VITELLOINTESTINAL DUCT /YOLK STALK OMPHALOMESENTERIC DUCT The endodermalconnection between the mid-gut and the yolk sac. During embryonic disc folding (humanweek 3) this structure is embroy Yolk sac initially a broad openconnection which is then restricted to a narrowtube and finally closed between the mid-gut and the yolk sac.
YOLK SAC ATTTACHED TO EMBROY THROUGH VITTELOINTESTINAL DUCT
The constituents of the vitelline duct vitelline veins ( Paired) (omphalomesenteric vein,The blood vessels which form in the yolk sac and have a blood flow towards the embryo. Derived from the extra-embryonic mesoderm surrounding the endoderm of the yolk sac. vitelline arteries ( Paired) . (omphalomesenteric artery The blood vessels which form in the yolk sac and have a blood flow away from embryo. Derived from the extraembryonic mesoderm surrounding the endoderm of the yolk sac. Vitellogenesis The term refers to the formation of yolk.
Doppler values of Vitelline artery Low velocity No diastolic flow PSV : 5.8 +_1.7cm/sec PI : 3.24 +_.94
Arachnoid cyst …..a brief Arachnoid cysts are benign intracranial non communicating collections in the arachnoid memberane. USUALLY STABLE CAN OCCUR INTRACRANIALLY OR IN SPINAL CANAL ALSO. EVEN IF LARGE ( RARELY CAUSE SYMPTOMS) MID LINE CYSTS MAY LEAD TO PITUITARY DYSFUNCTION. MAY INTERFERE WITH CSF CIRCULATION. COMMON LOCCATIONS ARE : 1. SYLVIAN FISSURE / TEMPORAL FOSSA 2. POSTERIOR FOSSA 3. ALONG CEREBERAL CONVEXITY 4. MIDLIINE ( SUPRASELLAR)
ARACHNOID CYST ………….FETAL MR IMAGECSF SIGNAL LARGECYSTIC LESION IN THELEFT TEMPORO-PARIETAL REGION( SYLVIAN FISSURECONFINES)/SUPRASELLAR / POSTERIORFOSSA REGION.( NEARLY OCCUPYING ALL THE COMMON SITES WHERE ARACHNOID CYST IS PRESENT )
Fetal MR and Multiplanar USG Reformation.FETAL MR SAGITTAL IMAGE USG SECTIONAL PLANE IMAGINGMASS EFFECT IS APPRECIATED ON OF LARGE INTRACRANIAL CYSTBRAIN STEM INDENTATED ALONGTHE VENTRAL SURFACE
DIFFERENTIAL DIAGNOSIS FOR ARACHNOID CYST DEPENDS ON POSITION MIDLINE Posterior fossa : Cavum veli interpositi Dandy walker Aneurysm of vein of galen malformation ( Midline cysts may Inferior vermian accompany corpus hypoplasia callosum dysgenesis Mega cisterna magna so in supratentorial cysts corpus callosum Blake’s pouch cysts should be assessed) .
ReferencesDiagnostic Ultrasound4th EditionCarol M. RumackStephanie R. WilsonJ. William CharboneauDeborah Levine