primary brain vesicles are already present fundamental regions of the heart have already formed
Prosencephalon most anterior brain region later divides into telencephalon (anterior) and diencephalon (posterior) both further divide into cerebral o hemispheres, thalamus, hypothalamus, and optic vesicles Prosocoel cavity of the prosencephalon will become ventricles I to III
Somites 11-12 pairs are present
Anterior Intestinal Intestinal Portal opening of the foregut as development progresses and the gut elongates, this opening will move to the posterior will also eventually be part of the yolk yolk stalk
Heart
single, tubular, S-shaped organ at right side of the body
Infundibulum ventral evagination on the floor of of the diencephalon forms the posterior lobe of pituitary gland
Mesencephalon midregion of the brain cavity: mesocoel fate of mesocoel is the aqueduct of Sylvius or o the cerebral aqueduct
Area vitellina vitellina same as 24-hour chick
Area opaca vasculosa Sinus terminalis vein that encircles the area vasculosa vasculosa o gives rise to terminal blood vessel of vitelline o circulation
o
Metencephalon anterior portion of hindbrain cavity: metacoel metacoel is part of the IV ventricle o
Myelencephalon posterior portion of hindbrain cavity: myelocoel myelocoel is part of the IV ventricle o
Spinal Cord neural tube posterior to the hindbrain cavity: central or spinal cord
Blood islands masses of splanchnic mesoderm o found in gut wall of amphibians and yolk sac o of amniotes form red blood cells and blood vessels o
Proamnion region that is anterior to the developing avian embryo surrounds the head contains endoderm and ectoderm will be invaded with mesoderm and become incorporated into the amnion
Subcephalic pocket cavity beneath the embryonic head as the head develops
Sinus Rhomboidalis rhomboid-shaped region located on the caudal part of the embryo this is the location of where the primitive pit and Hensen’s node are enclosed by unfused n eural folds
Notochord rod-like structure that is dorsal to the gut origin: mesoderm function: defines anterior/posterior axis and provides skeletal support for embryo
Nephrotome stalk-like connection between somites and lateral plate mesoderm forms the pronephros (anterior) and mesenchyme (posterior) mesenchyme will further differentiate into o mesonephros and metanephros
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Level of Optic Nerve Optic Vesicles lateral bulges of prosencephalon forerunners of the portions of the eyes will ind uce the head ectoderm to thicken, t hicken, invaginate, and form the lens vesicles cavity: opticoel
Proamnion region below the head fold consists of ectoderm underlain with a layer of endoderm will eventually be overgrown and disappear
Section through Oral Plate
Prosencephalon forebrain that consists of median vesicle and a lateral outpocket on each side cavity: prosocoel
Anterior neuropore neuropore median cleft at anterior tip of neural tube presence of this opening means the neural folds have not fused yet
Notochord ventral to mesencephalon mesoderm derived
Foregut smile-shaped cavity ventral to notochord walls are derived from endoderm middle portion of the foregut’s floor is slightly thickened
Lens Placode thickening of head ectoderm that surrounds the optic vessel forerunner of eye lenses
Infundibulum shallow depression of prosencephalic floor located at posterior border of optic vessels
Oral Plate thickened area formed by the ventral ectoderm and the adjacent endodermal evagination of pharynx ventral to the foregut will form the mouth when it perforates
Subcephalic Space below the head fold Extraembryonic Extraembryonic germ layers
Amniotic fold fold of somatopleure arise at the head region, the sides, and the caudal end fusion of amniotic folds will give rise to amnion (inner) and chorion (outer)
Mesencephalon oval-shaped brain vesicle posterior to prosencephalon
Yolk sac extra embryonic membrane encloses and absorbs yolk of amniote embryos endoderm + splanchnic mesoderm (splanchnopleure)
Anterior cardinal cardinal veins paired blood vessels at the lateral sides of the mesencephalon
Pharynx region of foregut at this level
Dorsal Aorta large, paired blood vessels dorsal to the pharynx
Other structures to be noted (description (description in 24-hour chick) Head ectoderm Mesenchyme Neural Crest Subcephalic pocket Area pellucida Coelom Area Vasculosa
Stomodeum shallow midventral depression in the ectoderm forerunner of buccal cavity
Ventra Aorta Aorta small paired blood vessels located below the pharynx one is at each side of a median depression in the floor of the foregut
First Aortic Arches connects the dorsal aorta with the ventral aorta can be seen at the anterolateral region of the foregut
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Neural Crest cells found at the edges of the neural plate and above the neural tube will form ganglia, pigment cells, and parts parts of the gills
Thyroid Gland endocrine gland that functions for control of metabolism and growth from ventral endoderm of pharynx seen as a thickened shallow depression of the foregut at the region of the dorsal mesocardium
Section at the level of the Heart: Posterior Sections Atrium
posterior level of the heart located now at the middle of the pericardial cavity becomes the future auricles
Sinus venosus caudal continuation of the atrium dorsoventrally flattened tube in the midline
Section at the level of the Heart: Anterior Section Ventral Aortae Aortae fusion of ventral aorta from earlier now a median, unpaired vessel
Bulbus arteriosus anterior chamber of heart embryo connects ventricle to the ventral aorta
Anterior Intestinal Intestinal Portal ventral opening of the gut into the yolk future midgut
Vitelline veins paired, large vessels that enter the atrium via sinus venosus at the caudal sections, these vessels will rise at the lateral part of the blastoderm
Epimyocardium outer, thicker layer of heart rudiment arises from splanchnic mesoderm fuses with the endocardium to form the heart’s wall will give rise to: epicardium (outer covering of the heart) and myocardium (cardiac musculature)
Anterior cardinal cardinal veins pair of small blood vessels above the dorsal aortae also lies adjacent to the rhombencephalon
Isthmus broad connection between heart and foregut synonymous to dorsal mesocardium
rhombencephalon by the time na mag-heart na
Section at the level of the Heart: Through the Ventricle Ventricle bends to one side of the coelom narrower dorsal mesocardium
Rhombencephalon posterior part of brain level of future ventricle possesses a thick wall
Auditory Pits Pits ectodermal thickenings at hindbrain level forerunners to the inner ears syn: auditory placodes
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Section through the Sinus Rhomboidalis Neural Tube neural groove has opened
Hensen’s node
large mass of compactly arranged cells displaces the notochordal tissue
Unsegmented mesoderm somites are not yet divided at this section Omphalomesenteric vein it is located far out in the splanchnopleure
Section through the Somites
Spinal Cord elongated with elliptical cavity
Notochord Somites Nephrotome
refer to the 24-hour chick description for these structures
Hypomere Dorsal Aortae pair of large vessels between the endoderm and the somites at more caudal sections, they continue laterally into the plexus of vessels -- emphalomesenteric arteries
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pictures are from: http://www.vcbio.science.ru.nl/images/embryology/c hicken-33hrs-dorsal-longitudinal-patten.gif http://nte-serveur.univlyon1.fr/nte/embryon/www.uoguelph.ca/zoology/devobio/33h rchck/33ckintr.htm https://embryology.med.unsw.edu.au/embryology/i mages/thumb/7/72/Patten028.jpg/600px-Patten028.jpg
