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Skin MS: Week 3 > Embryology of Bone and Muscle > Flashcards

Embryology of Bone and Muscle Flashcards

1
Q

Embryonic connective tisse

A

Mesenchyme

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2
Q

Mesenchyme is derived from _______ and _______

A

mesoderm and neural crest

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3
Q

defines axes, mechanical role in folding process, signaling role in formation of neural groove/tube, somites (indirectly) and musculoskeletal system (via Shh)
contributes to vertebral bodies and intervertebral discs

A

Notochord

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4
Q

_______ induces overlying ectoderm to invaginate –> neural groove and tube

A

notochord

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5
Q

Neural tube induces formation of _____/_____ from paraxial mesoderm

A

vertebrae/somites

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6
Q

clusters of mesodermal tissue that condense segmentally in rostral to caudal progression. They are derived from paraxial mesoderm.

A

Somites (somitomeres)

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7
Q

Somitomeres –> Somites

A

Compact and bound by epithelium = somites

Pairs 1-7 do not compact –> contribute to formation of head and neck

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8
Q

Mesodermal cells from somites migrate and give rise to

A

Dermomyotome –> dermatomes and myotomes

Sclerotome –> bone and cartilage

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9
Q

Membranous bone formation

A

Mesenchyme condenses into a very vascular CT. Mesenchymal cells produce matrix containing collagen fibers. Cells differentiate into osteoblasts and begin to lay down mineralized bone matrix, typical in the formation of flat bones (skull).

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10
Q

Endochondral bone formation

A

Mesenchymal cells differentiate into chondroblasts –> hyaline cartilage model of the (long) bone. Matrix calcifies around the periphery of the shaft. Interiorly, some cells differentiate into osteoblasts and begin to lay down mineralized bony matrix. —Primary ossification center.

Blood vessels invade the diaphysis and stimulate ossification. The diaphysis grows in length toward the ends of the bone. Later, secondary ossification centers form in the ends (epiphyses). The epiphyses grow toward the shaft, leaving a region of hyaline cartilage, the epiphyseal (growth) plate between. Growth of the long bone stops when the cartilage plate has completely ossified.

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11
Q

Timing of ossification centers for long bones

A

Primary oss centers at week 8 in certain order
Nearly all have primaries at birth
Most secondary centers appear after birth (epiphysis)

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12
Q

Joint formation (overall)

A

Loose mesenchyme between cartilage models differentiates into fibrous tissue or fibrocartilage. Surrounded by perichondrium .

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13
Q

Synovial joint formation

A

In synovial joints, programmed cell death (apoptosis) results in joint cavity between adjacent cartilage models. Perichondrium persists as joint capsule, lining differentiates into synovial membrane. Hyaline cartilage persists on articular surfaces.

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14
Q

Marfan Syndrome

A

Connective tissue disorder - excessive long bone growth
Fibrillin-1 gene mutation
Long, thin limbs
Also can affect heart, vessels, bones, eyes, lungs

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15
Q

Osteogenesis Imperfecta

A 
Defect in type 1 collagen gene
Autosomal recessive OR dominant
Extreme bone fragility
Frequent fractures
Hypermobile joints
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16
Q

Achondroplasia

A

Most common form of dwarfism
Affects long bones
Autosomal dominant or spontaneous mutation of FGFR3 gene

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17
Q

Gigantism

A

Excessive growth hormone during childhood BEFORE growth plates close
Overal large size, height and organs, normal proportions

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18
Q

Acromegaly

A

Excessive growth hormone AFTER growth plates closed

Large heavy bones especially hands and feet

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19
Q

Congenital Hip dysplasia/dislocation

A

Incomplete formation of acetabulum (hip joint)

Legs held in positions that don’t match, less movement, uneven leg length

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20
Q

Axial skeletal system

A

Skull, vertebral column, ribs/sternum

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21
Q

Appendicular skeletal system

A

pectoral and pelvic girdles

limbs

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22
Q

Sclerotome cells migrate ________ to form sheath around ______ and ______

A

ventromedially,

notochord and neural tube

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23
Q

Resegmentation of vertebral column

A

Caudal part of one segment fuses with rostral part of segment below (around the artery)

i.e. In the primitive stage, the artery appears to separate one vertebra from another. In the definitive stage, the artery lies in the middle of the vertebral body.

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24
Q

Each sclerotome segment is divided into two parts (____ and ______) by _______

A

Dense caudal and loose cranial part, intersclerotomic (Von ebner’s fissure)

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25
Q

Formation of intervertebral discs

A

Mesenchyme lying between the cephalic and caudal parts of the original sclerotome segment fills the space surrounding the notochord, becomes annulus fibrosis.
Notochord becomes nucleus pulposis.

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26
Q

Induced by _______, sclerotome migrate dorsally around neural tube to form vertebral arch

A

Neural tube

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27
Q

Sternum formation

A

2 sternal bars (mesenchyme) form in midline of thoracic ventral wall - bars fuse forming cartilage model of manubrium/sternum/xiphoid - multiple ossification centers develop and fuse

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28
Q

Rib formation

A

Form from costal processes of thoracic vertebrae
continuous w/ neural arch
costovertebral synovial joints form

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29
Q

Spina bifida

A

failure of neural tube to close
occulta - tuft of hair, lumbosacral
meningocele - meninges protrude through defect
meningomyelocele - meninge/spinal cord protrude through defect

30
Q

Congenital dermal sinus

A

form of occult spinal dysraphia
neural ectoderm fails to completely separate from surface ectoderm - spinal cord maybe tethered to skin, risk for meningitis

31
Q

Klippel-Feil Syndrome (congenital brevicollis)

A

Congenital fusion of any of cervical vertebrae

Scoliosis common, shortened neck d/t nonsegmentation of cervical vertebra

32
Q

Hemivertebra

A

Congenital scoliosis - only one chondrification center forms

33
Q

Cervical ribs

A

C7 forms rudimentary rib that can compress neurovascular structures supplying upper limb (thoracic outlet syndrome)

34
Q

Lumbar ribs

A

more common, asymptomatic

may mistake for fracture of L1 transverse process

35
Q

Pectus excavatum

A

Concave chest, can occur with marfan/scoliosis, worsens during puberty growth spurt
d/t to poorly coordinated growth of CT during development of sternum/costal cartilages

36
Q

Pectus carinatum

A

thoracic cage larger, hard to get normal breath (w/ exercise)

37
Q

Upper limb bud appears _____

Lower limb bud appears ______

A

Week 4
first (day 26), day 28

Most susceptible to teratogens through end of week 8

38
Q

Location of limb buds (patterning) controlled by _________

A

homeobox (Hox) genes

39
Q

Limb bud formation

A

Somitic and somatic (lateral plate) mesoderm - proliferates deep to extoderm – transfoorms into mesenchyme - small protrusions appear

40
Q

Upper limb bud somite levels

A

C5-T1

41
Q

Lower limb bud somite levels

A

L2-S2

42
Q

Thickening of the ectoderm over the distal border forms the _______ (induced by mesodermal mesenchyme)

A

Apical ectodermal ridge

43
Q

The AER plays a major role in limb formation by _________

A

inducing proliferation of undifferentiated mesenchymal cells (via fibroblast growth factors) in the adjacent progress zone

44
Q

Placode

A

region of thickened ectoderm responsible for induction of another structure or organ (i.e. AER)

45
Q

Core of limb bud is ________

Outside is _______

A

Mesoderm, ectoderm

46
Q

Limb growth and differentiation

A

AER secretes fibroblast growth factors that induce underlying mesenchyme to proliferate, so that the limb lengthens but the distal aspect of limb is inhibited from terminal differentiation.

Cartilage/muscle differentiation begins in the proximal part of limb and progresses in a proximal-distal direction.

47
Q

Digit formation

A

ZPA coalesces under influence of FGFs from AER

Shh gene activationShh proteins

Signals anterior/posterior polarity
(ie. little finger vs. thumb at this point)

48
Q

Limb rotation

A

day 50-60 (week 8)
Limbs rotate in opposite directions (thumbs laterally - elbow back, flexors anterior vs. big toe medially - knees forward, flexors posterior)

49
Q

Amelia

A

No limbs (bilateral or unilateral)

50
Q

Meromelia

A

partial absence of limbs

51
Q

Phocomelia

A

Hand or foot-like appendage attached almost directly to toroo (flipper)

52
Q

Polydactyly

A

extra digits
may be fully formed or only soft tissues
Autosomal dominant

53
Q

Syndactyly

A

Failure of apoptosis leading to fused digits or fused bony components

54
Q

Lobster claw deformity (ectrodactyly)

A

Absent central ray, deep cleft between digits

Autosomal dominant

55
Q

Myotomes are derived from _______ in segmental arrangement.

A

Somites

56
Q

Muscle formation: Mesenchyme differentiates into _______

A

spindle shaped myoblasts

57
Q

Myoblasts fuse into _____ and develop ______ within their cytoplasm

A

myotubes

myofilaments

58
Q

Myotubes fuse to form long mulitnucleated _______ that make up skeletal muscle

A

myofigers

59
Q

skeletal muscle formation

A

Somitesmyotomesmesenchymemyoblastsmyotubesmultinucleated muscle fibersstriated (skeletal) muscle

60
Q

As the myotome differentiates from the dermotome, it divides into the ____, _____

A

smaller more dorsal (epimere)
epaxial and larger
hypaxial (hypomere) divisions.

61
Q

Nerve fibers from the dorsal primary ramus are associated with the _______, which develops into the deep extensors of _______ .

A

Nerve fibers from the dorsal primary ramus are associated with the epimere, which develops into the deep extensors of the back.

62
Q

Myoblasts in the cervical region of the hypaxial division form the ______ flexors.

A

Myoblasts in the cervical region of the hypaxial division form the neck flexors.

63
Q

EPimere - deep back- innervated by

A

dorsal primary rami

64
Q

hypomere - trunk wall/trunk - innervated by

A

ventral primary rami

65
Q

Limb muscles developed via _______ myoblasts in _____ and ______ compartments

A

hypaxial

flexor and extensors

66
Q

Poland syndrome

A

Underdevelopment or absence of pectoralis muscles, usually unilateral, males>females, common w/ Marfan

67
Q

Prune Belly Syndrome

A

Poor development of abdominal muscles causing skin to wrinkle
Undescended testicles and UTIs

68
Q

Congenital torticollis

A

Sternocleidomastoid muscle on one side is spasmodic or shortened
Usually present at birth and discovered soon
May be related to small space in uterus, common w/ hip dysplasia

69
Q

Smooth muscle originates from ________ of lateral plate (except ________ and _______)

A

splanchnic mesoderm

somatic mesoderm – vascular system
ectoderm - myoepithelial cells of mammary and sweat glands and smooth muscle of iris

70
Q

Cardiac muscle originates from _________ located around __________

A

splanchnic mesoderm located around heart primordium

Skin MS: Week 3 (14 decks)

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