Intro to Embryo 8-24 Flashcards
Embryonic Period
Fertilization to 8 weeks - initial development of all major structures and establishment of all organ systems
Fetal Period
9th week (57 day) to 38th week - differentiation and growth of organs and tissues
Teratology
Study of abnormal development (generic/environmental causes)
LNMP
last normal menstrual period - 40 week pregnancy as opposed to 38 week pregnancy from fertilization to birth
Gametogenesis
Formation of PMGs, occurs at week 7
PMG
Primordial Germ cells - originate from endodermal cells of umbilical vesicle near origin of allantois as specific cells lining yolk sac. Migrate to gonads where they mature. Start as large cells recognizable 24 days after fertilization.
PMG
2N
Dorsal mesentary
Where germ cells migrate
Genital Ridge
Will form ovaries or testies
Indifferent Stage
Cannot differentiate between sexes
Oogenesis
Occurs in month 3 - at prophase I it halts. Only about 500 are ovulated. Oogonia to oocyte - 2 million oocytes.
Infundibulum
Like a funnel focused @ ovary.
Fimbriae
Little fingers over ovary from infundibulum. Smooth muscle then moves egg through ampula (fertilization likely occurs here).
Spermatogenesis
Spermatogonia to sperm
Maximum number of oocytes
Month 5 - 7 million oocytes
Month 9
All oocytes in meiosis I, birth, 600-800K oocytes
Menarche
First occurrence of menstruation, 400K oocytes
Oocyte wall
Immotile all are 23X, Corona radiata, Zona pellucida
Sperm
Motile, 23Y
2 hormones
FSH, LH (anterior pituitary) - prior to fertilization
FSH
follicular stimulating hormone. Tells 10-15 of the oocytes to start meiosis II and I.
LH
Leutinizing hormone - surge that causes oocyte to be spit out to be picked up by fimbriae
Zona RXN
causes only 1 sperm to be able to break into the nucleus
Monula
12-32 blastomeres. Important stage because of inner and outer cell mass.
Capacitation
Occurs after ejaculation 7hrs. Surface proteins remove acrosome, allows acrosome to interact with corona radiata and ZP.
Hyperactivation
Type of sperm motility, helps sperm penetrate ZP
Acrosome reaction
Allows sperm to break ZP.
Fertilization steps
Zona reaction, sperm and oocyte cell membranes break down and fuse. Oocyte completes meiosis and forms pronucleus. Haploid pronuclei fuse and form diploid zygote — initiates cleavage. 1. Coronal cells 2. Acrosomal reaction 3. Fusion
Blastomeres
Early embryonic cells from zygote that start to form within 30 hours of fertilization. Zona pellucida confines cells.
Compaction
Begins at 8 cells
Ectopic Pregnancy
Implantation occurs in abnormal position - usually in uterine tubes.
Lithopedium
Embryo in abdomen, calcifies
Cervical implantation
Results in heavy bleeding.
Blastocyst
no more zona pellucida. Fluid enters blastocystic cavity and separates blastomeres. Trophoblast and Embryoblast
Trophoblast
Forms extra embryonic structures (placenta). Troph=nutrients.
Posterior Wall
Best place for implantation. Tropoblast cells attach to endometrium. Once this occurs, tropoblast differentiates into cytotrophoblast and syncytiotrophoblast (day 7).
Cytotrophoblast
Line blastocystic cavity
Syncytiotrophoblast
“Finger” type cells that extend and attach to endometrium.
Hypoblast
Small cuboidal cells that form from embryoblast. These will form the primary endoderm.
