Laboratory Activity 6 - Organogenesis of the Chick PDF

Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Outline Chick Shits 24...

Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Outline Chick Shits 24 HOUR CHICK EMBRYO (WHOLE MOUNT) Area Opaca - peripheral region of chick blastodisc surrounding Area Pellucida and direct contact with the yolk 3 zones: 1. Peripheral zone, margin of growth, where the cells proliferated over the yolk without being adherent to it. 2. Zone junction, intermediate region where cells separate from the yolk and belongings to A.P. 3. Inner zone, the germ wall, from the zone junction that is why there is the presence of yolk granules. Mark the transition of A.O. and A.P. and develop into 2 regions. ➔ Area Opaca Vasculosa - inner region, thickening of the splanchnic mesoderm forming blood vessels ➔ Area Opaca Vitellina - outer region, no blood islands/vessels Area Pellucida - central region of the blastodisc where primitive streak forms. Lies directly over the subgerminal cavity. - Outer layer: Epiblast (later becomes the ectoderm and mesoderm) - Inner layer: Hypoblast Primitive Streak - longitudinal cleft formed by the convergence of cells. Gastrulation begins as the epiblast cells migrate towards and into the streak. - Primitive Groove: central furrow Page 1 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer - Primitive Ridges: margins on both - Anterior Border of the Mesoderm: sides of the streak faint line extending across the A.P. at - Primitive Pit: indented region of the the level of the anterior end of the blastoderm at the anterior end of the notochord P.S. - The Thickened Splanchnic - Hensen’s Node/Primitive Knot: Mesoderm: darker line of each of the thickened area at the anterior end of lateral borders of the A.I.P. formed the P.S. which the cells forms the by the delamination of the lateral notochord (aka dorsal lip of the plate mesoderm. Later forms the blastopore of the amphibian) heart, part of the circulatory system, Proamnion - region anterior of embryo. and many other structures. Contains only endoderm and ectoderm. Somites - apparent division of the dorsal Later invaded with mesoderm and mesoderm into 3-4 pairs of somites can be incorporated into the amnion seen lying immediately lateral to the neural Neural Folds - margins of the neural plate folds that are about to fuse at the mid dorsal Unsegmented Mesoderm - undivided region region of the embryo. of the mesoderm posterior to the somites Neural Groove - median longitudinal groped which is formed by the rolling up of the 24 HOUR CHICK EMBRYO (TRANSVERSE neural plate SECTION) Head Fold - folded region of the blastoderm, SECTION THROUGH THE PHARYNGEAL MEMBRANE dark crescentic line and boundary of the Head Ectoderm - layer of cuboidal cells head of the embryo enclosing the head Notochord - longitudinal band of cells Neural Folds - margins of the neural extending caudal from the region of the epithelium neural folds to the primitive knot Neural Groove Foregut - first part of the digestive tract, Prechordal Plate - mass of dome shaped, and with a flooring chordamesodermal cells anterior to the composed of endodermal cells notochord and forms the head mesenchyme Anterior Intestinal Portal - opening of the Notochord - small medial mass of cells foregut and appears like a prominent arched between the foregut and the neural plate line beneath the neural folds. As Foregut - dorsoventral flattened tube and development progresses and gut elongates, endodermal cells make up the wall. Beneath this moves posteriorly and becomes part of the neural plate the yolk stalk Oral Plate/Oropharyngeal Membrane - Mesenchyme of the Head - loose network region where the floor of the foregut is in of cells that occupies beneath the foregut contact with the neural ectoderm of the and ectoderm of the head head. Will later break open and forms the Mesoderm: mouth Mesenchyme Page 2 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Proamnion composed the somatopleure, forms the Subcephalic Pocket - cavity formed beneath amnion. the embryonic head as head fold develops Midgut - floorless region of the gut posterior Somatopleure - membrane composed of to the A.I.P. ectoderm and somatic mesoderm and will form part of the body wall as well as the 24 HOUR CHICK EMBRYO (TRANSVERSE chorion and amnion SECTION) Splanchnopleure - cellular layer consisting SECTION THROUGH THE SOMITE of the splanchnic mesoderm and endoderm Somites - segmented blocks located on and will later form part of the body wall, yolk either side of the developing spinal cord sac, and allantois which arises from the dorsal mesoderm Coelom - body cavity formed when the Nephrotome/Intermediate somatic mesoderm and the mesoderm Mesoderm/Mesomere/Nephromere - separates from one another stalk-like connection between the somites Subgerminal Cavity - space beneath the and lateral plate mesoderm which anteriorly hypoblast within the A.P. and will give rise to forms the pronephros and posteriorly forms the midgut. mesenchyme and later develops into the mesonephros and metanephros. 24 HOUR CHICK EMBRYO (TRANSVERSE SECTION) SECTION THROUGH THE ANTERIOR INTESTINAL PORTAL 24 HOUR CHICK EMBRYO (TRANSVERSE SECTION) Neural Tube - a tube of tissue formed by the SECTION THROUGH THE PRIMITIVE STREAK thickening and rolling up of the N.P. during Primitive Streak neurulation and will later form the brain and - Hensen’s Node spinal cord - Primitive Pit Neural Crest - group of cells at the edges of - Primitive Groove the neural plate and lying above embryo - Primitive Ridges forming the ganglia, migrate throughout the embryo forming the ganglia, pigmented cells, parts of the gill arches, etc. 33 HOUR CHICK EMBRYO (WHOLE MOUNT) Head Fold - marked by the downward bend of the membranes around the head region of the developing embryo Anterior Intestinal Portal Amnio-Cardiac Vesicle - region of coelom that gives rise to the amnion and heart. Thickened splanchnic mesoderm making up the proximal wall of the semi-cardiac vesicle is the forerunner of the heart. Meanwhile, the dorsal wall of this vesicle, which Page 3 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Prosencephalon/Forebrain - later divides into the telencephalon and diencephalon and differentiates into the cerebral hemisphere, thalamus, and optic vesicles Optic Vesicles - paired lateral evaginations with an opticoel Infundibulum - ventral evagination of the floor of the diencephalon and later forms the posterior lobe of the pituitary gland Prosocoel - cavity of the prosencephalon and gives rise to the ventricles I to III Mesencephalon/Midbrain - mid region with a cavity mesocoel, forerunner of the aqueduct of Sylvius or cerebral aqueduct Page 4 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Rhombencephalon/Hindbrain - divided into - Blood Islands: masses of splanchnic the anterior metencephalon and posterior mesoderm, forms the first RBCs and myelencephalon Blood vessels. Gut wall in Metencephalon - cavity is metacoel which is amphibians and Yolk sac of a part of the 4th ventricle amniotes Myelencephalon - cavity is muelocoel and - Proamnion: region anterior becomes a part of the 4th ventricle membrane that only contains Spinal Cord - region of the neural tube endoderm and ectoderm. Later posterior to the myelencephalon invaded with mesoderm and Sinus Rhomboidalis - rhomboid shaped becomes part of the amnion region at the caudal region where the - Subcephalic Pocket: cavity formed primitive pit and Hensen’s node are beneath the head of the embryo as enclosed by the unfused neural folds the head fold develops Notochord - mesoderm in origin and defines the anterior and posterior axis of the 33 HOUR CHICK EMBRYO (TRANSVERSE embryo. Provides temporary skeletal SECTION) support SECTION AT THE LEVEL OF THE OPTIC NERVE Nephrotome/Intermediate Prosencephalon - consists of a median Mesoderm/Mesomere/Nephromere - vesicle plus a lateral outpocketing on each stalk-like connection between the somites side and lateral plate mesoderm which anteriorly Anterior Neuropore - median cleft at the forms the pronephros and posteriorly forms anterior tip of the neural tube. Presence mesenchyme and later develops into the indicates that the neural folds have not yet mesonephros and metanephros. fused at the region of the embryo Somite - eleven to twelve pairs of somites Prosocoel - optic vesicle and opticoels are seen Lens Placode - thickening of the head Anterior Intestinal Portal - opening of the ectoderm overlying the optic vessel and is foregut. Will move posteriorly and becomes the forerunner of the eye lens part of the yolk stalk Infundibulum - shallow depression of the Foregut - marked by faint lines that extend prosencephalic floor at the posterior border forward from the margins of the A.I.P. of the optic vessels Heart - singular, tubular, S-shaped organ that Amniotic Fold - fold of somatopleure arising bulges to the right side of the body first at the region of the head, then along the Area Pellucida and Area Vitellina sides and eventually at the caudal region. Area Opaca Vasculosa Fusion of these folds form the amnion and - Sinus Terminalis: vein encircling the chorion AV from where the terminal blood Yolk Sac - extra embryonic membrane vessel of the vitelline circulation will enclosing and absorbing the yolk amniote arise embryos. Formed from a layer of endoderm Page 5 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer and a later splanchnic mesoderm of the Bulbus Arteriosus/Bulbus Cordis/Conus splanchnopleure Arteriosus/Truncus arteriosus - anterior Head Ectoderm chamber of the embryo’s heart which Mesenchyme functions to connect the ventricle to the Neural Crest ventral aorta Subcephalic Pocket Epimyocardium - outer thicker layer of the Area Pellucida heart rudiment that arises from the Coelom splanchnic mesoderm and fuses with the Area Vasculosa endocardium to form the heart wall. Will Proamnion give rise to the epicardium and myocardium. Foregut Isthmus/Dorsal Mesocardium - broad connection between the heart and the foregut 33 HOUR CHICK EMBRYO (TRANSVERSE SECTION) SECTION THROUGH THE ORAL PLATE 33 HOUR CHICK EMBRYO (TRANSVERSE Mesencephalon SECTION) Anterior Cardinal Veins - paired BV lying at SECTION THROUGH THE FUTURE VENTRICLE the lateral sides of the mesencephalon Ventricle - region of the heart that bends to Pharynx - region of the foregut one side of the coelom Dorsal Aorta - paired large BV dorsal to the Rhombencephalon - posterior part of the aorta brain at the level of the future ventricle Stomodeum - shallow midventral Auditory Pits/Auditory Placodes - paired depression in the ectoderm and the ectodermal thickenings at the level of the forerunner of the buccal cavity hindbrain and the forerunners of the inner Oral plate - thickened are formed by the ears ventral ectoderm of the head and the Neural Crest Cells - group of cells found at adjacent endodermal evagination of the the edge of the neural plate and lying above pharynx the neural tube after its formation. Migrate Ventral Aorta - small BV below the pharynx throughout the embryo to form the ganglia, one on each side of the median depression pigmented cells, part of gill arches, etc. in the floor of a foregut Thyroid Gland - endocrine gland of the First Aortic Arches - BV that connects the throat region responsible for controlling DA with the VA. metabolism and growth. Formed from a ventral diverticulum of the endoderm of the pharynx. 33 HOUR CHICK EMBRYO (TRANSVERSE SECTION) SECTION AT THE LEVEL OF THE HEART Ventral Aorta - median unpaired vessel 33 HOUR CHICK EMBRYO (TRANSVERSE formed by the fusion of the paired ventral SECTION) aorta POSTERIOR SECTIONS Page 6 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Atrium - posterior level of the heart and the Omphalomesenteric Vein - observed to be forerunner of the future auricles far out on the splanchnopleure. Sinus Venosus - caudal continuation of the atrium 48 HOUR CHICK EMBRYO (WHOLE MOUNT) Anterior Intestinal Portal - margin of the ventral opening of the gut into the yolk and this floorless gut later becomes the midgut Vitelline Veins - paired, large BV that enter the atrium via the sinus venosus Anterior Cardinal Veins - pair of small BV above the DA and adjacent to the rhombencephalon 33 HOUR CHICK EMBRYO (TRANSVERSE SECTION) SECTION THROUGH THE SOMITES Spinal Cord Notochord Somites Nephrotome Hypomere Dorsal Aorta - pair of large BV found between the endoderm and somites. More caudal sections reveal that they continue laterally into the plexus of vessels where they are now called omphalomesenteric arteries. 33 HOUR CHICK EMBRYO (TRANSVERSE SECTION) SECTION THROUGH THE SINUS RHOMBOIDALIS Neural Tube - neural groove is open Hensen’s Node - large mass of compactly arranged cells that displaces the notochordal tissue Unsegmented Mesoderm - somites are not yet divided Primitive Streak - neural groove flattened and disappeared and this is what remains of the PS Page 7 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Cranial half of the embryo is covered with the head fold of the amnion Shows both ventral flexion (bending) and dextral torsion (twisting) 3 fetal membranes: ○ Amnion - encircles the anterior portion of the embryo and consists of ectoderm (inner layer) and somatic mesoderm (outer layer) ○ Yolk Sac - double layered membrane on the left side with BV derived from endoderm and the splanchnic mesoderm ○ Chorion - double layered membrane on the right side and consists of ectoderm (outer layer) and somatic mesoderm (inner layer) 3 irregular white lines: 1st branchial groove, 2nd branchial groove, 3rd branchial groove Page 8 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Presence of the 1st to 3rd visceral arches of cells on each side of the body near the Maxillary and mandibular processes of the myelencephalon 1st visceral arch Jugular Ganglion - masses of cells found lateral to the myelencephalon and above the anterior cardinal veins and also the ganglion 48 HOUR CHICK EMBRYO (TRANSVERSE SECTION) of the X cranial nerve SECTION THROUGH THE MESENCEPHALON Anterior Cardinal Vein/Precardinal Vein - Mesencephalon - first brain cavity that space lined by very thin walls along each shows a frontal section of the several side of the myelencephalon divisions of the brain due to cranial flexure Notochord - small mass of vacuolated cells Isthmus - constriction at the length and that appear between the myelencephalon section of the brain and partially separates and diencephalon the mesencephalon from the hindbrain Myelencephalon - thin roof of the brain 48 HOUR CHICK EMBRYO (TRANSVERSE Metencephalon - underlined portion of the SECTION) brain section between the mesencephalon SECTION THROUGH THE OTIC VESICLE and isthmus Otic Vesicle/Auditory Vesicle/Otocyst - Mesenchyme - loose connective tissues paired vesicle on each side of the between the brain and epidermis myelencephalon, formed as an invagination Fetal membrane of the ectoderm, forerunner of the Extraembryonic coelom - space bounded by endolymphatic duct the mesoderm between the fetal Anterior Cardinal Vein membranes Acoustico-facialis Ganglion - dark accumulation of cells close to the otic vesicle and ACV which are the ganglia of the 48 HOUR CHICK EMBRYO (TRANSVERSE SECTION) VII and VIII cranial nerves SECTION THROUGH THE DIENCEPHALON Semilunar Ganglion Diencephalon - lower cavity when the brain Superior Ganglion - accumulation of cells separates into two on both of the myelencephalon when the Velum Transversum - depression found in otic vesicle is no longer present and is the the dorsal wall of the forebrain and serves ganglion of the XI cranial nerve as the demarcation between the mesencephalon and diencephalon. 48 HOUR CHICK EMBRYO (TRANSVERSE Metencephalon - anteriorly delimited by the SECTION) isthmus SECTION THROUGH THE OPTIC CUPS Myelencephalon - thinner roof, later forms Optic Cups - double walled structures on the posterior choroid plexus each side of the diencephalon. Derived from Semilunar Ganglion - ganglion of the the optic vesicle by invagination. The thicker trigeminal cranial nerve. Dark accumulation layer of the cup is a sensory retina, while the outer thinner layer is a pigmented retina. Page 9 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer ○ Presumptive retina - inner layer of the Rathke’s pouch - small vesicle between the cup infundibulum and the pharynx. Dorsal ○ Presumptive pigmented epithelium - evagination of the stomodeum that will later outer layer and becomes the pigmented form the Hypophysis layer of the retina Oral Plate/Pharyngeal Membrane - thin life Lens vesicles - little sac like cavity within of endoderm and ectoderm that separates the optic cups which arises as an the stomodeum and pharynx invagination of the retina Infundibulum - evagination from the Optic stalk - connects the optic cup to the diencephalon extending in the direction of diencephalon the foregut. Will later evaginate the Pharynx - cavity that started as a hole below posterior lobe of the hypophysis the notochord now triangular in shape. Diencephalon Middle portion of the pharynx and the arms Stomodeum - slit-like space where the of the triangle becomes the 1st pharyngeal rathke’s pouch opens pouch (hyomandibular pouch) which Notochord projects from the pharynx dorsolaterally and then invaginates to form the 1st branchial 48 HOUR CHICK EMBRYO (TRANSVERSE groove. The double layered membrane SECTION) formed is the 1st closing or 1st branchial SECTION THROUGH THE THYROID RUDIMENT AND THE plate. SECOND AORTIC ARCH Preoral Gut - anterior most part of the gut. Thyroid Rudiment - depression in floor of Extends forward as a fingerlike diverticulum the pharynx anterior to the first mouth 2nd aortic arch - BV that lies beneath the Carotid loop - extensions of the 1st aortic 2nd pharyngeal pouches. Contained within arches the 2nd visceral arches (hyoid arches) Internal carotid arteries - paired vessels 2nd Pharyngeal pouch - 2nd outpocketing extending from the carotid loops alongside of the pharynx. Visible posterior sections of the forebrain and medial to the optic cups the otic vesicle or if not present anymore Dorsal aorta - BV on either side of the Ventral Aorta.Aortic Sac - BV between the notochord and lies above the 1st pharyngeal pharynx. Ths starts where the bases of the pouch 1st aortic arches meet. The ventral ends of First aortic arch - BV that lies beneath the the 2nd aortic arches become continuous 1st pharyngeal arch with the sac or the ventral ends of the Mandibular Arch/1st Visceral Arch - the developing 3rd aortic arch. When traced more anterior of the 2 rounded ventrally, the appearance of 2 layers in the mesenchymal masses between which lies wall indicates the start of the bulbus cordis. the stomodeum. Will later form the jaws and bears the 1st aortic arch 48 HOUR CHICK EMBRYO (TRANSVERSE Maxillary Pouch - the rounded or flattened SECTION) masses on either side of the Rathke’s pouch SECTION THROUGH THE THIRD AORTIC ARCH Page 10 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer 3rd Pharyngeal Pouches - large Descending aorta - fused dorsal aorta outpocketing of the pharynx. Together with Dorsal intersegmented arteries - small BV the pharynx gives a laterally oriented oral arising at the intervals from the DA and cavity. extending dorsally between the spinal cord 3rd Aortic Arches - beneath the 3rd PP but and the somite. not fully developed. Conus arteriosus - chamber of the heart at 3rd Visceral Arch - between the 2nd and 3rd the right side of the embryo Pouches. Arches posterior to the hyoid arch Atrium - left side chamber and the are sometimes. referred to as branchial forerunner of the future auricles arches because in the lower vertebrates Ventricle - large loop chamber of the heart they bear the gills. which connects the conus and the atrium Bulbus Cordis - first heart cavity. Presence Laryngotracheal groove - deep v-shaped of endocardium and myocardium depression in the floor of the foregut. Later differentiate it from the ventral aorta of the develops into the larynx, trachea, and lung preceding section. buds Dorsal Mesocardium - mesodermal stock Future esophagus - dorsal portion of the gut that attaches the stock to the dorsal wall of and later will differentiate from the part of the coelom. the foregut dorsal to the LG Nasal placode - thickened skin ectoderm Cardinal veins lateral to the telencephalon. 1st Somite - contact cell masses lying 48 HOUR CHICK EMBRYO (TRANSVERSE immediately lateral to the myelencephalon. SECTION) Somite composition: SECTION THROUGH THE SINUS VENOSUS ○ Dermatome - plate of darkly stained Sinus Venosus - portion of the heart cells beneath the skin of the ectoderm attached to the foregut by the dorsal which will become the future dermis of mesocardium the skin. Common cardinal vein/Duct of cuvier - ○ Myotome - plate of lightly stained cells mesenchyme enclosing the CCV which then medial to the future dermatome which separate the pleural cavities from the will become the future muscle pericardial region of the coelom Anterior Cardinal Veins - separates into two Lung buds - slight evagination of the vessels at the level lateral to the foregut. ventro-lateral portions of the foregut into the The dorsal located vessel is a postcardinal pleural cavities while the ventrally located is a common Pleural cavity - paired portions of the cardinal vein. coelom lateral to the developing lung buds and continuous with the pericardial cavity 48 HOUR CHICK EMBRYO (TRANSVERSE Transverse septum - mesenchyme SECTION) surrounding the SV from where the dorsal SECTION THROUGH THE ATRIUM AND VENTRICLE mesocardium connects the heart to the Spinal cord - replaces the myelencephalon Page 11 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer dorsal body wall. It is connected with the by the delamination from the nephrogenic pleuropericardial cavity cord or nephrotome. Cranial liver diverticulum/Dorsal diverticulum - small mass of cells in the 48 HOUR CHICK EMBRYO (TRANSVERSE dorsal side of the sinus venosus lying in the SECTION) transverse septum ventral to the foregut. SECTION THROUGH THE LATERAL AMNIOTIC FOLDS Deliver arises as a diverticulum from the Lateral amniotic Folds - elevated and about wall of the gut to fuse folds. These are continuous with the Caudal liver rudiment/Ventral diverticulum - lateral body walls and consist of branch or branches on the ventral side of somatopleure that forms an inner amnion the cranial liver rudiment appearing in more and other chorion caudal sections Vitelline Blood Vessels - embedded within Duodenum - if the series is moved the splanchnic mesoderm posteriorly, the creation of liver rudiment Paired dorsal aorta - big pair of BV below becomes continuous with the foregut and the notochord this is a duodenum. Mesonephric Tubule Rudiments - around cavity medial to the mesonephric duct 48 HOUR CHICK EMBRYO (TRANSVERSE which is the first observed at this level SECTION) Nephrostome - opening of the mesonephric SECTION THROUGH THE ANTERIOR INTESTINAL tubule of the coelom PORTAL Vitelline arteries - trace the dorsal aorta Anterior intestinal portal - opening of the until it extends onto the yolk sac as the foregut to the midgut. The yolk is the floor vitelline arteries of the midgut so that after the removal of the yolk in the slide preparation as space is left which represents the midgut 48 HOUR CHICK EMBRYO (TRANSVERSE SECTION) Vitelline veins/Omphalomesenteric vein - SECTION THROUGH THE TAIL BUD BV posterior extensions of the sinus Tail bud - mass mesenchymal cells at the venosus and are the same blood vessels portal and of the embryo and is covered by that lie on each side of the anterior skin ectoderm intestinal portal Hingut - posterior religion of the gut where it Peritoneal cavity - cavity in which the acquires a floor internal organs are present Allantoic membrane - endoderm lined cavity Paired mesonephric duct - small tubules below the tail bud lateral to the descending aorta. Medial to Caudal intestinal portal - space where the this are the mesonephric tubule rudiments yolk of the allantoic rudiment disappears, which will undergo cavitation to form the opening of the hindgut in the yolk mesonephric tubules of the paired mesonephric kidneys. These were formed 72 HOUR CHICK EMBRYO (WHOLE MOUNT) Page 12 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Page 13 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer 72 HOUR CHICK EMBRYO (TRANSVERSE SECTION) 3 fetal membranes ○ Mesencephalon - anterior part of the hindbrain, thicker walls vs myelencephalon. Roof undergoes enlargement and becomes the cerebellum of the brain ○ Myelencephalon - posterior part of hindbrain. Thin roof plate gives rise to the future roof of the medulla and adjacent skin ectoderm ○ Neuromeres - segmented enlargements in the walls of the myelencephalon and metencephalon. Brain of the chick embryo is regarded as being composed of 11 neuromeres. (Forebrain: 1st to 3rd, midbrain 4th to 5th, hindbrain 6th to 11th) Posterior choroid plexus thin roof of the myelencephalon which folded in the myocoel and where vascularization occurs. Endolymphatic ducts - continuing posteriorly, structure appears alongside the walls of the myelencephalon. Small and thick-walled oval structure appearing before the auditory vesicle comes into view Cervical/nuchal Flexure at the level of the Auditory vesicle/Otic vesicle/otocysts - first somites, as well as a tail flexure at the found at the level of the 10th neuromere on caudal end appears in this stage from just each side of the myelencephalon the cranial/cephalic flexure observable in Acoustics-facialis ganglia - dark mass of the 48-hour chick cells lying against the cranial wall of the Amnion and Chorion encloses the entire auditory vesicles and the ganglia of the embryo VII/facial and VIII/auditory nerves Paired wings and lung buds are visible but Spinal cord not sharply bounded ○ Central canal - central cavity Allantois, a saclike structure, is somewhat ○ Roof plate - thin mid-dorsal wall encircled by the tail ○ Floor plate - mid-ventral wall Page 14 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer ○ Sulcus limitans - lateral depression of Oculomotor nerve (III) - nerve fibers from the central canal midway between the the neural ectodermal cells appearing as a floor and roof plates pair of streaks from the floor of the ○ Alar plates - dorsolateral wings of the mesencephalon. These nerves will innervate spinal cord, wall between sulcus 4 pairs of extrinsic eye muscles limitans and roof plate Anterior cardinal vein/Precardinal vein - ○ Basal plates - ventrolateral wings of the large vein laterally situated in the spinal cord, wall between sulcus mesenchyme of the floor of the limitans and floor plate myelencephalon Membranes Notochord ○ Marginal layer - outer region of the neural tube composed of several fibers 72 HOUR CHICK EMBRYO (TRANSVERSE and fewer nuclei SECTION) ○ Ependymal layer - single, innermost FOREGUT AND ASSOCIATED STRUCTURES layer of cells adjacent to the central and Closing plates - double layered membranes the cells are capable of mitosis formed by the endoderm of pharyngeal ○ Mantle - wide heavily nucleated between pouches and the ectoderm of the the marginal and ependymal layer pharyngeal furrows Semilunar ganglion/Gasserian ganglion - Pharyngeal furrows - results of the large dark mass anterior to the invagination of the pharyngeal pouches acoustic-facialis ganglion. Subdivided into projected lateral from the pharynx to three branches (all seen within the region of contact the adjacent region of the skin the first branchial arch) which are actually ectoderm the branches of the trigeminal nerve: First pharyngeal furrow and pouch - ○ Maxillary branch - medial branch endodermal evagination and a V-shaped ○ Ophthalmic branch - lateral branch ectodermal indentation closest to the mesencephalon Second pharyngeal furrow and pouch - more ○ Mandibular branch - lateral branch posterior and towards the spinal cord above the ophthalmic branch 3rd and 4th pharyngeal furrows and Superior ganglion - very small rounded pouches accumulation of cells located at the caudal Visceral arches - between adjacent side of each of the auditory vesicle pharyngeal furrows, greatly thickened lateral Somite - compact cell mass found lying walls and filled with mesenchymal cells immediately lateral to the myelencephalon. Mandibular arch - mass of mesenchyme Differentiate into dermatome, myotome, and anterior to the first furrow towards the sclerotome mesencephalon in this section Mesencephalon - small rounded region Maxillary arch - lobe-like mass of beneath the metencephalon. Cavity: mesenchyme to the stomodeum mesocoel which will become the future cerebral aqueduct/aqueduct of Sylvius Page 15 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Hyoid arch - mesenchyme between the first separates the stomodeum from the foregut, (hyomandibular pouch and furrow and the which ruptures to form the mouth opening. second furrow Preoral gut - small gut pocket located just Symphysis of the lower jaw - the ventral cranial to the pharyngeal membrane which fusion of the posterior part of the 2 becomes less conspicuous after the rupture mandibular arches of the oral plate Dorsal aorta - paired structures on each side Stomodeum - slit-like space which is lined of the foregut and appears as constricted by the ectoderm and lies between the two into two parts at the level of the 1st visceral masses next to the foregut pharyngeal. Rathke’s pouch - irregular cavity lined with 1st aortic arch - lies within the mandibular cuboidal epithelium that opens in more process posterior sections into the stomodeum and 2nd - 4th aortic arches - structures from the serves as a rudiment of the anterior pituitary dorsal aorta into the 2nd - 4th branchial gland arches respectively Laryngotracheal groove - V-shaped ventral Ventral aorta/Aortic sac/Truncus arteriosus most part of the posterior section of the - caudal part of the slides when 1st aortic foregut and is seen at the level of the 4th arch approaches one another and becomes pharyngeal pouch when the foregut starts to continuous. In posterior sections, the ventral elongate ventrally ends of the 2nd and 3rd aortic arch also Trachea - arises with the lung buds as unite in the ventral aorta ventrocaudal diverticulum of the pharynx in Descending aorta - fusion of the paired some sections found beneath the aorta seen posterior to the third aortic esophagus region pouch Lung buds - paired bilateral expansion of the Internal carotid artery - narrower vessel that laryngotracheal groove. Posterolaterally, arises as a cranial extension of the dorsal each lung bud is cut off from the aorta found in the mesenchyme lateral to laryngotracheal groove so that he donut like the notochord structure appears and these are the future Jugular ganglion - derived from a group of bronchi and they lead to the lung bud proper neural crest cells. Smaller mass of cells Pleural cavities - lying posterior to the IX nerve. Fades out within the 4th branchial arch 96 HOUR CHICK EMBRYO (WHOLE MOUNT) Thyroid rudiments - arises from the floor of the pharynx as a median diverticulum/depression at the first and second pair of pharyngeal pouches. Oral plate/Pharyngeal membrane - thin membranes are constituted by the opposition of the pharyngeal endoderm and stomodeal ectoderm. This structure Page 16 of 17 Developmental Biology Laboratory ZOO 3202L Transcribed by: Olsen N. Trinidad Reviewer Page 17 of 17