Conception Conception and and

Fetal DevelopmentFetal Development

Presented byJeanie Ward

Mr. and Mrs. Brown are at the clinic for family

planning.

They are planning on getting pregnant and

have questions regarding conception.

 

How does the Female How does the Female Body Prepare for Body Prepare for

ConceptionConceptionDescribe the process of maturation of an ovum

Maturation of the Maturation of the OvumOvum

Development of the Graafian Follicle

Ovulation

Formation of Corpus Luteum

Menstrual CycleMenstrual Cycle

Hormonal cycle

Ovarian cycle

Endometrial cycle

Maturation of Ovum

How will I know I am How will I know I am ovulating? ovulating?

Signs and SymptomsSigns and Symptomsof Ovulationof Ovulation

1. Body Temperature increase

2. Mittelschmerz

3. Cervical Mucus ChangesIncrease in amountBecomes thin, watery, and clearFerning Stretchable: SpinnbarkheitAlkaline

What happens to What happens to Corpus Luteum if I do Corpus Luteum if I do

not get Pregnant?not get Pregnant?

What happens to What happens to Corpus Luteum if I Corpus Luteum if I become Pregnant?become Pregnant?

Four Main Four Main HormonesHormones

• FSH -- Follicle Stimulating Hormone – Begins Growth and Maturation of graafian

follicle• LH -- Luteinizing Hormone

– assists in continued growth of graafian follicle

• ESTROGEN – responsible for proliferation of

endometrium• PROGESTERONE

– Pro-gestation. Corpus luteum produces progesterone so endometrium won’t slough

“I know that a woman will stop

having her periods when

she gets pregnant.

Why does that occur?”

Mrs. Brown asks

ConceptionConception

Maturation of Ovum and Sperm Cells– Pregnancy comes about

from the union of a female germ cell, ovum with a male germ cell, the spermatozoon.

– One ovum per month is discharged from the ovary. It is transported into the fallopian tube where it begins its journey through the tube in search for the sperm. Viable for 12- 24 hours

FertilizationFertilization When intercourse occurs, millions of

sperm travel in search of an ova. During travel through the female reproductive system, capicitation occurs.

Capicitation is the removal of plasma membrane and loss of seminal fluid

This leaves the sperm ready for fertilization.

FertilizationFertilizationAs the sperm swarm around the ova, the Acrosome caps of Sperm release zona digesting enzymes.

These enzymes break down the barrier and one sperm is able to penetrate – fertilization occurs

“I have been trying to get pregnant for over a year and my husband had a sperm count done last month.

Why is the number of sperm so important, I thought only one sperm enters the egg?”

Usually occurs in the distal portion of the fallopian tube Once sperm penetrates ova, physiological barrier

renders the ova impenetrable by other sperm, thus only one sperm enters a single ova

Each contributes 23Chromosomes making aTotal of 46 chromosomes

Sex of baby determinedat this time. X =female, Y = male

Fertilized Ovum begins Fertilized Ovum begins its travel to the uterusits travel to the uterus

Cellular MultiplicationCellular Multiplication The fertilized zygote begins its travel through

the fallopian tube toward the uterus.

Cell / mitotic division (cleavage) occurs

Morula eventually forms a fluid filled cavity within the cell mass. – Inner solid cell mass is called Blastocyst– Outer cell mass that surrounds the cavity is

the Trophoblast

Implantation

Small finger-like projections extend from the trophoblast And burrows into the endometriumImplantation enables the blastocyst to absorb nutrients

DeciduaDecidua

• Decidua Basalis part directly under the blastocyst

• Decidua capsularisportion that is pushed out by thegrowing blastocyst and covers the blastocyst

• Decidua Vera --portion which is not in immediate contact with the ovum

After implantation, the endometrium becomes more thickened,the cells enlarge, and is now called the Decidua.

TrophoblastOuter layer of cells

PlacentaChorion

BlastocystINNER CELL MASS

FetusAmnion

Morula

Cellular DifferentiationCellular Differentiation• At 10 – 14 days of age, the

blastocyst or beginning zygote begins cellular differentiation into the primary germ layers.

• All tissues, organs, and systems develop from these layers.

Germ LayersGerm LayersEctoderm•nervous• skin, hair, nails• sensory organs

• Mesoderm• muscle• connective tissue• blood vessels• bone marrow

• Endoderm• Genitourinary• Respiratory--larynx, trachea, lungs• Digestive

AmnionAmnion• Smooth, glistening membrane

know as the AMNION is the lining of a Fluid filled space that develops around the embryo.

Functions of Amniotic Functions of Amniotic FluidFluid

Keeps the fetus at an even temperature

Cushions the fetus against possible injury

Provides place for the fetus to move easily and grow symmetrically

Fetus drinks the fluid

Umbilical CordUmbilical Cord• Body stalk that attaches the embryo to

the yolk sac• Contains blood vessels that extend into

the chorionic villi• Protected by wharton’s jelly

ChorionChorion• Thick membrane with finger-like

projections called chorionic villi.• Chorionic villi contain blood

vessels that are main connection with mother.

• Chorionic villi produce human chorionic gonadotropin (HCG)

• Merges with the decidua basalis to form the PLACENTA.

• The placenta is one mechanism that the body has in providing protection to the growing fetus?

• How does this occur? • What are other functions of

the placenta?

Functions of the Functions of the PlacentaPlacentaFetal Respirations

Fetal Nutrition

Endocrine Functions

Elimination of Wastes

Barrier against certain substances

Ask Yourself ??Ask Yourself ??• The thickened endometrium in

which the fertilized embryo implants is called the:a. endodermb. deciduac. amniond. chorion

Answer this ...Answer this ...• The fetal nervous system is

formed by the germ layer known as the:a. ectodermb. mesodermc. entodermd. endoderm

Development StagesDevelopment Stages• Stage 1 -- zygote

– weeks 1 - 3• Stage 2 -- embryonic

– weeks 4 - 8– period of ORGANOGENESIS

• Stage 3 -- fetal– weeks 9 - 40

Zygote PeriodZygote PeriodWeeks 1-3Weeks 1-3

• Traveling in the fallopian tube where rapid cellular multiplication and

differentiation occurs.• The establishment of the embryonic

membranes and the germ layers.• Groove formed along middle of the back for the neural tube.

Embryonic PeriodEmbryonic PeriodWeeks 4-8Weeks 4-8

• Week 4 – anterior end of neural tube closes to form the brain and the posterior end closes to form the spinal cord– Heart begins to beat– Eyes appear– Limb Buds for arms and legs– CR = 4 mm

• Week 5– Head grows larger– Hand and feet plates develop– Facial features begin to develop– CR = 8 mm.

• Week 6– Fetal circulation is established– Chambers form in the heart– Upper lip and palate start fusing– Eyes move to front of face– Fingers are webbed– External ear develops

• Week 7– Eyelids start to form– Fingers develop; elbows visible– Diaphragm separates abdomen from chest– Bronchi develop– Arms and legs move

• Week 8– Fingers and toes distinct– Skeletal ossification begins– Testes and ovaries are distinguishable– Heart has four chambers– Circulation through umbilical cord occurs

– *** ALL essential external and internal structures are present and now will continue to grow

• Mrs. Brown tells the nurse that she is worried that the baby may have some defect because she was on antibiotics and other cold medications during the first week after intercourse / conception.

What is happening during the first week after

conception that would assist the nurse in answering her question?

 

Fetal PeriodFetal PeriodWeeks 9-40Weeks 9-40

12 weeks 18 weeks

16 weeks 24 weeks

32 weeks gestation

Weeks 9-12 Weeks 9-12 • Head size increases• Face is well formed• Nails appear • Eyelids appear and close and fuse shut• Kidneys excrete urine• Intestines are forming; peristalsis begins• Heartbeat can be heard via ultrasound• Tooth buds appear for the baby teeth

Weeks 13-16Weeks 13-16• Lips form, facial contour

develops• Ossification of bone begins• Meconium begins to form in

the intestines• Hair present on scalp• Sex can be determined visually

Weeks 17-20Weeks 17-20• Hair abundant on head• Lanugo covers the body• Vernix begins to form• Myelination of spinal

cord begins• Suck and swallow begin• Quickening occurs ~ 18

weeks

Weeks 21-24 weeksWeeks 21-24 weeks• Respiratory movement with air sacs

formed • Surfactant production begins ~ 24 weeks• Brain appears mature• Eyebrows and eyelashes can be seen• Reacts to sudden noise with active movement

Weeks 25 - 28Weeks 25 - 28• Eyelids open and close• Capillaries proliferate around

the lungs’ alveoli making gas exchange possible

• Skin has wrinkled red appearance

• Rapid brain development

Weeks 29- 32 Weeks 29- 32 • Subcutaneous fat forms• Testes start descending• Fingernails and toenails are

complete• Bones are fully developed, but

still soft and pliable

Weeks 33 - 40Weeks 33 - 40• Limbs start to flex• Muscle tone is developed• Lanugo disappears• Body begins to store fat• Maternal antibodies transfer to

the fetus• Exhibits sleep and awake patterns

• Mrs. Brown returns for her next prenatal check-up at 6 weeks gestation.

• Mrs. Brown asks what is happening in the development of her baby this week? (sixth week).

TeratogensTeratogens• Risk factors such as

environmental substances– Smoking– Alcohol– Drugs– Viruses– Occupational hazards

• During what period of time is the baby most susceptible to damage

from teratogens?

• Mrs. Brown wants to know when she can expect to feel the baby move?

• When is the normal time for the mom to feel movement?

• What is this called?

ReviewReview

•Describe the components of the process of fertilization.

• Ovum released into fallopian tube—viable for 24 hr. • Sperm deposited into vagina—viable for 48 to 72 hr

(highly fertile for 24 hr). • Sperm must undergo capacitation and acrosomal

reaction. • Sperm penetration causes a chemical reaction that

blocks more sperm penetration. • Fertilization occurs in the distal end of the fallopian

tube. • Sperm enters ovum. The nuclei of the ovum and

sperm unite and become a diploid zygote.

ReviewReview• How can knowledge of the

normal fertilization process assist in helping couples conceive?

ReviewReview• How can knowing the

gestational age of the fetus help in assessment for the potential effects of a teratogen?

The End

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Ovarian Cycle

Hormonal Cycle

Endometrial Cycle

MENSTRUAL CYCLESMENSTRUAL CYCLES