Processes of Conception (exam 1) Flashcards
Spermatogenesis
the meiotic process by which male gametes are produces
Oogenesis
the process by which female gametes are produced
Meiosis occurs when
the germ cell divides and decreases their chromosomal numbers by 1/2 and are called gametes or zygotes
In the mitosis stage
the 23 chromosomes of the ovum unite with the 23 of the sperm making 46 chromosomes (germ cell)
smallest cell in the male body
sperm
production of sperm begins
at puberty in response to testosterone
- predictable amount of sperm production from early teens to advanced age (not cyclic)
important factor in production of adequate numbers of sperm
temperature (Dartos muscle)
sperm are transported in secretions from the
seminal vesicles and the prostate gland (seminal fluid)
pH of seminal fluid
Alkaline -> helps to neutralize the normally acidic female vagina in an attempt to assure viability of the sperm until it can fertilize an ovum
largest single cell in the body
Ovum
lifespan of sperm after ejaculation
48-72 hours
of sperm per normal ejaculation
200-500 million
average sperm travel time to egg
4-6 hours, but can be as little as 5 minutes
motion that transports sperm
flagellated, whip like motion
oocytes form by
12 weeks gestation
- females have a lifetime supply of oocytes at birth
- born with the amount of eggs they will ever have
amount of eggs that mature in a lifetime
400-500
hypothalamic-pituitary-ovarian axis
hypothalamus exerts control through release and inhibiting factors
ovarian cycle
maturation and ovulation of primary ova follicle is cyclic
- ovulation occurs 14 +/- 2 days before the next menstrual period
- 1 ovum matures each month with supportive cells
- increase in estrogen increases motility of the Fallopian tubes and fimbriae (cilia)
- captures the ovum and propels it to the uterine cavity
*An ovum cannot move by itself
conception
sperm meets egg (fertilization) in the outer 1st 1/3 of the fallopian tube
Females 22XX
Males 22Xy
- 23 chromosomes = 22 pairs are autosomes (traits in the body), leaving 2 chromosomes to determine the sex
Zygote (2 cells) begins descent through FT to uterus
prep for conception
Hyaluronidase -> path through cells for sperm to reach ovum
One sperm penetrates the ovum
Membrane of the ovum changes -> prevents entry of other sperms
Capacitation also occurs
Blastocyst
Inner layer of cells
undifferentiated embryonic cell
Secretes HCG to make sure that the corpus luteum remains viable
capacitation
removes the protective coating from the heads of the sperm - cannot penetrate the ovum
Corpus Luteum
secretes estrogen and progesterone first 2-3 months of pregnancy
main source of estrogen and progesterone until the 3rd month of pregnancy -> placenta takes over
First weeks of human development:
Follicular development in the ovary, ovulation, fertilization, and transport of early embryo down uterine tube and into uterus, where implantation occurs
mitotic cellular replication (cleavage) occurs as
baby (zygote) is propelled toward uterus
morula
16 cells (3rd day)
trophoblast
outer layer of cells
outer layers are chorionic villi implants 6-7 days after fertilization
Implantation
Blastocyst implanted at the top of the uterine wall 6-8 days after ovulation
Trophoblast (outer layer) develops projections -> chorionic villi
- Chorionic villi extend into endometrium and tap maternal blood supply for O2 and nutrients
Endometrium is now call the decidua
Decidua basassi (beneath the blastocyst)
Inhibition of Implantaion
- IUD initiates foreign body response
- Interferes with both fertilization and implantation
Progesterone changes cervical mucus and endometrium to mature the uterine lining for implantation
Progestin prevents pregnancy
IUD may cause substances to accumulate in uterus and interfere with implantation
Ovum
conception to day 14
this period encompasses cellular replication -> zygote to blastocyst formation and differentiation into 3 primary germ layers of cells
Embryo
day 15 to eight weeks
organs are forming
greatest vulnerability
the embryonic stage is the most critical time in the development of the organ systems and the external features
fetus
eight weeks to birth
ectoderm
trophoblast (outer layer) develops into the placenta, integument, neural tissue, and glands
mesoderm
forms muscles, bones, connective tissue, circulatory system, and GU system
endoderm
forms digestive, respiratory, and parts of the gu system
teratogen
Environmental substances or exposures that result in functional or structural disability
Developing areas with rapid cell division are the most vulnerable to malformation by environmental teratogens
inner membranes that surround the baby
amniotic sac
fluid within the sac and around the baby
Amniotic fluid
- Source of oral fluid for fetus
- Repository for wastes (urine and meconium)
- Assists in lung development
- Volume = 800-1200 mL (fetal urine contributes to volume)
- Transparent yellow liquid
- Characteristic odor but should not be malodorous
meconium
First stool
- Green, tarry, sticky
- Released into AF when baby is stressed or distressed
Source of concern at delivery if AF is meconium stained -> meconium aspiration (if it’s their first breath, it could be fatal - think breathing in syrup)
Oligohydramnios
< 300 mL AF
Associated with fetal kidney obstruction or renal agenesis
(oli = too little)
Polyhydramnios
> 2000 mL AF
Associated with esophageal atresia and with severe CNS anomalies
(poly = too much)
“water break”
amniotic fluid made up of sterile baby urine
- amniotic fluid completely replaces itself every 3 hours, even after ROM
baby “practice breathing”
the cord gives baby oxygen, but they do “practice breathing” which includes breathing/swallowing amniotic fluid
- fluid is secreted by the respiratory and GI tracts of the fetus (replacing the fluid back into the amniotic sac)
Functions of Amniotic Fluid
- Protects fetus from mechanical injury & infection
- Maintains stable thermal environment
- Helps in fluid and electrolyte homeostasis
- Allows freedom of movement for baby
Amount of fluid increases weekly
Properties of Amniotic Fluid
- Slightly alkaline
Contains: albumin, urea, uric acid, creatinine, lecithin, sphingomyelin, bilirubin, fructose, fat, leukocytes, proteins, epithelial cells, enzymes, lanugo hair
Lecithin & Sphingomyelin
- a major component of Surfactant
- L:S ratio 2:1 indicates fetal lung maturity
*Turns nitrazine paper BLUE
(urine is acidic and turns it red/yellow)
ROM nursing action
Always check the fetal monitor for decelerations in FHR
Placenta
Provides nutrients (O2) and removes waste (CO2) (transfers O2 & CO2 through intervillous spaces)
Metabolizes drugs and other substances
Produces hormones estrogen/progesterone for maintenance of pregnancy
Flat, disc shaped
- when hCG is release it produces as the placenta and begins to grow
Highly vascular, operates as a lung
- Metabolic function are respiration, nutrition, excretion (esp. drugs), and storage
Intervillous spaces
Large spaces separating chorionic villi in the placenta
Blood enters the intervillous spaces from uterine arteries that penetrate the basal part of the placenta
- Oxygenated blood transported to fetus through the umbilical vein
- Oxygen depleted blood leaves the fetus -> chorionic villi by umbilical vein
umbilical arteries
Deoxygenated blood leaves the fetus through UA and enters the placenta, where it is oxygenated
umbilical vein
oxygenated blood leaves the placenta through the umbilical vein, which enters the fetus via the umbilical cord
endometrial artery
CO2, deoxygenated blood
endometrial vein
returns oxygenated blood to fetus
placenta has (veins, arteries)
2 arteries and 1 vein
- vein carries oxygenated to the embryo
- artery carries deoxygenated from the embryo
(opposite in fetus than adult and switches when the cord is cut)
approximately 1% of umbilical cords have one artery and one vein (sometimes associated with congenital malformations)
Wharton’s jelly (connective tissue)
cushions vessels from compression
battledore placenta
when the cord is located toward the edge
usually centrally located
dirty duncan
placental side next to uterine wall
shiny shultz
placental side nearest to the baby that holds the amniotic fluid
stimulates uterine development to provide environment for baby
estrogen (go go go)
relaxes uterine muscle to prevent spontaneous abortion
progesterone
- slows down for pregnancy
“Pro-Life”
Factors that Affect Placental Perfusion
Decreased blood flow r/t maternal position
- Vena Cava Syndrome (mother in recumbent position) -> cuts off O2 and nutrition to baby
- Heavy uterus presses on aorta and vena cava -> cuts off circulation to brain and to the uterine arteries that perfuse the placenta (often occurs during vaginal exam)
Blood pressure changes - increased or decreased (HTN or blood loss) = vasoconstriction -> perfusion limited -> blood supply to baby decreased
Vasoconstrictor drugs (includes nicotine)
Mom being dizzy and faint (baby suffocating)
Umbilical Cord
Connects fetus and placenta
Arises from center of fetal side of placenta
Contains 1 large vein and 2 arteries
Arteries carry deoxygenated blood and waste from fetus
Vein carries oxygenated blood and provides O2 and nutrients to fetus
Vein & arteries surrounded by Wharton’s jelly
Function of the Umbilical Cord
Transport of O2 and nutrients from mom to baby and waste back to maternal blood
Permits free movement for baby within the membranes
Complication:
- knotted and cut off circulation to baby
- may be caught between baby head and ischial spine during birth or ROM -> fetal hypoxia
