comparative vertebrate anatomy

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Comparative Comparative Vertebrate Anatomy Vertebrate Anatomy Chordate Origins & Chordate Origins & Phylogeny Phylogeny Presented by: Geonyzl Lepiten

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Page 1: Comparative Vertebrate Anatomy

Comparative Comparative Vertebrate Vertebrate AnatomyAnatomy

Chordate Origins & Chordate Origins & PhylogenyPhylogeny Presented by: Geonyzl Lepiten

Page 2: Comparative Vertebrate Anatomy

Comparative vertebrate anatomy - Comparative vertebrate anatomy - the study of structure, of the function the study of structure, of the function of structure, & of the range of of structure, & of the range of variation in structure & function variation in structure & function among vertebrates: among vertebrates:

Kingdom: Kingdom: Animal Animal Phylum:Phylum: Chordata Chordata Subphylum:Subphylum: Vertebrata Vertebrata

Page 3: Comparative Vertebrate Anatomy

Vertebrate Vertebrate characteristics:characteristics:

1 - notochord (at least 1 - notochord (at least in the embryo) in the embryo)

2 - pharynx with 2 - pharynx with pouches or slits in pouches or slits in wall (at least in the wall (at least in the embryo) embryo)

3 - dorsal, hollow 3 - dorsal, hollow nervous system nervous system

4 - vertebral column4 - vertebral column

Page 4: Comparative Vertebrate Anatomy

NotochordNotochord = rod of living cells ventral = rod of living cells ventral to central nervous system & dorsal to to central nervous system & dorsal to alimentary canal alimentary canal

Fate of notochord during development: Fate of notochord during development: Head region - incorporated into floor of Head region - incorporated into floor of

skull skull Trunk & tail - surrounded by Trunk & tail - surrounded by

cartilaginous or bony vertebrate cartilaginous or bony vertebrate (except in Agnathans) (except in Agnathans)

Page 5: Comparative Vertebrate Anatomy

Adults: Adults: Fishes & amphibians - notochord persists the Fishes & amphibians - notochord persists the

length of the trunk & tail but is constricted length of the trunk & tail but is constricted within the centrum of each vertebra within the centrum of each vertebra

Reptiles, birds, & mammals - notochord Reptiles, birds, & mammals - notochord almost disappears during development (e.g., almost disappears during development (e.g., remains as a pulpy nucleus in the vertebrae of remains as a pulpy nucleus in the vertebrae of mammals) mammals)

Protochordates - notochord remains as the Protochordates - notochord remains as the chief axial skeleton chief axial skeleton

Agnathans - Agnathans - lateral neural cartilageslateral neural cartilages are are located on notochord lateral to the spinal cord located on notochord lateral to the spinal cord

Page 6: Comparative Vertebrate Anatomy

PharynxPharynx - region of alimentary canal - region of alimentary canal exhibiting pharyngeal pouches in exhibiting pharyngeal pouches in embryo; pouches may open to the embryo; pouches may open to the exterior as exterior as slitsslits::

permanent slits - adults that live in permanent slits - adults that live in water & breathe via gills water & breathe via gills

temporary slits - adults live on land temporary slits - adults live on land

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Dorsal, hollow central nervous system - Dorsal, hollow central nervous system - consists of brain & consists of brain & spinal cordspinal cord & contains a & contains a central cavity (called the neurocoel) central cavity (called the neurocoel)

Page 9: Comparative Vertebrate Anatomy

Among the oldest & best known Among the oldest & best known = = ostracodermsostracoderms

fishes that occurred in the late Cambrian fishes that occurred in the late Cambrian period (see period (see The Cambrian ExplosionThe Cambrian Explosion) ) through the Devonian (about 400 - 525 through the Devonian (about 400 - 525 million years before present) million years before present)

had bony plates and scales (&, therefore, had bony plates and scales (&, therefore, were easily fossilized) were easily fossilized)

jawless vertebrates called 'armored fishes' jawless vertebrates called 'armored fishes'

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Before ostracoderms? Before ostracoderms? MyllokunmingiaMyllokunmingia fengjiaoafengjiaoa (pictured below) (pictured below)

& & HaikouichthysHaikouichthys ercaicunensisercaicunensis - primitive - primitive fish that have many similarities to living fish that have many similarities to living hagfishes and are the oldest vertebrates hagfishes and are the oldest vertebrates (530 mybf) ever found. (530 mybf) ever found.

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Before Vertebrates? Before Vertebrates? CathaymyrusCathaymyrus diadexusdiadexus (literally the (literally the

'Chinese eel of good fortune') 'Chinese eel of good fortune')

= is not the fossil of an eel. At just 5 = is not the fossil of an eel. At just 5 cm long, but 535 m.y. old, it is the cm long, but 535 m.y. old, it is the earliest known chordate. earliest known chordate.

= Researchers think that = Researchers think that CathaymyrusCathaymyrus is a fossil relative of is a fossil relative of modern lancelets (amphioxus). modern lancelets (amphioxus).

Page 12: Comparative Vertebrate Anatomy

CathaymyrusCathaymyrus

Page 13: Comparative Vertebrate Anatomy

Phylum Phylum ChordataChordata - established in - established in 1874 & included organisms with: 1874 & included organisms with:

1 - notochord 1 - notochord 2 - pharyngeal pouches or slits 2 - pharyngeal pouches or slits 3 - dorsal, hollow nervous system 3 - dorsal, hollow nervous system 4 - cells that produce the hormone 4 - cells that produce the hormone

thyroxine thyroxine

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Subphylum Subphylum UrochordataUrochordata = = tunicatestunicates Chordate 'ancestor' of vertebrates: Chordate 'ancestor' of vertebrates:

sessile (like adult tunicates) sessile (like adult tunicates) tail evolved as adaptation in tail evolved as adaptation in

larvae to increase mobility larvae to increase mobility 'higher forms' - came about 'higher forms' - came about

by retention of tail (neoteny) by retention of tail (neoteny) Tunicate larva - also called 'sea squirt' Tunicate larva - also called 'sea squirt'

notochord is confined to the tail notochord is confined to the tail notochord is lost during notochord is lost during

metamorphosis into sessile adult metamorphosis into sessile adult possess pharyngeal slits possess pharyngeal slits

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Tunicate anatomy Larval stage of the tunicate

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Subphylum Subphylum CephalochordataCephalochordata= Amphioxus (or = Amphioxus (or Branchiostoma) Branchiostoma)

Vertebrate featuresVertebrate features: : notochord notochord dorsal, hollow nervous system dorsal, hollow nervous system pharyngeal gill slits pharyngeal gill slits 'circulatory' system - vertebrate pattern 'circulatory' system - vertebrate pattern

with 'pumping vessels' (but no heart) with 'pumping vessels' (but no heart)

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Hemichordates Hemichordates = acorn worms = acorn worms Bateson added acorn worms to the Bateson added acorn worms to the

phylum Chordata in 1884 because phylum Chordata in 1884 because they have: they have:

1 - a dorsal, hollow nervous system 1 - a dorsal, hollow nervous system 2 - gill slits 2 - gill slits 3 - a short diverticulum of the gut 3 - a short diverticulum of the gut

called the stomochordcalled the stomochordPresent consensus = the stomochord Present consensus = the stomochord

is not homologous with the is not homologous with the notochord and Hemichordates are notochord and Hemichordates are placed in a separate phylum placed in a separate phylum

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Possible invertebrate ancestors: Possible invertebrate ancestors: 1 - 1 - annelid wormsannelid worms

    Evidence for:Evidence for:

– bilateral symmetry bilateral symmetry – segmented segmented – central nervous system with brain central nervous system with brain

& longitudinal nerve cord& longitudinal nerve cord Evidence against:Evidence against:

– nerve cord is solid nerve cord is solid – nerve cord is ventral nerve cord is ventral

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2 - 2 - echinodermataechinodermata - chordate - chordate characteristics include:characteristics include:– radial cleavage - blastomeres in adjacent radial cleavage - blastomeres in adjacent

tiers lie directly above one another (as tiers lie directly above one another (as opposed to spiral cleavage) opposed to spiral cleavage)

– anus forms near or at blastopore anus forms near or at blastopore (deuterostomous) (deuterostomous)

– mesoderm arises as outpocketing of the mesoderm arises as outpocketing of the gut wall gut wall

– indeterminate cleavage (i.e., fate of indeterminate cleavage (i.e., fate of blastomeres isn't predetermined) blastomeres isn't predetermined)

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Phylum: Phylum: ChordataChordata Subphylum: Vertebrata Subphylum: Vertebrata

Superclass: Superclass: PiscesPisces Class Class AgnathaAgnatha

Class Class PlacodermiiPlacodermii Class Class ChondricthyesChondricthyes Class Acanthodii Class Acanthodii Class Class OsteichthyesOsteichthyes

Superclass: Tetrapoda Superclass: Tetrapoda Class Class AmphibiaAmphibia

Class Class ReptiliaReptilia Class Class AvesAves Class Class MammaliaMammalia

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Agnathans vs. Gnathostomes:Agnathans vs. Gnathostomes: semicircular canals semicircular canals

– agnathans have 1 or 2 agnathans have 1 or 2 – gnathostomes have 3 gnathostomes have 3

jointed, paired lateral jointed, paired lateral appendages appendages – agnathansagnathans have none have none – gnathostomes do gnathostomes do

jaws jaws – agnathans have none agnathans have none – gnathostomes do gnathostomes do

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Class AgnathaClass Agnatha Orders: Orders: 1 - 1 - OsteostraciOsteostraci 2 - Anaspida 2 - Anaspida 3 - 3 - ThelodontiThelodonti 4 - 4 - GaleaspidaGaleaspida 5 - 5 - PituriaspidaPituriaspida 6 - Petromyzontia (lampreys) 6 - Petromyzontia (lampreys) 7 - Myxinoidea (hagfishes)7 - Myxinoidea (hagfishes)

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Ostracoderms (Osteostraci, Anaspida, Ostracoderms (Osteostraci, Anaspida, Heterostraci, & Coelolepid): Heterostraci, & Coelolepid):

1 - extinct Paleozoic (Cambrian to 1 - extinct Paleozoic (Cambrian to Devonian) jawless fish with an external Devonian) jawless fish with an external skeleton of bone ('bony armor') skeleton of bone ('bony armor') 2 - oldest known vertebrates 2 - oldest known vertebrates 3 - many had flattened appearance 3 - many had flattened appearance (some may have been bottom-dwellers)(some may have been bottom-dwellers)

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CyclostomesCyclostomes (Petromyzontia & (Petromyzontia & Myxinoidea): Myxinoidea):

LampreysLampreys - parasitic with horny, rasping - parasitic with horny, rasping teeth (see drawing at right) teeth (see drawing at right) HagfishesHagfishes - - primarily scavengersprimarily scavengers

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GnathostomesGnathostomes Acanthodians:Acanthodians: 1 - earliest known gnathostomes (1 - earliest known gnathostomes (

SilurianSilurian; about 440 mybp) ; about 440 mybp) 2 - 2 - probablyprobably related to modern bony related to modern bony

fishes fishes 3 - small (less than 20 cm long) with 3 - small (less than 20 cm long) with

large eyes large eyes 4 - 4 - AcanthodiansAcanthodians most likely died out most likely died out

because of the rapidly increasing because of the rapidly increasing number of ray-finned fishes and sharks number of ray-finned fishes and sharks during the during the PermianPermian

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Class Class PlacodermiiPlacodermii:: 1 - Silurian (about 420 million years 1 - Silurian (about 420 million years

before present) 2 - probably off the before present) 2 - probably off the main line of vertebrate evolution main line of vertebrate evolution

3 - many had bony dermal shields 3 - many had bony dermal shields 4 - some were probably predators 4 - some were probably predators

(with large, sharp 'tooth plates')(with large, sharp 'tooth plates')

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Vertebrate EggsVertebrate Eggs

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Types EggsTypes EggsA.A. Alecithal = Eggs with little yolkAlecithal = Eggs with little yolk ex. Amphioxus eggex. Amphioxus eggb. Mesolecithal = eggs with moderate b. Mesolecithal = eggs with moderate

amount of yolkamount of yolk ex. Freshwater lampreys ex. Freshwater lampreys ganoid fishesganoid fishes lungfishes lungfishes amphibians amphibians

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C. Megalecithal = massive amount of C. Megalecithal = massive amount of yolkyolk

ex. Monotremesex. Monotremes marine lampreysmarine lampreys teleostteleost

reptiles reptiles birdsbirds

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Types of distribution of Types of distribution of yolkyolk

a.a. Isolecithal = even distribution of yolkIsolecithal = even distribution of yolk present in alecithal eggspresent in alecithal eggsb. Telolecithal = the cytoplasm and yolk b. Telolecithal = the cytoplasm and yolk

tends to concentrate or accumulate at tends to concentrate or accumulate at the oposite poles. the oposite poles.

present in mesolecithal present in mesolecithal eggs eggs

and in megalecithal eggsand in megalecithal eggs

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Oviparity and ViviparityOviparity and Viviparity viviparyvivipary: the embryo develops inside the : the embryo develops inside the

body of the mother and living young is body of the mother and living young is delivereddelivered

: reared by the mother.: reared by the mother. : but the eggs of viviparous animals : but the eggs of viviparous animals

lack a hard outer covering or shell like the lack a hard outer covering or shell like the chicken egg. chicken egg.

:Viviparous young grow in the adult :Viviparous young grow in the adult female until they are able to survive on female until they are able to survive on their own outside her body. their own outside her body.

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:developing fetuses of viviparous :developing fetuses of viviparous animals are connected to a animals are connected to a placentaplacenta in in the mother's body the mother's body

Egg-laying, or Egg-laying, or oviparousoviparous, animals , animals obtain all nourishment as they develop obtain all nourishment as they develop from the yolk and the protein-rich from the yolk and the protein-rich albumen, or "white," in the egg itself, albumen, or "white," in the egg itself, not from direct contact with the not from direct contact with the mother, as is the case with viviparous mother, as is the case with viviparous young. young. : expulsion of undeveloped eggs rather : expulsion of undeveloped eggs rather than live young. than live young.

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ovoviviparityovoviviparity : :animalsanimals develop within develop within eggseggs that remain within the mother's that remain within the mother's body up until they hatch or are about to body up until they hatch or are about to hatch hatch

: employed by many : employed by many aquatic life forms such as aquatic life forms such as fishfish and some and some sharkssharks, , reptilesreptiles, and , and invertebratesinvertebrates. The . The young of ovoviviparous young of ovoviviparous amphibiansamphibians are are sometimes born as sometimes born as larvaelarvae, and undergo , and undergo metamorphosismetamorphosis outside the body of the outside the body of the mother.mother.

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In fertilization:In fertilization: Gametes are essential in fertilizing Gametes are essential in fertilizing

the eggsthe eggs - sperm which came from the - sperm which came from the

malemale - ovum from the females- ovum from the females when the female and male when the female and male

gametes unite it will form into gametes unite it will form into zygote.zygote.

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CleavageCleavage The fertilized egg (zygote) is The fertilized egg (zygote) is

transformed by cell division transformed by cell division (cleavage) into a mutlicellular (cleavage) into a mutlicellular cells called cells called BlastulaBlastula

During cleavage the individual During cleavage the individual cells are called cells are called blastomereblastomere

The blastula is a hollow ball of The blastula is a hollow ball of cells with a cavity is called cells with a cavity is called blastocoelblastocoel

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In microlecithal eggs In microlecithal eggs like in amphioxus have like in amphioxus have total or holoblastic total or holoblastic cleavage (the cleavage cleavage (the cleavage furrows the entire furrows the entire yolk)yolk)

Divided equallyDivided equally The resultant blastula The resultant blastula

is a hollow ball of cells is a hollow ball of cells with a cavity called with a cavity called blastocoelblastocoel

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In mesolecithal egg like In mesolecithal egg like in frog have a total in frog have a total but unequal cleavagebut unequal cleavage

Blastomere near the Blastomere near the vegetal pole are larger vegetal pole are larger than those in the than those in the animal pole.animal pole.

Development is slowDevelopment is slow The blastocoel is The blastocoel is

displaced on the animal displaced on the animal hemisphere.hemisphere.

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Macrolecithal egg have Macrolecithal egg have unequal and partial or unequal and partial or meroblastic cleavagemeroblastic cleavage

Limited to the relatively small Limited to the relatively small yolk-free region at the animal yolk-free region at the animal polepole

Yolk mass is to great to be Yolk mass is to great to be penetrately by the cleavage penetrately by the cleavage furrowsfurrows

A cellular blastoderm is A cellular blastoderm is separated from the uncleaved separated from the uncleaved yolk by a narrow cavityyolk by a narrow cavity

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Fish blastula

Page 43: Comparative Vertebrate Anatomy

GrastulaGrastula

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GastrulaGastrula When the blastula developed into an When the blastula developed into an

embryoembryo = at first the gastrula has two germ layer = at first the gastrula has two germ layer

(ectoderm and endoderm)(ectoderm and endoderm) = and then later to three germ layers = and then later to three germ layers

(ectoderm, mesoderm and endoderm)(ectoderm, mesoderm and endoderm)Gastrulation of a diploblast: The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).

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Neurulation and Neural Neurulation and Neural CrestCrest

Neurulation Neurulation is a process to convert the is a process to convert the gastrula into gastrula into neurulaneurula..

is a part of is a part of organogenesisorganogenesis in in vertebratevertebrate embryosembryos

Steps of neurulation include the formation of Steps of neurulation include the formation of the the dorsal nerve corddorsal nerve cord, and the eventual , and the eventual formation of the central nervous system. formation of the central nervous system.

The process begins when the The process begins when the notochordnotochord induces the formation of the induces the formation of the central nervous systemcentral nervous system (CNS) by signaling the (CNS) by signaling the ectoderm ectoderm germ layergerm layer above it to form the thick above it to form the thick and flat and flat neural plateneural plate

Page 46: Comparative Vertebrate Anatomy

The neural plate folds in upon itself to form The neural plate folds in upon itself to form the the neural tubeneural tube, which will later differentiate , which will later differentiate into the into the spinal cordspinal cord and the and the brainbrain, eventually , eventually forming the central nervous system. forming the central nervous system.

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Neurulation in vertebrates results in Neurulation in vertebrates results in the formation of the the formation of the neural tubeneural tube, , which gives rise to both the spinal which gives rise to both the spinal cord and the brain. cord and the brain. Neural crest Neural crest cellscells are also created during are also created during neurulation.  Neural crest cells neurulation.  Neural crest cells migrate away from the neural tube migrate away from the neural tube and give rise to a variety of cell and give rise to a variety of cell types, including pigment cells and types, including pigment cells and neurons. neurons.

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1. Neurulation begins with the formation of a 1. Neurulation begins with the formation of a neural plateneural plate, a thickening of the ectoderm , a thickening of the ectoderm caused when cuboidal epithelial cells caused when cuboidal epithelial cells become columnar. become columnar.

2. Changes in cell shape and cell adhesion 2. Changes in cell shape and cell adhesion cause the edges of the plate fold and rise, cause the edges of the plate fold and rise, meeting in the midline to form a meeting in the midline to form a tubetube..

3. The cells at the tips of the 3. The cells at the tips of the neural foldsneural folds come to lie between the come to lie between the neural tubeneural tube and and the overlying the overlying epidermisepidermis. .

4. These cells become the 4. These cells become the neural crest cellsneural crest cells. . Both Both epidermisepidermis and and neural plateneural plate are are capable of giving rise to capable of giving rise to neural crest cellsneural crest cells. .

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OrganogenesisOrganogenesis Organogenesis is the period of animal Organogenesis is the period of animal

development during which the embryo is development during which the embryo is becoming a fully functional organism becoming a fully functional organism capable of independent survivial. capable of independent survivial.

process by which specific organs and process by which specific organs and structures are formedstructures are formed, ,

and involves both and involves both cell movementscell movements and and cell differentiationcell differentiation. .

Organogenesis requires interactions Organogenesis requires interactions between different tissues. These are often between different tissues. These are often reciprocalreciprocal interactions between interactions between epithelial epithelial sheetssheets and and mesenchymal cellsmesenchymal cells. .

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The endoderm produces tissue within the lungs, thyroid, and pancreas. The mesoderm aids in the

production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells. The ectoderm produces tissues within the epidermis and aids in the formation of neurons

within the brain, and melanocytes.

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Organogenesis from EctodermOrganogenesis from Ectoderm 1. 1. From Somatic EctodermFrom Somatic Ectoderm - epidermis of skin- epidermis of skin - enamel- enamel - Stomodeum (mouth)- Stomodeum (mouth) - Proctodeum (cloaca or anus )- Proctodeum (cloaca or anus ) - Gill Epithelium- Gill Epithelium - Amnion and Chorion (in part) - Amnion and Chorion (in part)

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2. Neural Plate ectoderm2. Neural Plate ectoderm - Brain and Spinal Cord- Brain and Spinal Cord3. Epidermal Placodes3. Epidermal Placodes - Olfactory capsules- Olfactory capsules - Optic capsule- Optic capsule - Otic Capsule- Otic Capsule - Epibranchial capsule- Epibranchial capsule - Electroreceptors/ neuromsst - Electroreceptors/ neuromsst

organsorgans - ganglia of some cranial nerves - ganglia of some cranial nerves

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4. Neural Crest4. Neural Crest - Spinal Ganglia- Spinal Ganglia - Splanchnocranium- Splanchnocranium - Neurocranium- Neurocranium - Dermatocranium- Dermatocranium - Dentine- Dentine - Cornea- Cornea - Chromatophores- Chromatophores - Branchiomeric - Branchiomeric

musclesmuscles - aortic arches- aortic arches - heart septa - heart septa

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Organogenesis From the Organogenesis From the mesodermmesoderm

1.1. Epimere (dermatome) – DermisEpimere (dermatome) – Dermis2.2. Epimere (myotome) – Axial MuscleEpimere (myotome) – Axial Muscle

- Appendicular Muscle- Appendicular Muscle - Branchiomeric Muscle- Branchiomeric Muscle - Hypobranchial - Hypobranchial 3. Epimere (sclerotome) – Vertebrae3. Epimere (sclerotome) – Vertebrae4. Chordamesoderm – notochord4. Chordamesoderm – notochord

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5. Intermediate mesoderm 5. Intermediate mesoderm (Mesomere)(Mesomere)

-kidney and Urogenital ducts-kidney and Urogenital ducts6. Somatic hypomere = 6. Somatic hypomere = - ribs- ribs - Parietal peritoneum- Parietal peritoneum - -

SternumSternum - Genital Ridge- Genital Ridge - appendicular skeleton- appendicular skeleton - appendicular muscle - appendicular muscle - amnion and chorion- amnion and chorion

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7. Splanchnic hypomere7. Splanchnic hypomere - Blood - Blood - heart- heart - gut- gut - smooth muscle- smooth muscle - visceral peritoneum- visceral peritoneum - yolk sac and - yolk sac and

allantoisallantois

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Organogenesis of the Organogenesis of the EndodermEndoderm

1. Foregut – Oral Cavity1. Foregut – Oral Cavity - Gill Epithelium - Gill Epithelium - nasal cavity - Lung epithelium- nasal cavity - Lung epithelium - Pharynx epithelium- Pharynx epithelium2. Midgut - Stomach2. Midgut - Stomach - Liver - Liver - Bladder- Bladder - Pancreas - Pancreas - intestines- intestines - Allantois - Allantois - germ cells of gonads - germ cells of gonads - yolk sac membrane - yolk sac membrane 3. Hindgut – Urinary Bladder and Cloaca or 3. Hindgut – Urinary Bladder and Cloaca or

anusanus

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The End of the The End of the ChapterChapter