PREGNANCY

Edyta Mądry MD, PhD

Department of Physiology

Medical University

Poznań

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New Born

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Edyta Mądrycantact data: edytamadry@gmail.com

Please note! The information marked with a red star are the most important in the process of preparing up for the final exam.

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For mastery of the material, students should know:

•Meiosis process

•Testicular anatomy and function

• Spermatogenesis

• Ovarian anatomy and function

• Oogenesis

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Pregnancy  DefinitionThe period from conception to birth.

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Conception

Conception means a woman's egg has been fertilized by a man's sperm.

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Conception

A secondary oocyte can be fertilized for about 24 hours after ovulation

Sperm remain viable for up to 72 hours within the female reproductive tract

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Fertilization

Fertilization usually takes place in the outer one-third of the uterine tube (ampulla of oviduct), but can ocasionaly take place in the abdominal cavity cervics of uterus (ectopic pregnancy)

Sperm swim up the female reproductive tract, aided by muscular contractions of the uterus stimulated by prostaglandins in the semen.

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Capacitation

Sperm undergo a functional change in the female tract – called capacitation,

During this process the membrane around the acrosome becomes fragile, and its enzymes are released.

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How does it start? Sperm reach ovum

and cluster around it

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Only one sperm is allowed to penetrate egg

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Gestation

Assumption:

Fertilized 14 days after the first day of LNMP

Gives birth 38 weeks after fertilization (+ or - 2 weeks)

Gestation in singleton pregnancies lasts an average of 40 weeks (280 days) from the first day of the last normalmenstrual period (LNMP).

10 lunar months = 9 calendar months = 280 days

(+ or – 2 weeks)

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How to calculate the time of birthNaegele's rule 1. Determine first day of LNMP

2. Add one year3. Subtract three months4. Add seven days

For example: first day of LNMP April 21st, 2015

Resulting data of estimated data of birth : January 28 , 2016(+ or – 2 weeks )

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Fertilization

o 1 Oocyteo 300 Million Spermo 24 hours post ovulation

o size: 0.1 - 0.15 mm

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When the sperm

penetrates the egg,

the egg immediately

releases a chemicals

creating a hard “shell”

around it to keep all

other sperm out and

prevent polyspermy

Fertilization

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Fertilization

FERTILIZED EGG = ZYGOTE The fertilization process takes about 24

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.

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Cleavage First Cell Division, Mitotic division size 0.1 - 0.2 mm 1.5 - 3 days post-ovulation

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4 cell zygote

2 cell zygote

The zygote begins to develop

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Three to four days after fertilization. morula (mulberry

shaped)- about 16 cells

morula leaves the fallopian tube and enters the uterine cavity

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16 cell morula 8 cell zygote

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Early Blastocyst When zygote divides to 32 cells

it becomes known as a blastocyst size 0.1 - 0.2 mm 4 days post-ovulation blastocyst formation

Two cell types are forming:embryoblast (inner cell mass on the inside of

the blastocele)trophoblast (the cells on the outside of the

blastocele).

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Implantation Begins Human Chorionic Gonadotropin

(hCG) level 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 (see slide number 22)

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Blastocyst

Uterine lining

The blastocyst embeds into the uterine lining,

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Implantation 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 ( see slaids 26 and 27).

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Implantation

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Implantation Completed

Placental Circulation System Begins to form 0.1 - 0.2 mm

7 - 12 days post-ovulation

Trophoblast cells engulf and destroy cells of the uterine lining creating blood pools, both stimulating new capillaries to grow and foretelling the growth of the placenta.

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Implantation Completed

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.

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Inner cell mass forms two cavities:

yolk sacamniotic cavity

In humans the yolk sac produces blood cells and future sex cells

The amniotic cavity becomes the cavity in which the embryo floats.

Fluid is produced from fetal urine, and secretions from the skin, respiratory tract, and amniotic membranes.

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Symptoms of early pregnancy Food cravings or

aversions Smell sensitivity Heartburn Missed Period Morning Sickness Constipation Mood Swings/ Irritability Higher body temperature Low Back Pain Tender breast Bloating / Weight Gain Fatigue

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Four Weeks

After the cluster of cells attaches to

the womb it is called an embryo. .

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Day 22

Day 24

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Day 26 Day 28

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At the end of 4 weeks:

• Embryo is 1/4 inch in length

• Heart, digestive system, backbone and spinal cord begin to form

• Placenta (sometimes called "afterbirth") begins developing

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At the end of 8 weeks:

•Embryo is 1 1/8 inches in length

•Eyes, nose, lips, tongue, ears and teeth are forming

•Penis begins to appear in boys

•Embryo is moving, although the mother can not yet feel movement36

                                                                     

At the end of 12 weeks:

Fetus is 2 1/2 to 3 inches long

Weight is about 1/2 to 1 ounce

Nails start to develop and earlobes are formed

Arms, hands, fingers, legs, feet and toes are fully formed

Eyes are almost fully developed

By this stage, a fetus has developed most of his/her organs and tissues

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At the end of 4 months: •Fetus is 6 1/2 to 7 inches long

•Weight is about 6 to 7 ounces

•Fetus is developing reflexes such

as sucking and swallowing.

•Fingers and toes are well defined

•Sex is identifiable

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At the end of 5 months:

•Fetus is 8 to 10 inches long

•Weight is about 1 pound

•Hair begins to grow on his/her

head

•Soft woolly hair called lanugo

covers fetus body

Mother begins to feel fetal movement

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At the end of 6 months:

•Fetus is 11 to 14 inches long

•Weight is about 1 3/4 to 2 pounds

•Eyelids begin to part and eyes open occasionally for short periods of time

•Fetus is able to hiccup 40

•At the end of 7 months:

•Fetus is 14 to 16 inches long

•Weight is about 2 1/2 to 3 1/2

Pounds

•Fat layers are forming

•If born at this time, he/she will be

considered a premature baby

and require special care

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At the end of 8 months:

•Fetus is 16 1/2 to 18 inches long

•Weight is about 4 to 6 pounds

•Overall growth is rapid this month

•Tremendous brain growth occurs

•Most body organs are now developed

with the exception of the lungs

•Movements or "kicks" are strong enough

to be visible from the outside

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At the end of 9 months: •Fetus is 19 to 20 inches long

•Weight is about 7 to 7 ½

pounds

•The lungs are mature

•Baby is now fully developed and

can survive outside the mother's

body

•He/she settles down lower in the

abdomen in preparation for

birth and may seem less active

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Labor (parturition)- Stage one

the period from the onset of true labor contractions until the cervix is completely dilated at 10 cm.

The uterine contractions cause the cervix to dilate, and the amniotic sac may rupture.

Usually lasts 6 – 24 hours depending on the number of previous deliveries.

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Stage 2

Period from maximal cervical dilation until

the birth of the baby Lasts minutes to

an hour Contractions become more intense and

frequent.

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Stage 3

The expulsion of the placenta

Usually occurs within 15 minutes after the birth of the baby, but can range from 5 to 60 minutes.

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Placenta

10-12 weeks is the period of placenta formation

Trophoblast cells use same molecular mechanisms as tumors, but are highly regulated and controlled

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Placenta FETAL SIDE MATERNAL SIDE They provide…

protectionnutritionrespirationexcretionhormone production

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Functions of Placenta Exchange of gases between

fetus and mother Delivery of nutrients from

mother to fetus Delivery of antibodies from

mother to fetus Removal of fetus waste Secretion of hormons

including human chorionic gonadotropin ( hCG), progesterone, estrogen, and human chorinic somatotropin (hCS)

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Placental barrier Maternal and fetal blood

do not mix- “placental barrier”

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Metabolic Functions of the Placenta Glycogen synthesis and storage

Cholesterol synthesis: placental cholesterol is precursor for placental progesterone and estrogens

Protein production

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Endocrine Functions Placenta Produces Peptide hormones

Human Chorionic gonodotrophin (hCG) - secreted early and helps to maintain synthesis of progesterone

Human placental lactogen (hPL): increase supply of glucose to future by decreasing maternal stores of fatty acids by altering maternal secretion of insulin

Insulin-like growth factors (IGF): IGF signaling system is a major regulator of growth in fetus and infant

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Endocrine Functions Steroid hormones

Progesterone: produced by placenta, needed to maintain non-contractile uterus

Estrogen: produced by placenta drives many processes in pregnancy

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An XY individual with androgen insensitivity syndrome.

Despite the XY karyotype and the presence of testes, such individuals develop female secondary sex characteristics. Internally, however, these women lack the Müllerian duct derivatives and have undescended testes. (Photograph courtesy of C. B. Hammond.)

How important are hormones ?

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Sex differentiation

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The ovary makes thecal cells and granulosa cells, which

together are capable of synthesizing estrogen.

Under the influence of estrogen (first from the mother, then from the fetal gonads), the Müllerian duct differentiates into the female genitalia.

Female development

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3 hormones necessary for male development

1. Müllerian Inhibiting Substance (MIS) = anti-Müllerian duct factor (AMH), causes the Müllerian duct to regress.

2.Testosterone, causes the differentiation of the Wolffian duct into the male internal genitalia.

In the urogenital region, testosterone is converted into

3. Dihydrotestosterone (DHT), that causes the morphogenesis of the external genitali (penis) and prostate gland.

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In green organs form under the influence of Dihydrotestosterone

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Hormones in pregnancy

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Function of Human Chorionic Gonadotropin

Prevent degeneration of the corpus luteum

Stimulates the corpus luteum to secrete estrogen and progesteron

Stimulates steroid synthesis in the developing fetal adrenals

Stimulates fetal gonads, especially testosteron production by the fetal testes.

Suppresses maternal lymphocytes and reduces the possibility of immunoreactions against the fetus.

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What does progesterone do?

•It maintains the lining of the uterus which makes it possible for a fertilized egg to attach and survive

•Makes cervical mucous accessible by sperm

•Prevents immune rejection of the developing baby

•Increases libido around ovulation

•Protects against endometrial, breast, ovarian and prostrate cancer

•Normalizes blood clotting

•Incease body temperature64

Edyta Mądrycantact data: edytamadry@gmail.com

Please note! The information marked with a red star are the most important in the process of preparing up for the final exam.

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