The document summarizes the process of fertilization and early pregnancy development. It describes how a sperm fertilizes an ovum in the fallopian tube, forming a zygote. The zygote then undergoes cell division and implants in the uterus. An embryo and placenta form to receive nutrients from the mother's blood. The placenta also functions in gas exchange, waste removal, and hormone production for the growing fetus over a typical 38 week gestation period. The mother's body undergoes physiological changes to support the development and needs of the fetus until childbirth.

1. PREAMBLE
• So far we have coved the sexual functions of the
male and female reproductive system upto ovum &
sperm production and release.
• If the ovum becomes fertilized, a new sequence of
events called gestation, or pregnancy, takes place,
and the fertilized ovum eventually develops into a
full-term fetus.

2. Fertilization
• The process of fertilization involves the fusion of the
contents of the sperm and ova to make up a zygote
with 46 chromosomes.
• Of the almost half a billion sperm deposited in the
vagina, a few thousand succeed in reaching each
ampulla.
• Fertilization of the ovum normally takes place in the
ampulla of one of the fallopian tubes soon after
both the sperm and the ovum enter the ampulla.
• The sperm are helped along by
– the movement of the flagella.
– contractions of the uterine wall & FT (aided by
prostaglandins in semen and Oxytocin).
– The cilia in the tubal epithelium.

3. Events leading to fertilization
• A sperm first penetrate the multiple layers of
granulosa cells attached to the outside of the ovum
(the corona radiata) and
• Then bind to and penetrate the zona pellucida
surrounding the ovum itself.
• Acrosomal reaction – enzymes digest a slit
• Sperm passes through zona
• Fusion of a single sperm’s plasma membrane with
oocyte’s plasma membrane
• Cortical reaction: sperm receptors destroyed in
zona so no more enter; sperm nucleus engulfed by
egg’s cytoplasm

6. Fertilization
• Although about 200 million sperm are introduced into
the vagina, only about 100 reach the ova.
• Despite the fact that ultimately only one sperm is
required for this process, the enzymes located on the
head of the sperm are required to penetrate the layer
of cells from the ovarian follicle that surrounds the ova.
• The moment one sperm penetrates the cell membrane
of the ovum, rapid changes occur in the cell membrane
to prevent other sperm from entering.
• From this time, the zygote rapidly multiplies and
differentiates until a 3–4 kg (6.6–8.8 lb) infant is
formed at the end of 9 months.

7. 7
Transport of the Fertilized Ovum in the Fallopian
This transport is effected mainly by
a feeble fluid current in the tube resulting from epithelial secretion
plus action of the ciliated epithelium that lines the tube
Weak contractions of the fallopian tube may also aid the ovum passage.

8. 8
Implantation of the Blastocyst in the
Uterus.
Implantation results from the action
of trophoblast cells that develop
over the surface of the blastocyst.
These cells secrete proteolytic
enzymes that digest and liquefy the
adjacent cells of the uterine
endometrium.
Once implantation has taken place,
the trophoblast cells and other
adjacent cells (from the blastocyst
and the uterine endometrium)
proliferate rapidly, forming the
placenta and the various
membranes of pregnancy.

9. Gestation
• The time spent in prenatal (time in the uterus)
development is known as the period of
gestation.
• The gestation period is about 38 weeks,
calculating from the estimated date of
fertilization (approximately two weeks from the
first day of the last menstruation).
• This period, for convenience, is divided into 3
trimesters of 3 months each.

10. The 1st Trimester and Formation of Placenta
• About 4 days after fertilization, the dividing,
fertilized mass of cells (now known as the
blastocyst) reaches the uterine cavity where it
implants (attaches) in the endometrium of the
uterus.
• The cells closest to the endometrium undergo rapid
changes, eroding the maternal capillaries to form
the placenta
• The endometrium also changes and, together with
the fetal cells, forms the pancake shaped placenta.
• Thus, the fetal blood, although not mixing with the
mother’s blood, comes in close contact with it.

11. Eventually, the fetus
moves away from the
placenta, only connected
to it by blood vessels—
Two umbilical arteries and
one umbilical vein( this is
the umbilical cord).

12. Functions of the Placenta
• Respiratory,
– Oxygen from the maternal blood diffuses into the fetal blood
while the carbon dioxide diffuses in the opposite direction.
• Gastrointestinal,
– Nutrition required by the fetus is brought by the uterine
blood vessels to the placenta to be transported into the fetal
circulation
• Excretory system
– Waste products, such as urea ,uric acid and creatinine, are
removed from the fetus via the placenta
• Endocrine functions
– secretes many hormones such as human chorionic
gonadotropin (HCG), prolactin, relaxin, progesterone, and
estrogen.

14. Amniotic fluid.
• The cavity where this fluid is located is known as
the amniotic cavity.
• The fluid is initially derived from the mother’s
blood, later from fetus kidney, lungs & GIT.
• Averages between 500ls to 1 litre.
• water in amniotic fluid is replaced once every 3
hours, and the electrolytes sodium and potassium
are replaced an average of once every 15 hours.
• The amniotic fluid.
– cushions the developing fetus.
– The amniotic fluid regulates fetal body temperature,
– serves as a shock absorber, and prevents the fetal tissue
from adhering to the maternal tissue.

15. MATERNAL CHANGES IN PREGNANCY
• The fetus is solely dependent on the mother
for its nutrition, waste removal, and
respiratory functions.
• During pregnancy, major changes have to be
made in the various organ systems of the
mother to adapt to the new demands.
• Initially, the demands are minimal; however,
as the fetus grows, the demands greatly
increase.

16. MATERNAL CHANGES IN PREGNANCY
• First, changes occur in the reproductive
organs and breasts.
• Second, the metabolic functions are
increased to provide sufficient nutrients to
the fetus.
• Third, hormones secreted by the placenta
produce their own effects.

17. Weight Changes
• An average of 10 kg (22 lb) is gained by the mother
during pregnancy.
• This is contibuted by
– weight of the fetus about 3.63–3.88 kg ;
– the uterus, 0.90 kg ;
– placenta and membranes, 0.90 kg ;
– breasts, 0.68 kg (1.5 lb);
– with the remaining weight from fat and extracellular
fluid.

18. Changes in Metabolism
• The metabolism increases in proportion to the
weight gain.
• Other than supplying the fetus its needs, the energy
is utilized for the resultant increase in heart rate,
respiratory rate, and liver function.
• The increase in metabolism is aided by the increase
in thyroid hormone secretion caused by the thyroid
stimulating hormone from the pituitary gland.
• Often, the thyroid gland hypertrophies as a result
and may appear enlarged in about 70% of
individuals.

19. Changes in Body Fluids
• The sex hormones(estrogen) and adrenocortical
(aldosterone)hormones produced during pregnancy cause the
mother to gain weight by fluid retention.
• There is an increase in the number of red blood cells(by bone
marrow), as well as plasma, in the blood. As a result, the
blood volume increases as much as 1 liter .
• This, in turn, increases the amount of blood pumped by the
heart (CO) by 30%.
• At the time of birth of the baby, the mother has about 1 to 2
liters of extra blood in her circulatory system.
• At the time of labor, the mother loses about 200–300 mL of
blood.
• The changes in the hormonal secretion soon after delivery
bring the fluid levels close to normal.
• The total amount of electrolytes (ions such as sodium,
potassium, and calcium) in the blood is increased.

20. Respiratory Adjustments
• The respiratory rate increases together with the
volume of air inhaled with every breath (tidal
volume).
• Flaring out of the ribs and increased movement
of the diaphragm initiates this increase in
volume.
• The anterior-posterior and transverse diameter
of the chest increases by about 2 cm (0.8 in).
• It is also believed that the high levels of
progesterone during pregnancy increase the
minute ventilation even more, because
progesterone increases the respiratory center’s
sensitivity to carbon dioxide.

21. Respiratory Adjustments
• As the fetus grows and occupies more space in the
abdominal cavity late in pregnancy, the mother’s
breathing relies more on the movement of the ribs
than the diaphragm.
• The diaphragm is elevated by about 4 cm (1.6 in) as a
result of the abdominal contents, as well as the flaring
out of the ribs.
• The changes in hormonal secretion often alter the
caliber of the bronchi and, sometimes, mothers prone
to asthma feel better during pregnancy.
• All these changes result in an increased intake of
oxygen with improved supply to the fetus and a
decreased level of carbon dioxide, which enables easier
transfer of carbon dioxide from fetal to maternal blood.

22. Changes in the Cardiovascular System
• Both the increase in maternal metabolism and the
growth of the fetus place significant demands on
this system.
• The increase in metabolism requires a parallel
increase in blood supply
– To the lungs for gaseous exchange,
– To the kidneys for excreting the increased waste products,
and
– To the skin to dissipate the increased heat produced.
– To the placenta as the fetus grows.
• This demand is met by an increase in blood volume
by retaining fluid.
• The total body water increases on an average by 5
liters towards the end of pregnancy

23. Changes in the Cardiovascular System
• All this increases the workload of the heart.
• Both the heart rate and the volume pumped with
each stroke (stroke volume) are increased.
• The heart increases in size and is located at a higher
level as a result of the movement of the diaphragm.
• The total number of red blood cells and hemoglobin
content increases.
• Because the blood volume increases at a more rapid
rate than the cells and hemoglobin, the hemoglobin
levels may appear as less than normal.
• The number of platelets and white blood cells also
increase significantly.

24. Changes in the GIT
• In general, appetite and thirst are increased.
• In the first trimester, the mother may be nauseous or may
vomit.
• The increasing levels of progesterone tend to reduce the
motility of the gut and relaxation of sphincters. As a result,
relaxation of the sphincter in the lower end of the esophagus
can produce regurgitation of food into the esophagus from
the stomach and cause heartburn.
• Toward the later part of pregnancy, the growing fetus exerts
pressure on the gut, reducing the capacity for large meals.
• The slower movement in the small intestine may aid better
absorption of nutrients, while the slower activity of the large
intestines aids better absorption of water.
• However, the latter may be responsible for the constipation
often experienced by pregnant women.

25. Changes in Nutrient Requirements
• The mother’s requirements of vitamins and other
nutrients increase by as much as 10% to 30%.
• The total energy required by the mother in the
advanced stages of pregnancy is about 2,500
kcal/day (as compared with 2,100 kcal/day in a
nonpregnant state).
• During lactation, the requirements increase to
about 3,000 kcal/day.

26. Changes in the Renal System
• The kidney increases in length by about 1 cm (0.4 in).
• As a result of the increase in waste production, the fluid
filtered in the kidney (glomerular filtration) is significantly
increased.
• In early and late stages of pregnancy, there is frequency of
micturition.
– In early pregnancy, the enlarging uterus is still in the pelvis,
compressing the bladder.
– In late pregnancy, the fetal head descends into the pelvis,
irritating the bladder.
• The ureters appear to be dilated and the sphincter between
the bladder and the ureter is more relaxed, resulting in reflux
of urine into the ureter and predisposing the individual to
urinary tract infection.
• As a result of fluid retention, the total urine volume excreted
is less than that of nonpregnant individuals.

27. Changes in the Reproductive Organs
• The breasts are fully developed by the end of the sixth
month of pregnancy as a result of the action of many
hormones, such as prolactin, oxytocin, estrogen,
progesterone, thyroxin, growth hormone, and other
hormones from the placenta.
• The glands begin to secrete, and the secretions are stored
in the ducts.
• Significant changes take place in the uterus. It increases in
length from 7.6 cm (3 in) of a nonpregnant uterus to about
30.5 cm (12 in) at full term.
• At term, together with the contents and fluids, it weighs
about 10 kg (22.1 lb).
• Hormones, such as estrogen and relaxin, soften the
ligaments of the pelvic joints. This is to increase the
capacity of the pelvis and to make it more mobile.

28. BLOOD PRESSURE
• The blood pressure decreases early in pregnancy,
with a slight decrease in systolic pressure and a
marked decrease in diastolic pressure.
• The pressure decreases to its lowest level at mid
pregnancy, after which it gradually increases to
reach its preconception level by 6 weeks after
delivery.
• The change in blood pressure is mainly a result of
the distensibility of the blood vessels.

29. 29
Childbirth
• Gestational period: averages 266 days 40 WEEKS
(this is time post conception; 280 days post LMP)
• Parturition: the act of giving birth: 3 stages of labor
1. Dilation: 6-12h (or more in first child); begins with regular
uterine contractions and ends with full dilation of cervix
(10cm)
2. Expulsion: full dilation to delivery – minutes up to 2 hours
3. Placental delivery: 15 minutes
Dilation of cervis; head enters true pelvis
Late dilation with head rotation to AP position
Expulsion: head first safest as is largest part
Delivery of the placenta

30. • Modified sweat glands
• Both sexes but function (normally)
only in lactating female
• Produce milk to nourish baby
• Respond to hormonal stimulation
• Lymph drains into parasternal and
axillalry lymph nodes
• Nipple surrounded by pigmented ring
of skin, the areola
• Muscles underneath: pectoralis
major and minor, parts of serratus
anterior and external oblique
Mammary glands (breasts)

31. 31
• Mammary glands consist of 15-25 lobes
• Each a distinct compound alveolar gland opening at the nipple
• Separated by adipose and suspensory ligaments
• Smaller lobules composed of tiny alveoli or acini
– Like bunches of grapes
– Walls: simple cuboidal epithelium of milk-secreting cells
– Don’t develop until half-way through pregnancy (ducts grow during puberty)
• Milk passes from alveoli through progressively larger ducts
– Largest: lactiferous ducts, collect milk into sinuses