14. Human Development Flashcards
ferilization usually occurs at this site
ampulla of the uterine tubes
Approximately thirty hours after fertilisation, the fertilised oocyte (egg) splits into two cells of equal size; called
blastomeres
the fertilised oocyte (egg) splits into two cells of equal size; called blastomeres. After three more divisions, there are ___ cells
16 cells called morula
how many cells in morula
16 cells
Within the first week, the cells of the morula reorganise to form a cavity, known as the
blastocyst cavity (blastocoel)
Within the first week, the cells of the morula reorganise to form a cavity, known as the blastocyst cavity (blastocoel). From this point, the morula is known as
blastocyst
two diff cell types in the blastocyst
Outer cell mass (trophoblast)
Inner cell mass (embryoblast)
contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta.
Outer cell mass (trophoblast)
responsible for the formation of the embryo itself.
Inner cell mass (embryoblast)
During the ___ week, the trophoblast and embryoblast divide into increasingly specialised cell types.
second
The trophoblast divides into the
syncytiotrophoblast and cytotrophoblast.
embryoblast divides into the
epiblast and hypoblast, forming a two-layered structure; the bilaminar disk.
The amniotic cavity forms within the
epiblast
during implantation, _____ becomes continuous with the uterus
syncytiotrophoblast
During implantation, what specific structures become continuous
maternal blood vessels (known as sinusoids) invade the spaces within the syncytiotrophoblast (known as lacunae)
-> uteroplacental circulation
In placenta praevia, implantation of the embryo occurs in the
lower uterine segment (instead of in the normal position of the upper posterior uterine wall).
gastrulation occurs ___ week of development
3rd week
During this process, the two cell layers become three germ cell layers, and the bodily axes observed in the mature adult are created.
gastrulation
Gastrulation is a process of cellular rearrangement which involves migration, invagination and differentiation of the
epiblast
gastrulation is largely controlled and orchestrated by the
primitive streak
is a groove in the midline of the epiblast which appears during the third week.
primitive streak
this structure is at the cranial end of the primitive streak
primitive node
within the primitive node lies this structure
primitive pit
Cells of the epiblast layer break off and migrate toward the
primitive pit
Cells of the epiblast layer break off and migrate toward the primitive pit. Here, they detach and penetrate through the epiblast layer to form three new germ cell layers:
endoderm
mesoderm
ectoderm
formed by epiblast cells that migrate through the primitive pit and displace the hypoblast cells.
endoderm
formed by epiblast cells that migrate through the primitive pit and lie between the epiblast layer and the newly created endoderm.
mesoderm
formed by the epiblast cells that remain in position.
ectoderm
3 phases of fertilization
- sperm penetration of corona radiata
- sperm binding and penetratio of zona pellucida -> acrosome rxn -> releases acrosin
- fusion of sperm and oocyte cell membrane -> secondary oocyte completes meiosis II forming mature ovum and second polar body; male and female pronuclei fuse forming a zygote
results of fertilization
- formation of new individual
- restoration of diploid number of chromosomes
- determination of sex
- initiation of cleavage
series of mitotic divisions of zygote
cleavage
blastomeres form morula by undergoing
compaction
fertilization occurs after __ hours after ovulation
12-24 hours
2 cell stage is __ afters after fertilization
30 hours
morula is ___ days of age
30 days
blastocyst is __ days of age
5 days
implantation happens day __ after fetilization
7 days
implantation usually happens at this part of the uterus
posterior superior wall
at what layer of the endometrium do fertilization happens
secretory phase of the menstrual cycle
the most common type of ectopic pregnancy
tubal pregnancy 95%
most dependent part of entire peritoneal cavity when patient is in standing position
pouch of douglas
frequently becomes the site for accumulation of blood (ruptured ectopic pregnancy ) or pus (ruptured appendicitis or gonococcal peritonitis)
Pouch of douglas
needle passed into the pouch of douglas through the posterior fornix
culdocentesis
structures penetrated by culdocentesis
- mucous membrane - vagina
- muscular coat- vagina
- connective tissue coat- vagina
- visceral layer of pelvic fascia
- visceral layer of peritoneum
