ivth yr bsc nursing

1. Prepared by :Mrs Bemina JA
Assistant Professor
ESIC College of Nursing
Kalaburagi

2. Conception Other terms used to describe this phenomenon are
fertilization, impregnation or fecundation.
PRE EMBRYONIC PERIOD
Also known as ovular period or germinal period.
Embryogenesis start with the fertilization of the egg cell (ovum) by a
sperm cell (spermatozoon).
Once fertilized, the ovum is referred to as zygote, a single diploid cell.
DEFINITION
 Fertilization is the union of the ovum and a spermatozoa.
 Fertilization must occur fairly quickly after release of the ovum
because it usually occurs in the outer third of a fallopian tube, the
ampullar portion.
 The functional life span of a spermatozoa is about 48 hours / may be as
long as 72 hours or longer.
 Therefore, sexual coitus during this time may result in fertilization
/pregnancy.

3.  The acrosomal layer of the sperm secrete the enzyme
hyaluronidase which disperse the corona radiata
(outermost layer of oocyte) allowing assess to zona
pellucida.
 The sperm reaches to the zona pellucida and penetrates
it.
 Upon penetration a chemical reaction known as the
cortical reaction, which alters the zona pellucida
making it impermiable to other sperm.
 The plasma membranes of the sperm and oocyte
fuse, each pronucleus containing 23 chromosomes
refered as haploid, and become diploid having 46
numbers of chromosomes.
 This new cell is called zygote.

4.  During the first week the zygote travels along the
uterine tube towards the uterus, the zona pellucida
surrounds the zygote.
 It nourished by glycogen secreted by globlet cell of
uterine tube and later the secretory cells of uterus.
 The zygote undergoes mitotic cellular replication
refered as cleavage, resulting into the formation of
smaller cells known as blastomeres.

6.  Development of the Fertilized Ovum
 The zygote divides into two cells- at 1st day
 4 cells –at 2 days
 8 by – 2.5 days
 16 cells by- 3 days. Known as morula.
 The cells binds together tightly in a process known as
compaction.
 Cavitation occur whereby the outermost cells secrete
fluid into the morula and form blastula comprising of
58 cells.

8.  Next, fluid filled the cavity or blastocele appears in
the morula which now becomes known as the
blastocyst.
 Around the out side of the blastocyst there is a single
layer of cell known as the trophoblast while the
remaining cells are clumped together at one end
forming the inner cell mass.
 The trophoblast will form the placenta and chorion,
while the inner cell becomes the fetus, umbilical cord
and the amnion.
 Embedding of the blastocyst is normally completed by
the 11th day after ovulation and the endometrium
closes over it completely

9.  NIDATION
 Implantation occurs in the endometrium of the anterior
or posterior wall of the body near the fundus on 6th
day.
 The blastocyst possesses an inner cell mass or
embryoblast and outer cell mass or trophoblast.
 Trophoblast- becomes the placenta and chorion.
 Embryoblast- become embryo, amnion and umbilical
cord.

10.  This is the name given to the endometrium during
pregnancy.
Three layers are found in decidua.
 The basal layer lies immediately above the
myometrium.
 The functional layer consists of tortus glands which
are rich in secretions.
 The compact layer forms the surface of the decidua
and is composed of closely packed stroma cells and the
neck of the glands

11. Those trophoblastic cells differentiate into layers,
 The Outer Syncitiotrophoblast (syncitium), and
 Inner Cytotrophoblast and
 Below this, a Layer of Mesoderm or Primitive
Mesenchyme.

12.  The syncitiotrophoblast is composed of nucleated
protoplasm which is capable of breaking down tissue
as in the process of embedding.
 The cytotrophoblast is a well defined single layer of
cells which produces a hormone known as human
chorinic gonadotrophin (HCG)

13.  While the trophroblast is developing into the
placenta, which will nourish the fetus, the inner cell
mass is forming the fetus itself.
 The cells differentiate into three layers, each of which
will form particular parts of the fetus.

14.  THE ECTODERM mainly forms the skin and
nervous system
 THE MESODERM forms bones and muscles and
also the heart and blood vessles, including those
which are in placenta.
 THE ENDODERM forms mucous memberanes and
glands.

15.  The three layers together are known as the embryonic
plate.
 Embryoblast
 Develops the embryo, and differentiate into two types
of cells
 Epiblast- epiblast have three layers, which forms the
particular parts of the embryo. The first appearance of
these layers, collectively known as the primitive streak
is around 15 days.
 Hypoblast- the hypoblast cell migrate along with inner
cytotrophoblastic lining secreting extracellular tissue
which becomes the yolk sac.

16.  The amniotic cavity- lies on the side of the ectoderm;
 The yolk sac lies on the side of the endoderm and
provides
 Nourishment for the embryo until the trophoblast is
deficiently developed to take over

17. 1. Pre embryonic period
Week 1-2 – no developments occurs since fertilization
hasn’t actually occurred.
Week 3- from 15-21 days, embryonic 5-7 days.
Fertilization occur and form zygote.
The embryo hatches from its protein shell and perform
implantation (5-6 days).

18.  Week 4th – days 22-28 from LMP embryonic age 2
weeks-
 Events
 Trophoblast cells surrounding the embryonic cells
proliferate and invade deeper into uterine lining.
 Eventually form placenta and embryonic membrane.
 Formation of yolk sac.
 Primitive streak develop at 13 days.
 Primary stem villi appears at 13 days

19.  Week 5 Gestational age:
 4 weeks Embryonic age:
 Week no. 3
 A notochord forms in the center of the embryonic
disk. (day 16 of fert gastrulation commences.
 A neural groove (future spinal cord)forms over the
notochord with a brain bulge at one end.
 Neuromeres appear. (day 18 of fert.)
 Somites, the divisions of the future vertebra, form.
(day 20 of fert.)
 Primitive heart tube is forming.
 Vasculature begins to develop in embryonic disc.

20.  Week 6
 Gestational age-5 week
 Embryonic age 4 weeks
 Events
 Embryo measures 4 mm
 The heart bulge, and begins to beat in a regular rhythm.
 The neural tube closes.
 Arm buds and tail are visible.
 Pulmonary primordium appear
 Hepatic plate appear
 Buccopharyngeal membrane ruptures.
 This form the future mouth.
 Anterior and posterior horns differentiate in the spinal
cord.

21.  Week 7- Embryonic age 5 week
 Events-
 Length is 9 mm
 Lens pits and optic cups develops
 Nasal pits form
 Brain divides into 5 vessicles including the early
telencephalon.
 Leg buds form.
 The metanephros, precursor of kidney start to
develop.
 Stomach differentiation begins.

22.  Week 8
 The embryo measures 13 mm (1/2 inch) in length.
 Lungs begin to form.
 The brain continues to develop.
 Arms and legs have lengthened with foot and hand
areas distinguishable.
 The hands and feet have digits, but may still be
webbed.
 The gonadal ridge begins to be perceptible.
UROGENITAL
 The lymphatic system begins to develop.
 Main development of external genitalia starts.

23.  Week 9
 The embryo measures 18 mm (3/4 inch) in length.
 Fetal heart tone (the sound of the heart beat) can be
heard using doppler
 Nipples and hair follicles begin to form.
 Location of the elbows and toes are visible.
 Spontaneous limb movements may be detected by
ultrasound.
 All essential organs have at least begun.
 The vitelline duct normally closes connects the yolk
sac to the small intestine.

24.  From the 10 weeks of gestation (8th week of
embryogenic) the developing organism is called
FETUS.
 All the major structures are already formed in the
fetus but they continue to grow.

25.  Week 10 -12
 Embryo measures 30–80 mm (1.2–3.2 inches) in length.
 Intestines rotate.
 Facial features continue to develop.
 The eyelids are more developed.
 The external features of the ear begin to take their final
shape.
 The head comprises nearly half of the fetus' size.
 The face is well formed
 The eyelids close and will not reopen until about the
28th week.
 Tooth buds appear.
 The fetus can make a fist with its fingers.
 Genitals appear well differentiated.
 Red blood cells are produced in the liver

26.  Week 13-16
 The fetus reaches a length of about 15 cm (6 inches).
 A fine hair called lanugo develops on the head.
 Fetal skin is almost transparent.
 More muscle tissue and bones have developed, and the
bones become harder.
 Sucking motions are made with the mouth.
 Meconium is made in the intestinal tract.
 The liver and pancreas produce fluid secretions.
 From week 13, sex prediction
 At week 15, main development of external genitalia is
finished
 Abdominal wall closes.

27.  Week 17-21
 The fetus reaches a length of 20 cm (8 inches).
 Lanugo covers the entire body.
 Eyebrows and eyelashes appear.
 Nails appear on fingers and toes.
 The fetus is more active with increased muscle
development.
 "Quickening" usually occurs (the mother and others
can feel the fetus moving).
 The fetal heartbeat can be heard with a stethoscope.

28.  Week 23
 The fetus reaches a length of 28 cm (11.2 inches).
 The fetus weighs about 925g.
 Eyebrows and eyelashes are well formed.
 All of the eye components are developed.
 The fetus has a hand and startle reflex.
 Footprints and fingerprints continue forming.
 Alveoli (air sacs) are forming in lungs.

29.  Week 27
 The fetus reaches a length of 38 cm (15 inches).
 The fetus weighs about 1.2 kg.
 The brain develops rapidly.
 The nervous system develops enough to control some
body functions.
 The eyelids open and close.
 The respiratory system, while immature, has
developed to the point where gas exchange is
possible.

30.  Week 31
 The fetus reaches a length of about 38–43 cm (15– 17
inches).
 The fetus weighs about 1.5 kg (3lb 0 oz).
 The amount of body fat rapidly increases.
 Rhythmic breathing movements occur, but lungs are
not fully mature.
 Thalamic brain connections, which mediate sensory
input, form.
 Bones are fully developed, but are still soft and
pliable.
 The fetus begins storing a lot of iron, calcium and
phosphorus

31.  Week 35
 The fetus reaches a length of about 40–48 cm (16– 19
inches).
 The fetus weighs about 2.5 to 3 kg (5 lb 12 oz to 6 lb
12 oz).
 Lanugo begins to disappear.
 Body fat increases.
 Fingernails reach the end of the fingertips.
 A baby born at 36 weeks has a high chance of survival,
but may require medical interventions

32.  Week 36-40
 The fetus is considered full-term at the end of the
39th week of gestational age.
 It may be 48 to 53 cm (19 to 21 inches) in length.
 The lanugo is gone except on the upper arms and
shoulders.
 Fingernails extend beyond fingertips.
 Small breast buds are present on both sexes.
 Head hair is now coarse and thickest

33.  Respiration - As pulmonary exchange of gases does not take place in the uterus the fetus
must obtain oxygen and excrete carbon dioxide through the placenta
 Nutrition - Food for the fetus derives from the mother’s diet and has already been broken
down into forms by the time reachs the placenta site. The placenta is able to select those
substances required by the fetus, even depleting the mother’s own supply in some instances.
 Storage - The placent metabolises glucose and can also stores it in the form of glycogen and
reconverts it to glucose as required. The placenta store iron and the fat soluble vitamins.
 Excretion -The main substance excerted from the fetus is carbondioxide; bilrubin will also
be excreted as red blood cells are released relatively frequently.
 Protection - It provides a limited barrier to infection with the exception of the treponeona of
syphilis and, few bacteria can penetrate. Viruses, however, can cross freely and may cause
congenital abnormalities as in the case the rubella virus and HIV virus.
 Endocrine - Human chorinnic gondotroghin (HCG) is produced by the cytotrophoblastic
layer of the chorinonic villi. ƒ
Oestrogens as the activity of the corpus luteum declines, the
placenta takes over the production of oestrogen, which are secreted in large amounts through
out pregnancy. ƒ
Human placental lactogen (HpL) has a role in glucose metabolism in
pregnancy. ƒ
Progestrone

34.  The placenta is completely formed and functioning
from 10weeks after fertilization.
 Between 12 and 20 weeks gestation the placenta
weighs more than the fetus.
 Fetal blood, low in oxygen, is pumped by the fetal
heart towards the placenta along the umblical
arteries.
 Having absorbed oxygen the blood is returned to the
fetus via the umblical vein.

35.  Appearance of the Placenta at Term discoid- shape
 The placenta measures about 20 cm in diameter and 2.5cm thick from its
center.
 It weighs 500 to 600 gm approximately one sixth of the baby’s weight at
term.
 It has two surfaces.
 1. The maternal surface maternal blood gives this surface a dark red colour
and part of the basal decidua will have been separated with it. The surface is
arranged in about 20 lobes which are separated by sulci
 2. The fetal surface. The amnion covering the fetal surface of the placenta
gives it a whitish, shiny appearance. Branches of the umbilical veins and
arteries are visible and spreading out from the insertion of the umbilical cord
which is normally in the center.

36.  THE AMINOTIC SAC consists of a double
memberane.
 Chorion – Outer layer adher to the uterine wall.
 Amnion.-The inner layer of the aminotic sac
containing an aminotic fluid and cover the fetal
surface of the placenta and are what give the placenta
its typical shiny appearance.
 Protects the fetus from any infection and the
amniontic fluid is a clear, pale straw in colour.
 It secreted by the amnion and fetal urine also
contributes to the volume from the 10th weeks of the
gestation on wards.

37.  The total amount of amniotic fluid is about 1 litter and
diminished to 800ml at 38 weeks of gestation (term).
 If the total amount exceeds 1500 ml, the condition is known as
polyhdramnous and if less than 300ml it is known as
oligohydraminous.
 It constitutes 99% water and the remaining 1% is dissolved
organic maters including substances and waste products.
 FUNCTION
- Allows for free movement of the fetus
- Protects the fetus from injury
- Maintains a constant temperature for the fetus
- During labour it protects the placenta and umblical cord from
the pressure of uterine contraction
- Aids effeciement of the cervix and dilation of the uterine os

38.  • The placenta begins to develop upon implantation of the blastocyst into the maternal
endometrium.
 • Placenta grows throughout pregnancy.
 • Development of the maternal blood supply to the placenta is complete by the end of
the first trimester of pregnancy (approximately 12–13 weeks).
 Fertilization - Zygote The cleavage starts in the zygote immediately after fertilization
and on 4th day morula has formed.
 The morula consists of two groups of cells:
• Inner Cell Mass (Central Cells)
• Outer Cell Mass (Peripheral Cells)
 Within one day morula is converted into blastocyst consisting of same two groups of
cells, now with different names:
 – Embryoblast derived from Inner Cell Mass
 – Trophoblast derived from Outer Cell Mass
• Embryoblast forms the embryo proper
• Trophoblast forms the placenta and associated membranes.
 Development of placenta starts as soon as blastocyst is attached to the endometrium.
 Trophoblasts start proliferating rapidly and differentiate into two layers:
• Cytotrophoblast or cellular trophoblast
• Syncytial trophoblast (syncytiotrophoblast)

39.  3 weeks after fertilisation -Small projections appear on the
trophoblastic layer of the blastocyst , proliferate to form
chorionic villi
 • Abundant in decidua basalis called chorionic frontosum &
develops into placenta
 • The villi under decidua capsularis are less abundant and
atrophy to form chorionic leave which later form chorion
 Placental Development
 • Chorionic villi erode the walls of maternal blood vessels
and opens up to form a pool of maternal blood(sinuses)
 • Few villi attach deeply into decidua(anchoring villi)
 • Placental circulation establishes by 17th day
 • Placenta completely develops and functions by 10th week
after gestation

41.  SUCCENTURIATE LOBE OF PLACNETA:
 A small extra lobe is present, separate from the main
placenta and joined to it by blood vessles which ran
through the memebrane to reach it.
 The danger is that this small lobe may be retained in
utro after delivery, and if it is not removed it may lead
to haemorrhage and infection.
 Identification On inspection, the placenta will appear
torn at the edge, or torn blood vessles may extend
beyond the edge of the placenta.

43. Circum vallate placenta
 In this situation an opaque ring is seen on the fetal
surface.
 It is formed by a doubling back of the chorion and
amnion.
Danger
 May result in the membranes leaving the placenta
nearer the center instead of at the edges as usually..

45.  Battledore inseration of the cord
 The cord in this case is attached at the very edge of the
placenta in the manner of the table tennis bat.
 Danger
 Likely it is detached up on applying traction during
active management of the third stage of labour.

46.  Velamentous insertion of the cord
 It is inserted into the memberans some distance from
the edge of the placenta.
 The umblical vessles run through the memberanous
frorm the cord to the placneta.
 Danger
 The vessles may tear with cervical dilatation and would
result in sudden blood loss.

48.  Two complete and separate lobes are present, each with
a cord leaving it.
 The bipartite cord joins a short distance from the two
parts of the placenta.
 Danger-
 The extra lobe may retained during delivery
 A tripartite Placenta is similar but with three distinct
lobes.

51.  Placental infarction occurs when the blood supply to an
area of the placenta is blocked and tissue necrosis results.
 It appears most commonly on the maternal surfaces and
most often associated with vascular disease of the utero-
placental unit secondary to maternal hypertension.
 As the infarct at area becomes necrotic, fetal circulation is
reduced because blood flow through the placenta will
decrease.
 However, if the circulation through the rest of the organ is
sufficient, a fetus may survive when as much as 20% to
30% of the placenta is infracted. Placental infractions can
be treated.

52.  Placental tumors (Haemongiomata of the Placenta)
 These tumors are relatively common, being found in
approximately 1 percent of all placentas.
 Most tumors are small and without clinical significance
but a few are large and associated with hydraminious,
antepartum hemorrhage and premature labour.

53.  The umblical cord or funis extends from the fetus to the
placenta and transmits the umblical blood vessles, two
arteries and one vein.
 These are enclosed and protected by Wharton’s jelly,
(a gelatious substance formed from mesoderm).
 The whole cord is covered in a layer of amnion
continuous with that covering the placenta.
 The length of the average cord is about 50cm.
 A cord is considered to be short when it measures less
than 40cm

54. INTRODUCTION
 Fetal circulation is the term used to describe how
blood flows from the placenta through the
developing fetus.
 Fetal circulation is very fascinating and has several
unique components.
 In addition, fetal circulation is different from the
circulation in newborn babies.
 For one, before a baby is born the placenta is the sole
source of oxygen whereas in a newborn baby, the
lungs are the sole site of oxygen exchange.

55.  The fetal heart also has a connection called
the foramen ovale that allow blood flow from the right
atrium to the left atrium of the heart bypassing the
lungs since they are not needed for oxygen at this point.
 Once the baby is born, the increase pressure in the
left atrium and increased oxygenation in the fetal
blood causes the foramen ovale to close.
 This causes blood to flow through the lungs for
oxygenation postdelivery.

56.  The fetal circulation is the circulatory system of a
human fetus, often encompassing the entire
fetoplacental circulation which includes the umbilical
cord and the blood vessels within the placenta that
carry fetal blood.
 Umbilical Cord
2umbilical arteries: return non-oxygenated blood,
fecal waste, CO2 to placenta
1umbilical vein: brings oxygenated blood and
nutrients to the fetus

58.  It has a branch which joins the portal vein and supplies
the liver.
 The ductus vensous (from a vein to a vein) connects
the umblica vein to the inferior venacava.
 At this point the blood mixes with deoxygenated blood
returning from the lower parts of the body.
 Thus the blood throughout the body is at best partially
oxygenated.

59.  1. Ductus venosus: connects the umbilical vein to the
inferior vena cava
 2. Ductus arteriosus: connects the main pulmonary
artery to the aorta
 3. Foramen ovale: anatomic opening between the right
and left atrium.

60.  The foramen ovale (oval opening) is a temporary
opening between the atria which allows the majority of
blood entering from the inferior vencava to pass across
into the left atrium. The reason for this diversion is that
the blood does not need to pass through the lungs since
it is already oxygenated.

61.  The ductus arteriosus (from an artery to an artery)
leads from the bifuraction of the pulmonary artery to
the descending aorta, entering it just beyond the point
where the subclavian and carotid arteries leave.

62.  The hypogastric arteries branch off from the internal
iliac arteries and become umbilical arteries when they
enter the umblical cord. They return blood to the
placenta. This is the only vessel in the fetus which
carries unmixed blood.

63.  Starting from the red blood cells that make up blood,
fetal red blood cells and maternal red blood cells are
different.
 Blood cells are made of a key protein
called hemoglobin, which is responsible for binding and
transporting oxygen to tissues.
 Fetal hemoglobin has a higher affinity for oxygen than
maternal hemoglobin
 This difference facilitates the offloading of oxygen
from mom to fetus.
 Fetal circulation starts after oxygen rich maternal blood
is delivered to the placenta.

64.  The placenta is connected to the fetus via the umbilical
cord.
 The umbilical cord contains a single umbilical
vein and two umbilical arteries.
 The umbilical vein carries oxygenated blood from
the placenta to the fetus and the umbilical arteries
carry deoxygenated blood from the fetus to the
placenta and ultimately to maternal circulation.
 This is another unique feature of fetal circulation as
veins typically carry deoxygenated blood and
arteries carry oxygenated blood.
 Some blood from the umbilical vein flows through an
opening called the ductus venosus bypassing the liver
and going directly into the inferior vena cava (IVC).

65.  The IVC is large blood vessel that takes blood from the lower
half of the body to the heart.
 The blood from the umbilical vein that does not flow through
the ductus venosus enters the fetal liver via the portal vein.
 The blood from the IVC enters the heart via the right atrium.
 The foramen ovale is an opening between the right and left atria
allowing most of the blood bypass the fetal lungs which are
unable to provide oxygen until the baby is born.
 A small amount of blood will ultimately enter the right
ventricle and exit via the pulmonary artery heading for the
lungs.

66.  However, to maximize the amount of oxygenated blood
reaching the rest of the fetus another bypass exists
called the ductus arteriosus.
 The ductus arteriosus connects the pulmonary artery
to the aorta.
 The aorta is the largest artery in the body.
 It carries blood from the heart to the rest of the body.
 The blood from the left atrium then flows into the
left ventricle and out of the heart to the body via the
aorta.
 Once the blood has supplied most of its oxygen content
to the body, it picks up carbon dioxide and returns it to
the placenta via the umbilical arteries.

67.  At birth the baby takes a breath and blood is drawn
to the lungs through the pulmonary arteries.
 It is then collected and returned to the left a sudden
inflow of blood.
 The placental circulation ceases soon after birth and
so less blood returns to the right side of the heart.
 In this way the pressure in the left side of the heart
is greater while that in the right side of the heart
becomes less.

68.  This results in the closure of a flop over the formaen
ovale which separated the two sides of the heart and
stops the blood flowing from right to left.
 The cessation of the placenta circulation results in
the collapse of the umbilical vein, the ductus venosus
and the hypogastric arteries.

69.  These vessels after collapse change to the following
structure.
 The umbilical vein → the ligamentaum teres
 The ductus venosus → the ligamentum venosum
 The ductus arteriosus → the ligamentum
arteriousm
 The foramen ovale → the Fossa ovalis
 The hypogastric arteries → the obliterated
hypogastic arteries atrium via the pulmonary veins