Intro to Embryo Flashcards
40 weeks of pregnancy is measured from the _____
LNMP (last normal menstrual period); 280 days
38 weeks of pregnancy is measured from ______
fertilization (266 days)
the embryonic period spans from ____ to _____ and is ____ days
fertilization; 8 weeks; 56
the fetal period spans from the ____ to _____
9th week or 57th day; term or 38th week
initial development of all major structures and establishment of all organ systems
embryonic period
differentiation and growth of organs and tissues
fetal period
the study of abnormal development (genetic/environmental causes)
teratology
stages of mitosis
preprophase, prophase, metaphase, anaphase, telophase, cytokinesis
mitosis results in ___ ; 2 cells of ____ each
cell duplication; 2N
the process of the formation and development of male and female primordial germ cells (PGCs) into their specialized generative cells–gametes
gametogenesis
haploid numbers of chromosomes (23 chromosomes) is represented by ___
N
number of copies of chromosomes present in a cell nucleus
ploidy
number of copies of each unique double stranded DNA molecule is represented by ___
N
stages of meiosis I
preprophase, prophase, metaphase, anaphase, telophase, cytokinesis
stages of meiosis II
prophase, metaphase, anaphase, telophase, cytokinesis
primordial sex cells (germ cells) originate as specific cells lining the ____ or _____; they originate as large spherical cells first recognizable 24 days after fertilization
yolk sac; umbilical vesicle
PGCs are ___ and originate from the ____ of the umbilical vesicle near the origin of the allantois
diploid (2N); endodermal cells
PGCs migrate to occupy ____ and mature into ____
gonads; gametes (mature sex cells: spermatozoa & oocyte)
PGCs originate in the lining of the ____ and migrate along the ___ of the hindgut to the _____ during the 5th week of embryonic development
yolk sac; dorsal mesentery; gonadal ridge
during the 6th week the PGCs enter the underlying ____ and are incorporated into the _____; at this time the gonads of the 2 sexes are identical in appearance and are thus _____
mesenchyme; gonadal cords; indifferent gonads
process that reduces chromosomal number by 1/2; diploid to haploid 2N to N
gametogenesis
spermatogonia to sperm (begins at ____)
spermatogenesis; begins at puberty
oogonia to oocyte (begins before birth, halts, and continues at puberty)
oogenesis
ovulation: beginning at puberty, cyclic ____ released from the _____
FSH (follicle-stimulating hormone) + LH (luteinizing); anterior pituitary gland
FSH triggers ____ and LH surge triggers _____
follicular growth; ovulation
the mature oocyte is released from the ____ during ovulation
ovary
____ of the ____ is the normal site for fertilization
ampulla; uterine tube
begins after ejaculation, takes about 7 hours and is initiated by substances secreted in the uterus and uterine tubes
capacitation
capacitation is required to mature the sperm allowing removal of the ____ and _____ from the surface of the sperm ____ to allow the ____ to occur
glycoprotein coat; seminal proteins; acrosome; acrosomal reaction
_____ follows capacitation– increasing the activity of the sperm
hyperactivation
occurs when the capacitated sperm acrosome binds to the zona pellucida (ZP3 glycoprotein)
acrosomal reaction
during the acrosomal reaction, the acrosome begins to perforate in the presence of several enzymes and substances, breaking down the membranes producing aperatures; several enzymes are released, including ____ and ____ to facilitate fertilization
hyaluronidase; acrosin
about 30 hours after fertilization, the zygote undergoes cleavage (mitosis) to make early embryonic cells called _____
blastomeres
cell divisions result in successively smaller blastomeres that remain confined within the space available in the _____; this process is called ____
zona pellucida; compaction
compaction begins at about ____ stage
8 cell
3-4 days following fertilization, as the embryo is entering the uterus, the blastomere is in the ____ and is renamed the _____
12-32 cell stage; morula
during the morula stage, the blastmeres start to organize into _____
an inner cell mass and an outer cell mass
shortly after entering the uterus (days 4-5), the morula develops a fluid-filled cavity and is called a ______
blastocyst
upon creation of the blastocyst, the _____ degenerates
zona pellucida
blastocystic cavity splits blastomeres into two groups:
embryoblast and trophoblast
the embryoblast is the _____ and gives rise to the _____
inner cell mass; embryo
the trophoblast is _____ and becomes _____; also has ____ purpose
outer cell mass; extraembryonic structures (embryonic contribution to the placenta); nutritional
On day ___, the trophoblast cells attach to the _____
6; endometrium(lining of uterus), on either the posterior (ideal) or anterior wall of the body of the uterus
upon attachment, during day ___, the trophoblast differentiates into two distinct regions:
7; cytotrophoblast and syncytiotrophoblast
the syncytiotrophoblast is composed of cells that are ______
embedded in the endometrium
the cytotrophoblast is composed of cells that are _____
not embedded in the endometrium; just surrounding the developing embryo
the cytotrophoblast gives rise to _____
extraembryonic structures
blastocyst implants outside normal uterine locations
ectopic pregnancy
common ectopic locations:
- within the uterine tubes (most common, 95-98%)
- within the abdomen (ex: surface of the ovary, rectouterine pouch, mesentery)
- abnormal site within the uterus (internal os, cervix)
small cuboidal cells formed from the embryoblast
hypoblast
hypoblast occurs during day ___, and will become the _____
7; primary endoderm
the hypoblast sits ____ to the embryoblast
inferior
3 phases of fertilization
- coronal cells
- acrosomal reaction
- plasma membranes fuse, meiosis II resumes, and metabolism of oocyte increases
results of fertilization
- haploid pronuclei fuse, forming diploid zygote
- restoration of diploid number of chromosomes
- determination of genetic sex
- initiation of cleavage
process of oogenesis
- oogenesis begins before birth
- baby is born, oogenesis is halted during prophase I
- at puberty, oocytes finish meiosis I
- right before egg is ovulated, oogenesis is halted again at metaphase II
- when egg is fertilized, it finishes meiosis II in the fallopian tube
