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
The limb bud becomes subsequently patterned into three areas:
1st, 2nd, 3rd domain
is the earliest restriction in limb bud cell
potency from the pluripotent condition
specification of the anterior-posterior axis
A region in the mesoderm where the
anterior-posterior axis is specified
zone of polarizing activity
- plays a role in specifiying the location
where the limbs will form
● They also play a secondary role of specifying
whether a particular mesenchymal cell will become stylopod, zeugopod, or or autopod
● Its also plays another role in specifying both the ZPA and the identity of the digits and specifying code for limb skeleton identity
Hox genes
molecule that is important in specifying
dorsal-ventral polarity
Wnt7a
The synthesis of Sonic hedgehog is stimulated by the combination of ______________________
Fgf4 and Wnt7a proteins
This is crucial for the formation of joints and separation of fingers in the tetrapod limb.
cell death
They are separated from each other by an
interior necrotic zone, and two other regions, the anterior and
posterior necrotic zones
ulna and radius
is synthesized in the perichondrial cells
surrounding the condensing chondrocytes and
promotes cartilage formation
BMP7
without feathers, resembles a small
coelurosaur, such as Jurassic Park’s Velociraptor
archaeopteryx
This is a negative regulator of the Wnt/β-catenin signaling pathway
Dkk-1
front nears cartilage ends of the
cartilage model
ossification
Bone formation before birth limits ________ and _______
growth and size
spreads outward in long
bones of mammals, including humans.
endochondral ossification
cartilaginous areas at the
end of the long bones
epiphyseal growth plates
Epiphyseal Three Regions:
➢ Region of Chondrocyte
Proliferate
➢ Region of Mature Chondrocytes
➢ Region of Hypertrophic
Chondrocytes
inhibit proliferation of epiphyseal growth plate cells and facial cartilage.
fibroblast growth factors
dominant condition, is caused by
mutations in the transmembrane region of FGF receptor 3.
achondroplasia
Mutations in the extracellular portion or tyrosine kinase intracellular domain can result in _________________________, a lethal form of dwarfism
resembling homozygous achondroplasia.
thanatophoric dysplasia
- is essential for bone development in both
males and females. - regulates bone growth, even in men, with
some cases indicating continued growth in adulthood without estrogen.
estrogen
are found on growth
hormone-regulating cells and all human growth plate cells.
estrogen receptors
stimulate skeletal growth, while
high levels induce apoptosis and invasion of
osteoblasts into the growth plate.
low estrogen levels
occurs when osteoblasts stop
growing without further cartilage formation.
growth plate closure
This is required for maintaining chondrocyte cell division and preventing hypertrophy. In humans, loss-of-function mutations can cause severe growth defects.
Parathyroid hormone-related peptide
