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