Lecture 2 embryology Flashcards
Embryology
study of the origin and development of an individual person or organism
Prenatal period
the time between conception and birth
has two periods: embryonic period, and the fetal period
Embryonic period
First 8 weeks
by the end of this period all major organs are in place
Fetal period
8-30 weeks
the organs of the fetus grow larger and more complex
Ectoderm
The outermost layer of cells or tissue in early development. The parts derived from this, will form the epidermis and nerve tissue
Endoderm
the inner most layer of cells or tissue in early development. The parts derived from this, will form the primitive gut, digestive tract, liver, pancreas, and part of the lungs.
mesoderm
The middle layer of cells or tissue in early development. The parts derived from this, will form structure including the skeletal system, muscular system, and notochord. Divides later to form many important organ systems.
Fertilization
Fusion of the sperm and egg nuclei
Generally occurs in the lateral third of the uterine tube
Zygote
fertilized oocyte
Cleavage
rapid cell divisions without intervening growth periods. begins with a fertilized ovum and produces blastocyst
Morula
solid cluster of cells
after 72 hrs there’s about 12-16 cells
blastocyst
early embryonic development
a hollow ball of cells and the product of cleavage
Blastocyst stage
Inner cell mass: accumulation of cells in the blastocyst
Trophoblast: the external layer of cells in the blastocyst. forms placenta
Implantation: takes about a week, trophoblast erodes
Day 1
fertilization occurs. the egg is called a zygote
Day 2-4 cell stage
zygote continues to divide as it travels to the uterus, this is called cleavage
Day 3
the cleavage generates a cluster of cells called a morula
day 4-6
morula enters the uterus and is called a blastocyst. On day 6 blastocyst will burrow into the uterus
day 7
implanting the blastocyst
Inner cell mass
divides into epiblast and hypoblast
during gastrulation, it’ll become into a trilaminar disc
epiblast
The outermost layer of an embryo before it differentiates into the ectoderm and mesoderm
hypoblast
The innermost layer of an embryo before is gives rise to the yolk sac, and will contribute to the endoderm
gastrulation
An early developmental process in which the embryo transforms from a 1 dimensional layer of cells (epithelial) and reorganizes into a multilayers and multidimensional structure referred to as the gastrula
bilaminar disc
Refers to the two-layered structure of the epiblast and hypoblast
amniotic sac
The fluid-filled sac that contains and protects the embryo and eventually the fetus in the womb.
primitive streak
An elongated band of cells that forms along the axis of a developing embryo early in gastrulation
epiblast
The outermost layer of an embryo before it differentiates into the ectoderm and mesoderm.
primitive node
An area through which migrating cells are channeled into a rodlike structure of mesenchymal cells
notochord
cells that gather and form a cartilaginous skeletal rod
neurulation
folding process of the embryo
Neural plate
induces the overlying ectoderm (at the midline) to thicken and form an elongated structure called the neural plate. This will give rise to the CNS, brain, and spinal cord
neural Groove
Formed by infolding neural fold cells (from endoderm), this groove closes the neural tube which becomes separated from the overlying ectoderm. This closure is very important (folic acid)
