Intro to Embryology Flashcards
embryonic period
fertilization–> 8 weeks
-initial development of all major structures and establishment of all organ systems
human development
embryonic period
fetal period
fetal period
9th week to term (38 or 40 weeks)
- differentiation and growth of organs and tissues
- specialization takes place here
teratology
the study of abnormal development (genetic/ environmental causes)
N
haploid number of chromosomes (23 chromosomes)
ploidy
number of copies of each unique double stranded molecule
origin and maturation of Primordial Germ Cells (PGC)
- Originate as endodermal cells lining the yolk sac (umbilical vesicle) near origin of allanointis
- Diploid (2N)
- Migrate to occupy gonads and mature into gametes (mature sex cells: spermatozoa & oocyte)
gametogenesis
when primordial germ cells form and mature into the male and female gametes (spermatozoa and oocytes)
spermatogenesis
spermatogonia –> sperm *begins at puberty
oogenesis
oogonia –> oocyte *begins before birth, halts, restarts (one cell at a time) beginning at puberty
oocyte
Zona pellucida
Corona radiata
Immotile
All are 23X
sperm
Motile
23 X or 23Y
capacitation
Surface proteins removed from acrosome; allows acrosome to react with corona radiata & ZP, and release of enzymes
acrosome reaction
occurs on contact with ZP; results in release of enzymes, allows penetration of ZP and facilitates fertilization
hyperactivation
¥ follows capacitation – increasing the activity of the sperm.
¥ About 200 perm in the uterine tube at one time
¥ Sperm viability up to 3 ½ days
three steps of fertilization
Fertilization: 3 phases ***
1: Coronal cells
2: Acrosomal reaction
3: Plasma membranes fuse, Meiosis II resumes, metabolism of oocyte increases
zona pellucida
thick wall surrounding cytoplasm
corona radiata
sperm break through these layers (follicular cells) to access nucleus where chromosomes intermingle
blastomeres
early embryonic cells that are a result of the zygote undergoing mitosis (~30 hours after fertilization)
compaction
Cell divisions result in successively smaller blastomeres that remain confined within the space available within the zona pellucida
blastocyst
after 4-5 days, the morula reorganizes to form an inner and outer cell mass where fluid accumulates to form the blastocystic cavity–> now a blastocoel. Zone pellucid not degenergated
embryoblast
inner cell mass: gives rise to the embryo
trophoblast
◊ -outer cell mass; becomes extraembryonic structures (embryonic contribution to the placenta)
◊ -is the nutrition (“trophy”)
-differentiates at day 7 into cytotrophoblast and syncytiotrophoblast
cytotrophoblast
doesn’t embed in uterus-> becomes extra embryonic structures (surrounds embryonic structure)
syncytiotrophoblast
embeds in posterior wall of endometrium
ectopic pregnancy
Blastocyst implants outside normal uterine locations
hypoblast
small cuboidal cells formed from the embryoblast (inferior to)
Primary Endoderm
