Early Craniate MorphogenesisWhy study this material?

Morphology

What is Life History?

Distinct periods or times?

How should we refer to them?

generate list(s) on board

Craniate EggsTypes 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

*eggs… found in marine lampreys, cartilaginous fish, reptiles, monotremes

http://www.bio.unc.edu/faculty/harris/Courses/biol104/frog.jpg

Craniate EggsOviparity & 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 EggsViviparity:

http://www.biologie.uni-hamburg.de/zim/herpe/bilder/Ichthyophis_Embryo.jpg

Craniate EggsFertilization:

________________________modes 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/

salamandridae/triturus/cristatus/triturus_cristatus_mazzei.jpg

Early DevelopmentCleavage 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 DevelopmentLet’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 DevelopmentMesoderm 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 DevelopmentGastrulation:

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 DevelopmentWhat regulates differentiation of these cells into various germs, derms, tissues and organs?

Organizer area

_________________ (sonic hedgehog gene)

Proteins involved in signaling called ____________________

Defective homeotic genes can have severe developmental consequences…

http://health.yahoo.com/media/mayoclinic/images/image_popup/r7_spinabifida.jpg

http://www.humanillnesses.com/images/hdc_0000_0001_0_img0024.jpg

Early DevelopmentWhat is the fate of the different “derms”?

Germ LayersPlacental mammals have varying approaches to gastrulation

However, generally a ______________forms

__________develop resulting in a __________________

Neural folds unite forming a _______________

Process called ____________

Extraembryonic MembranesExtraembryonic 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/Resources/Pictures/embryo-1-wk.JPG

Extraembryonic MembranesReptiles 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 MembranesPlacentas 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