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IMF-085-02-0001-en	Why do all tissues of the embryo proper derive from epiblast?	Epiblast cells ingress through the primitive streak: the first displace hypoblast to form definitive endoderm, later ones spread as intraembryonic mesoderm, and those remaining at the surface become ectoderm.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0002-en	What cell-state change allows epiblast cells to pass inward at the primitive streak?	They loosen epithelial attachments and convert to a motile mesenchymal state, which lets them migrate between layers.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0003-en	Beyond marking the midline, what does the notochord do, and where does it persist in the adult?	It defines the primitive axis, patterns surrounding tissues and induces neural development; it degenerates within vertebral bodies but persists between them, mainly as nucleus pulposus.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0004-en	What is structurally special about the oropharyngeal and cloacal membranes, and what do they mark?	Ectoderm and endoderm are directly apposed there with no intervening mesoderm; they mark future openings of the oral cavity and of the terminal gut or urogenital pathways.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0005-en	How can persistence of primitive-streak cells cause a tumour containing several tissue types?	The streak cells are pluripotent, so if they persist they can form a sacrococcygeal teratoma with derivatives of multiple germ layers.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0006-en	What do liver and pancreas illustrate about germ-layer origins of mature organs?	Endoderm forms their parenchymal epithelium, while mesoderm supplies much of their connective tissue, vessels and muscle, so mature organs combine lineages.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0007-en	How does the notochord induce neural plate from overlying ectoderm?	Notochord and organiser signals inhibit pathways that would otherwise favour surface ectoderm, so the overlying ectoderm thickens into neural plate.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0008-en	Why does periconceptional folate reduce neural-tube defect risk, and why does it not prevent every case?	Folate supports one-carbon metabolism and nucleotide synthesis during rapid growth, but genetic susceptibility, maternal diabetes, medications, hyperthermia and other exposures also modify risk.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0009-en	How is the neural tube divided into sensory and motor regions?	Gradients including sonic hedgehog from notochord and floor plate pattern dorsal alar regions for sensory processing and ventral basal regions for motor function, separated by the sulcus limitans.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0010-en	Why can a single neural crest defect combine pigmentation, craniofacial, cardiac and intestinal abnormalities?	Neural crest cells migrate widely and generate melanocytes, craniofacial cartilage and bone, conotruncal cardiac septation and the enteric nervous system, so a migration or differentiation defect affects all of them.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0011-en	How does resegmentation of sclerotomes explain why spinal nerves exit between vertebrae?	Each vertebral body forms from the caudal half of one sclerotome joined to the cranial half of the next, so segmental nerves come to lie between vertebrae and myotomes bridge adjacent levels to move the column.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0012-en	What distinguishes somatopleure from splanchnopleure in composition and derivatives?	Somatopleure is somatic mesoderm plus ectoderm and forms body wall and limbs; splanchnopleure is splanchnic mesoderm plus endoderm and forms gut wall, visceral connective tissue and heart.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0013-en	Why can ciliary dysfunction combine laterality defects with respiratory disease?	Motile nodal cilia generate directional fluid flow that contributes to left-sided signalling at the primitive node, so the same ciliary defect can disturb left-right patterning and also cause respiratory disease.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending
IMF-085-02-0014-en	What drives embryonic folding in the fourth week, and how does cranial folding reposition the heart?	Rapid growth of neural tube and somites drives folding; cranial folding moves the cardiogenic region and septum transversum from a cranial position to the ventral thorax and upper abdomen, ventral to the foregut.	Integrated Medical Foundations; chapter 85, TTS module 2; https://theisegoria.github.io/medical-textbook/integrated-medical-foundations-expanded-english.md; module SHA256 at export: 1ed6e9281a72d468fff7a576dabf411ed0cf4a6f8d51c67fe9584a4a4b3f5993; editorial review pending	imf lang::en chapter::085 module::085-02 review::pending