Human Development Flashcards
embryonic period
end of week 3 through week 8, most important time of pregnancy for birth, developmental defects; after week 8 everything just grows in size
fetal period
end of week 8 through week 38
Gastrulation
is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar (“three-layered”) structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.
primitive streak
The primitive streak is a structure that forms in the blastula during the early stages of avian, reptilian and mammalian embryonic development. It forms on the dorsal (back) face of the developing embryo, toward the caudal or posterior end.
amniotic cavity
is the closed sac between the embryo and the amnion, containing the amniotic fluid. The amniotic cavity is formed by the fusion of the parts of the amniotic fold, which first makes its appearance at the cephalic extremity, and subsequently at the caudal end and sides of the embryo.
yolk sac
yolk sac is the first element seen in the gestational sac during pregnancy, usually at 3 days gestation. Identification of the gestational sac is a critical landmark in monitoring an early pregnancy, and can be reliably seen in human pregnancy using ultrasound.
primitive knot
is an enlarged group of cells located in the anterior portion of the primitive streak in a developing gastrula.
fertilization takes place (ideally) in…
the ampula of the uterine tube at which it will be unarrested from metaphase II
mitotic division that the fertilized egg undergos is called:
cleavage
insitio tropho blast
invades tissue of endometrium
after hatching from zona pallucida, the trophoblast differentiates into 2 distinct layers:
insitio trophoblast, and cytotrophoblast
gastrulation:
point at which we have 3 main stages: ectoderm, endoderm, mesoderm
The floor of the amniotic cavity is formed by the ______disc composed of a layer of prismatic cells, the embryonic ectoderm, derived from the inner cell-mass and lying in apposition with the endoderm.
embryonic
the embryonic disk is derived from
the epiblast layer, which lies between the hypoblast layer and the amnion. The epiblast layer is derived from the inner cell mass. Through the process of gastrulation, the bilaminar embryonic disc becomes trilaminar. The notochord forms thereafter. Through the process of neurulation, the notochord induces the formation of the neural tube in the embryonic disc
The amnion is:
The amnion is a membrane that closely covers the embryo when first formed. It fills with the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo
The ________ is a tissue type that forms from the inner cell mass. It lies beneath the epiblast and consists of small cuboidal cells. Extraembryonic endoderm (including Yolk sac) is derived from hypoblast cells.
hypoblast
the tri-laminar embryo is the stage at which:
there are 3 distinct germ layers:
ectoderm
mesoderm
endoderm
ectoderm layer will become:
skin, epidermis, CNS, give rise to neural crest cells, teeth, eyes
mesoderm layer will become:
muscles, notocord, skeletal components, RBC, cartilage, bones
endoderm gives rise to:
most organs on inner cavity: hearing GI, pulmonary, urination, breathing
before gastrulation, the bilayer pancake consists of :
epiblast (dorsal) and hypoblast (ventral)
the hypoblast is the first layer pushed out of the way and it is removed by:
epiblast cells migration
after being in a bilayer formation, the cells that move to form the notocord are called the:
axial mesoderm