MSK Embryology

Question 1

Okay let me start by saying

Answer 1

This lecture went into a lot of detail and was a bit confusing in places.
Realistically, if any of this comes up, it’ll be at most two questions.
These flashcards cover basics I think, but should be enough for a general idea.
Maybe rewatch the lecture before exams if worried.

xx

Question 2

What does the development of the limbs start?

Answer 2

End of week 4

Question 3

Where do limb buds form from?

Answer 3

Form deep to a thick band of ectoderm

Question 4

AER= apical ectodermal ridge

What is the AER?

Answer 4

Thickened ectoderm at the apex of a limb bud

Question 5

What induces the AER?

Answer 5

Paracrine Growth Factor FGF-10

Question 6

ZPA= zone of polarizing activity

What happens here?

Answer 6

Mesodermal cells aggravate the base of each limb bud

Question 7

Which are larger- upper limb buds or lower limb buds?

Answer 7

UL buds

Question 8

Where do UL buds appear?

Answer 8

Opposite the caudal and cervical segments (C4-T2)

Question 9

Where do LL buds appear?

Answer 9

Opposite the lumbar and upper sacral segments (L2-S2)

Question 10

In which week do the digits of the hands and feet become separated and how does this occur?

Answer 10

Week 8- do to apoptosis of the tissue between fingers and toes

->if this does not occur, there may be webbing of hands or feet

Question 11

By which process do limb buds elongate?

Answer 11

By mesenchymal proliferation

Question 12

All of the bones of the upper limb are formed from the lateral plate mesoderm except for which?

Answer 12

Clavicle

Question 13

Where are the primary ossification centres in the upper limb>

Answer 13

Clavicle
Humerus
Radius
Ulna

Question 14

What are all the bones of the lower limb formed from?

Answer 14

Lateral plate mesoderm

Question 15

How are myocytes (muscle cell precursors) formed?

Answer 15

Mesoderm from the dermamytomone regions of somites migrate into the limb bud and condense and differentiate into the myocytes

Question 16

Where are the primary ossification centres for the lower limbs during weeks 7-9?

Answer 16

Tibia and fibula

->more develop after birth e.g. ilium, ischium, pubis, talus, phalanges etc

Question 17

Which types of muscle in the upper limb does posterior condensation of myoblasts form?

Answer 17

Extensors and supinator muscle

Question 18

Which types of muscle in the upper limb does anterior condensation of myoblasts form?

Answer 18

Flexors and pronator muscles

Question 19

Which types of muscle in the lower limb does posterior condensation of myoblasts form?

Answer 19

Extensors and abductors

Question 20

Which types of muscle in the lower limb does anterior condensation of myoblasts form?

Answer 20

Flexors and abductors

Question 21

What does the 4th aortic arch form in terms of vasculature?

Answer 21

Proximal right subclavian artery

Question 22

Where does the distal part of the right subclavian artery and the entire left subclavian artery come from?

Answer 22

7th intersegmental artery

Question 23

What provides the axis artery of the upper limb?

Answer 23

Subclavian artery

Question 24

What provides the axis artery of the lower limb?

Answer 24

Umbilical artery

Question 25

Rotation occurs of the limbs. What type of rotation occurs in the upper and lower limb at week 6?

Answer 25

Limbs rotate horizontally into a sagittal orientation

Question 26

In week 7, the rotation of upper and lower limbs differs.
What happens in the upper limb?

Answer 26

Rotates laterally

->this is so elbows are dorsal with the extensors posterior of the UL

Question 27

In week 7, the rotation of upper and lower limbs differs.
What happens in the lower limb?

Answer 27

Rotates medially

->this is so knees are ventral with the extensors anterior and flexors posterior

Question 28

During which week do the peripheral nerves grow from the developing limb plexuses?

Answer 28

Week 5

Question 29

Dermatome?

Answer 29

Area of skin supplied by a single spinal nerve and its ganglion

Question 30

Cutaneous nerve area?

Answer 30

Area of skin supplied by a peripheral nerve

Question 31

If there are problems during development, the congenital defects are more severe when…?

Answer 31

They occur earlier in the development process

Question 32

What are some of the causes of congenital defects?

Answer 32

Genes
Environment e.g. drugs, alcohol

Question 33

Which drug in particular is known to lead to congenital problems e.g. amelia (lacking one or more limbs)?

Answer 33

Thalidomide

->can still be used today in myeloma and leprosy treatment but must be avoided in all women of child bearing age

Question 34

Amelia?

Answer 34

Loss of one or more limbs

Question 35

Meromelia?

Answer 35

Partial absence of at least one limb

Question 36

Brachydactyly?

Answer 36

Reduced number of digits

Question 37

Polydactyly?

Answer 37

Additional digits