48 hour chick Thicker than 33hr and more opaque Cranial half – covered with head fold of the amnion Meets the lateral amniotic body and forms Amniotic fold Caudal part – no such covering;Caudal fold establish caudal boundary Embryo is separated from blastoderm by Subcaudal pocket Beginning of fold – seen as concavity facing ant. End Cephalization – rapid growth at ant. Portion. Show: 1. Ventralflexion (bending) 2. Dextral torsion (twisting) 3. Cranial flexure @midbrain is pronounced 4. Cervical flexure Torsion involve all the head, both cranial & cervical flexure Heart – elongated and twisted upon itself Ventricle lie post to atrium, both lie outside the body Fetal membranes 1. Amnion – encircles the ant. Portion (inner ectoderm, outer somatic meso) 2. Yolk sac – double membrane structure lying on left side, has BV (endo & splanchnic meso) 3. Chorion – double layered membrane on right side (ecto & somatic meso) Branchial groove – 3 irregular white lines fr heart to auditory vesicle (A – P) – 1st branchial groove > 2nd > 3rd 1st visceral arch – mass of cell cranial to 1st branchial groove Splitted into by stomodeum 1. Maxillary process – ant. To stomodeum 2. Mandibular process – post. 2nd Visceral arch – bet. 1st and 2nd branchial groove 3rd Visceral arch – bet. 2nd and 3rd MESENCEPHALON - oval shaped & 1st cavity of brain to be observed - shows a frontal section due to cranial flexure Isthmus – constriction @ lengthened brain partially separate the mesen from hindbrain Myelencephalon – thin roof of brain @ opposite of mesen Metencephalon – underlined portion of brain bet. Myelen & isthmus Mesenchyme – loose CT bet. brain & epidermis Fetal membrane – extraembryonic Extraembryonic coelom – meso bonded space bet. chorion, yolk sac, amnion DIENCEPHALON - lower cavity when brain separate into 2 cavities - replaces the position occupied by mesen Ventral transversum – depression in the DW of forebrain demarcation bet. dien & telen Metencephalon – poorly defined & ant. Delimited by isthmus Myelencephalon – upper large cavity of two brain w/ thin roof will form Post. Choroid plexus Semilunar ganglion – ganglion of the trigeminal (V) cranial nerve dark accumulation of cells on each side close to myelen Jugular ganglion – ganglion of the X cranial nerve – mass of cell lateral to myelen & above the ant. Cardinal vein Ant. Cardinal Precardinal vein –space lined by thin wall; sides of mylen - post: breaks into long spaces toward dien - lies progressively more dorsal and lie on both ventrolateral side of myen Notochord – small elongated mass of vacuolated cells bet. myelen & dien - post: separate into 2 due to cranial flexure, then become 1 in ff section OTIC VESICLE/OTOCYST– paired vesicle on side of myelen - from invagination of ecto invagination on DW: forerunner of endolymphatic duct Ant. Cardinal vein – paired BV on ventrolateral side of otic vesicle Acoustico – facialis ganglion – ganglion VII & VIII cranial nerve – dark accumulation of cells (close/attached) to otic and ant. Cardinal vein - lateral to myelen Semilunar ganglion – ganglion of trigeminal V cranial nerve - root of ganglion : pink structure embedded in myelen & attached to gngl Superior Ganglion – ganglion of the glossopharyngeal (IX) nerve – accumulation of cells on sides of myelen - observed when otic vesicle is no longer present/ immediately post to it OPTIC CUP – double walled on sided of dien - from invagination of optic vesicle - thicker L: sensory retina, Othinner L: pigmented retina Presumptive retina – inner layer of cup Presumptive pigmented epithelium – outer layer - will become pigmented layer of retina Lens Vesicle – little sac like cavity w/in optic cup arise fr invagination of ectoderm Optic stalk – connects optic cup w/ dien Pharynx – triangular cavity w/c started as a hole below notochord 1st pharyngeal pouch / hyomandibular pouch – middle portion & arms of triangle; DL projects fr pharynx & - invaginate to form 1st branchial groove - 1st closing/branchial plate: double layer membrane formed Preoral gut – Anteriormost part of foregut; - small circle/ oval separated from pharynx by the oral plate extends forward as a fingerlike diverticulum ant. to future mouth Carotid loop – extension of the 1st aortic arches; elongated space medial to ant. Cardinal vein Int. carotid arteries – paired V extending fr carotid loop alongside forebrain & medial to optic cups Dorsal aorta – BV on side of notochord; above 1st pharyngeal pouch 1st aortic arch – BV beneath the 1st pharyngeal pouch post: becomes located w/in mandibular process paired arches become continuous w/ventral aorta Visceral arches – bet. 2 pharyngeal pouched. Lateral walls thick w/ mesenchyme Mandibular arch/ 1st Visceral arch –more ant. Of the 2 rounded mesenchymal masses bet. the stomodeum. form jaws; bears the 1st aortic arch Maxillary arch –other rounded/ flattened mass on side of Rathkes pocket Rathke’s pocket – small vesicle bet. infundibulum & pharynx dorsal evagination of stomodeum; form: hypophysis Oral plate – thin line (ecto & endo) separating stomodeum & pharynx Infundibulum – evagination from dien extending in direction of foregut evaginate to form post/neural lobe of hypophysis Diencephalon – more elongated shape in this section Stomodeum – slit like space where Rathke’s pocket opens THYROID RUDIMENT & 2nd AORTIC ARCH Thyroid rudiment - depression in the floor of pharynx 2nd Aortic arch – BV that lie beneath the 2nd pharyngeal pouches. Contained w/in 2nd visceral arches/ hyoid arches extend downward fr dorsal A; ventral end continuous w ventral A 2nd pharyngeal pouch – 2nd outpocketing of pharynx - observed when post. section otic vesicle/ no longer present Ventral Aorta/ aortic sac – BV beneath pharynx. Starts at the base where aortic arches meet Ventral end of 2nd & 3rd aortic arch is continuous w/ this * if ventral aorta is traced post. – appearance of 2 layers of wall indicates beginning of bulbus cordis 3rd AORTIC ARCH – beneath 3rd pharyngeal pouch but not so dev. Downward extension from dorsal aorta 3rd pharyngeal pouch – lateral outpocketing of pharynx Together w/ pharynx gives a lateral oriented oval cavity 3rd Visceral arch – bet. 2nd and 3rd pouches Arches post. To hyoid arch – branchial arches (bear gills) Bulbus cordis – 1st heart cavity; presence of endocardium & myocardium Dorsal mesocardium – mesodermal stalk that attaches the stalk to DW Nasal placode –thickened skin ectoderm; lateral to telen 1st somite – compact cell mass lying lateral to myelen Dermatome – plate of dark stained cell; below ecto o Will become dermis of the skin Myotome – plate of light stained cell; medial to dermatome o Become future muscle Ant. Cardinal vein – progressive ventrally. separates into 2 vessel @ level of foregut. 1. Postcardinal vein – dorsally located 2. Common cardinal vein – ventrally located ATRIUM & VENTRICLE Spinal cord – CNS in this section; replaces myelen Descending aorta – fused dorsal aorta Dorsal intersegmented arteries – small BV arising from intervals of dorsal aorta and extending dorsally bet. spinal cord & somite Conus Arteriosus – chamber of the heart @ right side. Endo & myocardium are largely separated Atrium – chamber of the heart @left side; endo & myo are close forerunner of future auricles Ventricle – large looped chamber; connect conus and atrium Laryngotracheal groove – deep V-shaped depression on floor of foregut develops the larynx, trachea, lung buds Future esophagus – dorsal position of gut; will differentiate from part of foregut dorsal to laryngotracheal groove Cardinal vein – paired precardinals progressively located ventrally. SINUS VENOSUS – portion of heart attached to foregut by D mesocardium Common cardinal vein/ duct of Culvier – BV to w/c sinus is attached Pleuropericardial membranes – mesenchyme enclosing the common cardinal vein w/c separated the pleural cavities from pericardial region Lung buds – slight evagination on the VL portion of the foregut into pleural cavity Pleural cavity – paired portions of coelom L to dev. Lung & continuous w/ pericardial Transverse septum – mesenchyme surrounding Sinus from where the Dmesocardium connects the heart to DW; connected w/ pleuropericardial membrane Cranial liver diverticulum/ Dorsal diverticulum – small mass of cells on the dorsal side of sinus lying in the transverse septum, ventral to the foregut - liver arises as a diverticulum from wall of foregut Caudal liver rudiment/ Ventral diverticulum – branch on ventral side of CLD connected to the gut Duodenum – when CLD becomes continuous w/ the foregut ANTERIOR INTESTINAL PORTAL- opening of foregut to midgut (floor=yolk) Vitelline veins/ Omphalomesentric – pair of BV, w/c are post extension of sinus - lie on side of ant. Intestinal portal; pass onto the yolk Peritoneal cavity – big space where organs are Paired mesonephric duct – small tubule L to descending aorta Medial: mesonephric tubule rudiments w/c will undergo cavitation to form mesonephric tubules of paired mesonephric kidney (formed by delimitation of nephrogenic cord / nephrotome) LATERAL AMNIOTIC FOLDS – elevated & about to fuse. Continuous w/ lateral body walls and consists somatopleure (form amnion and chorion) Vitelline blood vessels – small BV embedded w/in splanchnic meso Paired dorsal aortae – big paired BV below notochord Mesonephric tubule rudiments - round cavity medial to mesonephric duct Nephrostome – opening of the mesonephric tubule to the coelom Vitelline arteries – dorsal aorta when it extends onto the yolk as this TAIL BUD – mass of mesenchymal cells @ caudal; covered by skin ecto Hind gut – post. portion of the gut when it acquires floor Allantoic rudiment – endoderm lined cavity below tail bud Caudal intestinal portal – space where the floor of allantoic disappears Opening of the hind gut to yolk
