Development of the general body form

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Development of the general body form
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• FOLDING OF THE EMBRYO
• Folding of the Embryo in the Median Plane
• THE HEAD FOLD
• THE TAIL FOLD
• Folding of the Embryo in the Horizontal Plane

Horizontal plane
Median plane
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• THE HEAD FOLD
• Septum transversum??? develops into the central
  tendon of the diaphragm
• The longitudinal infolding turns yolk sac inward
  as foregut (primordium of pharynx, etc.).

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• THE TAIL FOLD
• Cloacal membrane??? on the caudal end of
  primitive streak develops into future anus.
• Neural tube growing over cloacal membrane causes
  infolding and turns part of yolk sac into embryo
  as hind gut.
• Connecting stalk turns to ventral surface, and
  allantois is incorporated into embryo.

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Folding of the Embryo in the Horizontal
Plane Lateral folding rolls the sides of embryo
disc and turns part of yolk sac into embryo as
midgut and the rest left outside (yolk stalk) and
will be incorporated into umbilical cord.
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• GERM LAYER DERIVATIVES
• Ectoderm
• Mesoderm
• Endoderm

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• CONTROL OF EMBRYONIC DEVELOPMENT
• Embryonic development is essentially a process
  off growth and increasing complexity of structure
  of structure and function.
• Genetic plan in chromosomes
• Environmental factors
• Development is growth and increasing complexity
• Interaction between tissues during development
  (induction????)

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• The methods of signal transduction
• Diffusion of signal substances
• Matrix-mediated interaction
• Cell contact-mediated interaction

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Highlights of fourth to eighth weeks (organogeneti
c period)
24 days -Mandibular (1st) arch--mandible
maxillary -Hyoid (2nd) arch -Slightly curves
(head and tail folds) -Heart prominence
Carnegie stage 11
??
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Carnegie stage 11
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26 days -Pharyngeal (branchial)
arches -Rostral neuropore closes -Forebrain
elevation -C-shaped curvature
Carnegie stage 12
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Carnegie stage 12
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28 days -4th pair pharyngeal arches -Upper and
lower limb buds show -Lens placodes, attenuated
tail are visible -Caudal neuropore closes
Carnegie stage 13
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Carnegie stage 13
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Carnegie stage 14
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Carnegie stage 14
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• Fifth Week
• Brain rapid grows face contacts heart prominence
• Hyoid (2nd) arch overgrows 3rd and 4th arches
• Forms cervical sinus??
• Upper limb with elbow and hand plate
• Mesonephric ridges??? indicate the sites of
  kidneys
• Spontaneous movements

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Carnegie stage 16
Carnegie stage 17
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Carnegie stage 17

• Sixth Week
• Rapid growth of upper limbs
• hand plates with digital rays???
• Groove between 1st and 2nd arch develops
  (external acoustic meatus)
• Swelling around it (auricular hillock???)
• Respond to touch

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Carnegie stage 18
Carnegie stage 19
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Carnegie stage 19

• Seventh Week
• Umbilical herniation??? with intestine
• Notches between digital rays of hand

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Carnegie stage 20
Carnegie stage 21
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Carnegie stage 21

• Eighth Week
• Final week of embryonic period
• Webbed digits of hand
• Notches between digits of foot
• Tail still present
• Scalp vascular plexus?????

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Carnegie stage 22
Carnegie stage 23
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Carnegie stage 23

• End of 8th week
• All region of limbs apparent, limbs move
• Head takes half of the embryo
• Neck established
• Intestine is still in the umbilical cord
• Sexual difference exists but sex still can not be
  told

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Carnegie stage 23
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ESTIMATION OF EMBRYONIC AGE 1. Onset of LNMP 2.
The probable time of fertilization 3.
Measurements of the chorionic sac and embryo 4.
External characteristic of embryo
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Methods of Measuring Embryos Greatest length
(GL)--3rd and early 4th weeks, straight
embryo Crown-rump length (CRL) or sitting
height--neck-rump measurement Crown-heel length
(CHL) or standing height Carnegie Embryonic
Staging system (Table 5-1)
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The Fetal Period Ninth Week to Birth
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• Viability of fetus
• Immature infants (extremely low birth weight,
  ELBW)--less than 500 gm, usually do not survive,
  but with expert postnatal care some may survive
• Low-birth-weight babies--full term but caused by
  intrauterine growth retardation
• Premature infants (1500 to 2500 gm) most may
  survive but with difficulties.

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ESTIMATION OF FETAL AGE By ultrasonic
measurements to determine the size of infant. To
provide the date of confinement (EDC???) the
calculation of age is done by 1. Gestational
age--the onset of the last normal menstrual
period (LNMP) 2. the estimated day of
fertilization the month is by calendar month
Days Weeks Calendar months Lunar months (28 days)
Fertilization 266 days 38 weeks 8 3/4 9 1/2
LNMP 280 days 40 weeks 9 1/4 10
Trimester--each lasting 3 calendar months The end
of the first trimester--all major systems
develops, crown-rump length (CRL) is used for
measuring The end of the second trimester--may
survive if born prematurely At 35 weeks--fetus
weighs 2500 gm, usually survive if born
prematurely
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External Characteristics of Fetuses Measuring
with ultrasonography and weight in the second and
third trimesters 1. Biparietal diameter (BPD) 2.
Head circumference?? 3. Abdominal
circumference?? 4. Femur length???? 5. Foot
length??? 6. Fetal weight???? (may have
discrepancy when mother has diabetes mellitus)
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Fetal Period
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• Ninth to Twelve Weeks
• Beginning of 9th week
• Head 1/2 CRL
• Legs are short, thighs are small
• End of 9th week
• External genitalia show difference
• 11th week
• Intestine return to abdomen
• 12th week
• -Fetal form of ext. genitalia established
• End of 12th week
• Head lt 1/2 CRL
• Primary ossification center appears
• Erythropoiesis site transfer from liver to spleen
• Between 9th to 12th week
• Urine forms and discharge to amniotic fluid,
  which is swallowed by fetus

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• Thirteen to Sixteen Weeks
• 14th week
• Rapid growth
• Coordinated limb movement
• Active ossification of skeleton
• Eye movements occur
• Scalp hair pattern determinated
• 16th week
• Bones can be seen on radiographs
• Ovaries differentiated and contain primordial
  follicles

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• Seventeen to Twenty Weeks
• Fetus grows 50 mm within period
• Fetal movements (quickening??) felt by mother
• Delivery day is 147 /- 15 days after first
  movement
• Skin is covered and protected by vernix caseosa??
• 20th week
• Covered by lanugo?? (fine downy hair)
• Eyebrows and head hairs are visible
• Testes begins to descend

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• Twenty-one to Twenty-five Weeks
• Substantial weight gain
• Skin is wrinkles and translucent, pink to red
• 21st week
• -Rapid eye movements begin
• 22nd to 23 weeks
• -Responds to noise (blink-startle responses)
• 24th week
• -Type II pneumocytes secrete surfactant
• -Fingernail present
• 22nd to 25th weeks
• -Born prematurely may survive under intensive
  care

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• Twenty-six to Twenty-nine Weeks
• Can breath air by functioning lungs
• CNS controls rhythmic breathing, body temperature
• 26th week
• Eyes reopen
• Toenails are visible
• Subcutaneous fat flattens wrinkled skin
• 28th week
• Spleen has been an important site of
  hematopoiesis
• Hematopoiesis shifts to bone marrow by the end of
  28th week.

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Thirty to Thirty-four Weeks 30th week -Pupillary
light reflex 32nd week -Born prematurely usually
survive -Born as normal weight (premature by
date) -White fat 8 body weight
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Thirty-five to Thirty-eight Weeks 35th
week -Grasp, spontaneous orientation to
light 36th week -Circumferences of head is
equal to that of abdomen -CRL 360 mm, weight
3400 gm -Slow growing before birth -White fat
16 body weight 37th to 38th weeks -Nervous
system is mature for integrative functions 38th
week -Add 14 gm per day in last week Full
term -Testes in scrotum
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• FACTORS INFLUENCING FETAL GROWTH
• Maternal Malnutrition
• Cigarette Smoking
• Multiple Pregnancy
• Social Drugs
• Impaired Uteroplacental Blood Flow
• Genetic Factors and Growth Retardation

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• Diagnostic Amniocentesis????
• A common technique for detecting genetic disorder
• After 14 weeks there is about 200 ml amniotic
  fluid, and 20-30 ml can be safely withdraw under
  guidance of ultrasonography.
• The risk of inducing an abortion is about 0.5
• Who may need amniocentesis
• gt 38 years of maternal age
• previous birth of a trisomy child
• chromosome abnormality in either parent
• a X-linked recessive disorders carrier
• neural tube defects in the family
• carriers of inborn errors of metabolism

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• Alpha-fetoprotein (AFP) Assay
• Produced by liver, yolk sac and instestine
• neural tube defects (NTDs) and ventral wall
  defects (VWDs) AFP ?
• ???,????18AFP ?

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Sex Chromatin Patterns--sex-linked hereditary
diseases, e.g. hemophilia and muscular dystrophy
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• Chorionic Villus Sampling (CVS)?????
• trophoblasts obtained by needle through mother's
  abdominal and uterine wall under ultrasound
  guidance
• Risk of fetal loss 1 risk of limb defects if
  done too early.

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Fetoscopy?????--few use Ultrasonography???--measur
ing placental and fetal size, multiple births,
and abnormal presentations, even male
genitalia Computed Tomography (CT) and Magnetic
Resonance Imaging (MRI)--providing more
information for treatment, but expensive and
limited resolution Amniography???? and
Fetography????--injecting water-soluble or
oil-soluble radiopaque substance into amniotic
cavity Fetal Monitoring????--for fetal heart rate
monitoring (fetal distress????-abnormal heart
rate)
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Ultrasonography???
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Magnetic Resonance Imaging (MRI)
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