rev m2-gastrulacao e neurulacao.pdf

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Neurulação

Tubo neural

Notocord

a

Ectoderma



Figure 4-11 Three newborns with myelomenigoceles. A, B, The myelomenigoceles extend from the thoracic to lumbosacral level. Note the location of the split vertebralelements to the left of the lesion in B. C, The myelomenigocele is localized to the lumbosacral level. In B and C, the infant's diapers (bottom of each illustration) are

shown for orientation.

Downloaded from: StudentConsult (on 26 July 2011 07:45 PM)

© 2005 Elsevier



Figure 4-8 Lumbosacral spina bifida occulta in a newborn with associated lipoma and angioma.


© 2005 Elsevier



Figure 4-9 A, Newborn with a large encephalocele. B, Corresponding magnetic resonance imaging (MRI) showing brain tissue herniating through the back of the skullinto a cele.


© 2005 Elsevier



Gastrulação

•Processo formativo pelo qual as três camadasgerminativas que são precursoras de todos ostecidos embrionário, e a orientação axial são

estabelecidos•Disco embrionário bilaminar → trilaminar • As células do epiblasto dão origem a todas as trêscamadas germinativas.

•Embrião = gástrula



Figure 3-1 View of dorsal surface of bilaminar embryonic disc through sectioned amnion and yolk sac. Inset at upper left shows relation of the embryo to the wall of thechorionic cavity. The primitive streak, now 1 day old, occupies 50% of the length of the embryonic disc. The future positions of oropharyngeal and cloacal membranes are

indicated.


© 2005 Elsevier



Formação do mesoderma intra-embrionário – 3ª semana



Figure 3-7 Paths of migration of mesoderm during gastrulation. Cells of the primitive node migrate cranially in the midline to form the notochordal process (not shown,occurs later). Cells that ingress more caudally through the primitive streak migrate to form the mesoderm lying on either side of the midline. The most cranially migratingof these cells form the cardiogenic mesoderm, which moves cranial to the future position of the oropharyngeal membrane (oval structures). The more laterally migrating

of these cells form the paraxial, intermediate, and lateral plate mesoderm.


© 2005 Elsevier



Figure 3-6 Embryonic discs sectioned through the region of primitive streak, showing ingression of epiblast cells during gastrulation. A, On days 14 and 15, ingressingepiblast cells displace hypoblast and form definitive endoderm. B, Epiblast that ingresses on day 16 migrates between endoderm and epiblast layers to form

intraembryonic mesoderm. C, Scanning electron micrograph of a cross section through the chick primitive streak.


© 2005 Elsevier



Figure 3-11 Formation of the notochordal process. A, C, Stages showing hollow notochordal process growing cranially from the primitive node. Note changes in relativelength of the notochordal process and primitive streak as the embryo grows. Also note fusion of ectoderm and endoderm in the oropharyngeal and cloacal membranes.

B, Cross section of the embryonic disc at the level indicated by the dotted lines.


© 2005 Elsevier



Figure 3-10 Prospective fate maps of the epiblast (based on data obtained from both chick and mouse embryos), showing the regions of epiblast that ingress through theprimitive streak and form the major subdivisions of the trilaminar embryonic disc. A, Early primitive streak stage showing locations of prospective gut endoderm (GE) in

epiblast and prospective prechordal plate (PP) in the cranial end of the primitive streak (PS; dark outline in subsequent figures). Oval at the cranial end of the epiblast (inall figures) indicates the location of the future oropharyngeal membrane; caudal oval indicates future clavical membrane. B, Early primitive streak stage showing locations

of prospective cardiogenic mesoderm (CM) and prospective extraembryonic mesoderm (PEEM) in epiblast and primitive streak. Arrows indicate the directions ofmigration of the cardiogenic mesoderm. C, Midprimitive streak stage showing locations of prospective mesoderm in epiblast and primitive streak. These include

prospective notochord (N), head mesoderm (HM), somites (S), intermediate mesoderm (IM), and lateral plate mesoderm (LPM). D, Fully elongated primi tive streak stageshowing locations of the neural plate (NP), surface ectoderm (SE), neural crest cells (NC), and placodal ectoderm (PE) after cells in the cranial half of the embryonic disc

have completed their ingression into the primitive streak. Some epiblast still remains caudally at this stage, where cells are still moving into and ingressing through theprimitive streak.Downloaded from: StudentConsult (on 26 July 2011 07:45 PM)

© 2005 Elsevier



Figure 3-9 Diagrammatic cross-sectional views showing that the medial-lateral axis of the mesodermal subdivisions (N, notochord; S, somite; I, intermediate mesoderm)of a flat embryo like that of the early human (embryonic disc) is equivalent to the dorsal-ventral axis of the same mesodermal subdivisions in tubular amphibian embryos.

NT, neural tube; E, endoderm.


© 2005 Elsevier



Formação do Embrião Tridérmico – 3ª semana



Figure 3-20 Schematic sequence showing growth of the neural plate and regression of the primitive streak between day 18 and day 20. The primitive streak shortens onlyslightly, but it occupies a progressively smaller proportion of the length of the embryonic disc as the neural plate and embryonic disc grow.


© 2005 Elsevier



NEURULAÇÃO

• Placa neural: espessamento na linha média doectoderma embrionário, em posição cefálica ao

nó primitivo (acima da notocorda).• Placa neural é induzida a formar-se pelodesenvolvimento da notocorda e domesênquima que lhe é adjacente

• Um sulco neural, longitudinal, forma-se na placaneural .



NEURULAÇÃO

• O sulco neural é flanqueado pelas pregasneurais, que se juntam e se fundem paraoriginarem o tubo neural. O desenvolvimento daplaca neural e o seu dobramento para formar otubo neural é chamado neurulação.

• O tubo neural é o primórdio do sistema nervosocentral.



22

NEURULAÇÃO



23

O Sistema Nervoso



24



25



26



28



gene expression

(chordin, noggin,follistatin)

Neuroectoderm

formation

BLOCKADE OFBMP SIGNALLING



Figure 4-4 Neurulation. A, Drawings of human embryos from day 21 through days 24 to 25 (top to bottom, respectively). The lateral edges of the neural folds first begin tofuse in the occipitocervical region on day 22, leaving the cranial and caudal neuropores open at each end. The neural tube lengthens as it zips up both cranially andcaudally, and the neuropores become progressively smaller. The cranial neuropore closes on day 24, and the caudal neuropore closes on day 26. B, Photographs of

human embryos from the dorsal (top) or lateral (bottom) side and comparable computer-generated images. C, Scanning electron micrograph of a mouse embryocomparable to a day 21 or day 22 human embryo. The cranial and caudal neuropores are both open.


© 2005 Elsevier



Figure 3-14 Scanning electron micrograph of the trunk region of a chick embryo with the surface ectoderm partially removed to show the underlying neural tube andmesoderm (cranial is toward the top). Note the somites and, more caudally, the paraxial mesoderm that has not yet segmented. Lateral to the somites the mesoderm has

subdivided into the intermediate and lateral plate mesoderm (somatic mesoderm, the layer just deep to the surface ectoderm, is visible).


© 2005 Elsevier



Superfície escamosa dascéls. ectodérmicas e as

células colunares do tubo

neural

Estomodeu (cavidade oralprimitiva), Coração, porçãointestinal anterior , porção

intestinal posterior



FORMAÇÃO DA CRISTA NEURAL

• Com a fusão das pregas neurais paraformar o tubo neural, célulasneuroectodérmicas migram

dorsolateralmente para constituírem acrista neural, entre o ectodermasuperficial e o tubo neural .

• A crista neural logo se divide em duasmassas que dão origem ao sistema

nervoso periférico.



Figure 4-20 Neural crest cells form two types of segmental ganglia along almost the entire length of the spinal cord: dorsal root ganglia and chain ganglia.


© 2005 Elsevier



Intestino anterior Intestino posterior



Derivados das CamadasGerminativas

• ECTODERMA: SNC, SNP, epitélios sensoriais,osolhos, orelha e nariz; epiderme e anexos; glândulasmamárias, hipófise, glândulas subcutâneas e esmaltedos dentes• CRISTA NEURAL: células dos gânglios espinais, docrânio e gânglios autônomos; células d abainha doSNP; células pigmentares da epiderme, medula da

supra-renal e meninges

C



Derivados das CamadasGerminativas

• MESODERMA: conjuntivo, cartilagem, osso,músculos estriados e lisos, coração, vasossanguíneos e linfáticos, rins, ovários, testículos,ductos genitais, membranas serosas que revestemcavidade do corpo, baço, córtex das supra-renais• ENDODERMA: revestimento epitelial dos tratosgastrointestinal e respiratório, parênquima das

tonsilas, da tireóide e paratireóides, do timo, do fígadoe do pâncreas, revestimento epitelial da bexiga emaior parte da uretra e revestimento epitelial dacavidade timpânica, antro do tímpano e tuba auditiva

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