BIOSCI 107 Embryology Definitions Flashcards
Oocyte
Cell in ovary - becomes ovum.
Fertilisation
When a sperm and egg join together.
Zygote
Eukaryotic cell formed by a fertilization event between two gametes.
Haploid
Half the usual number of chromosomes.
Diploid
Containing two complete sets of chromosomes.
Zona Pellucida
Thick transparent membrane surrounding a mammalian ovum before implantation.
Cleavage
Splitting or dividing of a cell.
Compaction
Blastomeres become tightly joined, forming gap junctions.
Blastomere
Cell produced by cleavage (cell division) of the zygote - forms blastula.
Morula
Early stage embryo - blastomeres in solid ball.
Embryoblast or Inner Cell Mass
Cellular mass on interior of embryo.
Blastocyst or Blastula
Thin-walled hollow structure in early embryonic development.
Blastocyst Cavity or Blastocoel
Space inside blastocyst.
Trophoblast
Cells forming the outer layer of a blastocyst.
Endometrium
Lining of uterus.
Uterus
Hollow muscular organ.
Uterine Tube
Conducting the egg from the ovary to the uterus.
Bilaminar Embryo
Two-layered embryo.
Epiblast
Derived from ICM - becomes germ layers.
Hypoblast
Tissue type that forms from the inner cell mass.
Amniotic Cavity
Fluid-filled cavity that surrounds the developing embryo.
Amnion
Tough, thin membrane that surrounds a developing fetus.
Amniotic Fluid
Fluid surrounding the developing fetus.
Cellular Trophoblast or Cytotrophoblast
Inner layer of the trophoblast.
Syncytial Trophoblast or Syncytiotrophoblast
Syncytial outer layer of the trophoblast.
Yolk Sac
Encloses a hollow cavity and loses its nutritive function as the placenta develops.
Extraembryonic Mesoderm
Forms from hypoblast.
Extraembryonic Coelom
Portion of the conceptus consisting of a cavity between Heuser’s membrane and the trophoblast.
Mesodermal Stalk
Band of mesoderm that connects the caudal end of the embryo to the chorion in development.
Gastrulation
The process in which the embryo develops into a gastrula (3 germ layers).
Ectoderm
Exterior germ layer.
Mesoderm
Middle germ layer.
Endoderm
Inner germ layer.
Germ Layer
Group of cells in an embryo that interact with each other as the embryo develops.
Primitive Streak
structure that forms in the blastula - marks start of gastrulation.
Primitive Node
Local thickening of the epiblast at the cephalic end of the primitive streak.
Convergence Extension
Process by which the tissue of an embryo is restructured to converge (narrow) along one axis.
Organising Centres (Organizers)
Where microtubules organise into tubular structures.
Morphogen
Substance that carries information relating to position in an embryo/
Midline
Plane through the very centre of your mouth perpendicular to your nose.
Rostral or Cranial
Involving the head.
Caudal
Towards hind part/tail.
Dorsal
Back of the body.
Ventral
Front of the body.
Amniotic Sac
Tough but thin transparent pair of membranes, which hold a developing embryo
Bucchopharyngeal Membrane
Where ectoderm and endoderm come into contact with each other.
Cloacal Membrane
Covers the embryonic cloaca during the development of the urinary and reproductive organs.
Allantois
Helps the embryo exchange gases and handle liquid waste.
Neural Tube
Precursor to the central nervous system
Non Neural Ectoderm
Ectoderm not involved in Neural activity.
Notochord
Primitive beginning to the backbone.
Notochord/Axial Mesoderm
Lies along the central axis.
Somite/Paraxial Mesoderm
Flanks and forms simultaneously with the neural tube.
Parietal Lateral Plate Mesoderm
Form the mesothelial membranes or serous membranes which line the cavities.
Splachnic Lateral Plate Mesoderm
Forms the walls of the gut tube.
Intermediate Mesoderm
Develops into the part of the urogenital system as well as the reproductive system.
Lateral Plate Mesoderm
Gives rise to heart, blood vessels, blood cells and the lining of the body cavities
Somites
Paired block-like segments of mesoderm.
Somitomeres
Segmented mesenchymal units.
Sclerotome
Subdivisions of somites.
Syndetome
Forms the tendons.
Myotome
Group of muscles that a single spinal nerve root innervates.
Dermatome
Area of skin that is supplied by a single spinal nerve.
Brain Vesicles
Derived from the anterior portion of the neural tube.
Pharyngeal Arches
Series of externally visible anterior tissue bands lying under the early brain.
Pharyngeal Pouches
Form on the endodermal side between the pharyngeal arches.
Frontonasal Prominence
Establishes the facial midline.
Nasal Placodes
Ectodermally derived tissue thickenings that arise from the anterior end of the neural plate.
Medial Nasal Prominence
Frontonasal prominence.
Maxillary Prominence
Gives rise to upper jaw and lip.
Cardiogenic Mesoderm or Heart Field
Forms inner lining of heart and gives rise to heart muscles.
Atrium, Ventricle
Atriums are each of the two upper cavities of the heart from which blood is passed to the ventricles.
Sinus Venosus
Large quadrangular cavity which precedes the atrium only in embryonic heart.
Bulbus Cordis
Lies ventral to the primitive ventricle after the developing heart assumes its S-shaped form.
Primitive Atrium
Stage in the embryonic development of the human heart.
Primitive Ventricle
Gives rise to left and right ventricles.
Decidua Basalis
Maternal part of the placenta.
Decidua Capsularis
Layer of endometrium overlying the implanted chorionic vesicle.
Decidua Parietalis
Mucous membrane lining the main cavity of the pregnant uterus.
Placenta
An organ attached to the lining of the womb.
Ectopic Pregnancy
Complication of pregnancy in which the embryo attaches outside the uterus.
Chorion
Outermost membrane surrounding an embryo contributing to placenta formation.
Chorionic Villi (Singular, Villus)
Villi that sprout from the chorion to provide maximum contact area with maternal blood.
Lacunae
Gaps between the lamellae filled with mother’s blood.
