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inner cell mass (ICM), aka pluriblast, which gives rise to endoderm, ectoderm, and mesoderm
forms on Day 8 from inner cell mass; gives rise to extraembryonic endoderm (e.g. yolk sac); cuboidal cells
formed by end of Week 2 from hypoblast cells (ventral); vestigial in humans, though perhaps early nutritional value
embryonic development phase whereby bilaminar germ disc acquires a third germ layer. Sequence: (1) embryo becomes asymmetric, (2) primitive streak forms, (3) cells from epiblast at primitive streak undergo epithelial to mesenchymal transition
formed in Week 3, initial event of gastrulation; establishes bilateral symmetry in embryo
forms gut epithelial lining, cloaca (future urethra and bladder), respiratory tract, tympanic cavity, parenchyma of thyroid, parathyroids, liver, pancreas, and reticular stroma of tonsils and thymus
Mesothelium (peritoneal, pleural, pericardial)/ Muscle (striated, smooth, cardiac)
Spleen/ Soft tissue/ Serous linings/ Sarcoma/ Somite
Osseous tissue/ Outer layer of suprarenal gland (cortex)/ Ovaries
Dura/ Ducts of genitalia
Microglia/ Mesenchyme/ Male gonad
Thin membrane where ectoderm and endoderm come into direct contact; forms septum between primitive mouth and pharynx
Thin membrane where ectoderm and endoderm come into direct contact; forms anal-urogentical opening
condensation of mesoderm cells extending rostrally from the primitive node in the midline
originally exists at most anterior end of trilaminar germ disk, but will fold ventrally and develop into the heart
connecting stalk; helps embryo exchange gases and handle liquid waste; vestigial in humans (like yolk sac)
transforms embryo from three flat germ layers to cylinder with tube of endoderm (gut) in the center
cephalic and caudal ends of three-layered germ disc fold ventrally, most notably bringing heart region down to thoracic region
Week 4 process in which flat neural ectoderm rolls up to become neural tube; upon completion the brain and spinal cord have been formed
Neural crest cells
specialized cells that form skin pigment cells, ganglia of autonomic nervous system, dorsal root ganglia, facial cartilage, spiral septum of developing heart, ciliary body of the eye, and adrenal medulla
segmental units added on a cranial to caudal manner and are a good indicator of precise embryonic age
layer continuous with mesoderm covering the amnioin; forms parietal pleura and peritoneum
long, narrow tube that joins yolk sac to midgut lumen of developing fetus. Appears at end of fourth week and normally closes by week VI (VI telline)
anterior part of alimentary canal, from mouth to duodenum (esophagus, stomach, duodenum, liver, gallbladder, pancreas, spleen)
part of alimentary canal (forms intestines) between foregut (at opening of bile duct) and hindgut. Includes latter parts of duodenum, jejunum, ileum, cecum, appendix, ascending colon, hepatic flexure of colon, transverse colon (proximal 2/3)
posterior (caudal) part of alimentary canal; includes distal 1/3 of transverse colon, splenic flexure, descending colon, sigmoid colon and rectum
highly conserved DNA region that codes for homeodomain proteins that are crucial for embryonic development
Hox combinational code
phrase used to describe association between segmentation in developing embryo and unique combinations of overlapping Hox gene expression
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