2. Pregnancy
1. Transport of spermatozoa and ova
2. Fertilization
3. Blastogenesis
4. Implantation
Dr. Misbah-ul-Qamar
3. Maturation and Fertilization of the
Ovum
• Primary oocyte-First meiotic division occurs at
the time of ovulation-23 unpaired
chromosomes in the secondary oocyte (each is a
double chromosome).
• Secondary oocyte-2nd meiotic division. Once a
sperm has entered the ovum the oocyte divides
again to form the mature ovum plus a second
polar body that is expelled.
• The mature Ovum has in its nucleus (now called
the female pronucleus) 23 chromosomes (each is
a single chromosome).Dr. Misbah-ul-Qamar
7. Fertilization
Where? /Uterine Tube ampulla
~ 100 sperm needed
When? After ovulation
Egg: 12-24 h post ovulation
Sperm: viable for up to 72 h
Then: 3-4 day journey to uterus
Dr. Misbah-ul-Qamar
8. Definition
• The fusion between
male and female
haploid gametes in the
ampullary region of
fallopian tube to
produce a diploid
zygote.
Dr. Misbah-ul-Qamar
14. Capacitation
• Period of conditioning
• 7 hours
• Interaction b/w
epithelial cells and
sperms
Dr. Misbah-ul-Qamar
15. Capacitation
• On the spermatozoa surface,
cholesterol efflux occurs along with
protein kinase A (PKA)-dependent
phosphorylation.
• Within the spermatozoa, there is an
alteration in mitochondrial
organization and morphology
• Removal of
– Glycoprotein coat
– Seminal plasma proteins
• Activation of acrosine
• Increase in motility
Dr. Misbah-ul-Qamar
17. • Sperms bind to a sperm receptor called ZP3 in
the zona pellucida, and this is followed by the
acrosomal reaction, ie, (the breakdown of the
acrosome, the lysosome-like organelle on the
head of the sperm ).
• Various enzymes are released, including the
trypsin-like protease acrosin. Acrosin
facilitates the penetration of the sperm
through the zona pellucida.
Dr. Misbah-ul-Qamar
20. Fertilization
• Sperm must penetrate
several layers
• Acrosomal reaction allows sperm
penetration
• 1st sperm reaching egg binds to sperm-
binding receptors on oocyte membrane
& enters
• Cortical reaction prevents
polyspermy
Dr. Misbah-ul-Qamar
21. Stages of fertilization
1. Penetration of corona
radiata
2. Penetration of zona
pellucida
3. Fusion of oocyte and
sperm cell membranes
Dr. Misbah-ul-Qamar
22. Penetration of corona radiata
• 200-300 million sperms
• 300-500 uterine tube
• 01
• Hyaluronidase –
acrosome
• Tubal mucosal enzymes
Dr. Misbah-ul-Qamar
23. Penetration of zona pellucida
• Acrosomal enzymes
– Estrases
– Acrosine
– Neuraminidase
• Zona reaction
Dr. Misbah-ul-Qamar
25. • When one sperm reaches the membrane of
the ovum, fusion to the ovum membrane is
mediated by fertilin,
• The fusion provides the signal that initiates
development. In addition, the fusion sets off a
reduction in the membrane potential of the
ovum that prevents polyspermy.
Dr. Misbah-ul-Qamar
30. Results of fertilization
• Formation of zygote
• Diploid chromosomes
• Genetic recombination
• Sex of the baby
• Initiation of cleavage
Dr. Misbah-ul-Qamar
31. Pregnancy test
• Early pregnancy factor –
trophoblast- 24-48 hrs
• Human chorionic
gonadotropin-
blood/urine – 6-12days
• Ultrasound- 41/2 weeks
Dr. Misbah-ul-Qamar
33. Fertilization and fertilized ovum
• 23 unpaired chromosomes of the male
pronucleus andthe 23 unpaired chromosomes
of the female pronucleus align themselves to
re-form a complete set of 46 chromosomes
(23 pairs) in the fertilized Ovum.
Dr. Misbah-ul-Qamar
38. Layers of uterine tube
3 layers
• Mucosa
– Extremely folded
– Ciliated columnar epithelium and secretory cells
• Muscularis externa
– Inner circular & outer longitudinal smooth muscle
• Serosa
– Consists of loose CT
Dr. Misbah-ul-Qamar
39. Movement of ovum
• Mucosa layer of the uterine tube contains
ciliated columnar epithelial cells (function:
moving) which convey the eggs in the
uterus direction & meet with sperm in the
ampulla due to muscular contractions.
Dr. Misbah-ul-Qamar
40. Movement of sperm
• Muscularis externa layer of uterine tube
contains an inner circular smooth muscle
and a thin outer longitudinal smooth
muscle due to the contraction of those 2
muscles, sperm is transported from uterus to
ampulla also some ciliated columnar
epithelium cells help in sperm transport
Dr. Misbah-ul-Qamar
42. Zygote formation
• Single cell
• After the egg has been fertilized by the sperm
• Merges chromosomes from both of the
gametes
• Production of embryonic cells at 4 days after
fertilization
• Lasts for only 4 days in total
• On 5th day, becomes blastocyst
Dr. Misbah-ul-Qamar
44. Movement of blastocyst
• After fertilization occurred, zygote is
transported to the uterus due to ciliated
columnar epithelium cells opposite
movement due to contraction of circular &
longitudinal smooth muscle
Dr. Misbah-ul-Qamar
45. • What is blastocyst?
• Thin walled hollow structure
• Contains a cluster of cellsfrom which the
embryo arises.
Dr. Misbah-ul-Qamar
47. Magic tube
• Sperm movement from uterus to ampulla
before fertilization
• After fertilization blastocyst movement is from
ampulla to uterus
• Travel time of ovum: 3 days
• Unfertilized egg lives only 24 hrs & dies
Dr. Misbah-ul-Qamar
49. Developing Zygote Implants in Secretory
Endometrium
• Dividing zygote moves from distal fallopian
tube to uterine cavity over period of 3-4 days
• Implantation of the blastocyst into the
endometrium~ 7 days after fertilization
with about 100 cells.
Dr. Misbah-ul-Qamar
62. • Once implantation has taken place,
trophoblast cells & other adjacent cells
proliferate rapidly forming placenta &
various membranes of pregnancy.
Dr. Misbah-ul-Qamar
63. Prenatal Genetic Testing
Amniocentesis: Fetus is 14-16 weeks old
• Biochemical analysis of fluid searches for disease markers
• Cell culture can take several weeks Karyotyping and DNA testing
• Biochemical analysis of fluid searches for disease markers
• Cell culture can take several weeks Karyotyping and DNA testing
Dr. Misbah-ul-Qamar
64. Chorionic Villi Sampling
• Placental chorionic villi can be analyzed for genetic
abnormalities
• Can be done at 8 weeks (recommendation: 10 weeks)
– Earlier than amniocentesis
• No cell culture necessary
Dr. Misbah-ul-Qamar
65. Maintenance of Pregnancy
• Progesterone is generally the hormone that maintains
pregnancy
– Quiescent uterus, no contractions
• hCG secreted by developing placenta Prevents CL from
degenerating and stimulates it to continue to produce
progesterone
• Week 7: placenta takes over progesterone production; CL
degenerates
• hCG also important in pregnancy testing (and for male sexual
development)
• hCG used for pregnancy testing
Dr. Misbah-ul-Qamar
66. • HCG behaves much like FSH & LH with one
crucial exception:
• It is not inhibited by a rising level of
progesterone
• Thus HCG prevents the deterioration of corpus
luteum at end of 4th week & enables
pregnancy to continue beyond the end of
normal menstrual cycle.
Dr. Misbah-ul-Qamar
67. • HCG on its own can stimulate testosterone
production, but not sperm production.
• On its own, it can also cause an increase in
testicular size & sensitivity as they start to
produce their own natural testosterone.
• For sperm production, if fertility is required,
HCG in combination with FSH medication is
required.
Dr. Misbah-ul-Qamar
68. Early Nutrition of the Embryo
• From Decidua alone till one week after
implantation
• The embryo continues to obtain its
• nutrition in this way for up to 8 weeks,
although the placenta also begins to provide
nutrition after aboutthe 16th day beyond
fertilization;
Dr. Misbah-ul-Qamar
69. Early nutrition
• Trophoblastic period of nutrition gradually
gives way to placental nutrition.
• As trophoblast cells invade decidua, digesting
& imbibing it, stored nutrients in decidua are
used by embryo
• During 1st week after implantation, this is only
means by which embryo can obtain nutrients
for upto 8 weeks.
• Although placenta also begins to provide
ntrition after 16th day beyond fertilization.Dr. Misbah-ul-Qamar
79. Placental permeability in early
pregnancy
• Total diffusion conductance is minuscule.
Reasons:
• placental membrane is still thick because it is
not fully developed low permeability.
• Further, surface area is small because placenta
has not grown significantly
Dr. Misbah-ul-Qamar
80. Placental permeability in later
pregnancy
• It increases tremendously because:
– thinning of membrane diffusion layers
– Surface area expands many times
Dr. Misbah-ul-Qamar
83. Diffusion of oxygen through the
placental membrane
• Same principals for O2 diffusion through
pulmonary membrane are applicable.
• Dissolved O2 passes from large maternal
sinuses to fetal blood by simple diffusion
(driven by O2 pressure gradient)
• Near the end of pregnancy, mean
gradient=20mmHg
Dr. Misbah-ul-Qamar
84. Means by which fetus receives O2
Although fetal blood leaving placents has PO2 of
only 30mmHb, Fetus is capable of receiving
more than adequate O2 through placental
membrane by following means:
– Fetal Hb
– Hb concentration of fetal blood is about 50%
greater than that of mother
– Bohr effect
Dr. Misbah-ul-Qamar
85. Fetal Hb
• This type of Hb is synthesized in fetus before
birth
• O2 dissociation curve for fetal Hb is shifted to
left of maternal Hb at low PO2 levels in fetal
blood, fetal Hb can carry 20-50% more O2 than
can maternal Hb.
Dr. Misbah-ul-Qamar
87. Bohr effect
• Hb can carry more O2 at a low PCO2 than it can
at high PCO2.
• Fetal blood entering the placenta carries large
amounts of CO2, but much of this CO2 diffuses
from fetal to maternal blood.
• Loss of CO2 makes fetal blood more alkaline &
maternal blood more acidic.
Dr. Misbah-ul-Qamar
88. Double Bohr effect
• Bohr shift operates in one direction in
maternal blood & in other direction in fetal
blood.
• These changes cause fetal blood’s capacity to
combine with O2 to increase & that of
maternal blood to decrease.
• It forces more O2 from maternal blood while
while enhancing O2 uptake by fetal blood
Dr. Misbah-ul-Qamar
89. Diffusing capacity for O2
• At term, it is about 1.2ml of O2/min/mm of
mercury O2 pressure difference across
membrane.
• It compares favourable with that of the lungs
of newborn baby.
Dr. Misbah-ul-Qamar
90. Diffusion of CO2 through the
placental membrane
• Partial pressure of CO2 in fetal blood is 2-
3mmHg higher than that in maternal blood.
• This small pressure gradient is sufficient to
allow adequate diffusion extreme solubility
of CO2 in placental membrane allows CO2to
diffuse about 20 times as rapidly as oxygen.
Dr. Misbah-ul-Qamar
91. Excretion of waste products
through the placental membrane
• Occurs in same manner that CO2 diffuses from
fetal to maternal blood.
• Other excretory products also diffuse through
placental membrane into maternal blood
then excreted along excretory products of
mother
Dr. Misbah-ul-Qamar
92. Fetal excretory products
• Non-protein nitrogens (urea, uric acid,
creatinine)
• Urea level in fetal blood is only slightly greater
than that in maternal blood.creatinine has a
fetal blood concentration considerably higher
than that in mother
• Reason: urea diffuses through placental
membrane with great ease. creatinine does
not diffuse easily
Dr. Misbah-ul-Qamar
93. Excretion from fetus
• It depends on diffusion gradients across
placental membrane & its permeability.
• There is continual diffusion of these
substances from fetal blood high
concentration to maternal blood lower
concentration.
Dr. Misbah-ul-Qamar
94. Diffusion of foodstuffs through the
placental membrane
• Metabolic substrate diffuse in same manner
as oxygen does.
• Example: glucose is transported by carrier
molecules in membrane’s trophoblast cells
• in late stages of pregnancy, trophoblast cells
lining the placental villi provide for facilitated
diffusion of glucose through placental
membrane.
Dr. Misbah-ul-Qamar
95. Diffusion of foodstuff through
placental membrane
• These diffuse from maternal to fetal blood but
more slowly than glucose so glucose is used
more easily by fetus for nutrition.
• Ketone bodies & ions (K+, Na+, Cl-) diffuse with
relative ease from maternal to fetal blood.
Dr. Misbah-ul-Qamar
100. Physiological maternal changes during
pregnancy (UQ)
• Changes in reproductive system
• Wt gain during pregnancy
• Metabolic changes
• Changes in endocrine—
• Hormones of placenta
• Changes in blood and circulatory system
• Changes in respiratory system
• Changes in urinary system
Dr. Misbah-ul-Qamar
101. Changes in reproductive system
• Ovaries;
• Corpus leutum secretes large amount of
progestrone.Involutes after 3 months till
placenta is fully developed.No secretion of
FSH and LH due to excessive est and prog so
no ovulation.
Dr. Misbah-ul-Qamar
102. • Uterus:
• Vol increases from 0 to 5-7 L at the end of
pregnancy.
• Shape pyriform to globular
• Weight 30-50grams---1000 to 1200 grams due
to hyperplasia and hypertrophy of
myometrium.
• 3 layers of decidua at the end of 3rd month.
Dr. Misbah-ul-Qamar
104. Pregnancy
• Menstruation occurs in non-pregnant woman
14 days after ovulationmost of
endometrium sloughs away from uterine wall.
• If this should happen after an ovum is
implanted, pregnancy would terminante.
• However, this sloughing is prevented by
secretion of HCG by newly developing
embryonic tissues.
Dr. Misbah-ul-Qamar
105. Essential hormonal factors in
pregnancy
• HCG
• Estrogens
• Progesterone
• Human chorionic somatomammotropin
Dr. Misbah-ul-Qamar
106. Changes in endocrine –hormones of
placenta
• Human Chorionic Gonadotropin
• human chorionic gonadotropin is secreted by the
syncytial trophoblast cells into the fluids of the
mother.
• The secretion of this hormone can first be
measured in the blood 8 to 9 days after ovulation
(MCQ), shortly after blastocyt implants.
Dr. Misbah-ul-Qamar
108. Human chorionic gonadotropin
• It causes persistence of corpus luteum &
prevents menstruation.
• Rate of secretion rises rapidly to reach a
maximum at about 10-12 weeks of pregnancy
&
decreases back to a lower value by
16-20 weeks.
It continues at this level for remainder
of pregnancy.
Dr. Misbah-ul-Qamar
109. Function of HCG
• It causes the corpus luteum to secrete larger
quantities of its sex hormones for next few
months.
• By far, the most important function of HCG is
to prevent involution of corpus luteum at end
of monthly cycle.
Dr. Misbah-ul-Qamar
110. Sex hormones secreted due to HCG
• These (progesterones & estrogens) prevent
menstruation.
• Cause the endometrium to continue to grow
& store large amounts of nutrients rather than
being shed in the menstruum.
• As a result, the decidua like cells that develop
in the endometrium during the normal female
sexual cycle become actual decidual cells
(greatly swollen & nutritious) at about the
time that the blastocyst implants.Dr. Misbah-ul-Qamar
111. UNDER THE INFLUENCE OF HCG
• The corpus luteum in the mother’s ovary
grows to about twice its initial size by a month
or so after pregnancy begins.
• Its continued secretion of estrogens &
progesterone maintains the decidual nature of
the uterine endometrium, which is necessary
for the early development of the fetus.
Dr. Misbah-ul-Qamar
112. Functions of HCG
• 1-CL to increase in size and secrete est and
progest.
• 2-Development and descent of testis in male
fetus.
Dr. Misbah-ul-Qamar
113. Functions of HCG
• 1-CL to increase in size and secrete est and
progest.
• If the corpus luteum is removed before
approximately the 7th week of
pregnancy,spontaneous almost always occurs,
sometimes even upto the 12th week.
• After that time, the placenta secretes
sufficient quantities of progesterone &
estrogens to maintain pregnancy for the
remainder of gestation period.Dr. Misbah-ul-Qamar
114. Functions of HCG
• 1-CL to increase in size and secrete est and
progest.
• The corpus luteum involutes slowly after the
13th to 17th week of gestation.
• After that time, the placenta secretes
sufficient quantities of progesterone &
estrogens to maintain pregnancy for the
remainder of gestation period.
Dr. Misbah-ul-Qamar
115. Functions of hCG
• 2-Development and descent of testis in male
fetus.
• Mechanism: HCG exerts interstitial cell-
stimulating effect on testes resulting in
production of testosterone in male fetus until
the time for birth this small secretion of
testosterone during gestation is what causes
the fetus to grow male sex organs instead of
female organs
Dr. Misbah-ul-Qamar
116. • Near the end of pregnancy, the testosterone
secreted by the fetal testes also causes the
testes to descend into the scrotum.
Dr. Misbah-ul-Qamar
118. Secretion of estrogens by the
placenta
• Placenta secretes both estrogens &
progesterone by the syncytial trophoblast cells
• Towards end of pregnancy, daily production of
placental estrogens increase to about 30 times
the mother’s normal level of production.
Dr. Misbah-ul-Qamar
119. Difference in ovarian & placental
estrogens
• Placental estrogens are not synthesized de
novo from basic substrates in placenta
formed almost entirely from androgenic
steroid compounds (dihydroepiandrosterone
& 16-hydroxydehydroepiandrosterone)
Dr. Misbah-ul-Qamar
120. • These steroids are weak androgens, formed
both in mother’s & fetal adrenal glands
transported by blood to placenta & converted
by trophoblast cells into:
– Estradiol
– Estrone
– estriol
Dr. Misbah-ul-Qamar
121. Role of fetus in estrogens
production
• The cortices of fetal adrenal glands are
extremely large
• About 80% consists of a so called fetal zone
which secrete dehydroepiandrosterone
Dr. Misbah-ul-Qamar
122. Main Functions of estrogen in
pregnancy
• Estrogens exert mainly a proliferative function on most
reproductive & associated organs of mother
• During pregnancy, the extreme quantities of estrogens cause
– (1) enlargement of the mother’s uterus,
– (2) enlargement of the mother’s breasts and growth of the breast
ductal structure
– (3) enlargement of the mother’s female external genitalia.
Dr. Misbah-ul-Qamar
123. Additional functions
• Estrogens relax pelvic ligaments of mother-->
allow easier passage of fetus through birth
canal
– sacroiliac joints become relatively limber
– Symphysis pubis becomes elastic
• General aspects of fetal development during
pregnancy by affecting rate of cell
reproduction in early embryo.
Dr. Misbah-ul-Qamar
124. Secretion of progesterone by the
placenta
• It is essential for successful pregnancy,
secreted by:
– corpus luteum in moderate quantities at
beginning of pregnancy
– Placenta in tremendous quantities later
Dr. Misbah-ul-Qamar
125. Effects of gestational Progesterone
• Progesterone causes decidual cells to develop
in the uterine endometrium (for nutrition of
early embryo)
• Progesterone decreases the contractility of
the pregnant uterus preventing
spontaneous abortion
• Contributes to the development of conceptus
• Acts on breast preprocessed by estrogen.
Dr. Misbah-ul-Qamar
126. Mechanism for development of
conceptus
• It occurs even before the implantation
• Increases the secretions of mother’s fallopian
tubes & uterus providing appropriate
nutritive matter for developing morula &
blastocyst
• Also affects cell cleavage in early developing
embryo
Dr. Misbah-ul-Qamar
129. Human Chorionic
Somatomammotropin; Human
placental lactogen
• it is a general metabolic hormone secreted by
placenta at 5th week of pregnancy
• Its secretion increases progressively in direct
proportion to placental weight
• it is secreted in quantities several times
greater than that of all other pregnancy
hormones combined.
• Functions: Lactation, growth, increase BSL
Dr. Misbah-ul-Qamar
130. Role in lactation
• It causes partial development of breasts & in
some instances causes lactation in animals
• Due to this effect, it was first named human
placental lactogen.
• However, attempts to use it to promote
lactation in humans have not been successful.
Dr. Misbah-ul-Qamar
131. Mechanism for growth
• It has weak (100 times) actions similar to
those of growth hormone
• Causes the formation of protein tissue in same
way that growth hormone does.
Dr. Misbah-ul-Qamar
132. Mechanism for increased BSL
• It has specific nutritional implication for both mother & fetus
• It causes decreased insulin sensitivity decreased utilization
of glucose in mother larger quantities of glucose available
to fetus.
• Significance of this nutritional effect:
– Glucose is the major substrate used by fetus to energize its
growth
– The hormone promotes the release of FFAs from fat stores
of mother which provide alternative source of energy
for mothe’s metabolism
Dr. Misbah-ul-Qamar
133. Other hormones’s role in
pregnancy
• Pituitary Secretion:corticotropin, thyrotropin,
• and prolactin increases,LH,FSH decreases
• Adrenal Cortex:Aldosterone and cortisol
increase in secretion.
• Secretion by the Thyroid Gland.
• Parathyroid Glands.
• “Relaxin” by the Ovaries and Placenta
Dr. Misbah-ul-Qamar
134. Pituitary secretion
• Almost all the non-sexual endocrine glands of
the mother also react markedly to
pregnanacy.
• This reaction results mainly from:
– the increased metabolic load on the mother
– from the effects of placental hormones on
pituitary & other glands
Dr. Misbah-ul-Qamar
135. Increased corticosteroid secretion
• Moderate increase in glucocorticoid
secretion possibly help mobilize AAs from
mother’s tissues for fetal tissue synthesis.
• Twofold increase in aldosterone secretion
(peaking at gestation end) reabsorption of
excess Na+ fluid retension may cause PIH
Dr. Misbah-ul-Qamar
136. Increased thyroid gland secretion
• Gland enlarges upto 50% equal increase in
thyroxine production
• Causes of increase
– Thyrotropic effect of placental hCG
– Thyroid specific stimulating effect of placental
hCT(human chorionic thyrotropin)
Dr. Misbah-ul-Qamar
137. Increased parathyroid gland
secretion
• Causes calcium absorption from mother’s
bones maintains normal [Ca2+] in mother’s
ECF even while fetus removes Ca2+ to ossify its
own bones.
• Its secretion is even more intensified during
lactation.
Dr. Misbah-ul-Qamar
138. Relaxin
• Secretion from CL of ovary & placental tissue.
• Its secretion is increased by hCG effect.
• Functions:
– Softens the cervix at delivery time
– Also serves as vasodilator(increasing blood flow to
kidneys & other tissues)
– Increases venous return & CO
– Relaxation of ligaments of symphysis pubis(slight
effect)
Dr. Misbah-ul-Qamar
140. Wt gain during pregnancy
• The average weight gain during pregnancy is about 24
• pounds, with most of this gain occurring during the last
• two trimesters.
• Of this, about 7 pounds is fetus and 4 pounds is
amniotic fluid, placenta, and fetal membranes.
• The uterus increases about 2 pounds and the breasts
• another 2 pounds,
• Out of rest of 9 pounds about 6 pounds of this is extra
• fluid in the blood and extracellular fluid, and the
• remaining 3 pounds is generally fat accumulation.
Dr. Misbah-ul-Qamar
142. Metabolic changes
• increased secretion of many hormones during
pregnancy, including thyroxine,
• adrenocortical hormones, and the sex
hormones, the basal metabolic rate of the
pregnant woman increases about 15 per cent
during the latter half of pregnancy.
• As a result, she frequently has sensations of
becoming overheated.
Dr. Misbah-ul-Qamar
144. Carbohydrate metabolism
• BSL increasesincreased liver breakdown of
glycogen,increased insulin,more possibility of
developing diabetes ,latent diabetics.
Dr. Misbah-ul-Qamar
145. Lipid metabolism
• It increases the blood cholestrol level and
ketosis.
Dr. Misbah-ul-Qamar
146. Water and mineral met
• Est. prog. Later aldosterone more and cause
retention of water and sodium.calcium and
phosphorus also.
Dr. Misbah-ul-Qamar
151. Changes in the Maternal Circulatory
System During Pregnancy
• Blood Flow Through the Placenta 625ml/min
during last month of pregnancy
• Cardiac Output During Pregnancy. increases
to 30-40% above normal by the 27th week of
pregnancy due to placental blood flow plus
general increase in mother’s metabolism
• Later CO falls to only a little above normal
during last 8 weeks of pregnancy.
Dr. Misbah-ul-Qamar
152. Blood Volume During Pregnancy
• The maternal blood volume shortly before
term is about 30% above normal. Therefore,
at the time of birth of the baby, the mother
has about 1 to 2 liters of extra blood in her
circulatory system.
• Cells the bone marrow becomes
increasingly active & produces extra RBCs
• Fluid increased fluid retention by kidneys
due to increased aldosterone & estrogen
Dr. Misbah-ul-Qamar
153. The increase occurs mainly during latter half of pregnancy
Dr. Misbah-ul-Qamar
154. Urinary System During Pregnancy
• Rate of urine formation: sligtly increased (due
to increased fluid intake &increased load of
excretory products)
Dr. Misbah-ul-Qamar
155. Special alterations of kidney
function
• normal pregnant woman ordinarily accumulates about 5
pounds of extra water and salt.
• 1st, the renal tubules’ reabsorptive capacity for sodium,
chloride, and water is increased(50%).
– Due to salt & water retaining steroid hormones of placenta
&adrenal cotex
• 2nd, the renal blood flow & GFR (as compensation for
increased tubular reabsorption) increases.
• Cause: renal vasodilation due to:
– Increased level of nitric oxide
– Ovarian hormone “relaxin”
Dr. Misbah-ul-Qamar
156. Maternal Respiration During
Pregnancy
Increase in minute
ventilation (50%) &
decrease in arterial PCO2 :
– Total Oxygen used is 20%
above normal (also CO2
fomed)
• Increased BMR of
pregnant woman
• Her greater size
• High levels of
progesterone which
increases sensitivity of
respiratory center to CO2
• The respiratory rate is
increased to maintain
the extra ventilation.
• Cause: growing uterus
presses upward against
diaphragm its total
excursion is decreased
Dr. Misbah-ul-Qamar
157. Amniotic Fluid and Its Formation
• What is amniotic fluid?
• Volume: 500-1000ml
• Formation:
– a large portion of fluid is derived from renal excretion by fetus
– A certain amout of absorption occurs by way of GIT & lungs of fetus
– Some of fluid is formed through amniotic membranes
• Rate of formation:
– water in amniotic fluid is replaced once every 3 hours
– Electrolytes are replaced once every 15 hours
Dr. Misbah-ul-Qamar
158. Preeclampsia and Eclampsia
• Hypertension,Odema,Proteinuria
• It is often characterized by excess
• salt and water retention by the mother’s
kidneys and byweight gain and development
of edema and hypertension in the mother.
Dr. Misbah-ul-Qamar
164. 3. Effect of fetal hormones on the
uterus
• The fetus’s piyuitary gland secretes increasing
quantities of oxytocin
• Adrenal glands secrete large quantities of
cortisol
• The fetal membranes release prostaglandins in
high concentrations at the time of labor.
Dr. Misbah-ul-Qamar
165. Mechanical factors
• Stretch of the uterine musculature
– Stretching of uterine smooth muscle because of
fetal movement will increase the uterine
contractility
• Stretch or irritation of the cervix
– It will initiate reflexes to the body of the uterus
which lead to eliciting uterine contractions
(Ferguson reflex)
Dr. Misbah-ul-Qamar
166. ONSET OF LABOUR-A POSITIVE FEEDBACK
MECHANISM FOR INITIATION
• During most of the months of pregnancy, the
uterus undergoes periodic episodes of weak
and slow rhythmical contractions called
Braxton Hicks contractions.
Dr. Misbah-ul-Qamar
167. • These contractions become progressively
stronger
• toward the end of pregnancy; then they
change suddenly, within hours, to become
exceptionally strong contractions that start
stretching the cervix
• This forces the baby through the birth canal,
thereby causing parturition. This process is
called labor
• The contractions that result in final parturition
are called labor contractions.
Dr. Misbah-ul-Qamar
168. A CHANGE IN THE NATURE OF
CONTRACTIONS
Towards the end of pregnancy, strong contractions start stretching the
cervix & later force the baby through the birth canal!
Dr. Misbah-ul-Qamar
169. Onset of labor– A +ve feedback mechanism
The changes from the slow, weak rhythmicity of the uterus into strong
labor contractions!
Dr. Misbah-ul-Qamar
171. • We do not know what suddenly changes the slow,
weak rhythmicity of the uterus into strong labor
contractions, based on experience with other types
of physiological control systems, a theory has been
proposed for explaining the onset of labor, the
positive feedback theory ..
Dr. Misbah-ul-Qamar
172. • Two known types of positive feedback that
increase uterine contractions during labor:
• (1) Stretching of the cervix causes the entire
body of the uterus to contract, and this
contraction stretches the cervix even more
because of the downward thrust of the baby’s
head.
• (2) Cervical stretching also causes the pituitary
gland to secrete oxytocin, which is another
means for increasing uterine contractility.
Dr. Misbah-ul-Qamar
174. Abdominal Muscle Contractions
During Labor
• Once uterine contractions become strong
during labor, pain signals originate both
from the uterus itself and from the birth
canal.
• These signals,elicit neurogenic reflexes in
the spinal cord to the abdominal muscles,
causing intense contractions of these
muscles. The abdominal contractions add
greatly to the force that causes expulsion of
the baby. Dr. Misbah-ul-Qamar
175. • In the early part of labor, the contractions might
occur only once every 30 minutes.
• As labor progresses, the contractions finally
appear as often as once every 1 to 3 minutes, and
the intensity of contraction increases greatly.
• The combined contractions of the uterine and
abdominal musculature during delivery of the baby
cause a downward force on the fetus of about 25
pounds during each strong contraction.
Dr. Misbah-ul-Qamar
178. FIRST STAGE OF LABOUR
• Toward the end of pregnancy, the cervix becomes
soft, which allows it to stretch when labor
contractions begin in the uterus. The so-called
first stage of labor.
• This is a period of progressive cervical dilation.
• It lasts until the cervical opening is as large as the
head of the fetus.
• This stage usually lasts for 8 to 24 hours.
Dr. Misbah-ul-Qamar
180. SECOND STAGE OF LABOUR
• Once the cervix has dilated fully, the fetal
membranes usually rupture and the amniotic fluid
is lost suddenly through the vagina.
• Then the fetus’s head moves rapidly into the birth
canal, and with additional force and it continues
to wedge its way through the canal until delivery
is effected. This is called the second stage of labor.
• it may last from as little as 1 minute after many
pregnancies to 30 minutes or more in the first
• pregnancy.
Dr. Misbah-ul-Qamar
182. THIRD STAGE OF DELIVERY
• Separation and Delivery of the Placenta
• For 10 to 45 minutes after birth of the baby, the
uterus continues to contract to a smaller and
smaller size.
• This causes a shearing effect between the walls
of the uterus and the placenta, thus separating
the placenta from its implantation site.
• Separation of the placenta opens the placental
sinuses and causes bleeding.
Dr. Misbah-ul-Qamar
188. Initiation of Lactation—Function
of Prolactin
• Estrogen and progesteron inhibit the actual
secretion of milk.
• Conversely, the hormone prolactin has exactly the
opposite effect on milk secretion—promoting it.
• This hormone is secreted by the mother’s
anterior pituitary gland, and its concentration in
her blood rises steadily from the fifth week of
pregnancy until birth of the baby, at which time it
has risen to 10 to 20 times the normal
nonpregnant level.
Dr. Misbah-ul-Qamar
189. • In addition, the placenta secretes large quantities
of human chorionic somatomammotropin, which
probably has lactogenic properties, thus
supporting the prolactin from the mother’s
pituitary during pregnancy.
• Because of the suppressive effects of estrogen
and progesterone, no more than a few milliliters of
fluid are secreted each day until after the baby is
born.
Dr. Misbah-ul-Qamar
190. • The fluid secreted during the last few days
before and the first few days after parturition
is called colostrum.
• It contains essentially the same
concentrations of proteins and lactose as milk,
but it has almost no fat.
• its maximum rate of production is about
1/100 the subsequent rate of milk
production.
Dr. Misbah-ul-Qamar
191. • Immediately after the baby is born, the
sudden loss of both estrogen and
progesterone secretion from the
placenta allows the lactogenic effect of
prolactin from the mother’s pituitary
gland to assume its natural milk
promoting role.
.
Dr. Misbah-ul-Qamar
192. • This secretion of milk requires an adequate
background secretion of most of the mother’s
other hormones as well, but most important
are growth hormone, cortisol, parathyroid
hormone
• These hormones are necessary to provide the
amino acids, fatty acids, glucose, and calcium
required for milk formation.
Dr. Misbah-ul-Qamar
193. • After birth of the baby, the basal level of
prolactin secretion returns to the nonpregnant
level over the next few weeks.
• However, each time the mother nurses her baby,
nervous signals to the hypothalamus cause a 10-
to 20-fold surge in prolactin secretion that lasts
for about 1 hour.
• This prolactin acts to keep the mammary glands
secreting milk into the alveoli for the subsequent
nursing periods.
Dr. Misbah-ul-Qamar
194. • Ejection (or “Let-Down”) Process in
• Milk Secretion—Function of Oxytocin
• Milk is secreted continuously into the alveoli of
the breasts, but milk does not flow easily from
the alveoli into the ductal system and,
therefore, does not continually leak.
• Instead, the milk must be ejected from the
alveoli into the ducts before the baby can obtain
it.
• This is caused by a combined neurogenic and
hormonal reflex that involves the posterior
pituitary hormone oxytocin.Dr. Misbah-ul-Qamar
196. • When the baby suckles, it receives virtually
no milk for the first half minute or so.
Sensory impulses must first be transmitted
through somatic nerves from the mother’s
spinal cord and then to her hypothalamus,
where they cause nerve signals that
promote oxytocin secretion at the same
time that they cause prolactin secretion.
Dr. Misbah-ul-Qamar
197. • The oxytocin is carried in the blood to the
breasts, where it causes myoepithelial cells
• (which surround the outer walls of the alveoli) to
contract, thereby expressing the milk from the
alveoli into the ducts at a pressure of +10 to 20
mm Hg.
• Then the baby’s suckling becomes effective in
removing the milk. Thus, within 30 seconds to 1
minute after a baby begins to suckle, milk begins
to flow.
Dr. Misbah-ul-Qamar
199. LACTATION
• BREASTS DEVELOP UNDER
INFLUENCE OF ESTROGENS IN THE
MONTHLY SEXUAL CYCLE.
• ENHANCED GROWTH OCCURS
DURING PREGNANCY.
Dr. Misbah-ul-Qamar
200. LACTATION
• Growth of the Ductal System
All through pregnancy, the large quantities of
estrogens cause the ductal system of the
breasts to grow and branch.
Dr. Misbah-ul-Qamar
201. LACTATION
• Development of the Lobule-Alveolar
System—
Final development of the breasts into milk-
secreting organs also requires Progesterone
Dr. Misbah-ul-Qamar
203. LACTATION
• The fundamental secretory unit of the
breast is the alveolus.
• Surrounded by contractile myoepithelial
cells and adipose cells.
• Alveoli are organized into lobule.
• Lobules drain into a ductule.
• The lactiferous duct carries the secretions
to the outside. Dr. Misbah-ul-Qamar
205. LACTATION
• PROLACTIN:
– Prolactin is a polypeptide hormone.
– Structurally related to growth hormone (GH),
– Like GH, PRL is made and released in the
anterior pituitary.
Dr. Misbah-ul-Qamar
206. LACTATION
• Prolactin is the classic lactogenic
hormone.
• PRL binds to a tyrosine-kinase-associated
receptor and stimulates transcription of the
genes that encode several milk proteins,
including lactalbumin and casein.
Dr. Misbah-ul-Qamar
207. LACTATION
• Suckling is the most powerful physiologic
stimulus for prolactin release.
• Afferent neural pathway is through the spinal
cord, inhibiting dopaminergic neurons in the
median eminence of the hypothalamus.
• Prolactin releasing factors: thyrotropin-releasing
hormone (TRH), angiotensin II, substance P, β-
endorphin, and vasopressin.
Dr. Misbah-ul-Qamar
213. LACTATION
• Ejection (or “Let-Down”) Process in
Milk Secretion—Function of Oxytocin.
Suckling nerve impulses to spinal cord
hypothalamus oxytocin secretion
from the posterior pituitary carried to the
breasts contraction of the myoepithelial
cells
Dr. Misbah-ul-Qamar
215. LACTATION
• MILK PRODUCTION CAN BE UPTO 1.5
LITRES.
• PROVIDES IMMUNOLOGICAL
PROTECTION TO THE BABY.
Dr. Misbah-ul-Qamar
216. Milk composition & metabolic
drain on mother caused by
lactation
• Large amount of metabolic substrates are lost
from the mother
• About 2-3 grams calcium phosphate may be
lost each day, unless the mother is drinking
large quantities of milk & has an adequate
intake of vitaminD, the output of calcium &
phosphate by lactating mother will often be
much graeter than intake.
Dr. Misbah-ul-Qamar
217. Antibodies & other anti-infectious
agents in milk
• Antibodies and other anti-infectious agents
are secreted in milk along with nutrients
• Also different types of WBCs are secreted,
including both neutrophils & macrophages
• Antibodies & macrophages destroy
Escherichia coli bacteria which often cause
lethal diarrhea in newborns.
Dr. Misbah-ul-Qamar
