Lecture 10: Objective 1 Flashcards

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1
Q

Step 1 in notochord formation: role of primitive node

A

primitive node provides cells that will form notochord

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2
Q

Step 2 in notochord formation: migration

A

cellular precursors migrate anteriorly

left behind as rodlike aggregation structure when primitive groove recedes

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3
Q

Step 3 in notochord: fusion

A

notochord cells fuse with flanking endodermal cells forming temporary neurenteric canal

neurenteric canal is just a small area connecting aminotic sac with yolk sac,

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4
Q

Step 4 in notochord: Separation

A

notochordal cells separate from endoderm to form definite notochord

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5
Q

Oropharyngeal membrane

A

superior to notochord, area is missing mesoderm and only consists of “abutting” ectoderm and endoderm

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6
Q

Prechordal plate

A

Referred to as head organizer

releases sonic hedgehog (involved in ventral patterning of forebrain)

source of “survival signals” for neural crest cell migration into early forebrain

first cells to pass through primitive node, superior to notochord, small clench of mesoderm unattached to notochord

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7
Q

Inductive functions of notochord

A

important in formation of axial structures: uses Shh (sonic hedgehog) (signaling molecules)

induces overlying embryonic ectoderm to form neural ectoderm

foxa-s and goosecoid (transcription factors) induce noggin and chordin, neural inducers

specifies identity of certain cells within early nervous system

transforms certain mesodermal cells of the somites into vertebral bodies

stimulates earliest steps in the development of the pancreas

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8
Q

Foxa-2+Goosecoid

A

transcription factors which cause notochord cells to produce noggin and chordin

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9
Q

noggin and chordin

A

potent neural inducers

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