Frog
Development
1.
Fertilization
2.
Cleavage
· egg is divided into progressively smaller units
· blastomeres to cells
3.
Gastrulation
· completed with formation of mesoderm and
notochord
2 Primary
Germ Layers
a.
Epiblast
à
presumptive ectoderm
à
mesoderm
b.
Endoderm
Archenteron
· formed from integrated movements of sheets of cells
· primary embroynic gut cavity
Blastopore
· opening into archenteron
· located approximately in region of posterior end of gut
cavity/anus
Notochord
· comes from epiblast
· axis around which vertebral column will be built
4.
Organogenesis
(Neurulation)
· embryo starts to elongate dorsal thickening of ectoderm à neural or medullary plate
· gives rise to entire nervous system
· closes over dorsally to form neural and brain cavities
· acquisition of characteristic shape of tadpole
5.
External
Gill Stage
· hatches from jelly capsule
· known as larva/tadpole
· organ systems are not developed to the adult form until
metamorphosis is achieved
· external gills
à
respiration
à
function
until replaced by internal gills
6.
Metamorphosis
· change in structure and function of different parts of the
body
· ceases to feed
· lose outer skin, horny jaw, and frilled lips
· mouth changes from small oval suctorial organ to wide slit
with enlarged tongue
· intestine shortens and changes histologically
· stomach and liver enlarge
· from herbivorous to carnivorous
· respiratory organ from external gills to lungs
· tail regression
· sex differentiation
7. Adult
THE MALE FROG
Distinguishing Characteristics of
Male Frog
1.
smaller
2.
darkened
thumb pad
3.
low,
guttural croaking sound
4.
slender
and streamlined body
5.
absence
of coelomic cilia except in kidneys
Mesorchium
- double fold of peritoneum
- suspends testis to kidneys
- surrounds each testis
- continuous with peritoneum epithelium
Spermatogenesis
- seasonal
- completed within the testis
- Meiotic arrests (?)
1. Spermatogonium
· after breeding season à frog ceases all
metabolic activity
· enters period of rest
· granular, oval nucleus
· found near basement membrane of seminiferous tubules
· small, closely packed cells
2. Primary
Spermatocyte
· large cells
· irregularly spherical
· large and vesicular nuclei
· extended prophase à nucleus undergoes series of changes
a.
Leptotene
à cytoplasm and nucleus grow
b.
Zygotene
c.
Pachytene
d.
Diplo-diakinesis
à homologous chromosomes start to separate
à chromatin material, volume of nucleus and cytoplasm
increases
à nuclear membrane breaks down
3. Secondary
Spermatocyte
· half the size of primary spermatocyte
· lie towards the lumen
· darkly staining nucleus
· cytoplasm may be tapered on one side
4. Spermatid
· smaller
· condensed nucleus of irregular shape
· clusters of spermatids appear as cluster of granules
5. Spermatozoon
· Elongated, solid-staining head (nucleus)
· Has acrosome
Sertoli Cells
- Relatively large, columnar-type basal cell
- Where head of spermatozoon converge
- Functionally a nurse cell à supply nutrition
to spermatozoon
THE FEMALE FROG
Distinguishing Characteristics of
the Female Frog
1.
generally
larger
2.
absence
of dark thumb pad
3.
inability
to produce lateral cheek pouches from croaking
4.
flabby
and distended abdomen
5.
presence
of peritoneal cilia
The Ovary
Mesovarium
-
2-layered
-
continuous
with theca externa
Theca Interna
-
“cyst
wall”
-
contains
smooth muscle fibers
-
derived
from retro-peritoneal tissue
Ovarian Follicle
1.
theca
externa
2.
theca
interna
3.
follicle
cells
· oval and granular nucleus
· derived from oogonia
· surround developing oocyte
The Egg
1.
Animal
Pole
a.
cytoplasm
b.
germinal
vesicle
2.
Vegetal
Pole à Yolk
Vitelline
Membrane
-
enclosed
within follicle cells
-
closely
applied to mature egg
-
non-cellular
and transparent
-
sometimes
designated as primary of several egg membranes
Jelly Coats
-
“albumen”
Layers
-
largely
water
-
greater
than diameter of egg
-
(Inner
to outer)
1.
thin,
heavy consistency
2.
thin,
more fluid
3.
greater
in thickness, less viscous
Oogenesis
-
after
breeding season à only oogonia
· no pigment
· little or no yolk
· represents an ovarian unit
à many follicle cells
à 1 ovum
Process of Egg
Maturation
1.
chromatin
nucleoli aid in synthesis of yolk
2.
breakdon
of germinal vesicle à intermingling of cytoplasmic and nuclear components
Growth Period to
Primary Oocyte Stage
-
achieved
by accumulation of yolk
1.
cells
no longer divide by mitosis and is known as an oocyte rather than oogonia
2.
yolk
nuclei
· granules within cytoplasm
· function as centers of yolk accumulation
· source of yolk: digested food of female
3.
accumulation
of yolk à concentrated in one side of oocyte
First Indicators
of Egg Polarity
1.
growth
changes
2.
unequal
distribution of pigment, yolk, cytoplasm
Established
Polarity of the Frog’s Telocithal Egg
1.
Animal
Hemisphere
a.
cytoplasm
b.
melanin
c.
nucleus
2.
Vegetal
à Yolk
Surface layer of amphibian egg
-
contains
yolk grains and black pigment granules
-
with
each cleavage, the superficial coat is divided between blastomeres
Vitelline
Membrane at Growth Period
1.
thin
2.
transparent
3.
nonliving
4.
closely
adherent
Ovulation and
Maturation
-
brought
about by LH
-
liberation
of egg from ovary
-
rupture
and emergence of eggs from individual follicles
-
theca
externa ruptures
Maturation
Divisions
1.
First
maturation division
· occurs during ovulation
a.
primary
oocyte
b.
first
polar body
à small amount of cytoplasm
à no yolk
2.
Second
maturation division
· begins without any intermediate rest period
· occurs around the time the egg enters the oviduct
· egg reaches uterus arrested at Metaphase II
· maturation is not completed until egg is activated by sperm
a.
secondary
oocyte
b.
second
polar body
CLEAVAGE
Egg: Telocithal
à large amount of yolk concentrated at one pole
à yolk is opposite to the concentration of cytoplasm and
location of nucleus
Cleavage: Holoblastic
Blastomeres
-
cell
of the embryo (from 1st cleavage to late blastula)
1.
micromeres à upper, smaller
2.
macromeres à lower, larger
BLASTULATION
-
segmentation
of the egg à division into smaller cellular units
-
appearance
of internal cavity à blastocoel
Blastula
-
stage
of development where blastocoel is present
-
overlaps
stages of cleavage
-
coeloblastula
Blastocoel
-
filled
with albuminous fluid from surrounding cells
-
eccentric
position
· above level of equator
· slightly toward gray crescent side of cleaving egg
-
size
increases with formation of smaller and smaller surrounding cells
-
later
displaced by archenteron
Gradient of Cleavage
-
active
region à animal pole
-
least
active region à vegetal pole
Changes in Embryo
1.
actual
migration of small and pigmented ccells toward vegetal pole à thinning of roof
of blastocoel
2.
outermost
layer of cells
a.
single
outer layer of cells
à contains most of superficial pigments
à recognized as epidermal
layer
à gives rise to epithelium
Ø integument
Ø lining
of nervous system
b.
inner
tiers of cells of blastular roof
à less pigmented
à collectively known as nervous
layer
à give rise largely to neuroblasts
of nervous system
Germ Ring
-
where
yolk is most actively being transformed into cytoplasm
-
has
something to do with subsequent formation of lips of future blastopore
GASTRULATION
-
dynamic
process
-
results
in transformation of single layered blastula to two-layered embryo
-
involves
but is independent of mitosis
Germ Layers
1. ectoderm
2. ectoblast
· outermost layer of blastula
a. mesoderm
b. endoderm
-
first
distinguishable with gastrulation
-
definable
by fate in embryonic devt
Basis for Distinction of Germ
Layers
1.
position
in developing organism
2.
fate
Importance of Gastrulation
1.
cell
division
2.
cell
differentiation
3.
morphogenetic
movements
-
independence
and interdependence of various areas
Embryos at Gastrulation
Senstive
to…
1.
changes
in physical environment
2.
genetic
incompatibilities within chromosomes
Morphogenetic Movements
1. Invagination
· Insinking of the egg surface followed by forward migration
which involves displacement of inner materials
2. Involution
· turning inward
· a rotation of material upon itself so that movement is
directed toward the interior of the egg
3. Epiboly
· progressive extension of cortical layer of animal hemisphere
toward vegetal hemisphere, or,
· the expansion from animal to vegetal hemisphere
Gastrulation Proper
1.
thinning
of gray crescent side of blastula wall
· migration of deeper layers of blastula away from original
site of gray crescent
· region where involution first occurs
· eventually known as dorsal
lip
2.
continued
epiboly toward vegetal hemisphere so that diameter of marginal zone becomes
progressively smaller as it passes below the equator
· marginal zone à high rigidity à inward pressure on yolk cells à arch upward
toward blastocoel
· yolk endoderm cells toward gray crescent side are forced
upward à reduction in blastocoel size
3.
initial
involution at lower margin of original gray crescent
· lateral extension of this involution along epibolic marginal
zone
· initial involution dorsal lip
4.
further
epiboly of entire marginal zone toward vegetal hemisphere
5.
piling
up of animal hemisphere cells
· many are destined to move inside over blastoporal lips
6.
continued
lateral extension of involuting marginal zone
· circumferential meeting of blastoporal lips
· yolk plug
7.
reduction
in size of circumblastoporal lips and exposed yolk plug
8.
the
origin of endoderm à arising from involuted dorsal lip cells
· endoderm fans out to give rise to archenteron
9.
simultaneous
with origin of endoderm, some cellsa re proliferated between roof of
archenteron and dorsal epiblast à notochord
chordamesoderm à before differentiation
-
involuted
cells extend anteriorly
-
inturned
endoderm surrounds archenteron
-
archenteron
expands
-
blastocoel
becomes progressively smaller
-
involuting
cells + expanding endoderm à enlarged archenteron lined with endoderm
-
Blastopore
· opens into archenteron
· occluded by yolk endoderm cells
-
overlying
ectoderm thickens
-
whole
embryo elongates
-
start
of neurulation
NEURULATION AND
EARLY ORGANOGENY
Factors Inducing Ectodermal
Thickening
1.
notochord
2.
roof
of archenteron
Neural Plate (Medullary Plate)
-
ectodermal
thickening
-
extends
from dorsal lip of blastopore in an anterior direction
-
median
band of thickened ectoderm
-
where
the brain will develop
Beginning of Central Nervous
System Formation
1.
lateral
folds
2.
transverse
neural fold
3.
neural
groove
Surface Changes
-
shape
becomes elongate
-
neural
plate provides slightly elevated (convex) dorsal surface à becomes flattened
à concave
-
distinct
head
-
ovoid
body à due to yolk
Causal Factor in Change in Shape
of Embryo
-
appearance
of thickened and elongating neural plate
-
subsequent
formation of neural tube
Neurula Stage
-
nervous
structures are being formed
1.
transverse
neural fold
· anterior junction of folds
· represents anterior extremity of developing brain
2.
lateral
neural folds
· paired
· extensive
· more posterior
· represent posterior parts of the brain and spinal cord
levels
· more toward each other
Neural Tube
-
neurocoel
-
fusion
occurs last at the extremities
-
enclosed
canal lined with ciliated and pigmented epithelium
-
found
as the central canal in brain and spinal cord of adult
Sense Plates
-
elevated
ridge of ectoderm
-
gives
rise to
1.
mandibular
arches
2.
lens
of the eye
3.
nasal
placodes
4.
oral
suckers
Stomodeal Cleft
-
ventral
groove
-
sperated
by two mandibular ridges
Oral Suckers
-
adhesive
-
mucus-secreting
glands
Stomodeum
-
ectodermal
-
mouth
-
part
of mouth derived from stomodeum will be lined with ectoderm
Proctodeum
-
invaginating
pit ventral to blastopore
-
ectodermal
-
primordium
of anus
-
establishes
a new ectodermally lined opening into hindgut
Dorsal Fin
-
developed
initially by posterior growth of myotomes
Ependymal Layer
-
lining
of central canal
-
ciliated
and pigmented cells
Nervous Ectoderm
-
nervous
layer of ectoderm of blastular roof
-
gives
rise to neuroblasts of CNS
Neural Crest
-
nervous
layer at level of dorsal fusion is pinched off
-
part
of original ectodermal neural folds which don’t form an integral part of neural
tube
-
paired
-
extend
the full length of CNS
-
give
rise to
1.
ganglia
of CNS
2.
ganglia
of sympathetic nervous system
3.
chromatophores
Level of Brain
1.
ganglia
of CNS
2.
ganglia
of sympathetic nervous system
3.
chromatophores
4.
visceral
cartilage
5.
cranial
cartilage
Body Level
1.
paired
spinal ganglia
2.
sympathetic
nervous system
3.
chromatophores
4.
medulla
of adrenal gland
SURVEY OF MAJOR
DEVELOPMENTAL CHANGES
Primary Parts of Embryonic Brain
1.
Prosencephalon
à forebrain
2.
Mesencephalon
à midbrain
3.
Rhombencephalon
à hindbrain
Prosencephalon
-
primary
forebrain
-
develops
almost immediately
-
gives
rise to optic vesicles
NOTE: prosencephalon à optic vesicles à (walls) lens and
cornea
Derivatives of
Forebrain
1. infundibulum
· ventral to notochord
· vesicular outpocketing of floor of prosencephalon
· along with epithelial hypophysis à posterior
pituitary (?)
· hypophysis
à pigmented ectodermal cells
à between infundibulum and roof of pharynx
2. optic
chiasma
· floor of forebrain
· thickening
· crossing-over
3. optic
recess
· depression associated with lateral optic vesicles
· anterior to optic chiasma
· connected with optic stalk
4. epiphysis
· roof of prosencephalon
· evagination of roof
· forerunner of pineal body
5. anterior
choroid plexus
· anterior to epiphysis
· non-nervous
· vascular
· folded
6. optic
vesicles
· paired primordia of eye
· paired lateral vesicular evaginations of forebrain
7. olfactory
placodes
· paired
· button-like thickening of pigmented surface ectoderm
Rhombencephalon
1.
auditory
placodes
The Enteron
(Gut Cavity)
1.
Foregut
2.
Midgut
3.
Hindgut
Foregut
1.
oral
evagination
· evagination of endoderm
· oral evagination + stomodeal invagination à oral plate à
mouth
2. pharynx
· large cavity of foregut
· expands laterally to form endodermally lined visceral
pouches
3. liver
diverticulum
· forerunner of
a. bile
duct
b. gall
bladder
c. liver
Axial
Skeleton
1.
notochord
· mesodermal origin
· expands and becomes vacuolated
Mesoderm
and Its Derivatives
Mesenchyme
-
embryonic,
loosely dispersed presumptive mesoderm
-
most
anterior mesoderm is in this form
a.
head
b.
pharyngeal
region
Arches
-
vertical
concentrations of mesoderm
Somites
-
mesoderm
posterior to pharynx and lateral to notochord
-
inverted
horseshoe shape around archenteron and yolk
1.
Epimere
à Mesodermal Somite
· posterior to pharynx
a.
dermatome
à cutis plate
à dermis
à appendage musculature
b.
myotome
à skeletal muscles of back
à and body
c.
sclerotome
à mesenchymal
à between myotome and notochord
à vertebral skeleton
2.
Mesomere
à Intermediate Mesoderm
a.
Excretory
System
Mesomere à nephrotome à nephrocoel à pronephros
b.
Urogenital
Tract
3.
Hypomere
à Lateral Plate Mesoderm
a.
Somatic
à somatic + ectoderm = somatopleure à skin, its blood
and CT
à pericardial membrane
b.
Splanchnic
à splanchnic + gut endoderm = splanchnopleure
Ø lining of epithelium
Ø muscles
Ø blood vessels of midgut
Ø blood vessels of hindgut
à myocardium
c.
Coelom
à pleuro-peritoneal cavity
à pericardial cavity
7 mm TADPOLE
INVAGINATION
|
of
|
|
Anterior choroid plexus
|
Roof of prosencephalon
|
|
External nares
|
Epidermal
|
|
Optic cup
|
Optic vesicle
|
|
Otic vesicle
|
Epidermal ectoderm
|
|
External ear
|
ectoderm
|
EVAGINATION
|
of
|
|
Infundibulum
|
Diencephalon
|
|
Ventral pancreas
|
Duodenum
|
|
Epiphysis
|
Prosencephalon
|
|
Optic recess
|
Median ventral
|
|
Optic vesicle
|
Forebrain
|
Mesenchymal Cells
1.
dermatome
2.
sclerotome
Condensations of Mesenchyme
1.
larval
brain case
2.
visceral
arches
Brain Divisions
1.
Prosencephalon
2.
Mesencephalon
3.
Rhombencephalon
Structures Associated with
Prosencephalon
1.
prosocoel
2.
epiphysis
3.
anterior
choroid plexus
4.
future
telencephalon
5.
future
diencephalon
6.
external
nares – olfactory pits
7.
olfactory
canal
8.
olfactory
epithelium
9.
internal
naris
10.
olfactory
nerve
Structures Associated with Diencephalon
1.
optic
vesicles
a.
optic
cup
b.
optic
lens
c.
retina
c.1 rods
c.2 cones
d.
pigmented
epithelium
2.
optic
recess
3.
optic
chiasma
4.
optic
nerve
a.
stalk
b.
ganglion
cells
c.
bipolar
neurons
Structures Associated with
Mesencephalon
1.
infundibulum
2.
hypophysis
3.
mesocoel
4.
trigeminal
ganglion
Structures Associated with
Rhombencephalon
1.
rhombocoel
(4th ventricle)
2.
basal
plates
3.
posterior
choroid plexus
4.
otic
vesicles
5.
acoustico-facialis
a.
facial
(VII)
b.
auditory
(VIII)
6.
endolymphatic
duct
7.
glossopharyngeal
ganglion (IX)
Spinal Cord
1.
central
canal
2.
ependymal
layer
3.
mantle
layer
4.
marginal
layer
Digestive System
Anterior
to posterior
1.
oral
cavity
2.
pharynx
– up to external gill section
3.
esophagus
a.
esophageal
plug
4.
stomach
5.
duodenum
6.
midgut
7.
hindgut
8.
cloaca
9.
proctodeum
– anus
Mesodermal Derivatives
1.
bulk of
skeleton and muscle
2.
entire
circulatory system
3.
epithelium
lining of body cavity
Blood Tracing
*starting from the heart*
Arterial System: Pulmonary Circuit
1.
conus
arteriosus
2.
truncus
arteriosus
3.
afferent
branchial vessels of the aortic arches
4.
gill
capillaries
*efferent
branchial vessels* à vein(?)
Arterial System: Systemic Circuit
1.
conus
arteriosus
2.
truncus
arteriosus
3.
afferent
branchial vessels of the aortic arches
4.
dorsal
aortae
5.
dorsal
aorta (merging at level of stomach)
6.
caudal
artery (after cloaca)
Venous System: Draining the head
part
1.
sinus
venosus
2.
common
cardinal vein (ducts of Cuvier)
3.
anterior
cardinal vein
Venous System: Draining the
posterior part
1.
sinus
venosus
2.
common
cardinal veins
3.
posterior
cardinal veins
4.
posterior
cardinal vein (merge at level of cloaca)
5.
caudal
vein (anus)
SUPER DOOPER MEGA TABLE
Ectodermal Derivatives
Neural Tube
1.
Prosencephalon
a.
future
telen
b.
future
diencephalon
2.
mesencephalon
3.
rhombencephalon
4.
anterior
choroid plexus
5.
epiphysis
6.
infundibulum
7.
hypophysis
(+outer epithelium)
8.
basal
plates
9.
posterior
choroid plexus
10.
spinal
cord
11.
optic
cup
12.
optic
lens
13.
pigmented
epithelium
14.
optic
recess
15.
retina
16.
optic
chiasma
Neurocoel
1.
prosocoel
2.
diocoel
3.
mesocoel
4.
telocoel
5.
rhombocoel
6.
central
canal
Neural Folds
1.
ependymal
layer
2.
mantle
layer
3.
marginal
layer
Neural Crest
1.
bipolar
neurons
2.
ganglion
cells
3.
trigeminal
(V)
4.
acoustico-facialis
(VII-VIII)
5.
glossopharyngeal
(IX)
6.
optic
(II)
Epidermal Ectoderm
1.
endolymphatic
duct
2.
otic
vesicle
3.
olfactory
epithelium
4.
olfactory
canal
5.
external
nares
6.
epidermis
7.
oral
suckers
8.
stomodeum
depression
Mesoderm Derivatives
1.
mesenchyme
2.
germinal
ridge
3.
branchial
muscles
4.
notochord
Epimere (mesenchyme)
1.
dermatome
2.
myotome
3.
sclerotome
4.
branchiometric
muscles
5.
parachordal
cartilage
6.
trabecular
cartilage
7.
visceral
arches
8.
hypobranchial
Mesomere
1.
pronephros
2.
pronephric
duct
Hypomere: Coelom
1.
pericardial
cavity
2.
peritoneal
cavity
Hypomere: Somatic
1.
parietal
pericardium
2.
parietal
peritoneum
Hypomere: Splanchnic
1.
Visceral
pericardium
2.
Visceral
peritoneum
3.
Efferent
branchial vessels
4.
Afferent
branchial vessels
5.
Dorsal
aorta
6.
Truncus
7.
Conus
8.
Atrium
9.
Ventricle
10.
CCV
11.
SV
12.
Vitelline
veins
13.
ACV
14.
PCV
15.
Caudal
artery
16.
Caudal
vein
17.
Gill
capillaries
18.
Hepatic
vein
Endodermal Derivatives
1.
laryngotracheal
groove
2.
thyroid
gland
3.
yolk
Archenteron
1.
pharynx
2.
pharyngeal
pouches
3.
lung
buds
4.
trachea
5.
esophagus
6.
stomach
7.
liver
8.
gall
bladder
9.
midgut
10.
hindgut
11.
pancreas
12.
cloaca
Blastopore
1.
anus
Ectodermal
Derivatives
I.
Neural
Ectoderm
A.
Neural
Tube
1.
Brain
2.
Spinal
Cord
B.
Layers
1.
Ependymal
Layer
2.
Mantle
Layer à Gray matter
a.
Neuroblasts
b.
Glioblasts
3.
Marginal
Layer à White matter
a.
Neurites
b.
Glial
cells
II.
Epidermal
Ectoderm
A.
Epidermis
B.
Epidermal
Derivatives
C.
Lens
D.
Sense
Organs (Invaginations)
1.
Olfactory
2.
Otic
III.
Neural
Crest
A.
Level
of the Brain
1.
Ganglia
of CNS
2.
Ganglia
of Sympathetic Nervous System
3.
Melanophores/Chromatophores
4.
Visceral
Cartilage
5.
Cranial
Cartilage
6.
Dura
Mater
7.
Pia
mater
B.
Level
of the Body
1.
paired
spinal ganglia
2.
sympathetic
nervous system
3.
chromatophores
4.
medulla
of adrenal gland
Endodermal Derivatives
I.
Gametogenic
Cells (?)
II.
Trachea
III.
Lungs
IV.
Gut
Appendages
A.
Pharyngeal
Arches
B.
Pharyngeal
Pouches
V.
Foregut
A.
Lining
of esophagus
B.
Lining
of stomach
C.
Anterior
portion of duodenum
VI.
Midgut
A.
remaining
lining of small intestine
VII.
Hindgut
A.
Large
Intestine
B.
Rectum
Mesodermal Derivatives
I.
Axial
Mesoderm
II.
Paraxial
Mesoderm à Somites
A.
Epimere
1.
Dermatome
a.
Dermis
b.
Connective
Tissue
c.
Appendage
Musculature
2.
Myotome
a.
Skeletal
muscles of back
b.
Skeletal
muscles of body
3.
Sclerotome
a.
Vertebra
b.
Axial
Skeleton
B.
Mesomere
1.
Excretory
System
2.
Urogenital
Tract
C.
Hypomere
1.
Somatic
Layer
a.
Sompatopleure
a.1 Skin, its blood
and connective tissue
b.
Pericardial
membrane (parietal pericardium)
c.
Parietal
Peritoneum
2.
Splanchnic
Layer
a.
Splanchnopleure
a.1 Lining
Epithelium
a.2 Muscles
a.2.1 smooth
a.2.2 myocardium (cardiac)
a.3 Blood vessels
of midgut
a. 4 Blood vessels
of hindgut
b.
Visceral
Pericardium
c.
Visceral
Peritoneum
3.
Coelom
a.
pleuro-peritoneal
cavity
b.
pericardial
cavity
|
|
ECTODERM
|
MESODERM
|
ENDODERM
|
Position
|
Outermost layer of cells
|
Middle layer of cells
|
Innermost layer of cells
|
Origin
|
Cells from
animal hemisphere and equatorial plate cells
(Fate map: presumptive ectoderm)
|
Lips of blastopore
|
Vegetal hemisphere area
|
Derivatives
|
1. epidermis
2. epidermal structures
3. nervous system
4. sense organs
5. stomodeum
6. proctodeum
|
1. skeleton
2. connective tissue
3. muscles
4.
blood
and vascular system
5.
coelomic
epithelium and derivatives
6.
urogenital
system
7.
notochord
|
Lining
epithelium of alimentary tract and its outgrowths…
a. thyroid
b. lungs
c. liver
d. pancreas
e. etc.
|
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