Chapter 13- Reporting Flashcards
- the bones of any tetrapod limb, be it arm
or leg, wing or flipper
stylopod
(radius-ulna/tibia-fibula) in the middle of
the region
zeugopod
- (Carpals-fingers/Tarsals-Toes)
autopod
- is the set of processes by which
embryonic cells form ordered spatial arrangements of
differentiated tissues
pattern formation
is an extremely complex organ
with an asymmetrical arrangement of parts.
vertebrate limb
The first dimension is the _______________________
(“close-far”; shoulder-finger or hip-toe). The bones of the limb are formed by endochondral ossification.
Proximal-distal axis
The second dimension is the_______________ (thumb-pinkie). Our little fingers or toes mark the Posterior side, while our thumbs or big toes are at the
anterior end.
Anterior-Posterior Axis
limbs have a _________________: our palms
(ventral) are readily distinguishable from our
knuckles (dorsal).
Dorsal-Ventral Axis
what is the step for the development of the tetrapod limb?
- A. Proliferation of mesenchymal cells
- B. Entry of myoblast (purple) into the limb bud
This larger region, representing all the cells in the area capable of forming a limb, is called the ______________.
limb field
These mesenchymal cells accumulate under the ectodermal tissue to create a circular bulge called a ________________
limb bud
- This is capable of initiating the limb forming interactions between ectoderm and mesoderm.
- capable of initiating the limb-forming interactions between the
ectoderm and the mesoderm
Fgf10
The loss-of-function data were equivocal:
humans heterozygous for the TBX5 gene
have ____________________, characterized
by abnormalities of the heart and upper
limbs (Basson et al. 1996; Li et al. 1996).
The legs are not affected, but neither are
the arms transformed into a pair of legs
Holt-Oram syndrome
As mesenchyme cells enter the limb region, they secrete factors
that induce the overlying ectoderm to form a structure called the ___________________
apical ectodermal ridge (AER)
This ridge runs along the distal margin of the limb bud and will become a major signaling center for the developing limb. Its roles include
- (1) maintaining the mesenchyme beneath it in a plastic, proliferating phase that enables the linear (proximal-distal) growth of the limb;
- (2) maintaining the expression of those molecules that generate the anterior posterior (thumb-pinky) axis; and
- (3) interacting with the proteins specifying the anterior posterior and dorsal-ventral axes so that each cell is given instructions on how to differentiate.
is capable of inducing the AER in the
competent ectoderm between the dorsal and ventral sides of the embryo.
FGF10
The proximal-distal growth and differentiation of the limb bud is made possible by a series of interactions between the _________________________________
limb bud mesenchyme and the AER.
The AER initiates limb bud elongation by promoting the ___________________ cells underneath it
proliferation of mesenchyme
is the region of cell division
responsible for this elongation, and it extends about 200 μm in from the AER.
progress zone
if an FGF-containing bead is
placed in the hole left by the removal of the AER, a normal limb will form. This process is known as the
FGF- induced limb regeneration
first cells to leave
the PZ
proximal (stylopod) structures
When older AERs combined with younger mesoderm should produce _____________________________
limbs with deletions in the middle
When younger AERs combined with older mesoderm should produce ________________________
duplications of structures
who invented the activator-inhibitor model?
Newman and Baht
