Early Craniate Morphogenesis
Why study this material?
Morphology
What is Life History?
Distinct periods or times?
How should we refer to them?
generate list(s) on board
Craniate Eggs
Types of eggs:
*
distribution of yolk… found in
placental mammals and
amphioxus
*
distribution of yolk concentrated
at the vegetal pole… found in
lampreys, bony fish, amphibians
http://www.bio.unc.edu/faculty/harris/Courses/biol104/
frog.jpg
*
eggs… found in marine lampreys,
cartilaginous fish, reptiles,
monotremes
Craniate Eggs
Oviparity & Viviparity:
Animals that “lay” their eggs are
considered _________________.
Animals that give birth are
considered _________________.
If the embryo could develop
without maternal tissue then
_____________, while
dependent strategies are
__________________
No viviparous …
http://www.nationalaquarium.ie/images/dogfishEgg.jpg
Craniate Eggs
Viviparity:
http://www.biologie.unihamburg.de/zim/herpe/bilder/Ichthyophis_Embryo.jpg
Craniate Eggs
Fertilization:
________________________mode
s exist
In which type of “–parity” are eggs
by necessity internally fertilized?
Usually external fertilization
requires …
Urodeles (salamanders) may use …
http://www.amphibiainfo.com/gallery/caudata/salamandrid
ae/triturus/cristatus/triturus_cristatus_mazzei.jpg
Early Development
Cleavage and the blastula:
As fertilized egg cells divide this is called
_____________.
What happens to cell size initially?
Hollow sphere is called the ________
and it contains a hollow space… the
_____________.
Excessive yolk impedes cell division…
such that a ______________ develops on
an otherwise undivided yolk.
What taxonomic group(s) would
utilize this mode?
Early Development
Let’s review what we can infer since we know this
is “Chordate” development…
What type of cleavage pattern?
What does the 1st opening become?
How many germ layers do we have?
Early Development
_______________ is the process
in which 3 primitive germ layers
are formed
Amphioxous eggs lack yolk and
provide a clear picture
Involution of blastula
Resultant opening is the
______________________
Early Development
Mesoderm forms from the
___________ and then creates
pouches (coelomic or
mesodermal)
Lateral/superficial layer becomes
___________________
Inner/deep layer becomes
___________________
What becomes of the ectoderm?
How about the endoderm?
Early Development
Gastrulation:
Frog – because the yolk
cells are slow… involution
is delayed.
Consequently, slightly
different process
accomplishes same ends.
Lateral mesoderm moves
in from sides and ventral
area of blastopore
heading for the head.
Early Development
Gastrulation:
Chick – Special consideration required when we
have a marolecithal egg.
Blastoderm (epiblast and hypoblast)
______________ continues around the yolk to
become part of the yolk sac
______________ has cells migrating inward that
become endoderm
Cells destined to become the mesoderm migrate
in between the other 2 “derms”
Early Development
What regulates differentiation of
these cells into various germs,
derms, tissues and organs?
Organizer area
_________________
(sonic hedgehog gene)
Proteins involved in signaling called
____________________
http://health.yahoo.com/media/mayoclinic/images/image_p
opup/r7_spinabifida.jpg
Defective homeotic genes can have
severe developmental
consequences…
http://www.humanillnesses.com/images/hdc_0000_0001_0_img0024.jpg
Early Development
What is the
fate of the
different
“derms”?
Germ Layers
Placental mammals have
varying approaches to
gastrulation
However, generally a
______________forms
__________develop
resulting in a
__________________
Neural folds unite forming
a _______________
Process called
____________
Extraembryonic Membranes
Extraembryonic membranes include:
http://embryology.med.unsw.edu.au/Movies/larsen/fetalmembranes.jpg
Extraembryonic Membranes
__________is a highly vascular membrane
that surrounds the yolk.
Empties into the …
Can secrete …
Can serve as …
Can absorb nutrients from mother…
functions as a simple
yolk sac placenta or
a “__________________”
http://www.minkhollow.ca/HatchingProgram/Re
sources/Pictures/embryo-1-wk.JPG
Extraembryonic Membranes
Reptiles and mammals develop inside
2 sacs…
___________surrounds the embryo
___________surrounds the amnion
and the yolk sac
Important feature that allows eggs to
be laid on land (with less dependence
on water)
Amniotic fluid surrounds the embryo
and is contained by the amnion
Where does this water come from?
Extraembryonic Membranes
___________ is an evagination of the
___________
Communicates with the inner surface of the
chorion forming the …
Reptiles and monotremes aids in …
In most mammals serves as a membrane of
the placenta… transferring …
Base of this sac becomes the …
Extraembryonic Membranes
___________ generally is
any place embryonic and
maternal tissues come
together for exchange
More
specifically/restricted
definition…
organ containing highly
vascular region of
extraembryonic
membrane in
communication with
highly vascular region of
maternal tissue
http://www.acmc.uq.edu.au/images/projectimages/Fresh_Placenta.jpg
Extraembryonic Membranes
Placentas can have a
simple communication
with maternal tissue…
___________________
Or
They can have chorionic
villi that invade
endometrium and pull
part of this lining off with
birth…
__________________
Villi can be positioned
variously on the chorion
http://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Human
_placenta_uterine_side.jpg/799px-Human_placenta_uterine_side.jpg