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BIOL 314 Exam 4 > Pregnancy and Birth > Flashcards

Pregnancy and Birth Flashcards

(104 cards)

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1
Q

fertilization

A

the union of a sperm with an egg to form a zygote

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2
Q

fertilization typically occurs in

A

the ampulla of a Fallopian tube

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3
Q

semen is deposited into the vagina as a liquid, but

A

fibrinogenase converts fibrinogen into a fibrin clot within one minute to prevent semen from leaking out of the vagina, and also to protect the sperm from the acidity of the vagina

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4
Q

after about 20 minutes,

A

vaginal acidity in neutralized and sperm can survive so semen clot liquefies

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5
Q

of the several hundred million sperm ejaculated into vagina,

A

fewer than 1% survive

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6
Q

the cervix contains a maze of

A

folds and outpocketings that can easily trap sperm

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7
Q

shortly before ovulation,

A

cervical mucus becomes thinner to facilitate passage of sperm through cervix

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8
Q

approx one million sperm survive

A

journey through cervix

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9
Q

the uterine cavity is filled with

A

a watery fluid through which sperm can easily pass

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10
Q

only a few thousand sperm survive to enter the Fallopian tubes and

A

they move through the Fallopian tubes assisted by ciliary action

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11
Q

only 50 to 100 sperm will actually reach

A

a secondary oocyte

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12
Q

sperm appear to be drawn toward

A

an oocyte by some type of chemical communication, but before they can fertilize an oocyte they must undergo capacitation

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13
Q

capacitation probably removes

A

a protective coating from head of a sperm that blocks release of acrosome enzymes needed for penetration of secondary oocyte

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14
Q

when sperm approach a secondary oocyte,

A

small openings form in the acrosome which allows enzymes to escape and digest a path for sperm to enter into the secondary oocyte

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15
Q

the secondary oocyte responds to sperm penetration by

A

blocking entry of more than one sperm, which prevents polyspermy from occuring

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16
Q

cortical granules inside membrane of

A

secondary oocyte are released

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17
Q

secondary oocyte completes

A

second meiotic division to produce ovum and polar body

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18
Q

the sperm fuses with the ovum to produce

A

a zygote and the chromosomes unite, which restores the diploid condition

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19
Q

secondary oocyte will degenerate within 24 hours of

A

ovulation unless it is fertilized

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20
Q

sperm can survive in female reproductive tract for

A

7 days so fertilization can occur during a one week “window of opportunity” around time of ovulation

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21
Q

if two oocytes are released during ovulation and each gets penetrated by a separate sperm,

A

two eggs may be fertilized and dizygotic (fraternal) twins result

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22
Q

approx 30 hours after fertilization,

A

the zygote divides by mitosis and forms two identical daughter cells

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23
Q

mitotic divisions continue to occur every

A

16 to 20 hours, which produces a collection of blastomeres that form a solid morula

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24
Q

these divisions occur quite rapidly and blastomeres

A

get progressively smaller, morula remains same size as original zygote

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25
the cells of the morula become
tightly packed through compaction and blastomeres of unequal size begin to form, which creates hollow blastocyst
26
outer layer of smaller trophoblast cells form
layers around developing embryo
27
larger cells inside trophoblast make up
inner cell mass
28
if a single zygote separates completely during cleavage
monozygotic (identical) twins will result
29
implantation begins
when a blastocyst comes into contact with the endometrium
30
spontaneous abortions (miscarriages) may occur at this time because
2 out of every 3 blastocysts may not implant due to genetic abnormalities in embyro
31
as a blastocyst begins to implant,
cells of the trophoblast divide and differentiate and grow into the endometrium to anchor the blastocyst in place and the inner cell mass separates from the trophoblast and differentiates into the primary germ layers of the embryo
32
ectoderm will form
skin, hair, nails, neural tissue, and linings of mouth and throat
33
mesoderm will form
bone, cartilage, muscle, and parts of heart, kidneys, and gonads
34
endoderm will form
most of gut and parts of liver and pancreas, linings of digestive tract and respiratory, and reproductive ducts
35
four extraembryonic membranes form from the
primary germ layers of the embryo
36
yolk sac develops from
endoderm and mesoderm to form embryonic blood until liver is established
37
amnion develops from
ectoderm and mesoderm to surround embryo
38
amniotic sac fills with
amniotic fluid which cushions and protects developing embryo; also maintains constant temp and pressure
39
allantois
develops from endoderm near base of yolk sac; contributes to development of urinary bladder
40
blood vessels in the allantois
become umbilical vein and umbilical arteries
41
chorion
develops from mesoderm and forms finger-like chorionic villi that penetrate endometrium to establish network of blood vessels
42
the placenta forms in part from
maternal tissue and in part from embryonic tissue
43
chorionic villi contain
blood vessels and grow into the endometrium, where they get surrounded by maternal blood sinuses to form the placenta
44
placenta serves as
a selectively permeable barrier between maternal bloodstream and embryonic bloodstream
45
blood is never
exchanged and materials "cross the placenta" by simple diffusion
46
umbilical cord
the amnion fuses with the chorion and they surround the allantoic vessels to form an umbilical cord
47
umbilical cord attaches belly of
embryo to middle of placenta
48
umbilical cord contains
two umbilical arteries and one umbilical vein
49
umbilical vein
carries blood that is rich in oxygen and nutrients from placenta to embryo/fetus
50
umbilical arteries
carry blood that contains carbon dioxide and wastes from embryo/fetus to placenta to be eliminated
51
placenta produces
several hormones that are needed to maintain pregnancy
52
a full term pregnancy lasts for approximately
9 months, or 40 weeks or 266 days and can be divided into two major periods
53
embryonic stage
typically refers to first 8 weeks of gestation; characterized by development of major organ systems in embryo
54
fetal stage
typically refers to the last 30-32 weeks of gestation; characterized by organ growth and maturation of fetus
55
the corpus luteum in the ovary
secretes estrogens and progesterone to maintain the endometrium and prepare the mammary glands for lactation
56
chorionic villi secrete
human chorionic gonadotropin (hCG) to maintain the corpus luteum, which prevents menstruation that would eliminate the developing embryo
57
hCG levels in the urine
serve as basis for home pregnancy tests
58
hCG levels may be cause of
nausea and vomiting associated with morning sickness during first trimester of pregnancy
59
the placenta eventually secretes
hormones that are needed to maintain the pregnancy
60
the exact trigger of labor and birth
is not known, but various hormones are involved
61
steroid hormones
released by fetus from cortex of its adrenal gland
62
falling progesterone levels
increase sensitivity of uterine smooth muscles to oxytocin (near end of gestation)
63
oxytocin
released from the posterior lobe of the pituitary gland to stimulate uterine smooth muscle to contract
64
rising levels of oxytocin
stimulate production of prostaglandins that also contribute to uterine smooth muscle contractions
65
relaxin
produced by placenta to soften pubic symphysis and dilate cervix
66
2-3 weeks before labor begins
the fetus drops lower into the pelvic cavity in a process called "lightening" which reduces the pressure on the mother's abdomen and diaphragm making it easier for her to breathe
67
during the last week of gestation
the fetus will rotate in the uterus in order to present itself for delivery
68
the head of fetus
usually moves into the cervix in order to exit first
69
during the final weeks of gestation
a woman may experience "false labor" characterized by Braxton-Hick's contractions that are regular and not very strong
70
true labor is characterized by
contractions that become stronger at regular intervals
71
Stage I of birth involves
cervical effacement and dilation and lasts from 4-24 hours
72
cervix during birth
relatively inflexible and must retract upward to expose fetus's head
73
cervical canal during birth
has been blocked by a mucus plug during gestation; removal of plug creates bloody discharge into vagina
74
amniotic sac during birth
ruptures, giving rise to expression "having the water break"
75
contractions during birth
occur at short intervals and intensity as cervix completely dilates
76
Stage II of birth involves
the expulsion of the fetus and lasts from 15 minutes to 2 hours
77
contractions during stage II
reach maximum intensity at 1-2 minutes intervals
78
head of the fetus during stage Ii
rotates from side-facing to downward facing and extends forward to pass beneath pubic bone
79
once the head clears the birth canal
shoulders and rest of body slide past pubic bone
80
crowning
appearance of head of fetus outside the birth canal
81
episiotomy
may be performed if vaginal canal is too small to permit passage of fetus or if there is danger of perineal tearing
82
incision of episiotomy
made from vagina to anus; can be repaired with sutures and will heal much faster than uncontrolled perineal tearing
83
cesarean section
if complications occur during delivery, cesarean section can be performed
84
breech birth
feet would be delivered first or umbilical cord could become tangled around baby's neck
85
size of baby- need for cesarean section
baby might be too large to be delivered vaginally
86
placenta might detach
prematurely, which could cause uterine hemorrhage
87
stage II involves
expulsion of the placenta within 15-30 minutes after parturition
88
uterine contractions during stage III
tear placenta from endometrium to expel "afterbirth"
89
forceful contractions constrict (during stage III)
uterine blood vessles to reduce hemorrhage
90
actual milk production is stimulated by
the hormone prolactin (PRL)
91
high levels of estrogens and progesterone during pregnancy
cause hypothalamus to release prolactin-inhibiting hormone (PIH); blocks secretion of prolactin
92
without prolactin
mammary glands cannot produce milk
93
elimination of the plcenta during afterbirth
reduces levels of estrogens and progesterone and allows prolactin to stimulate alveoli in breasts to produce milk
94
the principal stimulus that maintains milk production
the sucking action of the infant
95
sensory nerve endings in the nipple
activated by sucking and send signals to hypothalamus so more prolactin is relased' promotes production and secretion of milk from alveoli into mammary ducts
96
sucking also triggers
the milk-ejection reflex (milk letdown)
97
sensory nerves in the nipples send signals to
hypothalamus to release oxytocin
98
oxytocin stimulates contractions of
myoepithelial cells along lactiferous ducts to pump milk from alveoli through ducts and into nipple
99
"milk letdown" can become
a conditioned reflex; nursing mother may find that hearing her baby cry or seeing her baby suck its thumb triggers release of milk
100
the first liquid produced by the mammary glands
colostrum- a yellowish fluid that is high in protein but lower in lactose and fat than milk
101
colostrum contains
important antibodies and iron-binding proteins
102
breast feeding maintains
higher levels of oxytocin in a mother's bloodstream, which causes contractions of uterine smooth muscles that can help restore the uterus to its pre-pregnant state
103
breast feeding may provide
natural contraception for some women because nursing will reduce GnRH secretion by the hypothalamus, which reduces the amount of FSH and LH released by the pituitary gland
104
reduction in FSH and LH will
inhibit follicle development and ovulation

BIOL 314 Exam 4 (13 decks)

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