Embryology of human body

1. 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

2. 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.).

3. 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.

4. 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.

6. GERM LAYER DERIVATIVES
-Ectoderm
-Mesoderm
-Endoderm

7. CONTROL OF EMBRYONIC DEVELOPMENT
Embryonic development is essentially a process off growth and increasing
complexity 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)

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

10. 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

11. Carnegie stage 11

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

13. Carnegie stage 12

14. 28 days
-4th pair pharyngeal arches
-Upper and lower limb buds show
-Lens placodes, attenuated tail are visible
-Caudal neuropore closes
Carnegie stage 13

15. Carnegie stage 13

16. Carnegie stage 14

17. Carnegie stage 14

18. 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

19. Carnegie stage 16 Carnegie stage 17

20. 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

21. Carnegie stage 18
Carnegie stage 19

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

23. Carnegie stage 20
Carnegie stage 21

24. 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

25. Carnegie stage 22
Carnegie stage 23

26. 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

27. Carnegie stage 23

28. 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

29. 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)

30. The Fetal Period: Ninth Week to Birth

31. 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.
你知道全球最小的早產兒有多重嗎?
6 months, 243.8g
62cm, 8700g

32. 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

33. 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)

34. Fetal Period

36. 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

37. 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

38. 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

39. 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

40. Twenty-six to Twenty-nine Weeks
-Can breath air by functioning lungs
-Taste buds have functions
-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.

41. 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

42. 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

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

45. Diagnostic Amniocentesis羊膜穿刺
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:
- > 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

46. 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 ↓

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

50. 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.

51. 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)

52. Magnetic Resonance Imaging (MRI)

53. Ultrasonography超音波

54. 4D-Ultrasonography