Offspring Development
Ovulation
Oocyte and corona radiata are expelled
Swept into infundibulum of fallopian tube by fimbriae
Fertilization may or may not occur
Passes into uterus
2 Regions:
Body
Cervix
- opens into vagina by external os
- cervical glands secrete mucus that blocks external os
3 layers:
Perimetrium
- secretes serous fluid
Myometrium
- muscular layer
Endometrium
- epithelial and vascular layer
Remaining Anatomical Structures:
Vaginal Structures:
Fornix: pockets around external os
Vaginal Orifice: external opening
Vestibular Glands:
- secrete mucus for lubrication
Prenatal Development
Fertilization:
- in uterine tube
- hyaluronidase from acrosomes
penetrates corona radiata and zona pellucida
- zona pellucida “hardens”
-oocyte continues meiosis
- nuclei of sperm cell and egg cell
unite = zygote
Blocks to Polyspermy:
1.) Fast Block
1 sperm contacts oocyte membrane
Na+ channels open and Na+ enters
oocyte
membrane depolarizes
no other sperm can fuse with
membrane
2.) Slow Block
ER releases Ca++
signals cortical granules to release
enzymes into space
beneath zona pellucida
sperm receptors are destroyed
enzymes bind water, swelling layer
and forcing away other
attached sperm from oocyte
Prenatal Development
Embryonic Period
Sperm nucleus travels towards ovum nucleus
Mitotic spindle forms
Pronuclei degenerate and chromosomes form
Homologous chromosomes attach to mitotic spindle
Mitosis continues and first cleavage completes
Prenatal Development
Embryonic Period
Mitosis continues until morula forms
16 cells
3-4 day journey to uterus
Blastocyst forms
- cells are dividing and
differentiating
- two portions develop:
Trophoblast = contributes to
placenta
Inner Cell Mass = eventually
forms embryo
-Fluid fills intercellular space
between two layers =
blastocyst cavity
Blastocyst is released from
zona pellucida
Prenatal Development
Embryonic Period
Implantation begins around day 6 or 7
-Trophoblast secretes enzymes that allow it
to bury into endometrium
Prenatal Development
Embryonic Period
Embryo forms embryonic disc:
Primary germ layers
- become baby’s
tissues
cells on ventral side = endoderm
cells on dorsal side = ectoderm
Space between embryo
and trophoblast = amniotic
cavity (dorsal side)
Chorion
-Forms from trophoblast
-Later becomes part of placenta
Amnion
-expands amniotic cavity until it
surrounds embryo
Prenatal Development
Embryonic Period
Gastrulation:
-Occurs during third week of
development
-Endoderm depends on yolk sac
-Primitive streak thickens along
embryo’s midline,
folds inward = mesoderm
Embryo = gastrula
Prenatal Development
Embryonic Period
Neurulation:
-Mesoderm cells form rodlike
notochord
-Ectoderm folds into neural tube
and neural crest
-Embryo = neurula
Prenatal Development
Embryonic Period
Organogenesis:
-Weeks 4-8
-Further folding of all
layers results in body
cavities and organs
Embryo is considered a fetus at about 9 weeks
Prenatal Development
Embryonic Period
Prenatal Development
Fetal Period