Transcript development_from_conception_to_birth

Stages of Development
From Conception to Birth
Overview
• Development of the embryo is broken into 3
Trimesters each with 12 weeks
• Up to the 9th week=embryo
• Beyond 9th week=fetus
• At 36-37 weeks, safe to deliver
• 40 weeks considered full term
Ovarian Cycle
Fetal Development Stages – Sutterhealth
Visible Embryo – PBS
Medline Plus
1 Day Post-Ovulation
• Sperm fertilizes egg
• Creation of ZYGOTE
1.5 – 3 Days Post-Ovulation
Development Picture
• Cleavage of zygote-picture
• First cell divisions repeat
approximately every 20
hours
• When cell division creates
about 16 cells, the mass is
called a MORULA
• Morula leaves oviduct to
uterus 3-4 days after
fertilization
Day 4 (Week 1)
Development Picture
• Early Blastocyst phase
• In uterus, cell division
continues
• Cells move to outer
areas leaving open
cavity inside—this is
called the BLASTOCYST
(Blastula)
Day 5-6 (Week 1)
Development Picture
• Implantation Begins
• Considered pregnant
• Progesterone
produced to maintain
thickness of uterine
lining
Day 7-12 (Week 2)
Development Picture
• Implantation
complete
• Growth of placenta
begins
• Inner cells divide
rapidly forming a
two layered disc
– Top layer will become
embryo and amniotic
cavity
– Bottom layer becomes
the yolk sac
(Week 2)
• Gastrulation and formation of
chorionic villi (“fingers” that
form placenta anchor to
uterus)
• Formation of blood and blood
vessels
• Gastrulation, a process that
gives rise to all three tissue
layers of the embryo:
ectoderm, mesoderm and
endoderm.
• Gastrulation Picture
DAY 16
Tissue Layers
• Endoderm form the lining of lungs, tongue, tonsils,
urethra and associated glands, bladder and digestive
tract.
• Mesoderm form the muscles, bones, lymphatic tissue,
spleen, blood cells, heart, lungs, and reproductive and
excretory systems.
• Ectoderm form the skin, nails, hair, lens of eye, lining
of the internal and external ear, nose, sinuses, mouth,
anus, tooth enamel, pituitary gland, mammary glands,
and all parts of the nervous system.
Week 3
• Beginning development of
the brain, spinal cord, and
heart
• Nervous system first to
develop
• Beginning development of
the gastrointestinal tract
1st Month Diagram
Week 4-5
• Beginning of vertebra and bones
• Development of the heart which now
beats at a regular rhythm
• Movement of basic blood through the main
vessels
• Beginning of the structures of the eye
and ears
• Brain develops into five areas and some
cranial nerves are visible
• Arm and leg buds are visible
Week 6
• Beginning of formation of the lungs
• Further development of the brain
• Arms and legs have lengthened with foot and
hand areas distinguishable
• Hands and feet have digits, but may still
be webbed
Week 7-8
• Nipples and hair follicles form
• Elbows and toes visible
• All essential organs have at
least begun to form
• Facial features continue to
develop
• Eyelids are more developed
• External features of the ear begin
to take their final shape
Week 9-12
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Fetus reaches a length of 3.2 inches
Head comprises nearly half of the fetus' size
Development of four-chambered heart
Fingernails formation begins
Tooth buds appear for the baby teeth
Fetus can make a fist with its fingers
Genitals appear well differentiated
Vocal cords can make sounds
Bone hardening begins
First detectable brain waves-Involuntary
movements possible
Week 13-16
• Fetus about 6 inches
• Fine hair develops on the
head called lanugo
• More muscle tissue and bones
have developed, and the bones
become harder
• Fetus makes active
movements
• Sucking motions are made
with the mouth
• Muconium is made in the
intestinal tract
Week 17-20
• Fetus reaches a length of 8 in
• Lanugo hair covers entire
body
• Eyebrows and lashes appear
• Nails appear on fingers and
toes
• Fingerprints formed
• More active with increased
muscle development-mom can
feel the fetus moving
• Taste buds formed
Week 21-24
• Fetus length of 11.2 inches
• Weighs about 1 lb. 10 oz.
• All the eye components are
developed
• Hand and startle reflex
• Air sacs forming in lungs
• Thumb sucking
• Rapid brain growth
• Can sense light/sound
Week 25-28
• Length of 15 inches; about 2 lbs. 11 oz.
• Nervous system developed enough to
control some body functions
• Eyelids open and close
• Respiratory system, while immature, has
developed to the point where gas
exchange is possible
• Baby born at this time may survive, but the
possibilities for complications and death
remain high
Week 29-32
• Length of about 15-17 inchesabout 4 lbs. 6 oz.
• Rapid increase in the amount
of body fat
• Rhythmic breathing
movements occur, but lungs
are not fully mature
• Bones are fully developed, but
still soft and pliable
• Eyes open when active and
shut when asleep
• Fetus begins storing minerals
Week 33-36
• Length of about 16-19 inches;
5 lbs. 12 oz. to 6 lbs. 12 oz.
• Lanugo begins to disappear
• Increase in body fat
• Fingernails reach the end of
the fingertips
• Baby born at 36 weeks has a high
chance of survival, but may
require some medical
interventions
Week 37-40
• 19 to 21 inches in length
• Lanugo is gone except for on
the upper arms and shoulders
• Fingernails extend beyond
fingertips
• Small breast buds are present
on both sexes
• Head hair is now coarse and
thicker
• Lungs finalize development
Development Comparison
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1st Month
Cleavage
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Week 2