Download Embryology

Introduction: Week One
Three Germ Layers:
I.
II.
Ectoderm:
Endoderm:
III.
Mesoderm:
Lines the outside of the embryo; gives rise to epidermis and CNS
Lines gut tube of embryo; inner lining of digestive tract and tissues that sprout
off of digestive tract.
Gives rise to bone, muscles, blood, and connective tissue
Epithelium (what tissues? where’s it located?)
Mesoderm subdivisions (where? structural differences?)
Coelom (how’s it formed? what arises from it?)
Dorsal Messentery (how’s it formed?)
Primordial Germ Cells
-Arise from where?
-Precursors of?
-Undergo which types of division?
-How do they stain?
-Migrate from where to where?
-Fate of non-migratory PGCs
-Migratory PGCs give rise to what?
Sex Cords and Genital Ridges
-Form as what event takes place?
-Germ layer(s) involved in formation?
-Differences between primary and secondary
-location of sex cords
-male/female (alternate names?)
-give rise to?
Adult Gametogenesis
-Sperm structures
-DNA composition (ploidy and chrom. count)
-Oocyte structures
-Arrested in what phase of division?
-Function of various structures
Female Gross Anatomy
-Ovaries
-Oviduct
-Uterus
-Vagina
-Site of copulation and sperm deposit?
-Site of fertilization?
-Site of implantation?
-Site of immature oocyte storage?
Fertilization
-Sperm undergo what in order to fertilize?
-Generally takes place where?
-Function of Sperm Receptor Molecule?
-Function of Cortical Granules?
-What is polyspermy? How is it prevented?
-Presence of what stimulates completion of meiosis? What phase was oocyte arrested in?
What results from completion of meiosis?
-Chromosome count of zygote?
The First Week of Development
-What happens as zygote travels through oviduct toward uterus?
-What does this process form? (a mass structure composed of individual...)
-Toward the end of this process, compaction occurs, resulting in?
-At the end of this, fluid absorption creates what? How does this affect the look of the embryo?What new
structures are formed (in the now polarized cell)?
-What happens when zygote reaches uterus?
-Name the inner lining of the uterus.
-What is a decidual reaction?
-Where does implantation occur (in regards to both uterus and alignment of zygote)?
-What is an egtopic pregnancy?
-How does the early embryo receive nutrients?
-Contact between embryo and uterus causes what to occur?
-Eventually, two structures emerge, what are they and how do they differ? What are their
functions?
-What is a coagulation plug?
Early Uteroplacental Circulation
-What first forms in the embryo as a primitive circulatory mechanism, and where does it emerge?
-At the maternal end, how are nutrients provided to the embryo?
-How do primary stem villi emerge?
-Secondary?
-What is necessary for the formation of tertiary stem villi?
-List the layers of passage between maternal and fetal circulation.
Chromosomal Abnormalities: Clinical Application
-Nondisjunction
-Point Mutations
-Translocation
-Missense vs. Nonsense
-Deletions
-Clinical Manifestations (Trisomy 21)
-Inversions
Assisted Reproduction
-in vitro Fertilization
-GIFT
-ZIFT
Experimental Principles
-Transgenic Mice
-How are they made?
-Knockout Mice
-How are they made?
-Define totipotent and chimeras
Weeks Two and Three
The Second Week (characterized by the five 2s)
-Embryoblast differentiates into two layers. What are they (both names)?
-This structure is referred to as what type of disc?
-Fluid accumulation in one of the layers (which one?) forms what structure?
-The surrounding cells are now named differently. How?
-Which cells migrate toward abembryonic pole? What do they form? Once migration is complete,what is
this structure referred to as?
-Placental tissues are derived from which cell types?
-Embryo Proper is developed from which cell types?
-What tissue type emerges next, and at what places is it seen? Splitting of this tissue forms a new
cavity. What is it called?
-Describe mesodermal appearance (three locations) and the structures it helps to form.
-What is a connecting stalk? What will it become?
-Another cell migration (same cells as last time) occurs. What will this give rise to?
Clinical Application: Hydatidiform mole
-What is a hydatidiform mole?
-Differentiate between complete and partial.
-What is the parental origin?
-How do the two embryos (complete and partial) differ?
-Define Persistent Trophoblastic Disease.
-What is an invasive mole? (aka metastatic choriocarcinoma)
-How is persistent trophoblastic disease detected?
-What is the normal function of the chemical used in detecting PTD?
Genomic Imprinting
-What is it?
-How is it carried out?
-What base is altered? What must it be following?
The Third Week (Gastrulation)
-The new disc will be what?
Primitive Streak
-What is it?
-What are its three components, and where do they form?
Formation of Definitive Germ Layers
-Which cells are migratory?
-What layer is formed first?
-How do they migrate (through which structure?)
-How is the next layer formed?
-What layer is renamed and what is it called once the other two layers are completely formed?
-What is the significance of the two “membranes” and what are their names? Which layer was not
formed in their emergence?
Midline Mesodermal Structures
-The notochord is formed from cells of what layer?
-What structure disappears as the notochord forms?
-What is the remnant of this structure, and what does it give rise to?
-What is a sacrococcygeal teratoma, and how does it form?
Lateral Mesoderm Structures
-Differentiation into three layers, which are what?
-Medial most layer segments into what?
-Describe the differentation between more “cranial” and “the rest”
-What do “the rest” develop into?
-Describe the somite differentation (levels).
-Middle layer (called?) gives rise to?
-Lateral layer (called?) splits into two layers. What are they?
-What is the gap between them called? What will it form?
-Which layer is dorsal, which is ventral?
-What does it give rise to?
-Specifically:
-splanchnopleuric?
-somatopleuric?
Abnormal Gastrulation: Clinical Applications
-What is caudal regression (syndrome)?
-Specifically, what is sirenomelia?
-How is body axis established?
-What is cell tracing used for?
-What is epigenic development?
The Fourth Week (Neurulation)
-What are the major components of the fourth week?
Neural Plate
-What germ layer is responsible?
-Where does it form?
-What are these cells called? The tissue?
Neural Tube
-What is the midline crease called?
-What are the areas lateral of the midline now called?
-Describe the formation of the tube.
-Is there directionality of the folding? How?
-The fluid in the neural tube is continuous with what fluid? How? When do these structures
close?
Neural Crest
-How does it form?
-What does it give rise to?
-What is Hirschsprung’s disease, and how does it involve the neural crest? What gene family is
thought to be responsible for this disease?
Somite Differentiation
-Develop a central mass called what?
-Rupture forms what? (central mass forms [?] and remaining somite forms [?]).
Sclerotome
-What will they form?
-What do the sclerotome cells surrounding the notochord form? The neural tube?
-How do spinal nerves arrive?
-How do they affect the surrounding sclerotome?
-What’s the axis?
-What’s the atlas?
-Between the vertebral bodies, the notochord forms what? The sclerotome?
-Each vertebra, depending on location, forms processes called?
-What are sternal bars?
Dermomyotome
-Splits to form?
-What do these structures form?
-The myotome splits to form what two structures? (which is dorsal, which ventral)
-What are their innervations?
-What do they give rise to?
Embryonic Folding
-What two axes does it occur on?
-Fusion of ectoderm, endoderm, and mesoderm occurs during folding on which axis?
-How does fusion occur (directionality)?
-Is fusion complete?
-What happens to intraembryonic coelom (which was formed by what?)?
-What was the intraembryonic coelom continuous with prior to folding?
-When does this continuity cease?
-What is the septum transversum, and how does its and the heart’s location change via folding?
-What happens to the chorion?
-What happens to the amnion?
Clinical Applications: Malformations of Neural Tube
-What is cranioachischisis totalis? Is it viable?
-What is Exencephaly/Anencephaly/Cranioorachischisis? Is it viable?
-What is rachischisis/myeloschisis? Is it viable?
-What is Inionschisis?
-What is Spina bifida occulta? Is it viable?
-What is a cele? How does it relate to spina bifida?
-Meningocele?
-Meningomyelocele? (spina bifida)
-Hydrocephaly?
-What is the role of folic acid?
-What is the role of valproic acid?
-Cranium bifida:
-Cranial menngocele
-Meningocephalocele
-Meningohydroencephalocele
Experimental Principles: Segmentation
-What family of genes controls segmentation?
-Where does expression of a certain gene begin?
-Where do they end, in general?
-Why are these genes called “caudalizing factors?”
Induction
-What is it?
Embryology: Fetal Diagnostics and Teratology
Fetal Diagnostics
-What is amniocentesis?
-What is the role of alpha-fetoprotein?
-What is chorionic villus sampling?
-What is a disadvantage of this technique?
-What is percutaneous umbilical cord sampling?
-What is an ultrasound?
-What is emitted onto the developing embryo?
Teratology
-What is it?
-What sorts of substances are classified as teratogens?
-Principles:
1. Susceptibility to the teratogen depends on an interaction between the teratogen
and the genotype of the individual.
2. Susceptibility of the developing organism to a teratogen is dependant on the
developmental stage of the organism at the time of exposure.
- critical or sensitive period (what weeks?)
3. The severity of the insult depends on the dose and duration of exposure of the
organism to the teratogen.
-A teratogen gets across the placenta uncharged, and under the higher pH loses
its proton and therefore cannot recross the placenta.
-Teratogens most effectively disrupt the development in a single, strong dose.
4. Teratogens produce their effects in very specific ways.
-Syndrome vs. Association
-What is meant by the term sequence?
5. The manifestations of abnormal development can be broadly categorized into
four groups: death, malformations, functional disorders, and growth
retardation.
-Intrauterine growth retardation (IUGR)