A&P 28: Pregnancy & Human Development Flashcards
Pregnancy
events that occur from the time of fertilization (conception) until the infant is born
Conceptus
pregnant woman’s developing offspring
Gestation period
development extends from the last menstrual period until birth (280 days)
Embryo
fertilization through week 8, the conceptus is called this
Fetus
from week 9 through birth, the conceptus is called this
Fertilization
occurs when a sperm’s chromosomes combine with those of an egg (secondary oocyte)
Zygote
fertilized egg
Capacitated
motility of the sperm must be enhanced and their membranes must become fragile so that the hydrolytic enzymes in their acrosomes can be released
Acrosomal reaction
involves the release of acrosomal enzymes (hyaluronidase, acrosin, proteases, and others) that digest holes through the zona pellucida
Polyspermy
entry of several sperm into an egg; occurs in some animals
Monospermy
in humans, only 1 sperm is allowed to penetrate the oocyte, ensuring this
Cortical reaction
calcium surges cause this reaction, in which granules located just outside the plasma membrane spill their enzymes into the extracellular space beneath the zona pellucida
Male pronucleus
nucleus of the sperm swells to 5x times its normal size
Female pronucleus
ovum nucleus swells
Cleavage
period of fairly rapid mitotic divisions of the zygote without intervening growth
Morula
berry-shaped cluster of 16 or more cells
Blastocyst
fluid-filled hollow sphere composed of a single layer of large, flattened cells (trophoblast cells)
Trophoblast cells
single layer of large, flattened cells that compose the blastocyst
Inner cell mass
small cluster of 20-30 rounded cells
Implantation
6-7 days after ovulation, given a properly prepared endometrium, this begins
Cytotrophoblast
cells in the inner layer of a trophoblast; AKA cellular trophoblast
Syncytiotrophoblast (syncytial trophoblast)
cells in the outer layer of a trophoblast that lose their plasma membranes and form this multinuclear cytoplasmic mass
Human chorionic gonadotropin (hCG)
viability of the corpus luteum is maintained by this LH-like hormone secreted by trophoblast cells
Placentation
formation of a placenta, a temporary organ that originates from both embryonic and maternal (endometrial) tissues
Chorion
outermost fetal membrane; helps form the placenta
Chorionic villi
fingerlike projections developed from the chorion which become especially elaborate where they are in contact with maternal blood
Lacunae
large, blood-filled, intervillous spaces in the stratum functionalis of the endometrium
Decidua basalis
part of the endometrium that lies beneath the embryo
Decidua capsularis
part of the endometrium surrounding the uterine cavity face of the implanted embryo
Gastrula
even while implantation is occurring, the blastocyst is being converted to this, in which the 3 primary germ layers form
Embryonic disc
subdivided inner cell mass
Extraembryonic membranes
membranes that form during the 1st 2-3 weeks of development, including the amnion, yolk sac, allantois, and chorion
Amnion
develops when cells of the epiblast fashion themselves into a transparent membranous sac
Amniotic fluid
fluid inside the amnion
Yolk sac
forms from cells of the primitive gut, which arrange themselves into a sac that hangs from the ventral surface of the embryo; in humans, forms part of the gut (digestive tube) and is the source of the earliest blood cells and blood vessels
Allantois
forms as a small outpocketing of embryonic tissue at the caudal end of the yolk sac; structural base for the umbilical cord
Umbilical cord
links the embryo to the placenta; ultimately becomes part of the urinary bladder
Primary germ layers
ectoderm, mesoderm, endoderm
Gastrulation
process of forming a 3-layered embryo; involves cellular rearrangements and migrations
Primitive streak
gastrulation begins when this groove with raised edges appears on the dorsal surface of the embryonic disc and establishes the longitudinal axis of the embryo
Endoderm
most inferior germ layer
Mesoderm
middle germ layer
Notochord
rod of mesodermal cells; 1st axial support of the embryo
Ectoderm
cells that remain on the embryo’s dorsal surface
Organogenesis
formation of body organs and organ systems
Primitive gut
tube of endoderm formed by the folding process
Neurulation
1st major event of organogenesis; differentiation of ectoderm that produces the brain and spinal cord; induced by chemical signals from the notochord
Neural plate
ectoderm overlying the notochord thickens, forming this
Neural groove
once the neural plate has formed, the ectoderm starts to fold inward as this
Neural folds
the neural groove deepens to form these prominent folds
Neural tube
by day 22, the superior margins of the neural folds fuse, forming this, which soon pinches off from the ectodermal layer and becomes covered by surface ectoderm
Neural crest cells
cells that migrate widely and give rise to the cranial, spinal, and sympathetic ganglia and associated nerves, to the chromaffin cells of the adrenal medulla, to pigment cells of the skin, and contribute to some connective tissues
Somite
largest of the 3 mesodermal aggregates; all 40 pairs are present by the end of week 4
Sclerotome
part of a somite; migrates medially, gathers around the notochord and neural tube, and produces the vertebra and rib a the associated level
Dermatome
part of a somite; helps form the dermis of the skin in the dorsal part of the body
Myotome
part of a somite; develops in conjunction with vertebrae
Limb buds
help form the muscles of the limbs
Intermediate mesoderm
cells of this part of the mesoderm form the gonads and kidneys
Lateral plate mesoderm
consists of paired mesodermal plates - somatic and splanchnic
Coelom
ventral body cavity
Umbilical arteries and vein
unique cardiovascular modifications seen only during prenatal development
Ductus venosus
most of the blood coursing through the umbilical vein enters this venous shunt that bypasses the liver sinusoids
Foramen ovale
opening in the interatrial septum loosely closed by a flap of tissue
Ductus arteriosus
2nd shunt; transfers most of the blood directly into the aorta, bypassing the pulmonary circuit
Relaxin
placental production of this hormone causes pelvic ligaments and the pubic symphysis to relax, widen, and become more flexible
Human placental lactogen (hPL)
AKA human chorionic somatomammotropin (hCS); as the placenta enlarges, it secretes increasing amounts of this; works cooperatively with estrogens and progesterone to stimulate maturation of the breasts for lactation, promotes growth of the fetus, and exerts a glucose-sparing effect in the mother
Teratogens
factors that may cause severe congenital abnormalities or fetal death (alcohol, nicotine, many drugs, maternal infections ~ German measles)
Thalidomide
sedative used by 1000s of women in the 1960s to alleviate morning sickness; when taken during the period of limb bud differentiation (days 26-56), it sometimes resulted in tragically deformed infants with short flipperlike legs and arms
Preeclampsia
dangerous complication of pregnancy; results in insufficient placental blood supply, which can starve a fetus of oxygen
Parturition
culmination of pregnancy; giving birth
Labor
series of events that expel the infant from the uterus
False labor
Braxton Hicks contractions
Oxytocin
substance produced by certain fetal cells; powerful uterine muscle stimulant; causes the placenta to release prostaglandins
Prostaglandins
stimulate the synthesis of more gap junctions in uterine smooth muscle; powerful uterine muscle stimulant
Dilation stage
time from labor’s onset until the cervix is fully dilated by the baby’s head (10cm)
Expulsion stage
lasts from full dilation to delivery of the infant
Placental stage
delivery of the placenta and its attached fetal membranes
Afterbirth
placenta and its attached fetal membranes
Neonatal period
4-week period immediately after birth
Apgar score
1-5 minutes after birth, the infant’s physical status is assessed based on 5 signs: heart rate, respiration, color, muscle tone, and reflexes; each observation is given a score of 0 to 2; the total is called this; 8-10 = healthy baby
Transitional period
for 6-8 hours after birth, infants pass through this unstable period marked by alternating periods of increased activity and sleep; vital signs are irregular and the baby gags frequently as it regurgitates mucus and debris
Medial umbilical ligaments
distal parts of the umbilical arteries; become these ligaments
Round ligament of the liver
the remnant of the umbilical vein becomes this ligament (ligamentum teres)
Ligamentum venosum
the ductus venosus collapses as blood stops flowing through the umbilical vein and is eventually converted to this on the liver’s undersurface
Fossa ovalis
slight depression leftover from the closed foramen ovale
Ligamentum arteriosum
ductus arteriosus constricts and is converted to this cordlike structure
Lactation
production of milk by the hormone-prepared mammary glands
Prolactin
anterior pituitary gland secretes this to stimulate milk production
Colostrum
during the initial delay of lactation and during late gestation, mammary glands secrete this yellowish fluid; has less lactose than milk and almost no fat, but contains more protein, vitamin A and minerals than true milk; rich in IgA antibodies
Let-down reflex
oxytocin causes this reflex, the actual ejection of milk from the alveoli of the mammary glands
Meconium
tarry, green-black paste containing sloughed-off epithelial cells, bile, and other substances
Behavior methods
coitus interruptus, rhythm method, abstinence; altering behavior to prevent pregnancy
Barrier methods
diaphragms, cervical caps, male/female condoms, spermicides; techniques that prevent the sperm and egg from meeting and implanting
Hormonal methods
include a broad variety of hormone-containing contraceptive products (pill, IUD, patches, vaginal ring, implanted/injected agents)
Sterilization techniques
permanently prevent gamete release; tubal ligation, vasectomy
