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