28) Pregnancy, Growth, & Development Flashcards
1-15 quiz, 16-?? lecture notes
this is the term for the developing organism from eight weeks until birth
fetus
the process of developing the tree germ layers
gastrulation
this is the term for developing organism up until eight weeks
embryo
hormone secreted by the corpus luteum that maintains the uterine lining
progesterone
hormone that targets mammary glands for milk production
prolactin
hormone secreted by extraembryonic tissue to maintain pregnancy
human chorionic gonadotropin
the term for the structure that is a ball of cells
morula
the process of forming organs
organogenesis
the structure that implants in the endometrium
blastocytes
the name for the dividing cells via mitosis in the early embryo
cleavage
structure that is formed from embryonic and maternal tissue
placenta
implantation normally takes place here
uterus
fertilization normally takes place here
uterine tube
term for the embryonic structure that has developed the three germ layers
gastrula
the name for the structure that is formed when the sperm and egg combine
zygote
pregnancy
*presence of a developing offspring in the uterus
*3 trimesters (each 3 months long)
*sperm reach secondary oocyte, fertilized 24-48hrs
*after 38weeks cell division, grow distinctive organs/tissue
*prenatal- period from fertilization to birth
*postnatal- birth to death
fertilization
*sperms chromosomes combine with those of secondary oocyte
*fertilized oocyte is called a Zygote
sperm transport
*sperm viable for up to 6 days after ejaculation
*most sperm doesnt make the 12cm trip to egg
*a few thousand out of millions make it to oocyte
*once at ovulated oocyte, must breach the outer layer to fertilize egg
layers of ovulated oocyte
*corona radiata
*zona pellucida
*secondary oocyte
acrosomal reaction
several steps to sperm reaching oocyte:
1)approach, 2)acrosomal reaction, 3)binding, 4)fusion of membranes
1) approach
*aided by enzymes, sperm weaves thru corona radiata
*binds to sperm-binding receptors in zona pellucida, causing calcium channels of sperm to open, triggers acrosomal reaction
2) acrosomal reaction
*calcium influx, enzymes from many sperm are released, they digest holes in zona pellucida
*acrosomes in region release enzymes to digest zona pellucida
*many needed to clear path to oocyte membrane
3) binding
*after path cleared, sperm forcibly swims to oocyte membrane
*acrosomal collar on rear portion of acrosomal membrane binds to oocyte plasma & sperm-binding receptors
*oocyte form microvilli that wrap around sperm, triggers fusion of oocyte & sperm
4) fusion of membrane
*oocyte & sperm fuse
*cytoplasmic contents of sperm enter oocyte
*tail and other parts are left behind on oocyte membrane surface
polyspermy & monospermy
*polyspermy- many sperm enter oocyte
*monospermy- one sperm enters oocyte
blocks to polyspermy
*oocyte membrane blocks
*zona reaction
*cortical reaction
oocyte membrane block
when sperm binds to sperm-binding receptor on oocyte:
*sodium ion cates open > depolarize entire membrane
*other sperm cannot bind to oocyte membrane
*aka Fast block to polyspermy
zona reaction
entry of sperm into oocyte triggers calcium surge
*activation of second meiotic division
cortical reaction
granules inside oocyte membrane release zona inhibiting protein
*ZIP enzyme, into extracellular space below zona pellucida
*zip destroys zona pellucida sperm-binding receptors
*fragments swell, detaching any other sperm still around
completion of meiosis II and fertilization
*calcium surge triggers completion of meiosis II
*ovum nucleus swells to become female pronucleus
*sperm moves towards oocyte, swells, forms male pronucleus
*DNA in each replicates, nuclear envelope dissolves, releases chromosomes near mitotic spindle
*chromosomes combine, forming diploid zygote, fertilization occurs
cleavage
*occurs while zygote moves towards uterus
*rapid miotic division, 36hrs, produces blastomeres
*after 72hrs, cluster of cells contains 16 or more ells: morula
blastocyst formation
*around day 4-5, embryo reaches uterus
*approx 100 cells, called a blastocyte-fluid filled hollow sphere
*blastocyte: trophoblast cells & embryoblast
*float for 2-3days, nourished by uterine secretions
trophoblast
*participates in placenta formation
*displays immunosuppressive factors
embryolast
*cluster of 20-30rounded cells
*becomes embryonic disc, will form embryo & 3-4 extraembryonic membranes
implantation
*6-7 days after ovulation, trophoblasts adhere to site
*endometrium/uterine blood vessels become permeable & leaky
emndometrium eroded, blastocyte burrows>lining, endometrium covers implanted blastocyte corpus luteum maintained by hCG
**
human chorionic gonadotropin (hCG)
*prevents menstruation
*secreted by trophoblasts & chorion>
*corpus luteum secretion of progesterone & estrogen>
*placental development
placenta
*temporary organ that originates from embryonic & maternal tissue
*fully formed & functional by 3months
*provides nutritive, respiratory, excretory & endocrine function
*maternal & embryo blood supplies do not intermix
embryonic stage
*extends from beginning of 2nd week thru 8th week
extraembryonic membrane
forms during first 2-3 weeks of development from gastrula
amnion
*epiblast cells form transparent sac filled with amniotic fluid
*buoyant environment, protects/free movement of embryo/fetus
*maintains constant temp
yolk sac
*sac that hangs from ventral surface of embryo
*forms part of digestive tube
*source of earliest blood cells and blood vessels
allantois
*small out pocketing at caudal end of yolk sac
*structural base for umbilical cord
*becomes part of urinary bladder
chorion
*helps form placenta
*encloses embryonic body & other membranes
gastrulation
*movement of cells within the embryonic disc form multiple layers
germ layer formation
gastrulation occurs 3weeks, embryonic disc transforms into 3 layer embryo with 3 layers:
*ectoderm, *mesoderm, *endoderm (all primitive tissues, organs derive from)
ectoderm
become nervous system & skin epidermis
endoderm
become epithelial lining of digestive, respiratory, urogenital, & glands
mesoderm
becomes everything else
