Embryology Flashcards
sex cell, haploids: oocyte (F), spermatozoan (M) come together to form a zygote
Gamete
fertilization of egg and sperm
Zygote
glycoprotein layer that surrounds the egg, it hardens once the sperm enters to prevent another sperm from gaining entry (zygote), leaves after mitosis to allow for growth
Zona pellucida
cell division, forms the morula (ball of cells) (2 4 8 16) 16 total once mitosis is complete
Mitosis
hollow ball of cells with blastocele (cavity)
Inner cell mass forms the embryo, multiplies and divides into 3 germ layers
Blastocyst (blastula)
on exterior become the placenta (extraembryonic membranes)
Trophoblast
Order of embryology
Gamete fertilizes, zygote forms, sona pellucida forms, mitosis, morula and blastocyst
Formation of 3 germ layers from the inner cell mass
Gastrulation
Portion of inner cell mass that is closest to the trophoblast
The cavity dorsal to the epiblast becomes the amniotic cavity
Develops into the ectoderm
Epiblast
A portion of inner cell mass next to blastocoel
becomes the endoderm
Hypoblast
The cells in between the epiblast and the hypoblast that become the
Mesoderm
The Germ Layers
Ectoderm, Endoderm and mesoderm
outer layer
Forms from epiblast cells
Becomes epidermis, hair, hooves, epithelium of sense organs, nerve tissue
Ectoderm
inner layer
Forms from hypoblast cells
Grows down and forms archenteron (primitive gut)—gastrulation
Becomes epithelium of gut, respiratory tract, and lower urinary tract
Endoderm
middle layer
Forms from cell in between ectoderm and endoderm
Divides into two layers coelom (precursor to body cavities.)
Becomes muscle, all connective tissue, and epithelium of gonads and joints
Mesoderm
Primitive streak dorsally on embryo
Ventral
Develops from mesoderm
First support structure, rod like
Vertebrates all have one
Replaced by vertebrae of spine in later embryo
Small remnant as nucleus pulposus inside intervertebral disk
Notochord
Ectoderm dorsal to notochord thickens, folds into a groove, meets to form a tube
Dorsal, hollow nerve cord
Will develop and thicken at cranial end to become brain
Hollow is filled with CSF (cerebrospinal fluid)
Spine forms
Peripheral nerves grow laterally along somites
Neurulation
Adjacent to ectoderm
Gives rise to the bones, ligaments, blood vessels, and connective tissue of the limbs
Lengthwise segments called somites
Somatic Layer
Coelom and mesoderm development
Mesoderm divides into somatic and splanchnic layer
Adjacent to the endoderm
Forms the heart, gut muscles and blood vessels
Splanchnic layer
Cavity the forms in between these two layers
Precursor to body cavities
Coelom
Embryo continues to differentiate
Germ layers form tissues
Tissues form organs
Organs form organ systems
Fetus forms when organs are in place (1st trimester)
