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Sperm can live up to _____ with adequate cervical secretions
When is the fertile window?
- 3-5 days prior to ovulation
- 24 hours after ovulation
- (total of 6 days)
mid-cycle (+/- 3 days)
Day 14 of a 28 day cycle
What happens during ovulation?
- When a woman ovulates the egg will burst from the follicle. Then what is left of the
- follicle will become the corpus luteum.
- The corpus luteum produces progesterone. Progesterone makes the lining of the uterus thick for implantation and is necessary to
- sustain a healthy pregnancy. The corpus luteum produces progesterone until the placenta begins to take over progesterone production around ten weeks gestation.
- After a woman ovulates, the corpus luteum only lasts for about 12-14 days unless it begins receiving HCG (human chorionic
- gonadotropin) from a developing embryo. If the egg is not fertilized, the corpus luteum dies and progesterone production stops. When progesterone levels drop, the uterus lining stops thickening and is consequently shed during menstruation.
- If the egg is fertilized, the corpus luteum
- will begin receiving HCG from the embryo. HCG tells the corpus luteum to keep producing progesterone. The corpus luteum lasts for about ten weeks after ovulation. After ten weeks the placenta takes over progesterone production through the end of pregnancy.
Process of Conception:
the nucleus of a single sperm enters the nucleus of the oocyte (egg)
(sperm passes through the Corona Radiata and Zona Pellucida to reach the nucleus)
50-150 out of 35-200 million sperm reach the ovum
Fertilization is complete when the ovum and spermatozoon's nuclei merge...a zygote is formed and contains the diploid number of chromosomes (46)...Cell Division Begins
Stages of Growth:
- Pre-embryonic: 0-2 weeks (most women don't know they are pregnant)
- Embryonic: 3-8 weeks, all internal organs formed
- Fetal: 9+ weeks, Details!!!
What happens during the Pre-Embryonic Stage:
- Single cell zygote --> cleavage
- 3 days after fertilization, the zygote forms into a 16 cell solid sphere called a morula.
Mitosis continues and around day 5
it is known as a blastocyst
and enters the uterus.
Implantation takes from day 6-10
Normally in UPPER uterus
- Surge of HCG – protein that shows up on pregnancy test
- Progesterone– supports endometrium
- 2 weeks from Conception: implantaion is complete...
- The blastocyst is composed of an inner cell mass called the embryoblast, which will develop into the embryo and an outer cell mass called the trophoblast which will assist in implantation and will become the
Two important hormones during pre-embryonic stage:
What happens during the Embryonic Stage?
lasts from weeks 3-8
Basic structures of all major body organs are completed!
What happens in fetal growth 3 weeks from conception
Beginning of Embryonic Stage
- Heart begins beating at 22-23 days
- 3 germ layers form: ectoderm (external), mesoderm (muscle/blood cells), endoderm (lung, thyroid, pancreatic cells)
- CNS begins to develop
What happens in fetal growth at 4 weeks from conception:
- C-shaped cylinder
- -4-6mm in length
- Heart beat visible on ultrasound
- Neural Tube Closes- failure to close causes neural tube defects...suggest women to take folic acid!
- Eyes/Ears begin to develop
Limb Buds present
What happens in fetal development at 5 weeks from conception:
7-9 mm in length
Heart develops 4 chambers
Nasal pits and hand plates develop
What happens in fetal development at 6 weeks from conception:
11-14mm in length
Heart chambers completed
Upper/Lower extremities more defined
Intestines contained in umbilical cord
What happens in fetal development at 7 weeks from conception:
2 cm in length
What happens in fetal development at 8 weeks from conception?
End of embryonic stage
3 cm in length
External Genitalia well developed
Heart rate audible by doppler! (some people wait until they hear heartbeat to tell people about pregnancy!)
Chemical or infectious agent that causes birth defects
- IE: medication for epilepsy
(1st 8 weeks of pregnancy are most dangerous/vulnerable bc many women don't know they are pregnant yet)
The effect on the fetus from a teratogen is highly dependent on:
- Gestational age at time of exposure
- (0-2 weeks not risk, but 3-8 are highest risk!)
Types of Teratogens
- -Rubella, Syphilis, Cytomegalovirus
- -Accutane, Tetracycline (baby's teeth), Warfarin, Valproic Acid (depakote)
- External Agents:
- -Radiation, Hyperthermia, ETOH, Tobacco
- Maternal disorders (suggest counseling)
Medication Pregnancy Categories:
- A- no human risk
- Folic Acid, very few other drugs
- B- animals show no risk, but not many human studies done
- Penicillin, Zyrtec
- C- no good studies
- Macrobid (UTI med)D- fetal risk clear cut, but benefits outweigh risks
- Tetracylcine, Paxil, Dilantin
- X- Fetal Risks outweigh benefits
- ETOH, Warfarin, DES, Valproic Acid, Accutane
What happens in fetal development at 9-12 weeks from conception:
Beginning of Fetal Stage
Fetal Head is 1/2 body
Urine starts to form
Nasal Septum and palate
Digestive tract patent
What happens during fetal development at 13-16 weeks from conception:
- Rapid growth, fetus doubles in size
- Lanugo present
- Eyes face anteriorly
- Fully formed placenta
What happens during fetal development at 17-23 weeks from conception:
- Growth slows down
- Lower limbs fully formed
- Lanugo over entire body
- Vernix caseosa by 20 weeks (waxy covering)
- Eyebrows and head hair
- Brown Fat forms
What happens in fetal growth at 24-27 weeks from conception
Red, wrinkled skin
Eyes re-open, eyelashes form
Lungs begin to make surfactant
Alveoli develop (increased chance of survival outside of womb)
What happens in fetal growth at 28-31 weeks from conception:
Capable of breathin air
If born, may have RDS (because not enough surfactant)
SQ white fat
Bone marrow makes RBC
What happens in fetal development at 33-38 weeks from conception
Pulmonary system maturation (deliver after 38 weeks to avoid lung problems)
Growth of all body systems
Skin becomes smoother
Disk shaped organ that has critical functions to pregnancy (metabolic functions, transfer functions and endocrine functions)
Maternal side of the placenta:
Rough, attaches to uterus
Maternal blood flows through the placenta's intervillous space
Exchange occurs in the intervillous spaces
Maternal and fetal blood do not mix
Fetal side of Placenta
Smooth, covered with membranes
Develops from outer cell layer (trophoblast) of the blastocyst
Chorionic villi with maternal blood in the intervillous spaces
Membranes separate chorionic villi from maternal blood
Transfer Placenta Functions:
- Gas Exchange (O2 and CO2)
- Nutrient Transfer- glucose, fatty acids, vitamins, electrolytes, amino acids
- Waste Removal
- Antibody Transfer- passive immunity, IgG antibodies
Metabolic Placenta Functions
Placenta produces glycogen, cholesterol, fatty acids
Used for: placental functions and growing embryo
Endocrine Placenta Function
- Placental Hormones:
- hCG- maintains corpus luteum
- (reason for positive pregnancy tests)
- Estrogen- growth of uterus and breasts
- Progesterone- maintains endometrium, relaxes smooth muscle
- Human Placental Lactogen (hPL)- ensures fetal glucose supply
- Relaxin- inhibits uterine activity, softens connective tissue
- Amnion- inner membrane
- Chorion- outer membrane
Both make up the Bag of Waters
Amniotic Fluid provides:
- Room for fetal movement
- Constant temp
- Prevents membranes from adhering to fetal parts
- Serves as a source of oral fluid for baby
The Umbilical cord consists of:
*LIFELINE from placental to fetus
1 vein, 2 arteries, Wharton's Jelly
- Vein-- Carries O2 and nutrients rich blood TO
- Arteries- Carry De-O2 and waste blood AWAY
Process of Fetal Circulation:
O2 from mom, fetus doesn't need to breath and liver metabolic functions are minimized
2. Fetal Circulation is altered to BYPASS the fetal lungs and liver
3. 3 Shunts
in the fetal circulation cause Highest O2 Blood to Brain and Heart
Ductus Venosus- bypasses liver, enters inferior vena cava
- *Foramen Ovale- bypass lungs
- *Ductus Arteriosus- blood enters aorta through pulmonary artery
Infant Circulation AFTER Birth:
- First breath= lungs expand and change
- *Foramen Ovale closes > Arterial O2 > Ductus Arteriosis Constricts > baby breathes in and has normal system now
- The fetus is connected by the umbilical cord to the placenta, the organ that develops and implants in the mother's uterus during
- Through the blood vessels in the umbilical cord, the fetus receives all the necessary nutrition, oxygen, and life support from the
- mother through the placenta.
- Waste products and carbon dioxide from the fetus are sent back through the umbilical cord and placenta to the mother's circulation
- to be eliminated.
- Blood from the mother enters the fetus
- through the vein in the umbilical cord. It goes to the liver and splits into three branches. The blood then reaches the inferior vena cava, a major vein connected to the heart.
- Inside the fetal heart:
- Blood enters the right atrium, the chamber on the upper right side of the heart. Most of the blood flows to the left side through a
- special fetal opening between the left and right atria, called the foramen ovale.
- Blood then passes into the left ventricle (lower chamber of the heart) and then to the aorta, (the large artery coming from the heart).
- From the aorta, blood is sent to the head and upper extremities. After circulating there, the blood returns to the right atrium of the heart through the superior vena cava.
- About one-third of the blood entering the right atrium does not flow through the foramen ovale, but, instead, stays in the right side of the heart, eventually flowing into the pulmonary artery.
- Because the placenta does the work of
- exchanging oxygen (O2) and carbon dioxide (CO2) through the mother's circulation, the fetal lungs are not used for breathing. Instead of blood flowing to the lungs to pick up oxygen and then flowing to the rest of the body, the fetal circulation shunts (bypasses) most of the blood away from the
- lungs. In the fetus, blood is shunted from the pulmonary artery to the aorta through a connecting blood vessel called the ductus arteriosus.
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