1. Development of the general body form
陳建榮

2. 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
Median plane
Horizontal plane

3. THE HEAD FOLD
Septum transversum橫中膈 develops into the central tendon of the diaphragm
The longitudinal infolding turns yolk sac inward as foregut (primordium of pharynx, etc.).

4. THE TAIL FOLD
Cloacal membrane泄殖膜 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.

5. 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.

7. GERM LAYER DERIVATIVES
Ectoderm
Mesoderm
Endoderm

8. 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誘導作用)

9. The methods of signal transduction:
Diffusion of signal substances
Matrix-mediated interaction
Cell contact-mediated interaction

11. Highlights of fourth to eighth weeks (organogenetic period)
24 days
-Mandibular (1st) arch--mandible & maxillary
-Hyoid (2nd) arch
-Slightly curves (head and tail folds)
-Heart prominence
Carnegie stage 11 咽弓

12. Carnegie stage 11

13. 26 days Carnegie stage 12 -Pharyngeal (branchial) arches
-Rostral neuropore closes
-Forebrain elevation
-C-shaped curvature
Carnegie stage 12

14. Carnegie stage 12

15. 28 days Carnegie stage 13 -4th pair pharyngeal arches
-Upper and lower limb buds show
-Lens placodes, attenuated tail are visible
-Caudal neuropore closes
Carnegie stage 13

16. Carnegie stage 13

17. Carnegie stage 14

18. Carnegie stage 14

19. Fifth Week Brain rapid grows; face contacts heart prominence
Hyoid (2nd) arch overgrows 3rd and 4th arches
Forms cervical sinus頸竇
Upper limb with elbow and hand plate
Mesonephric ridges中腎脊 indicate the sites of kidneys
Spontaneous movements

20. Carnegie stage 16
Carnegie stage 17

21. Carnegie stage 17 Sixth Week Rapid growth of upper limbs
hand plates with digital rays指放射
Groove between 1st and 2nd arch develops (external acoustic meatus)
Swelling around it (auricular hillock耳狀丘)
Respond to touch

22. Carnegie stage 18
Carnegie stage 19

23. Carnegie stage 19 Seventh Week Umbilical herniation臍疝氣 with intestine
Notches between digital rays of hand

24. Carnegie stage 20
Carnegie stage 21

25. 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頭皮血管叢

26. Carnegie stage 22
Carnegie stage 23

27. 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

28. Carnegie stage 23

29. 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

30. 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)

31. The Fetal Period: Ninth Week to Birth

32. 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.

33. ESTIMATION OF FETAL AGE
By ultrasonic measurements to determine the size of infant.
To provide the date of confinement (EDC預產期) 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

34. External Characteristics of Fetuses
Measuring with ultrasonography and weight in the second and third trimesters:
1. Biparietal diameter (BPD)
2. Head circumference頭圍
3. Abdominal circumference腹圍
4. Femur length股骨長度
5. Foot length足長度
6. Fetal weight胎兒重量 (may have discrepancy when mother has diabetes mellitus)

35. Fetal Period

37. 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 < 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

38. 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

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

40. 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

41. 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.

42. 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

43. 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

44. FACTORS INFLUENCING FETAL GROWTH
Maternal Malnutrition
Cigarette Smoking
Multiple Pregnancy
Social Drugs
Impaired Uteroplacental Blood Flow
Genetic Factors and Growth Retardation

46. Diagnostic Amniocentesis羊膜穿刺
A common technique for detecting genetic disorder
After 14 weeks there is about 200 ml amniotic fluid, and ml can be safely withdraw under guidance of ultrasonography.
The risk of inducing an abortion is about 0.5%
Who may need amniocentesis:
> 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

47. Alpha-fetoprotein (AFP) Assay
Produced by liver, yolk sac and instestine
neural tube defects (NTDs) and ventral wall defects (VWDs): AFP ↑
唐氏症,三染色體18：AFP ↓

48. Sex Chromatin Patterns--sex-linked hereditary diseases, e. g
Sex Chromatin Patterns--sex-linked hereditary diseases, e.g. hemophilia and muscular dystrophy

49. Chorionic Villus Sampling (CVS)絨毛膜取樣
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.

50. Fetoscopy胎內內視鏡--few use
Ultrasonography超音波--measuring 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羊膜攝影 and Fetography胎兒攝影--injecting water-soluble or oil-soluble radiopaque substance into amniotic cavity
Fetal Monitoring胎兒監測--for fetal heart rate monitoring (fetal distress胎兒窘迫-abnormal heart rate)

51. Ultrasonography超音波

52. Magnetic Resonance Imaging (MRI)