A type of insulating fat called brown fat starts accumulating.
This helps the fetus retain heat as it develops.
-Skin: The skin develops specialized structures including sebaceous and sweat
glands. The hair and nails continue to grow steadily.
-Digestive System: At approximately this stage in the pregnancy, accumulated
waste in the fetal digestive tract will be excreted in an initial bowel
Week 20
movement known as meconium.
-Immune System: B and T lymphocytes, cells important to the immune system,
begin forming and accumulating in lymphoid tissue such as the bone marrow and
spleen.
-Fingers: At this stage, the fetus is likely able to suck its thumb and swallow.
-Fetus: The fetus becomes increasingly active and continues to grow in size.
-Genitalia: The reproductive systems and external genitalia continue to become
Week 21
more refined.
In the coming weeks, the vaginal canal will finish forming and the testes will
descend.
-Heart: At approximately week 22, the heartbeat is likely detectable with
a stethoscope.
Week 22 -Hormones: The hormone levels in the fetus fluctuate as the pituitary gland
develops.
-Eyes: Eyebrows, eyelashes, and tear ducts have started to form.
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PM
NR327-FETAL DEVELOPMENT DETAILED VERSION EXAM
QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
LATEST UPDATE
Terms in this set (40)
First Trimester 1-13 weeks
Second Trimester 14-26 weeks
Third Trimester 27-40 weeks
-Amniotic sac forms-Embryo (is not called embryo because sac is formed)
Week 4 -Nervous system (brain and spinal cord start to develop)
-Placenta is attached to uterine wall
-Organs start to form: the brain, spinal cord, nerves, heart, blood vessels, kidneys,
GI tract
Week 5 -Embryo: digestive, circulatory, and nervous system are in early stages of
development
-Placenta: is continuing to develop along with the embryo
-Eyes and ears begin to develop during weeks 6 and 7
Week 6 -Arms and Leg buds start to form
-Bones: spine and other bones are in the early stages of development
-Heart: is beating at a regular rhythm, allowing blood to flow through the early
circulatory system. Average 90-110bpm, can likely be detected by ultrasound
Week 7 -Kidneys: during approx. the first 10 weeks 3 sets of kidneys form - the
metanephros kidneys turn into adult kidneys
-Umbilical cord: now fully formed
-Arms and Legs: Arms and legs lengthen and the embryonic tail becomes less
noticeable
Week 8 -Organs: Brain becomes larger and lungs begin to form
-Genitalia: during approx. weeks 7-14 the reproductive organs and external
genitalia develop. During week 8, testes or ovaries have formed
-Embryo: continues to grow in size and may start to move around
-Heart: during approx. weeks 6-9, thin walls called septa form between the four
heart chambers to create the upper atria and lower ventricles. Valves also
Week 9
begin to form
Limbs: Upper and lower limbs continue to lengthen, and individual fingers
and toes are distinguishable.
-Fetus: at week 10 the embryo is considered a fetus. Notably during week 10, the
intestines rotate
-Umbilical cord and placenta continue to grow, the umbilical cord may be
Week 10 detectable with US
-Head: the features are more distinguishable, particularly the outer ears, nose,
and eyelids
-Placenta and Umbilical cord: continue to grow, the cord appears thicker due to
increased size and number of blood vessels
-Face: features become more defined and move into place. Ears move further
Week 11 along the side of the head. The eyelids, nose, and nasal passages become more
developed
Genitalia: weeks 7-14 the reproductive and external genitalia develop. The penis or
clitoris and labia majora have started to form
1/
5
, 4/4/25, 6:09 NR327-Fetal Development DETAILED VERSION |
PM
-Face: features are more defined. Vocal cords and nasal passages become more
developed.
Week 12
-Nails: fingernails and toenails start to appear
-Kidneys: kidneys begin to function
Head: continues to develop. 1/3 the total length of the fetus
Week 13 -Fetus: large enough to fill the amniotic sac and uterus
-Lanugo: soft, fine hair starts to appear
-Head: position of the head starts to lift and straighten. Eyes are still wide-set but
Week 14 they start to move toward the front of the face.
-Genitalia: external continue to develop
-Hair: hair growth may start to become more apparent during week 15
and upcoming weeks
-Ears: External become more defined. Inner ear structures including the tympanic
Week 15
membrane and small bones (ossicles) continue to develop
-Bones: Musculoskeletal tissues in the fetus continue to develop rapidly. Bones
lengthen and become more solid, while muscles strengthen.
-Head: lifted into an upright position and the neck is more defined
-Mouth: Inside the mouth, taste buds have started to form on the tongue
Week 16
-Toes: fingernails and toenails continue to strengthen. Toenails may lengthen and
become more noticable during approx week 18
-Organs: The liver, pancreas, and spleen are developed and produce secretions
Week 17 -Musculoskeletal system: continue to develop and bones steadily harden. Fetus
may become increasingly active in the coming weeks
Eyes: At this stage, most structures of the eye including the cornea, iris, lens,
retina, and ciliary body have formed but are not fully refined yet.
The eyelids remain closed. The eyes, eyelashes, eyebrows, and eyelids will
Week 18
continue developing until the final trimester.
-Ears: The structures of the inner and outer ear are nearly fully
developed. As a result, the fetus starts to hear sounds.
-Vernix caseosa: A waxy, cream-colored coating called the vernix caseosa
appears around week 19.
The vernix caseosa protects the growing fetus from abrasions and chafing from
Week 19
the amniotic fluid and immediately after birth.
-A type of insulating fat called brown fat starts accumulating.
This helps the fetus retain heat as it develops.
-Skin: The skin develops specialized structures including sebaceous and sweat
glands. The hair and nails continue to grow steadily.
-Digestive System: At approximately this stage in the pregnancy, accumulated
waste in the fetal digestive tract will be excreted in an initial bowel
Week 20
movement known as meconium.
-Immune System: B and T lymphocytes, cells important to the immune system,
begin forming and accumulating in lymphoid tissue such as the bone marrow and
spleen.
-Fingers: At this stage, the fetus is likely able to suck its thumb and swallow.
-Fetus: The fetus becomes increasingly active and continues to grow in size.
-Genitalia: The reproductive systems and external genitalia continue to become
Week 21
more refined.
In the coming weeks, the vaginal canal will finish forming and the testes will
descend.
-Heart: At approximately week 22, the heartbeat is likely detectable with
a stethoscope.
Week 22 -Hormones: The hormone levels in the fetus fluctuate as the pituitary gland
develops.
-Eyes: Eyebrows, eyelashes, and tear ducts have started to form.
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