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Embryology Final Exam > Limb Development > Flashcards

Limb Development Flashcards

1
Q

Sclerotome will give rise to ___ bones

A

axial

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2
Q

Dermomyotome will give rise to ___ ______ muscles

A

all skeletal

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3
Q

somatic mesoderm will give rise to _____ bones

A

appendicular

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4
Q

Intramembranous ossification

A

no cartilaginous cells are involved, forms flat bones (aka dermal or membrane bones) - facial bones, cranial vault, part of clavicle

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5
Q

endochondral ossification

A

cartilaginous cells are replaced by osseous cells, forms most bones of the body - cranial base, pharyngeal cartilages, vertebrae, thoracic cage, appendicular bones, part of clavicle

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6
Q

Synovial joint formation

A

Interzonal mesenchyme differentiates into fibroblastic tissues, which give rise to peripheral and central structures. Peripherally - articular cartilages & joint capsule. Centrally - synovial cavity, enclosed joint ligaments, menisci

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7
Q

Cells of skeletal myogenesis - cell origins

A

segmented paraxial mesoderm, unsegmented paraxial mesoderm, prechordal plate mesoderm

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8
Q

Cells of skeletal myogenesis - cell types

A

myoblasts (myofibers) & satellite cells (myofibers)

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9
Q

Cells of skeletal myogenesis - development waves

A

embryonic (myoblasts), fetal (myoblasts), and postnatal/adult (satellite cells)

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10
Q

Dermamyotomes differentiate into

A

dermatomes and myotomes

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11
Q

Myotomes further differentiate into

A

epimere and hypomere populations

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12
Q

Dermamyotome derivatives

A

dermatome, epimeres, and hypomeres

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13
Q

dermatome give rise to

A

primarily dermis of the back and neck

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14
Q

epimeres give rise to

A

intrinsic back muscles (epaxial muscles)

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15
Q

Hypomeres give rise to

A

all other skeletal muscles (hypaxial muscles)

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16
Q

The hypomere associates with and divides into 2 distinct populations on either side of the somatic lateral plate mesoderm -

A

ventral muscle mass and dorsal muscle mass

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17
Q

Ventral muscle mass (AKA preaxial muscle mass)

A

Will form the flexors, adductors, and pronators in the upper limb and in the lower limb

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18
Q

Muscles formed from ventral muscle mass in upper limbs

A

pectoralis major and minor, subclavius, anterior arm muscles, anterior/volar forearm muscles, palmar/volar hand muscles

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19
Q

Muscles formed from ventral muscle mass in lower limbs

A

medial thigh muscles, posterior thigh muscles, posterior leg muscles, plantar foot muscles, gemellus superior and inferior, obturator internus, and quadratus femoris

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20
Q

Dorsal muscle mass (AKA postaxial muscle mass)

A

will form extensors, abductors, and supinators in the upper limbs and lower limbs

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21
Q

Muscles formed from dorsal muscle mass in upper limbs

A

scapular muscles, latissimus dorsi, posterior arm muscles, posterior forearm muscles, lateral hand muscles

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22
Q

Muscles formed from dorsal muscle mass in lower limbs

A

gluteal muscles, anterior thigh muscles, biceps femoris, anterior leg muscles, lateral leg muscles, dorsal foot muscles

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23
Q

When and where do limb buds begin developing?

A

They begin forming on the ventrolateral body wall during week 4 of development

24
Q

When are both limb buds fully developed?

A

By the end of week 8

25
Q

Limb buds differentiate and grow in 3 axis -

A

proximal-distal axis, cranial-caudal axis, dorsal-ventral axis

26
Q

Proximal-distal axis

A

defined along the length of the limb, such as from the shoulder to fingers or hip to toes

27
Q

Cranial-caudal axis

A

defined along the breadth of the limb, such as from thumb to pinky or big to little toes

28
Q

Dorsal-ventral axis

A

defined along the depth of the limb, such as from the knuckles to the palm or knee to popliteal region

29
Q

What is the Apical ectodermal ridge (AER)

A

required for proximodistal growth, it is a thickened portion of ectoderm at the apex of the limb bud

30
Q

What induces the formation of the AER?

A

Underlying mesenchyme

31
Q

What hormone does the AER produce in order to stimulate the mesenchymal core of the limb bud to proliferate, pushing the AER away from body wall?

A

fetal growth factor (Fgf)

32
Q

stylopod

A

the most proximal region and first to develop from AER, forms the arm and thigh bones

33
Q

zeugopod

A

the intermediate region and second to develop from AER, forms the forearm and leg bones

34
Q

autopod

A

the distal region and last to develop from AER, forms the hand and foot bones

35
Q

Disruption in AER will result in

A

distal deletions

36
Q

amelia

A

an anomaly where no structures of the limb formed due to early complete loss or disruption of AER

37
Q

meromelia

A

an anomaly where the distal structures present are malformed with the most distal structures of the limb completely absent due to late complete loss or disruption of AER

38
Q

cleft hands or feet (AER)

A

anomalies where the middle digits of a limb are absent due to late partial loss or disruption of AER

39
Q

Homebox (HOX) genes

A

critical in determining proximodistal patterning - they direct morphological changes during development.

40
Q

Absence of 1 or more HOX genes during development can lead to

A

middle deletions such as phocomelia - an anomaly where distal limb structures formed on proximal structures and intermediate structures are missing

41
Q

Zone of polarizing activity (ZPA)

A

drives craniocaudal differentiation - it is a defined region along the caudal/postaxial border of the limb bud that produces sonic hedgehog (Shh)

42
Q

When does Shh expression happen and what does it do?

A

After the hand or foot plate forms, Shh expression will happen to stimulate the formation of digits

43
Q

Disruption of the ZPA can result in

A

aberrant digit enumeration

44
Q

Polydactyly

A

an anomaly where there are more than 5 digits present on a limb, which can be caused by excessive Shh expression or a larger than normal ZPA

45
Q

Oligodactyly or adactyly

A

anomalies where there are less than 5 digits present on a limb or a complete absence of digits, respectively, which can result from insufficient Shh expression or an absent ZPA

46
Q

Cleft hands or feet (ZPA)

A

anomalies where the middle digits of a limb are absent, which can result from complex disruptions of the ZPA

47
Q

what is the role of lmx1b, wnt7a, and en1?

A

dorsoventral patterning

48
Q

Lmx1b

A

a specific hox gene involved in limb morphogenesis in the dorsal-ventral axis, expressed in the dorsal mesenchymal core of the limb bud, mediates the activity of Wnt7a

49
Q

Wnt7a

A

A member of the Wnt family of genes, expressed by the dorsal ectoderm covering the limb bud, stimulates dorsalization via Lmx1b

50
Q

En1

A

expressed by the ventral ectoderm covering the limb bud, inhibits activity of Wnt7a, thereby promoting ventralization

51
Q

Nail-patella syndrome

A

an anomaly characterized by soft or absent nail beds in the limbs and a lack of a patella due to mutation in Lmx1b

52
Q

Upper limb rotates _____ to position structures

A

laterally

53
Q

Lower limb rotates ______ to position structures

A

medially

54
Q

amniotic band syndrome

A

an anomaly similar to meromelia where the most distal structures of the limb are absent, however proximal portions of limbs are normal - occurs due to amniotic bands (scar tissue that can form in the womb) that wraps around the limb or digits during development and causing ischemic amputation

55
Q

Club foot

A

an anomaly that is characterized by a sharp medial curvature of the foot and ankle. Caused by reduced space in the womb due to oligohydramnios or a naturally small womb with a large fetus.

56
Q

Thalidomide and limb development

A

Embryology Final Exam (5 decks)

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