Anatomy (Other) Flashcards
During embryonic development, when do upper and lower limb buds appear?
24 to 28 days
During embryonic development, when does limb development take place?
4th to 8th weeks
During embryonic development, what is the skin of the limbs derived from?
Ectoderm
During embryonic development, what is the skeletomuscular system derived from?
Mesoderm
What structure forms from the ectoderm at the distal end of each limb bud ?
Apical ectodermal ridge (AER)
AER is a critical structure for normal limb development, what kind of growth does it promote?
Proximodistal growth of the limb
How does the AER promote growth of the limb?
Promotes proliferation of the cells underlying the mesenchyme via molecular signalling
This triggers the mesenchymal cells to form cartilage and muscle
What is mesenchyme?
Undifferentiated embryonic connective tissue which develops into connective and skeletal tissues
What happens at the distal part of the limbs 6 weeks into development?
The limb buds form handplates and footplates
How are digits formed?
By cell death (apoptosis) occurring in sections of the AER
During the 4th and 5th embryonic weeks, lim development is sensitive to environmental toxins or drugs, what is a name given to these toxins or drugs ?
Teratogen
Give an example of a teratogen?
Thalidomide
What is the name given to the complete absence of a limb due to a development abnormality?
Amelia
What is the name given to the partial absence of a limb due to a development abnormality?
Meromelia
What is an axial line?
Line between two adjacent dermatomes that are not represented by immediately adjacent spinal levels.
