Limb development Flashcards
Appearance of the Limbs
Day 24: (1)_____ extends from body;
(2)____ follows on day 26;
distinct (3)_____ present in week 5, gradually disappears as lower limbs enlarge
- upper limb bud
- lower limb bud
- tail segment
Appearance of the Limbs
distinct tail segment present in week 5, gradually disappears as _____ enlarge
lower limbs
Appearance of the Limbs
Limb buds appear as flippers, will form___ and ____
hand plate and foot plate
Appearance of the Limbs
fingers and toes form from ____ in the plates
digital rays
Appearance of the Limbs
Limb buds appear as flippers, will form hand plate and foot plate
→ fingers and toes form from digital rays in the plates
→ tissue between rays undergoes ___; typically completed by day 52 and 56
apoptosis
Limb Rotation
Upper and lower limb buds bend at ____ and ____ with the palms and soles of the feet facing medially.
→ By day 56 they have rotated in opposite directions so that the elbow points posteriorly and the knee points anteriorly.
the elbow and knee
Limb Rotation
(1)___ and ____ bend at the elbow and knee with (2)____ and ___ facing medially.
→ By day 56 they have rotated in opposite directions so that the elbow points posteriorly and the knee points anteriorly.
- Upper and lower limb buds
- the palms and soles of the feet
Limb Rotation
Upper and lower limb buds bend at the elbow and knee with the palms and soles of the feet facing medially.
→ By day 56 they have rotated in opposite directions so that the elbow points (1)_____ and the knee points (2)____
- posteriorly
- anteriorly.
Limb Rotation
Upper and lower limb buds bend at ____ and ____ with the palms and soles of the feet facing medially.
→ By day 56 they have rotated in opposite directions so that the elbow points posteriorly and the knee points anteriorly.
the elbow and knee
The role of Apical Epidermal Ridge (AER)
An outgrowth of limb buds that exerts an inductive influence on the limb mesenchyme, promoting growth and development of the limbs
What is the signal produced in AER?
Fibroblast Growth Factor 8 (FGF8
The role of Fibroblast Growth Factor 8 (FGF8)
It interacts with the underlying mesenchyme to keep the limb
(Implanting FGF8 into an embryo can induce the formation of additional limbs)
The molecular signals that interact with the AER and set up proximo-distal patterning are members of ___
the Hox gene family
Hox Gene Expressure in Limbs
The molecular signals that interact with the AER and set up proximo-distal patterning are members of the Hox gene family
→ As the bud extends more Hox family genes are expressed distally, signaling for ___
more distal structures, such as the carpal bones, to condense.
Hox Gene Expressure in Limbs
If FGF8 is not produced or its expression is interrupted, what happen to the limbs?
the limbs will not form or will be disrupted
Zone of Polarizing Activity
The molecular marker that signals for medio-lateral patterning is ____
the protein Sonic Hedgehog (Shh)
Zone of Polarizing Activity
What is the protein Sonic Hedgehog (Shh)?
The molecular marker that signals for medio-lateral patterning
Zone of Polarizing Activity
The molecular marker that signals for medio-lateral patterning is the protein Sonic Hedgehog (Shh)
→ it is localized in ____
the medial region of the developing limb, the Zone of Polarizing Activity (ZPA).
Zone of Polarizing Activity
What is the Zone of Polarizing Activity (ZPA)?
the medial region of the developing limb
Zone of Polarizing Activity
The more exposure a region has to Shh, the more it develops into ____
a medial digit
