L2: Clinical Correlates & Cleavage Flashcards
Clinical Correlates, Cleavage to Blastomere, Implantation
Contraceptives: Barrier Method
condoms containing spermicides
female condom lining vagina
Contraceptives: Hormonal Method
estrogen and/or progestin – inhibits ovulating by preventing release of FSH & LH, changing the lining of uterus & thickening cervical mucus = difficult for sperm to enter uterus
Contraceptives: Intrauterine Device (IUD)
Hormonal: releases progestin = thicker cervical mucus = less active sperm
Copper: release copper to uterus = prevents fertilization or inhibits fertilized egg from attaching to uterine wall, prevents sperm from entering uterine tubes
Contraceptives: Emergency Contraceptive Pill (ECP)
prevents pregnancy if taken 120hrs aft sex; high dose of progestin
Contraceptives: Sterilization
Vasectomy (cut them balls)
Tubal Ligation (tie them tubes)
Cleavage (or Segmentation)
once zygote has reached 2 cell stage, it undergoes mitotic divisions = inc numbers of cells
cells that become smaller c each cleavage division are known as blastomeres
aft 3rd cleavage, blastomeres maximize their contact c e/o, forming a compact ball of cells held together by tight junctions (process of compaction)
compaction segregates inner cells which communicate extensively by gap junctions, from outer cells
Day 1 of Cleavage
fertilized one-celled zygote will go through 2 cell stage
Day 2 of Cleavage
4 cell stage
Day 3 of Cleavage
12 cell stage
Day 4 of Cleavage
16 cell stage
Morula Formation
Day 4 aft fertilization
continuous division till they form a 16-cell morula (mulberry)
Blastocyst Formation
fluid begins to penetrate through the ZP into the intercellular spaces of inner cell mass
single cavity, blastocele forms, so embryo is now called blastocyst
cells of inner cell mass (now called embryoblast) are at one pole
those of outer cell mass (trophoblast) flatten and form the epithelial wall of the blastocyst
Day 6 of Cleavage
blastocyst hatches from the pellucid zone, wanders from ampulla through fallopian tube into the uterine cavity, where it embeds itself in the endometrium
fertilized oocyte/embryo is transported via the movement of cilia of tubal epithelium & the contractions of its muscular layer
trophoblast attaches to _____
fundus of uterine wall
integrin receptors for ____ promote _____, while those for ______ stimulate _____
laminin, attachment; fibronectin, migration
molecules also interact along signal transduction pathways to regulate ____ so implantation is result of ___ & ____
trophoblast differentiation; mutual trophoblastic & endometrial action
by the end of 1st week of development, human zygote has passed through the ___ & blastocyst stages & has begun ____ in the ____
morula; implantation; uterine mucosa
Implantation
process of blastocyst embedding into endometrial lining of uterus (Week 2)
at this stage of prenatal development (implantation), the conceptus is called
blastocyst
it is by this adhesion that the embryo receives ___ & ___ from the mother to be able to grow
oxygen & nutrients
Day 8 of Cleavage
blastocyst is partially embedded in endometrial stroma
in the area over embryoblast, the trophoblast has differentiated into two layers: cytotrophoblast & syncytiotrophoblast
cytotrophoblast
inner layer of mononucleated cells (darker green)
syncytiotrophoblast
outer multinucleated zone without distinct cell boundaries (lighter green)
digests endometrial cells to firmly secure blastocyst into uterine wall
trophoblast secretes ___
hCG or human chorionic gonadotropin hormone
hCG/ human chorionic gonadotropin hormone
directs corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses
creates an environment suitable for developing embryo
accumulates in maternal blood stream and excreted in urine
