Embryology Weeks 1-3 Flashcards
(23 cards)
Where does fertilization take place?
Ampulla of the uterine tubes
What is the acrosome reaction?
Acrosomal enzymes released by the sperm allow it to penetrate the oocyte
What is the cortical reaction?
Renders the oocyte impenetrable to other sperm
What is a morula?
Zygote consisting of 12-32 blastomeres
Forms approximately 3 days after fertilization
Describe implantation
Implants within the functional layer of the endometrium during the secretory phase of the menstrual cycle
Usually in the posterior wall of the uterus
Begins at the end of the first week and is completed by the end of the second week
What is an ectopic tubal pregnancy?
When the blastocyst implants within the uterine tube
What is the role of the syncytiotrophoblast?
Grows into the endotemtrium, does not divide mitotically
Produces human chorionic gonadotropin hormone
What is the function of hCG?
Stimulates the production of progesterone in the corpus luteum
Can be detected at 10 days for pregnancy tests
What is the role of the cytotrophoblast?
Divides mitotically, adding to the growth of the syncytiotrophoblast
What are Primary chorionic villi?
Protrusions of the cytotrophoblast into the syncytiotrophoblast and are the first stage in development of the chorionic villi of the placenta
What is the role of the extra-embryonic somatic mesoderm?
Lines the inner side of the cytotrophoblast (together forming the chorion)
What is the role of the extra-embryonic visceral mesoderm?
Covers the yolk sac
What is a hydatidiform mole?
A blighted blastocyst leads to the death of the embryo, followed by hyperplastic proliferation of the trophoblast within the uterine wall
What is a choriocarcinoma?
Malignant tumor arising from trophoblastic cells that may occur following a normal pregnancy, abortion, or hydatidiform mole
What is week 3 of human development characterized by?
Appearance of primitive streak
Development of the notochord
Differentiation of the three germ layers
What is gastrulation?
Conversion of the epiblast from a bilaminar disc into a trilaminar embryonic disc consisting of ectoderm, mesoderm, and endoderm.
Begins with the formation of the primitive streak
What is the primitive streak?
Linear band of thickened epiblast that first appears at the caudal end of the embryo and grows cranially
Normally undergoes degeneration and disappears by the end of the fourth week
How is the mesoderm formed?
Epiblastic cells migrate into the ECF between the epiblast and hypoblast (endoderm) as mesenchymal cells, eventually forming the mesoderm
What is a sacrococcygeal teratoma?
Remnants of the primitive streak may persist and give rise to this germ cell tumor.
Can be benign or malignant
Most common tumor in neonates
What is the notochord?
Cord of mesodermal cells
Signals ectoderm to make nervous system and some mesoderm to make vertebral bodies
Eventually becomes the nucleus pulposus of the vertebral discs
What is the oropharyngeal membrane?
Site of the future mouth where ecotderm and endoderm connect directly with no mesoderm
What is the prechordal plate?
Thickened mesoderm between the oropharyngeal membrane and the notochord
Contributes to forebrain and oral cavity structure
What is the cloacal membrane?
Site of future anus where ectoderm and endoderm meet directly
