Development of the Nervous and Musculoskeletal Systems for Limb Formation 2 Flashcards Preview

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Flashcards in Development of the Nervous and Musculoskeletal Systems for Limb Formation 2 Deck (77):
1

The sternum and appendicular skeleton, including the shoulder and pelvic girdles and limbs, arise from

Somatic mesoderm

2

Projects from the anterolateral body wall and contains mesenchyme originating from somatic mesoderm and myoblasts originating from somitic

Limb bud

3

The mesenchyme (somatic mesoderm) and myoblasts (somitic mesoderm) of the limb bud will differentiate to form

Connective tissues and skeletal muscles of limb respectively

4

The chick embryo skull shows an unstained mesenchyme membrane that will soon undergo
intramembranous ossification to form

Flat bones of the skull

5

Ossification continues after birth and ossification centers are completed at specific ages with varying rates between

Male and female

6

Mesenchymal cells of the somitic dermatome and somatic mesoderm invade tissues deep to the surface ectoderm to form the

Dermis

7

Forms the epidermis and epidermal derivatives like hair, nails, and sweat glands

Surface ectoderm

8

Form the mesenchyme that differentiates into dermis connective tissue in the face and neck

Neural crest cells

9

With the exception of some smooth muscle, skeletal, smooth, and cardiac muscle are all formed from the

Mesoderm

10

In the MSK system, skeletal muscle is derived from

Paraxial mesoderm (which differentiates into somites and then myotomes)

11

Myotomes contain cells that either remain in the somite region or migrate to the somatic mesoderm. These precursor muscle cells are called

Myoblasts

12

Forms from the migration of somitic mesoderm cells into the somatic mesoderm

Skeletal muscle

13

Myoblasts that do not migrate form the

Primaxial skeletal muscles of the back

14

Include rhomboids, levator scapulae, latissimus dorsi, intercostals, and shoulder girdle muscles

Primaxial muscles

15

Myoblasts that migrate to the somatic mesoderm form

Abaxial muscles of anterolateral body wall and limbs

16

To form the large, cylindrical, multinucleate muscle fibers/cells seen in skeletal muscle, myoblasts fuse to form a

Syncytium

17

Lie adjacent to skeletal muscle fibers and serve as stem cells to offer limited capacity for regeneration of damages skeletal muscle tissue

Satellite cells

18

Nerves and muscle cells arise from the same level
adjacent to the

Neural tube

19

A defect characterized by absence of the pectoralis muscles

Poland's sequence

20

Can present clinically with a flattened pectoral region, a missing anterior axillary fold, and a displaced nipple

Poland's sequence

21

Curves the embryo into a C-shape, with the embryo curving out towards the dorsal side

Cephalo/cranial-caudal folding of the embryo

22

The process where the edges of the flat embryo bend and fuse ventrally in the midline to form a cylindrically shaped embryo

Lateral folding

23

In lateral folding, the embryo is now a tube with two internal tubes, which are the

Gut tube and neural tube

24

The epidermis and underlying tissues along
the anterior body wall are derived from the ventral folding and fusion of

Ectoderm and parietal mesoderm

25

Also with folding of the lateral edges, the endoderm
fuses and creates the

Gut tube

26

The gut tube is surrounded by the

-lies between the lateral plate mesoderm layers with parietal and visceral mesoderm

Intraembryonic coelom (body cavity)

27

Defects can arise when the ventral body wall of the thorax, abdomen, or pelvis fail to

Fuse

28

Incomplete fusion in the thorax can lead to

Ectopia cordis (heart on the outside), gastroschisis (abdominal viscera on outside), and bladder extrophy (bladder on outside)

29

Limb buds project from the anterolateral body wall by the end of

Week 4 of development

30

Made up of a core of somatic mesoderm derived
mesenchyme covered by ectoderm

Limb buds

31

The upper limb appears first, at day 24, followed by the hind limb at

Day 28

32

Occurs between the fifth and eighth weeks and
involves growth, induction, apoptosis, and patterning, as described below

Differentiation of the limb buds

33

Surface ectoderm cells overlying the distal border of
the limb thickens into an

Apical ectodermal ridge (AER)

34

Acts as a signaling center that induces nearby mesenchyme (through FGF secretion) to proliferate rapidly without differentiating to maintain distal outgrowth of limb mesenchyme

The AER

35

The area of mesenchyme proliferation and elongation is called the

Progress zone

36

As the limb elongates, the AER moves distally. This distal movement allows the proximal portions of the limb to

Differentiate and develop into cartilage and bone

37

As the limb grows, cells near the proximal end are exposed to retinoic acid that causes them to differentiate into

Proximal bones

38

Digits begin formation at the DISTAL end when apoptosis occurs in the

AER

39

Final separation by apoptosis occurs between the webbing or rays in the interdigital spaces to form

Digits

40

The fusion of two or more digits that may result from incomplete apoptosis between digits

Syndactyly

41

Responsible for the differences in the structure of digits so that there is a “pinky side” and a “thumb side”

Zone of polarizing activity (ZPA)

42

Communicates with the ZPA, which is a cluster of mesenchymal cells that secrete SHH to induce differentiation of anterior-posterior patterning of digits

The AER

43

Dorsalizing factors that interact with ventralizing factors (such as engrailed-1) to establish the dorso-ventral axis of the limb

WNT7 and LMX1

44

WNT7 and LMX1 lead to a limb with an

Extensor muscle side and a flexor muscle side

45

Disruption of the proximal-distal development of the limbs results from loss of

FGF signaling

46

Disruption of the proximal-distal development of the limbs can result in

Amelia (lack of limb), Meromelia (partial lack of limb), and adactylyl (absense of digits)

47

Polydactyly (extra digits) and syndactylyl (fusion of digits) may be the result of

BMP or SHH disregulation or disruption

48

At 7 weeks, what happens to the limbs?

They rotate

49

Most cartilage templates of limb bones form between

5 and 12 weeks

50

Ossification of proximal bones in the upper limb begins in the

7th week

51

Ossification of proximal bones in the lower limb begins in the

8th week

52

Most bones show ossification by the 12th week, although ischium and pubis not until the

15th and 20th weeks

53

Smaller tarsal and carpal bones are not ossified until

Childhood

54

As the AER advances distally with mesenchymal cell proliferation, proximal mesenchymal cells differentiate into

Chondroblasts (during week 6)

55

Bone is vascular and replaces the avascular cartilage, which has a size limit due to reliance on

Diffusion through matrix for nutrients/waste exchange

56

Cartilage calcification in the diaphysis (shaft) of long bones results in poor oxygen diffusion through the

Avascular cartilage

57

As a result, the cartilaghe breaks down and is removed by

Osteoclasts

58

Blood vessels invade the diaphysis and are accompanied by

Osteoblasts

59

As cartilage is removed by osteoclasts, osteoblasts secrete bone matrix to form the

-occurs during prenatal development

Primary ossification center

60

Primary ossification centers are formed during prenatal development and are present in all long bones of limbs by the

12th week of development

61

At birth, diaphyses of bones are completely ossified, but the ends, the epiphyses, are still

Hyaline cartilage

62

Primary and secondary ossification centers form on either side of a cartilaginous

Epiphyseal growth plate

63

The growth plate is made of hyaline cartilage that has chondrocytes that can proliferate in response to

Growth hormone from adenohypohpysis

64

Located at the growth plate retain the ability to divide when stimulated by growth factors in order to increase length of long bones

Chondrocytes

65

Once growth is completed into adulthood (20-25 years of age), the original primary and secondary ossification centers will meet as bone fills in the growth plates to
form the

Epiphyseal line (and bone lengthening stops)

66

The most common form of skeletal dysplasia (1/20,000 live births) and primarily affects long bones

Achondroplasia

67

A gene associated with achondroplasia is

FGFR3

68

One of the results of achondroplasia is shortened extremities due to reduced chondrocyte proliferation at

Growth plates

69

Occurs while connective tissues are developing in somatic mesoderm

Muscle formation

70

Somitic mesoderm invades somatic mesoderm during

Week 5

71

Develops from ventral and dorsal condensations of somitic mesenchyme

Limb musculature

72

The dorsal mass forms

Extensors and supinators of upper limb

and

Extensors and abductors of lower limb

73

The ventral mass forms

Flexors and pronators of upper limb

and

Flexors and adductors of lower limb

74

Based on induction of neuroepithelium to form neurons and neuroglia of the CNS and of neural crest to form neurons and neuroglia of the PNS

Nervous System Formation

75

Based on origins from somites and somatic mesoderm

MSK formation

76

Transforms the flat trilaminar disc into a cylindrical, C-shaped embryo whose limb buds project from the anterolateral wall

Body folding

77

Involves orchestration of somatic mesoderm differentiation and migration of myotome myoblast cells with their innervation

Limb formation

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