conception and fetal development revised fall 2012
TRANSCRIPT
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CONCEPTION AND FETAL DEVELOPMENT
Revised Fall 2012
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HOW DOES THE FEMALE BODY PREPARE FOR CONCEPTION?Describe the process of maturation of an ovum
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Menstrual Cycle
Varies every 28 - 35 days
The time between ovulation and menstruation is relatively constant (14 days). Luteal phase.
The variable is from menses to ovulation. It can not be predicted, the Follicular phase.
Affected by various physical and emotional factors
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Maturation of the OvumOvarian Cycle
Follicular Phase- Development of the graafian follicle (ovum)
Ovulatory Phase- about 2 days before ovulation
Luteal Phase- Formation of corpus luteum
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HOW WILL THE PATIENT KNOW THAT SHE IS OVULATING?
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Signs and Symptoms of Ovulation
1. Body temperature increase 2. Mittelshmerz 3. Cervical mucus changes
Increase in amount Becomes thin, watery, and clear Ferning Stretchable: spinnbarkheit Alkaline
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WHAT HAPPENS TO THE CORPUS LETEUM OF I DO NOT GET PREGNANT?
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WHAT HAPPENS TO THE CORPUS LUTEUM IF I BECOME PREGNANT?
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Endometrial Cycle
The uterine endometrium repsonds to ovarian hormones and goes through the phases in building up the lining of the uterus in preparation for implantation Proliferative Secretory Menstural
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Hormonal Cycle
FSH- Follicle stimulating hormone Begins growth and maturation of the graafian
follicle LH- Luteinizing hormone
Assists in continued growth of the graafian follicle Estrogen
Responsible for proliferation of endometrium Progesterone
“Pro gestation”. The corpus luteum produces progesterone so the endometrium won’t slough off
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Conception
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
Conception
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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 of the sperm. Viable for 12-24 hours
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Fertalization
When intercourse occurs, millions of sperm travel in search of an ova. During travel through the female reproductive system, capacitation occurs
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Fertilization
As the sperm swarm around the ova, the Acromosome caps of sperm release zona digesting enzymes
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WHY IS THE NUMBER OF SPERM SO IMPORTANT IF ONLY ONE SPERM ENTERS THE EGG?
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Fertilization
Distal portion of the fallopian tube
Only one sperm penetrates ova
Each contributes 23 chromosomes
Sex of baby determined at this time
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PRE-EMBRYONIC DEVELOPMENT
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Fertilized ovum begins its travel to the uterus
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Cellular Multiplication
Morula eventually forms a fluid filled cavity within the cell mass. Inner solid cell
mass is called the blastocyst
Outer cell mass that surrounds the cavity is called the trophobast
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TrophoblastOuter layer of cells
BlastocystInner cell mass
PlacentaChorion
FetusAmnion
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Implantation
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Germ Layers
Ectoderm Mesoderm Endoderm
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Development Periods
Stage 1 – pre-embryonic weeks 1 - 2
Stage 2 -- embryonic weeks 3 - 8 period of ORGANOGENESIS
Stage 3 -- fetal weeks 9 - 40
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Embryonic PeriodWeeks 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
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Week 5 Head grows larger Hand and feet plates develop Facial features begin to develop CR = 8 mm.
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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
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Week 7 Eyelids start to form Fingers develop; elbows visible Diaphragm separates abdomen from chest Bronchi develop Arms and legs move
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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
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The patient tells the nurse that she is worried that the baby may have some defect because she was on antibiotics and other cold medication 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?
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Fetal PeriodWeeks 9-40
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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
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Weeks 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
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Weeks 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
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Weeks 21-24
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
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Weeks 25-28
Eyelids open and close Capillaries proliferate around the lungs’
alveoli making gas exchange possible Skin has wrinkled red appearance Rapid brain development
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Weeks 29-32
Subcutaneous fat forms Testes start descending Fingernails and toenails are complete Bones are fully developed, but still soft
and pliable
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Weeks 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
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Answer this……
The fetal nervous system is formed by the germ layer known as the:a. ectoderm
b. mesoderm c. entoderm d. endoderm
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AUXILLARY STRUCTURESPlacenta
Fetal Membranes
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Functions of the Placenta
Fetal Respirations
Fetal Nutrition
Endocrine Functions
Elimination of Wastes
Barrier against certain substances
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Amnion
Smooth, glistening membrane known as the Amnion is the lining of a fluid filled space that develops around the embryo
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Functions of Amniotic Fluid
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
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Chorion
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.
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Umbilical 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
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Teratogens
Risk factors such as environmental substances Smoking Alcohol Drugs Viruses Occupational hazards
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During what period of time is the baby most susceptible to damage from teratogens?
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Review
Describe the components of the process of fertilization.
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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.
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Review
How can knowledge of the normal fertilization process assist in helping couples conceive?
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Review
How can knowing the gestational age of the fetus help in assessment for the
potential effects of a teratogen?