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LECOM MS1 Embryology > Axial Skeleton (Exam 1) > Flashcards

Axial Skeleton (Exam 1) Flashcards

1
Q

What mesoderm layer gives rise to the axial skeleton

A

paraxial mesoderm

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2
Q

What does the paraxial mesoderm give rise to

A

Somitomeres

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3
Q

What occurs to most of the somitomeres

A

they condense into somites

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4
Q

When will somites begin to form

A

Day 20

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5
Q

By day 35, how many somites are formed

A

between 42-44 pairs

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6
Q

Which somitomeres do not give rise to somites

A

the first 7 cranial pairs

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7
Q

What does the somite differentiate into

A

sclerotome and dermatomyotome

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8
Q

What does the dermatomyotome give rise to

A

portion of the dermis and nuscle

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9
Q

How many somites in cervical region

A

8

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10
Q

How many somites in thoracic region

A

12

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11
Q

How many somites in lumbar region

A

5

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12
Q

How many somites in sacral region

A

5

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13
Q

How many somites in coccygeal region

A

8-10

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14
Q

How many somites in occipital region

A

4

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15
Q

What will cranial somitomeres form

A

structures of the head

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16
Q

What will the occipital somites form

A

the base of the skull

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17
Q

What do somites from the other regions form

A

the vertebral bodies

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18
Q

What is the notochord composed of

A

endoderm and mesoderm

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19
Q

What is the notochord function

A

establishes body axes (midline)

form the nucleus pulposus of the IV disc

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20
Q

How are vertebra formed

A

Sclerotomes shift and surround spinal cord and notocord

Each sclerotome splits into cranial and caudal sections and joins up with other sclerotome sections to form pre-cartilaginous vertebral body

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21
Q

How are myotomes related to sclerotomes

A

each myotome has an associated nerve or artery along the sclerotomes

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22
Q

How is the vertebral column organized from sclerotomes

A

Sclerotome portion of each somite undergoes resegmentation

caudal half of each sclerotome fuses with cranial half of adjacent sclerotome

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23
Q

How is the occipital bone formed

A

4th occipital somite and the first cervical sclerotome

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24
Q

How is the atlas formed

A

caudal half of the first cervical sclerotome and cranial half of second cervical sclerotome

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25
Q

How is T1 vertebrae formed

A

caudal half of 8th cervical and cranial half of 1st thoracic

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26
Q

What do the ribs form from

A

Paraxial mesoderm

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27
Q

What does the sternum form from

A

somatic mesoderm

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28
Q

What gives rise to IV discs

A

thin layer of mesenchymal cells between the caudal and cranial portions of the original sclerotome

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29
Q

How will the myotome be affected by the rearrangement of the sclerotome to form IV discs

A

myotomes spanning the intervertebral discs, allows movement of vertebral column

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30
Q

Incomplete formation of neural arc is a result of what not forming properly

A

sclerotomes

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31
Q

What is a chordoma

A

remnants of the notochord that may give rise to malignant tumors that invade bone

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32
Q

Where does chordoma develop

A

at the base of the skull and in the lumbar region

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33
Q

What is Klippel-Feil syndrome

A

short neck from reduced number of cervical vertebrae (fusion of vertebrae)

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34
Q

What is scoliosis

A

abnormal curvature because of improper fusion or formation

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35
Q

What are variations in the number of vertebrae caused by

A

additions or subtractions in the number of vertebrae

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36
Q

What are anomalies of the sternum

A

pes excavatum

cleft sternum

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37
Q

What is hemivertabrae

A

abnormal fusion resulting in misformed vertebrae

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38
Q

What are accessory fibs/ fused ribs

A

extra ribs

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39
Q

What is Spina Bifida Occulta

A

incomplete neural arc; usually asymptomatic and accompanied by a patch of hair over the lesion

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40
Q

What are the muscles of the head derived from

A

the first 7 somitomeres

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41
Q

Where are the muscles of the tongue, torso, and limbs derived from

A

the somites

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42
Q

What will the dermomyotome give rise to

A

dermatome and myotome

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43
Q

Where does the dermatome form in relationship to the myotome from the dermomyotome

A

dermatome forms laterally

Myotome forms medially

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44
Q

What will myotomes of the trunk split into

A

primaxial and abaxial muscle cell precursors

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45
Q

What does the primaxial muscle cell precursors form

A

muscles of the back

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46
Q

What does the abaxial muscle cell precursors form

A

muscles of the body wall (adnominal) and limb muscles

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47
Q

Describe the innervation to muscles from the myotomes of the dorsal part of the myotome

A

Dorsal part of the myotome is formed by primaxial muscle cell precursors and migrate further dorsally to form epaxial muscles : innervated by dorsal rami

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48
Q

Describe the innervation to muscles from the myotomes of the lateral part of the myotome

A

Lateral part of the myotome is formed by abaxial muscle cell precursors and gives rise to hypaxial muscles (body wall and limbs) and innervated by ventral rami

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49
Q

What are Lateral part myotomes innervated by

A

ventral rami

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50
Q

What are dorsal part of the myotomes innervated by

A

dorsal rami

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51
Q

Cells of the myotome give rise ultimately to what

A

skeletal muscle

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52
Q

Cells of the myotome become what

A

myoblasts

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53
Q

What occurs to the myoblasts

A

they elongate, migrate, and fuse together to form myotubes

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54
Q

What occurs to myotubes

A

contractile filaments appear in the cytoplasm to form muscle fibers

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55
Q

What is prune belly syndrome

A

Where abaxial muscles fail to develop, loose skin, openings in abdomen

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56
Q

What is Poland anomaly

A

where muscles fail to develop , most common is a pectoral

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57
Q

How is muscle modified after it is formed

A

fusion of myotomes

splitting of myotomes

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58
Q

What does fusion of myotomes result in

A

muscles innervated by more than one spinal cord level

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59
Q

What does splitting of myotomes result in

A

one cord level innervates more than one muscle

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60
Q

What is congenital torticollis

A

contracture of shortening of sternocleidomastoid

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61
Q

What is muscular dystrophies

A

conditions that result in weakness and muscle atrophy

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62
Q

What are accessory muscles

A

rectus sternalis, etc

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63
Q

What is a dermatome

A

area of skin innervated by a single spinal cord segment

dermatomes are segmental and overlapping

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64
Q

What occurs on day 16 of development

A

gastrulation

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65
Q

How is the neural plate formed

A

notochord induces ectoderm to thicken and form the neural plate

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66
Q

What cells are seen within the walls of the closed neurotube

A

neuroepithelial cells

pseudostratified

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67
Q

What does the neuoepithelium (neuroectoderm) give rise to

A

neuroblasts

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68
Q

What are neuroblasts

A

primitive nerve cells

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69
Q

What are the 3 layers formed by the neural tube

A

Ependymal layer
Mantle layer
Marginal layer

70
Q

What is the ependymal layer

A

innermost layer that surrounds the central canal

71
Q

What is the mantle layer

A

middle layer, contains cell bodies and astrocytes

72
Q

What is the marginal layer

A

outermost layer; contains nerve fibers and oligodendrocytes

73
Q

Where do neuroepithelial cells start

A

at the ventricular layer and migrate to the mantle layer

74
Q

What do neuroepithelial cells in the mantle layer form

A

gray matter

75
Q

Axons from the neuroepithelial cells reach where

A

into the marginal layer

76
Q

What do the axons from the neuroepithelial cells in the marginal layer form

A

white matter

77
Q

What will neuroepithelial cells differentiate into

A

neuroblasts

78
Q

What does a second wave of cells arising result in

A

macroglioblasts

79
Q

What do macroglioblast cells become

A

glia cells:

80
Q

What do astroblasts become and what are they associated with

A

astrocytes

associated with and support cell bodies

81
Q

What do oligodendroblasts become and what are they associated with

A

oligodendrocytes

forms the myelin sheath around axons

82
Q

Cells in the ventricular layer become what

A

ependymal cells

83
Q

What do ependymal cells do

A

secrete CSF

84
Q

What are microglial cells derived from

A

mesenchymal cells surrounding the neural tube

85
Q

What is pathfinding

A

where sensory neurons follow the paths of motor neurons in development

86
Q

What are the types of pathfinding

A

Tropic substance
Contact guidance theory
Chemoaffinity hypothesis

87
Q

What is tropic substance pathfinding

A

lamin-related proteins

88
Q

What is contact guidance theory

A

extracellular matrix

89
Q

What is Chemoaffinity hypothesis

A

Axons can have differing affinities for molecules: can be attractive or repulsive

fibronectin, laminin, neural cell adhesion molecule

90
Q

What is a pioneer axon

A

first axon to develop that play a special role: use pathfinding to find and target, other axons then follow

91
Q

What are growth cones

A

specializations at the end of an axon that are used to survey the environment

92
Q

How will the neural tube be separated into dorsal and ventral areas

A

Sulcus limitans

93
Q

The mantal layer develops into what

A

2 regions

94
Q

WHat are the 2 regions of the mantle layer

A

basal plate

Alar plate

95
Q

Where does the Basal plate develop

A

ventral portion

96
Q

What does the basal plate develop

A

motor cell bodies

97
Q

Where does the alar plate develop

A

dorsal portion

98
Q

What does the alar plate develop into

A

sensory relay cells

99
Q

What will the ventral and dorsal thickening of the neural tube become

A

ventrally: motor horns
dorsally: sensory areas

100
Q

What is the sulcus limitans

A

a longitudinal groove marks the boundary between the two

101
Q

What type of cells will line the central canal and what will they do

A

ependymal cells that will secrete CSF

102
Q

What will spinal nerves develop from

A

neural crest cells and neuroblasts

103
Q

What is the sequence that the functional components of spinal nerves will form

A

GSE
GVE
all sensory nerves (GSA and GVA)

104
Q

How will the functional components of spinal nerves in relationship to the whole embryo

A

cranial to caudal sequence

105
Q

What will neural crest cells that remain close to the neural tube form

A

ganglia: dorsal root and sensory ganglia for cranial nerves

106
Q

What will neural crest cells form in the head

A 
all CT tissue elements
- fascia, ligaments, and tendons
- blood and lymphatic vessels
cartilage and many bones of the skull
contributes to sensory ganglia
107
Q

What is the fate of neural crest cells in the torso

A 
autonomic ganglia
sympathetic chain
prevertebral ganglia
suprarenal medulla
parasympathetic ganglia
enteric ganglia

Heart:
endocardial cushions
septa within the bubus cordis and tuncus arteriosus

108
Q

What will happen to the last cells to leave the neural crest

A

migrate to dermis and give rise to melanocytes

109
Q

WHat will neural crest cells contribute to the ANS and PNSA

A

ganglia (DRG, sympathetic chain, suprarenal gland, prevertebral ganglia, and enteric ganglia in the gut)

110
Q

How are neurons in the DRG formed

A

sensory bodies are situated in the DRG and derive from neural crest cells

ventral roots approaches the corresponding DRG, neurons in the DRG begin to send out processes. The cell body gives rise to a central process and peripheral process

111
Q

Where does the central process of the sensory neuron cell body go

A

enters the spinal cord

112
Q

Where does the peripheral process of the sensory neuron cell body go

A

follow formed efferent axons

113
Q

When will myelination begin

A

late fetal period (20 weeks)

114
Q

Which type of neurons are myelinated first

A

motor before sensory

115
Q

When is the process of myelination complete

A

by 8 years of age, but in the frontal lobe not until 20’s

116
Q

What is the segmental pattern of sympathetic innervation

A

Sympathetic trunk

117
Q

Where does sympathetic innervation to the head arise

A

from T1-T4

118
Q

Where does sympathetic innervation to the heart aris

A

T1-T4

119
Q

Where does sympathetic innervation to organs in the abdomen and pelvis arise from

A

T5-L2

120
Q

Where do parasympathetic fibers arise from

A

neurons in the brainstem and sacral region (vagus, and S2-S4

121
Q

Where are postganglionic fibers derived from

A

neural crest cells and pass to structures they innervate

122
Q

What are the different types of spina bifida

A 
Spina bifida occulta
Spina bifida cystica
Spina bifida with meningocele
Spina bifida with meningomyelocele
Spina bifida with myeloschis
123
Q

What is spina bifida occulta

A

involves only the vertebral arch, usually the only evidence is a small tuft of hair over lesion

124
Q

What is spina bifida cystica

A

involves a cyst like sac containing CSF

125
Q

What is spina bifida with meningocele

A

only meninges in the sac

126
Q

What is spina bifida with meningomyelocele

A

Involves some neural tissue (rootlets), meninges, and CSF

127
Q

What is spina bifida with myeloschisis

A

neural folds fail to fuse posteriorly
spinal cord is open to the exterior
very serious defect

128
Q

What does spinal dura sinus present as

A

dimple in the lumbar region

129
Q

What does a spinal dura sinus indicate

A

indicates region of closure of the caudal neuropore can be connected through a fibrous cord to dura mater

130
Q

What is Hirschsprung’s disease presentation

A

delay in the passage of meconium; results in constipation, vomiting, abdominal distension, and rupture of the cecum

131
Q

What causes Hirschsprung’s disease

A

mutation in RET proto-oncogene; neural crest cells fail to reach the hindgut; this part of the gut is non-peristaltic

132
Q

What causes neurofibromatosis (type 1)

A

congenital disorder that affects all derivatives of neural crest cell

133
Q

What does neurofibromatosis (type 1) result in

A

nerve sheath tumors and

cafe au lait spots-pigemented spots in the skin

134
Q

Where does the annulus fibrosus develop from

A

sclerotome

135
Q

Where do extrinsic muscles of the eye develop from

A

pre-otic somites

136
Q

What are the two ways myotomes may split

A

longitudinally and tangentially

137
Q

Where do bones develop from

A

mesenchymal cells that arose from the sclerotome

138
Q

What do mesenchymal cells develop into

A

fibroblasts
chondroblasts
osteoblasts

139
Q

What does the somatic layer of lateral plate mesoderm give rise to

A

sternum, shoulder, and pelvic girdles

140
Q

What do neural crest cells give rise to bone wise

A

the bones of the skull

141
Q

Head somitomeres will form what bones

A

of the cranial vault and base of the skull

142
Q

Bone first appears as condensations of what

A

mesenchyme cells that form bone models

143
Q

Bone develops from two types of what

A

connective tissue

144
Q

What are the two types of connective tissue bone develops from

A

cartilage and mesenchyme

145
Q

What are the two methods of bone development

A

Intramembraneous ossification

Endochondral ossification

146
Q

What is Intramembraneous ossification

A

occurs in mesenchyme that has formed a membraneous sheath

mesenchyme condenses and becomes highly vascular, osteoblasts lay down a matrix and calcium is depositied

147
Q

Intramembraneous ossification makes what types of bones

A

flat bones of the skull and most of clavicle

148
Q

What is endochondral ossification from

A

hyaline cartilage

149
Q

What is endochondral ossification

A

ossification that occurs in a preexisting cartilaginous model

primary centers of ossification appear in the diaphysis (shaft). Cartilage cells hypertrophy, the matrix becomes calcified and cells die. Thin layer of bone is deposited under the perichondrium and becomes the periosteium.

150
Q

What do invading cells of endochondral ossification become

A

hemopoietic cells

151
Q

What bones develop via endochondral ossification

A

most limb bones develop in this manner

152
Q

Active movement of an axon toward a target is called what

A

pathfinding

153
Q

What two types of cells arise from the ventricular zone of neuroepithelial cells

A

neuroblasts

glia cells

154
Q

What does the mantle layer contain

A

cell bodies and astrocytes

155
Q

What does the marginal layer contain

A

nerve fibers and oligodendrocytes

156
Q

What are the two ways that neural crest cells migrate

A

passively

actively

157
Q

What is passive movement of neural crest cells

A

differential growth

158
Q

What is active movement of neural crest cells

A

crawling movements of the cell

159
Q

Cells that remain close to the neural tube form what

A

ganglia

160
Q

Cells that migrate away from the neural tube leave in what 3 waves

A
  1. to the head and pharyngeal arches
  2. autonomic ganglia in torso
  3. melanocytes
161
Q

Associated with neural crest cells is what

A

population of cells that stay within the surface ectoderm during neural folding and form ectodermal placodes

162
Q

Axons in the spinal nerve grow to specific sites

A

epimere

hypomere

163
Q

In embryo, how long does the spinal cord run

A

the entire length of the vertebral column

164
Q

In adults, the spinal cord ends at what level

A

L2

165
Q

Where does the pia and arachnoid mater arise from

A

neural crest cells

166
Q

Where does the dura mater arise from

A

mesoderm

167
Q

What are neural tube defects

A

improper closing of the neural tube

168
Q

How can neural tube defects be detected

A

elevated alpha fetoprotein in amniocentesis

169
Q

What is tethered cord syndrome

A

defect in secondary neurulation; the conus medullaris and filum terminale are abnormally fixed to vertebral column

170
Q

What is tethered cord syndrome associated with

A

lower limb and bladder control

171
Q

How frequently does Hirschsprung’s disease occur

A

1 in 5000 births

172
Q

How frequently does Neurofibromatosis (type 1) occur

A

1 in 4000 births

LECOM MS1 Embryology (19 decks)

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