for 4th year Basic Bsc nursing students

1. Physiology of Pregnancy &
Reproduction
Embryology

2. Embryology
• Definition: the study of the origin and
development of an organism
• Prenatal period: before birth
– 38 weeks from conception to birth (average) “fetal”
age

3. Traditional (artificial) division:
• “Embryonic” period: first 8 weeks
– All major organs formed
• “Fetal” period: remaining 30 weeks
– Organs grow larger and become more complex

7. Stage 1
• Fertilization
Fertilization
• 1 Oocyte
• 300 Million Sperm
• 24 Hours
• 0.1 - 0.15 mm
• 1 day post-ovulation

8. Fertilization
• SPERM + EGG(OOCYTE) = ZYGOTE
• The fertilization process takes about 24
hours.
• Sperm life = 48 hours
– It takes about ten hours to navigate the female
productive track, moving up the vaginal canal,
through the cervix, and into the fallopian tube
where fertilization begins.

9. Mr.SPERM +
Mrs. EGG

11. Fertilization
• 300 million sperm enter the the vagina...
only 1%, 3 million, enter the uterus
• The next step is the penetration of the zona
pellucida, a tough membrane surrounding
the oocyte.
• Penetration of the zona pellucida takes
about twenty minutes.

12. One ova with many sperms

14. Fertilization
• Within 11 hours following fertilization, the
oocyte has extruded a polar body with its
excess chromosomes. The fusion of the
oocyte and sperm nuclei marks the creation
of the zygote and the end of fertilization.

15. Stage 2
Cleavage
• First Cell Division, Blastomeres,
• Mitotic division
• 0.1 - 0.2 mm
• 1.5 - 3 days post-ovulation

17. Cleavage
• The zygote now begins to cleave, with each
division occurring into two cells called
blastomeres
• The zygote's first cell division begins a
series of divisions, with each division
occurring approximately every twenty
hours

19. Cleavage
• When cell division ungenerated about
sixteen cells, the zygote becomes a morula
(mulberry shaped)
• It leaves the fallopian tube and enters the
uterine cavity three to four days after
fertilization.

20. Stage 4
Implantation Begins
• HCG Levels Rise
• 0.1 - 0.2 mm
• 5 - 6 days post-ovulation
• The trophoblast cells secretes an enzyme
which erodes the epithelial uterine lining
and creates an implantation site for the
blastocyst.

21. Stage 4
Implantation Begins
• ovary continues producing progesterone
• trophoblast cells continue releasing human
chorionic gonadotropin (hCG)
• Endometrial glands in the uterus enlarge in
response to the blastocyst and the
implantation site becomes swollen with new
capillaries. Circulation begins, a process
needed for the continuation of pregnancy.

22. Fertilization to Implantation

23. Stage 5
Implantation Complete
• The inner cell mass divides, rapidly forming a
two-layered disc
• The top layer of cells...
– will become the embryo and amniotic cavity
– the lower cells will become the yolk sac.
• Ectopic pregnancies can occur at this time and
sometimes continue for up to 16 weeks of
pregnancy before being noticed

25. Implantation of the Blastocyst
Figure 3.4 (1 of 3)

26. Implantation of the Blastocyst
Figure 3.4 (2 of 3)

27. Implantation of the Blastocyst
Figure 3.4 (3 of 3)

28. Week 2
Inner cell mass
divides into
epiblast and
hypoblast
2 fluid filled sacs
Amniotic sac
from epiblast
Yolk sac from
hypoblast
Bilaminar
embryonic disc:
area of contact
(gives rise to the
whole body)

29. Stage 6
Gastrulation, Chorionic Villi Formation
• 0.2 mm
• 13 days post-ovulation
• The formation of blood and blood vessels of
the embryo begins
• Yolk sac begins to produce hematopoietic or
non-nucleated blood cells.
• Gastrulation three layers of the embryo:
ectoderm, mesoderm and endoderm.

31. • Bilaminar to trilaminar disc
• Three primary “germ” layers: all body tissues develop
from these
• Ectoderm
• Endoderm
• Mesoderm

32. Week 3

34. • Primitive streak (groove) on dorsal surface of
epiblast
• Grastrulation: invagination of epiblast cells
• Days 14-15: they replace hypoblast becoming
endoderm
• Day 16: mesoderm (a new third layer) formed
in between
• Epiblast cells remaining on surface: ectoderm

35. Stage 7
• Neurulation and Notochordal Process
• 0.4 mm
• 16 days post-ovulation
• Endoderm forms the lining of lungs,
tongue, tonsils, urethra and associated
glands, bladder and digestive tract.

36. Stage 7
• Mesoderm forms the muscles, bones,
lymphatic tissue, spleen, blood cells, heart,
lungs, and reproductive and excretory systems.
• Ectoderm forms 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

37. The Basic Body Plan
Figure 3.2

38. Stage 8
• Notochordal Canal and Neurenteric Canals
• 1.0 - 1.5 mm
• 17-19 days post-ovulation
• Neural plate with a neural groove
• The blood cells of the embryo are already
developed and they begin to form channels
along the epithelial cells which form
consecutively with the blood cells.

39. Notochord

40. Neurulation

41. Stage 9
• Appearance of Somites(condensations of
mesoderm, appear on either side of the neural
groove
• 1.5 - 2.5 mm
• 19 - 21 days post-ovulation
• Primitive streak
• Endocardial (muscle) cells begin to fuse
and form into the early embryo's two heart
tubes.

43. Stage 10
• Neural Folds Begin to Fuse, Heart Tube
fuses
• 1.5 - 3.0 mm
• 21 - 23 days post-ovulation
• Cardiac muscle contraction begins
• Eye & ear cells are present
• Neural tube starts closing

45. Stage 11
• Optic Vesicle Appears, Two Pharyngeal Arches
Appear
• 2.5 - 3.0 mm
• 23 - 25 days post-ovulation
• A primitive S-shaped tubal heart is beating and
peristalsis, the rhythmic flow propelling fluids
throughout the body, begins.
• At this stage, the neural tube determines the form
of the embryo
•

46. Stage 12
• Caudal Neuropore Closes, Three to
Four Pharyngeal Arches Appear, Upper
Limb Buds Appear
• 3.0 - 5.0 mm
• 25 - 27 days post-ovulation
• The brain and spinal cord together are the
largest and most compact tissue of the
embryo.

47. Stage 12
• Valve & septa appear in the heart
• The digestive epithelium layer begins to
differentiate into the future locations of the
liver, lung, stomach and pancreas.
• The beginning cells of the liver form before
the rest of the digestive system.

48. Stage 13 (approximately 27-29
postovulatory days)
• Forebrain, midbrain and hindbrain. forms

49. Cylindrical
human body
plan, day 28
(about ½ cm)
Simplified
cross section
through
abdomen of
an adult
(essentially the
same as above)

51. Stage 13
• Lymphatic & thyroid start to develop
• Limb buds
• First thin layer of skin
• Liver & heart, etc.

52. 28 days

53. 4
Weeks

54. Stage 14
(4 to 8 weeks post
fertilization)
• Nervous sys developing further
• 4 chamber heart
• lung sacs
• Ureteric bud appear
• Nerve distribution process, innervation,
begins in the upper limbs.

55. 41 days

56. Stage 15
• 6 to 8 weeks post fertilization
• Further development of nervous system,
heart.
• Innervation, the distribution of nerves,
begins in the lower limb buds.

57. Stage 17
• approximately 41 postovulatory days
• A Four Chambered Heart and a Sense of
Smell
• Primitive germ cells arrive at the genital
area and will respond to genetic instructions
to develop into either female or male
genitals.

58. Stage 19
• approximately 47-48 post ovulatory days
• Brain Waves and Muscles
• The trunk elongates and straightens and the
bone cartilage begins to form a more solid
structure. Muscles develop and get stronger.

59. Stage 20
• 48-52 days post ovulation
• Spontaneous Involuntary Movement
• Brain is connected to tiny muscles and
nerves and enables the embryo to make
spontaneous movements
• Testes or ovaries are distinguishable

60. 51 days

61. Stage 23
• approximately 56 - 57 postovular days
• Essential External and Internal
Structures Complete
• Layer of rather flattened cells, Tail has
disappeared.

62. 56days

63. Two Months

64. 6 Weeks 7 Weeks 8 Weeks

65. 7 weeks 8 weeks

66. 9weeks

68. Week 10 - 11
• Vocal cords formed
• Liver secretes bile, stored in the GB
• Pancreas produces insulin
• Reflexes present
• Male/female differentiate

69. Week 12 - 13
• Fetus begins to move
• Heartbeat can be found with doppler
• Fetal sex now clearly distinguished
• Body begins to grow hair

70. 3 Months

71. 11 Weeks
12 Weeks

73. Week 16 Post Fertilization...
• Growth continues, but no new
structures form after this point
• Meconium begins to accumulate in the
bowels. Meconium is the product of cell
loss, digestive secretion and swallowed
amniotic fluid.
• Placenta equal in size to fetus

74. 17 week

75. The Fetus—Month 4
• Fetus is 3 inches long and weights 5 oz.
• Your baby is covered with a layer of thick, downy
hair called lanugo.
• His heartbeat can be heard clearly.
• This may be when you feel your baby's first kick.
• The baby can such thumb, swallow and hiccup.

76. 4 months

77. 15 Weeks
16 Weeks
18 Weeks

78. Week 18 Post Fertilization...
• A dramatic growth period for the fetus.
• Fetus has phases of sleep and waking and
may prefer a favorite sleep position.
• Ovaries containing primitive egg cells &
uterus present
• Brown fat & vernix
• Placenta is fully formed and grows in
diameter though not in thickness.

80. Week 20
• Fetus sucks thumb
• Extremely rapid brain growth (which lasts
until five years after birth) begins.
• Testes of male fetuses begin descending
from the pelvis into the scrotum.
• Arms and legs move with more force, as
muscles strengthen.

81. Smallest baby in the
world born
At just 22 weeks
• She was 10 OUNCES when born and 9.5
inches. That's just longer than the length of
your hand. She weighed less than a can of
soda!
Her little feet

82. The Fetus—Month 6
• The fetus is 8-10 inches long and weighs 4-
5 oz.
• Your baby's lungs are filled with amniotic
fluid, and he has started breathing motions.
• If you talk or sing, he can hear you.
• Fat is starting to deposit under the skin

83. 6 Months

84. Week 26
• Lungs may be mature enough to breath air!
• Fetal body is two to three percent body fat.
• Eyes are partially open and eyelashes
present.
• Sucking and swallowing improves.

85. The Fetus—Month 7
• Fetus is 10-12 inches long and weighs about
1-2 pounds.
• Fetus is active and then rests.
• The baby now uses the four senses of
vision, hearing, taste and touch

86. Seven Months

87. Week 30
• Body growth slows down
• The iris is colored and the pupil reflexes
responding to light.

88. Week 32
• Fetus rests on uterus - no longer floating.
• Eyes open during alert times and close
during sleep. Eye color is usually blue,
regardless of the permanent color as
pigmentation is not fully developed

90. The Fetus—Month 8
• The fetus is 14-16 inches long and weighs
2-3 pounds
• Layers of fat are piling on.
• Fetus has probably turned head-down in
preparation for birth.
• Fetus may react to noises with a jerking
action

91. Eight Month

92. Week 34
• Head may now position (head-down) into
pelvis before labor.
• Gastrointestinal system is very immature
and will stay that way until three or fourth
years after birth.
• Fetus stores about 15% of weight in fat to
keep temperature of body warm

93. The Fetus—Month 9
• Fetus is about 17-18 inches long and weighs 5-6
pounds
• Skin is smooth because of the fat
• Baby’s movement slows down due to lack of room
• “Lightening” occurs when the baby drops in the
pelvis
• Disease fighting antibodies are taken from the
mother’s blood

94. 40 weeks
• Fullterm
• Fifteen percent of body is fat, eighty
percent of which is underneath the skin, the
other twenty percent around the organs.

98. Developmental Events of the Fetal
Period
Table 3.1 (2 of 3)

99. Table 3.1 (3 of 3)

100. Table 3.1 (3 of 3)