Development of the body plan Flashcards
What animals are used as models in body plans?
Chicks, zebrafish, insects (small animals)
Role of Gastrulation
Lay down body plan
Changes cell shape and establish germ layers.
Form coelom
What are the germ layers
Ectoderm (outside)
Endoderm(inside)
Mesoderm (middle)
Fate of blastopore
Protostomes - Mouth
Deuterostomes - anus
What is cleavage?
Process of cells dividing but not gaining mass.
Increase in number not size.
Steps of chick gastrulation
1 Blastodisc - single celled - goes through cleavage
2 Once more cells formed they migrate to primitive streak, which cause cell to elongate and growth posterior- anterior.
3 Hansen node causes more cells to accumulate at head region and form there.
Steps in Neurulation
1- mesoderm condenses and forms notochord
2 Neural ridge (ectoderm) formed by notochord
3 Neural fold of ridge to form neural tube (brain and spinal cord)
4 Morphogen signals from notochord instruct cells of neural tube, their positional pattern (where to go)
Details of morphogenic signals in neurulation.
Opposing SHH and BMP/Wht pattern the neural tube.
What becomes the bones
Somite’s
Explain the signals controlling positional pattern of somite’s.
Morphogen signals.
Clock and wave models.
The more/faster chemical signals the more somites accumulate in the area.
What controls limb growth and position
Apical epidermal ridge.
Describe what happens to gills in humans.
All organisms have gills in early gestation.
Embryonic pharyngeal arches modify to form head and ears of humans.
3 planes of body plans
Midsagittal, transverse, horizontal
Term for back region of an organism
Dorsal
Term for belly region of organism?
Ventral
Term for head region of organism
Anterior
Term for feet region of organism
Posterior
Term for ends of limbs
Distal
Term for section of limb which attaches to main body
Proximal
Term for outer sections of body
Lateral
