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66 Cards in this Set
- Front
- Back
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Series of events leading to the development of the notochord |
1. Convergent extension of chordomesoderm 2. Reorganization of cells 3. sheath formation 4. Directed dilation |
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Reorganization of cells in notochord development |
cells become shaped like pie wedges cells take on the appearance of a stack of coins |
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Sheath formation in notochord develpment |
stack of cells becomes surrounded by a dense ECM of collages, which is then surrounded by a loose layer of connective tissue |
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Directed dilation in notochord development |
Vacoule formation inside cells Contain large amounts of GAGs (glucosaminoglycans) Influx of water = hydrostatic pressure Cannot expand in circumference because of strong sheath; must expand logitudinally |
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Methods of neurulation |
Primary neurulation- CNS / neural tube from epithelium Secondary neurulation- neural tube from mesenchyme |
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Steps of primary neurulation |
1. columnization of neural ectoderm (= neural plate) 2. Bending of neural plate 3. Convergence of folds neural tube and neural crest cells are pushed under epidermis |
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Bending of neural plate during neurulation |
1. furrowing of notoplate- apical constriction 2. folding of lateral neural plate margins epidermal ectoderm undergoes epiboly (stretching, flattening of cell layer) leads to a basal extension of neural plate cells |
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neurulation variation in teleost fish |
neural keel formation instead of primary neurulation no folding neural plate buckles down, forming neural keel lumen eventually forms |
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neurulation variation in cephalochordates |
medullary plate forms |
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Secondary neurulation |
CNS from mesenchyme Occurs with tailbud formation |
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what is the chordoneural hinge |
continuous connection between chordomesoderm & neural tube (notoplate) remnant of the organizer: produces tailbud proliferation produces the medullary cord (the mesenchyme of the tailbud) forms neural tube, notochord, and somites |
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secondary neurulation: condensation of mesenchyme vs. epithelialization vs. cavitation |
Condensation of mesenchyme: mesenchyme cells want to get to one space increases local density Epithelialization: mesenchyme to epithelial transition (MET) cavitation: formation of a lumen |
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When do humans gain and lose a tail |
develop "caudal prominence" at ~28 days usually regresses by ~56 days |
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neuropores |
present inhuman neurula during neurulation located at both anterior and posterior ends form because the neural folding initiated at mid/hindbrain and continues in both directions failure of neuropores to close causes neural tube defects |
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mild spina bifida |
failure of posterior neuropore to close skin covers neuropore can cause vertebral bone abnormalities -mild skeletal defects -hair tuft |
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severe spina bifida |
failure of posterior neuropore to close myelomenengocele no covering tissue skeletal sefects herniationof CNS (exposed to outside) can be partially fixed surgically, however: -paralysis -decreased life expectency |
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rachischisis |
failure of anterior neuropore to close no covering tissues exposed CNS exhibit anencephaly/microcephaly |
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anencepholy |
aka microcephaly failure of anterior neuropore to close small/no head |
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iniencephaly |
failure of anterior neuropore to close retroflexion of the head head flexes back no neck |
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induction of neurulation |
1. notochord to notoplate induction- establishes floorplate 2. floorplate becomes inductive and notochord maintains inductions- establishes polarity |
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Brain compartmentalization (primary and secondary vesicles) |
prosencephalon (6 prosomeres)- telencephalon (5&6), diencephalon (1-4) (optic vesicle between p3 & p4) mesencephalon (next to 1st prosomere and rhombomere) rhambencephalon (8 rhombomeres)- metencephalon (1&2), myelencephalon (3-8) (otic vesicle between r5 &r6) |
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brain luminal compartments |
telecoel diocoel mesocoel (w/cranial flexure) metacoel myelocoel (w/pontine flexure & cervical flexure) spinal cord produce ventricles later |
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Brain compartmentalization (secondary vesicles and ventricles) |
telocoel- ventricle I, II, & III diocoel- ventricle III mesocoel-aqueduct metacoel & myelocoel- ventricle IV |
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steps of ventricle formation |
1. lumen inflation 2. ventricular expansion- choroid plexus |
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cerebrospinal fluid (CSF) |
surrounds CNS/brain cusions brain and provides nutrients |
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choroid plexus |
comosed of pia mater & vasculature produces cerebrospinal fluid located in all 4 ventricles (small) |
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circulation of CSF |
2 paths: spinal cord foramina (surrounding CNS) circulates posteriorly reenters circulatory system via arachnoid villi |
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Defects of flow of CSF |
Cause increased pressure in ventricles- hydrocephalus 1. decreased reabsorption of CSF into blood 2. tumors in choroid plexus 3. stenosis-narrowing at aqueduct |
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mechanisms of brain elaboration |
Early mechanisms: -lumen inflation- Na/K pumps pump ions into lumen, increasing hydroststic pressure - proliferation domains Later mecanisms (associated w/cardiovascular function): -ventricular expansion- choroid plexus |
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Hazel Sive |
studiedtraced lumen development in zebrafish marked developing lumen with fluorescent tracer |
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hydrocephalus |
enlarged head caused by abnormally increased pressure of CSF pressure causes enlarged brain can lead to brain damage treated with ventriculoperitoneal shunt |
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Somitogenesis |
occurs anteriorly to posteriorly along spinal cord (pattern is autonomous) somitomeres 8 and beyond form somites somite precursor tissue is paraxial/somitic mesoderm (segmental plate)- a mesenchyme |
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Tissues somitomeres contribute to |
migrate throughout head to form: head mesenchyme extrinsic eye muscles migrate to pharyngeal arches & eventually form neck & face muscles & posterior cranial bones |
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Tissues somites contribute to |
trunk muscle & bone |
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mechanisms of somite formation |
1. condensation 2. epithelialization -mesenchyme to epithelial transition (MET) -spherical epithelium (surrounded by basal lamina) w/somitocoel ----somitocoel is a space in the center of the epithelium containing mesenchyme |
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Further somite differentiation |
sclerotome (1/2 of epithelial cells + somitocoel) -trunkbone dermomyotome: dermotome- dermis myotome- muscle |
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neural crest |
vertebrate-specific tssue ectomesenchyme -mesenchyme derivative of ectoderm (usually ectoderm dericatives are epithelium) -ectoderm that behaves like mesenchyme |
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neural crest derivatives |
peripheral nervous system cartilage, bone, dermis, blood vessels- typically associated with the mesoderm |
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methods to trace neural crest migration |
1. antibodies against neural crest 2. label individual neural crest cells -fluorescent tags 3. quail-chick chimeras |
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quail-chick chimeras |
transplant donate quail neural crest to chick embryos when in a similar stage of development later section & stain w/Feulgen stain -can distinguish chick & quail cells |
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neural crest migratory pathways |
cranial neural crest circumpharyngeal neural crest -cardiac stream -vagal enteric stream trunk neural crest -dorsolateral -ventral sacral enteric |
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cranial neural crest |
frontonasal process & pharyngeal arches contribute to: head skeleton (face & jaw) head PNS pigment |
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circumpharyngeal neural crest |
cardiac stream: minor incorporations in the heart & aorta contribute to endocrine organs (thmus, thyroid, parathyroids, pineal) vagal-enteric stream: enteric system of the GI tract enteric nervous system |
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trunk neural crest |
dorsolateral stream: associates w/dermis and epidermis- pigment cells ventral stream: dorsal root ganglia additional PNS adrenal medulla |
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sacral enteric neural crest |
posterior portion of enteric nervous system |
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dorsolateral stream of trunk neural crest |
cells migrate into anterior somite contribute to dorsal root ganglia contribute to a piece of the adrenal gland- adrenal medulla chromaffin cells: epinephrine-producing |
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plasticity of neural crest cells |
pluripotent stem cell ->multipotent progenitors ->bipotent/unipotent precursors |
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teleost embryogenesis (zebrafish model) |
produce telolecithal eggs meriblastic cleavage to form a discoblastula external fertilization transparent embryos |
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discoblastula |
blastoderm (& yolk) -deep cells- the embryo -enveloping layer- extra-embryonic, produces periderm -nuclei of yolk syncytial layer (YSL)- donated by marginal cells, extra-embryonic marginal cells- outside layer, retain cytoplasmic bridges inner cells- complete cells (no bridges, complete membrane) |
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zebrafish gastrulation (importance of germ band) |
essentially an amphibian embryo on a huge mass of yolk- very similar gastrulation 1. epiboly- spreading of blastoderm over yolk -YSL directs epiboly via migration to the vegetal pole 2. involution of the deep cells (at germ ring)- fold underneath themseves -happens concurrently throughout embyo 3. convergent extension- extension of deep cells towards animal pole -creates embryonic shield |
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embryonic shield |
created during gastrulation by the involution and convergence (toward the animal pole) of the deep cells organizer for a teleost |
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zebrafish beginning organogenesis |
segmentation phase: near-synchrony of neurulation and somitogenesis (also notochord and tailbud formation) forms pharyngula (embryo)- pectoral fins, pharyngeal arches, head elevation, heartbeat, fertilization envelope (still in tact) |
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amniotes |
development in a terrestrial environment took water with them- amnion allows for this to happen |
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ovipary |
amniotes with eggs enclosing the embryo avians, most reptiles, few mammals |
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vivipary |
amniotes exhibit gestation of embryo in maternal environment most mammals, few reptiles |
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avian egg general structure |
egg white (ECM, albumen) shell w/ shell membranes telolecithal egg: blastoderm (embryo) + yolk yolk blancher vitelline membrane air sac |
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avian fertilization |
internal sperm cannot penetrate egg female stores sperm |
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egg passing through urethra |
infundibulum- fertilization magnum- albumen isthmus- shell membranes shell gland cloaca |
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egg extra-embryonic membranes |
amnion yolk sac allantois chorion chorioallantoic membrane |
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avian cleavage & gastrulation |
area opaca undergoes epiboly to undertake yolk 1. cleavage furrows create subgerminal space 2. delamination creates hypoblast and epiblast (Kohller's sickle) 2.5. endoderm displaces hypoblast, creates new layer (mesoderm) 3. formation of primitive streak via Polonaise movement of the mesoderm & ingression of the endoderm from the epiblast to the hypoblast 4. regression of Henson's node / primitive streak (forms notochord, etc. in its wake) 3.primitive streak formation by ingression and convergent extension (mostly mesoderm, some ectoderm?) |
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epiblast |
neural ectoderm- migrates anteriorly mesoderm- Polonaise movement (posterior migration outside, anterior inside) (forms primitive streak - axial mesoderm -paraxial mesoderm -intermediate mesoderm -lateral plate mesoderm |
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primitive streak |
cells from Kohller's sickle (aka axial mesoderm) for Henson's node & rimitive know w/primitive pit) Speman-Mangold embryonic shield- organizer |
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chick flexures |
cranial pontine cervical dorsal caudal |
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human fertilization, implantation, and cleavage |
fertilization in uterine tube blastocyst after 4 days implantation after 6 days (hatches from zona pellucida first) |
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human blastocyst |
rotational cleavage 2-cell stage: polar body associated with the A-P axis morula- 16-cell stage (close association of blastomeres, tight junctions) blastocyst- zona pellucida (surrounds whole thing) inner cell mass trophoblast (extra-embryonic, around inner cell mass & blastocoele) blastocoele (formed by cavitation of inner cell mass) embryonic & abembryonic poles |
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inside-out hypothesis |
fate of cell is determined by its location within morula zona pellucida may be the source for inductions |
