Axial Skeleton (Exam 1) Flashcards
(172 cards)
1
Q
What mesoderm layer gives rise to the axial skeleton
A
paraxial mesoderm
2
Q
What does the paraxial mesoderm give rise to
A
Somitomeres
3
Q
What occurs to most of the somitomeres
A
they condense into somites
4
Q
When will somites begin to form
A
Day 20
5
Q
By day 35, how many somites are formed
A
between 42-44 pairs
6
Q
Which somitomeres do not give rise to somites
A
the first 7 cranial pairs
7
Q
What does the somite differentiate into
A
sclerotome and dermatomyotome
8
Q
What does the dermatomyotome give rise to
A
portion of the dermis and nuscle
9
Q
How many somites in cervical region
A
8
10
Q
How many somites in thoracic region
A
12
11
Q
How many somites in lumbar region
A
5
12
Q
How many somites in sacral region
A
5
13
Q
How many somites in coccygeal region
A
8-10
14
Q
How many somites in occipital region
A
4
15
Q
What will cranial somitomeres form
A
structures of the head
16
Q
What will the occipital somites form
A
the base of the skull
17
Q
What do somites from the other regions form
A
the vertebral bodies
18
Q
What is the notochord composed of
A
endoderm and mesoderm
19
Q
What is the notochord function
A
establishes body axes (midline)
form the nucleus pulposus of the IV disc
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
21
Q
How are myotomes related to sclerotomes
A
each myotome has an associated nerve or artery along the sclerotomes
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
23
Q
How is the occipital bone formed
A
4th occipital somite and the first cervical sclerotome
24
Q
How is the atlas formed
A
caudal half of the first cervical sclerotome and cranial half of second cervical sclerotome
25
How is T1 vertebrae formed
caudal half of 8th cervical and cranial half of 1st thoracic
26
What do the ribs form from
Paraxial mesoderm
27
What does the sternum form from
somatic mesoderm
28
What gives rise to IV discs
thin layer of mesenchymal cells between the caudal and cranial portions of the original sclerotome
29
How will the myotome be affected by the rearrangement of the sclerotome to form IV discs
myotomes spanning the intervertebral discs, allows movement of vertebral column
30
Incomplete formation of neural arc is a result of what not forming properly
sclerotomes
31
What is a chordoma
remnants of the notochord that may give rise to malignant tumors that invade bone
32
Where does chordoma develop
at the base of the skull and in the lumbar region
33
What is Klippel-Feil syndrome
short neck from reduced number of cervical vertebrae (fusion of vertebrae)
34
What is scoliosis
abnormal curvature because of improper fusion or formation
35
What are variations in the number of vertebrae caused by
additions or subtractions in the number of vertebrae
36
What are anomalies of the sternum
pes excavatum
| cleft sternum
37
What is hemivertabrae
abnormal fusion resulting in misformed vertebrae
38
What are accessory fibs/ fused ribs
extra ribs
39
What is Spina Bifida Occulta
incomplete neural arc; usually asymptomatic and accompanied by a patch of hair over the lesion
40
What are the muscles of the head derived from
the first 7 somitomeres
41
Where are the muscles of the tongue, torso, and limbs derived from
the somites
42
What will the dermomyotome give rise to
dermatome and myotome
43
Where does the dermatome form in relationship to the myotome from the dermomyotome
dermatome forms laterally
Myotome forms medially
44
What will myotomes of the trunk split into
primaxial and abaxial muscle cell precursors
45
What does the primaxial muscle cell precursors form
muscles of the back
46
What does the abaxial muscle cell precursors form
muscles of the body wall (adnominal) and limb muscles
47
Describe the innervation to muscles from the myotomes of the dorsal part of the myotome
Dorsal part of the myotome is formed by primaxial muscle cell precursors and migrate further dorsally to form epaxial muscles : innervated by dorsal rami
48
Describe the innervation to muscles from the myotomes of the lateral part of the myotome
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
49
What are Lateral part myotomes innervated by
ventral rami
50
What are dorsal part of the myotomes innervated by
dorsal rami
51
Cells of the myotome give rise ultimately to what
skeletal muscle
52
Cells of the myotome become what
myoblasts
53
What occurs to the myoblasts
they elongate, migrate, and fuse together to form myotubes
54
What occurs to myotubes
contractile filaments appear in the cytoplasm to form muscle fibers
55
What is prune belly syndrome
Where abaxial muscles fail to develop, loose skin, openings in abdomen
56
What is Poland anomaly
where muscles fail to develop , most common is a pectoral
57
How is muscle modified after it is formed
fusion of myotomes
| splitting of myotomes
58
What does fusion of myotomes result in
muscles innervated by more than one spinal cord level
59
What does splitting of myotomes result in
one cord level innervates more than one muscle
60
What is congenital torticollis
contracture of shortening of sternocleidomastoid
61
What is muscular dystrophies
conditions that result in weakness and muscle atrophy
62
What are accessory muscles
rectus sternalis, etc
63
What is a dermatome
area of skin innervated by a single spinal cord segment
| dermatomes are segmental and overlapping
64
What occurs on day 16 of development
gastrulation
65
How is the neural plate formed
notochord induces ectoderm to thicken and form the neural plate
66
What cells are seen within the walls of the closed neurotube
neuroepithelial cells
| pseudostratified
67
What does the neuoepithelium (neuroectoderm) give rise to
neuroblasts
68
What are neuroblasts
primitive nerve cells
69
What are the 3 layers formed by the neural tube
Ependymal layer
Mantle layer
Marginal layer
70
What is the ependymal layer
innermost layer that surrounds the central canal
71
What is the mantle layer
middle layer, contains cell bodies and astrocytes
72
What is the marginal layer
outermost layer; contains nerve fibers and oligodendrocytes
73
Where do neuroepithelial cells start
at the ventricular layer and migrate to the mantle layer
74
What do neuroepithelial cells in the mantle layer form
gray matter
75
Axons from the neuroepithelial cells reach where
into the marginal layer
76
What do the axons from the neuroepithelial cells in the marginal layer form
white matter
77
What will neuroepithelial cells differentiate into
neuroblasts
78
What does a second wave of cells arising result in
macroglioblasts
79
What do macroglioblast cells become
glia cells:
80
What do astroblasts become and what are they associated with
astrocytes
| associated with and support cell bodies
81
What do oligodendroblasts become and what are they associated with
oligodendrocytes
| forms the myelin sheath around axons
82
Cells in the ventricular layer become what
ependymal cells
83
What do ependymal cells do
secrete CSF
84
What are microglial cells derived from
mesenchymal cells surrounding the neural tube
85
What is pathfinding
where sensory neurons follow the paths of motor neurons in development
86
What are the types of pathfinding
Tropic substance
Contact guidance theory
Chemoaffinity hypothesis
87
What is tropic substance pathfinding
lamin-related proteins
88
What is contact guidance theory
extracellular matrix
89
What is Chemoaffinity hypothesis
Axons can have differing affinities for molecules: can be attractive or repulsive
fibronectin, laminin, neural cell adhesion molecule
90
What is a pioneer axon
first axon to develop that play a special role: use pathfinding to find and target, other axons then follow
91
What are growth cones
specializations at the end of an axon that are used to survey the environment
92
How will the neural tube be separated into dorsal and ventral areas
Sulcus limitans
93
The mantal layer develops into what
2 regions
94
WHat are the 2 regions of the mantle layer
basal plate
| Alar plate
95
Where does the Basal plate develop
ventral portion
96
What does the basal plate develop
motor cell bodies
97
Where does the alar plate develop
dorsal portion
98
What does the alar plate develop into
sensory relay cells
99
What will the ventral and dorsal thickening of the neural tube become
ventrally: motor horns
dorsally: sensory areas
100
What is the sulcus limitans
a longitudinal groove marks the boundary between the two
101
What type of cells will line the central canal and what will they do
ependymal cells that will secrete CSF
102
What will spinal nerves develop from
neural crest cells and neuroblasts
103
What is the sequence that the functional components of spinal nerves will form
GSE
GVE
all sensory nerves (GSA and GVA)
104
How will the functional components of spinal nerves in relationship to the whole embryo
cranial to caudal sequence
105
What will neural crest cells that remain close to the neural tube form
ganglia: dorsal root and sensory ganglia for cranial nerves
106
What will neural crest cells form in the head
```
all CT tissue elements
- fascia, ligaments, and tendons
- blood and lymphatic vessels
cartilage and many bones of the skull
contributes to sensory ganglia
```
107
What is the fate of neural crest cells in the torso
```
autonomic ganglia
sympathetic chain
prevertebral ganglia
suprarenal medulla
parasympathetic ganglia
enteric ganglia
```
Heart:
endocardial cushions
septa within the bubus cordis and tuncus arteriosus
108
What will happen to the last cells to leave the neural crest
migrate to dermis and give rise to melanocytes
109
WHat will neural crest cells contribute to the ANS and PNSA
ganglia (DRG, sympathetic chain, suprarenal gland, prevertebral ganglia, and enteric ganglia in the gut)
110
How are neurons in the DRG formed
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
Where does the central process of the sensory neuron cell body go
enters the spinal cord
112
Where does the peripheral process of the sensory neuron cell body go
follow formed efferent axons
113
When will myelination begin
late fetal period (20 weeks)
114
Which type of neurons are myelinated first
motor before sensory
115
When is the process of myelination complete
by 8 years of age, but in the frontal lobe not until 20's
116
What is the segmental pattern of sympathetic innervation
Sympathetic trunk
117
Where does sympathetic innervation to the head arise
from T1-T4
118
Where does sympathetic innervation to the heart aris
T1-T4
119
Where does sympathetic innervation to organs in the abdomen and pelvis arise from
T5-L2
120
Where do parasympathetic fibers arise from
neurons in the brainstem and sacral region (vagus, and S2-S4
121
Where are postganglionic fibers derived from
neural crest cells and pass to structures they innervate
122
What are the different types of spina bifida
```
Spina bifida occulta
Spina bifida cystica
Spina bifida with meningocele
Spina bifida with meningomyelocele
Spina bifida with myeloschis
```
123
What is spina bifida occulta
involves only the vertebral arch, usually the only evidence is a small tuft of hair over lesion
124
What is spina bifida cystica
involves a cyst like sac containing CSF
125
What is spina bifida with meningocele
only meninges in the sac
126
What is spina bifida with meningomyelocele
Involves some neural tissue (rootlets), meninges, and CSF
127
What is spina bifida with myeloschisis
neural folds fail to fuse posteriorly
spinal cord is open to the exterior
very serious defect
128
What does spinal dura sinus present as
dimple in the lumbar region
129
What does a spinal dura sinus indicate
indicates region of closure of the caudal neuropore can be connected through a fibrous cord to dura mater
130
What is Hirschsprung's disease presentation
delay in the passage of meconium; results in constipation, vomiting, abdominal distension, and rupture of the cecum
131
What causes Hirschsprung's disease
mutation in RET proto-oncogene; neural crest cells fail to reach the hindgut; this part of the gut is non-peristaltic
132
What causes neurofibromatosis (type 1)
congenital disorder that affects all derivatives of neural crest cell
133
What does neurofibromatosis (type 1) result in
nerve sheath tumors and
| cafe au lait spots-pigemented spots in the skin
134
Where does the annulus fibrosus develop from
sclerotome
135
Where do extrinsic muscles of the eye develop from
pre-otic somites
136
What are the two ways myotomes may split
longitudinally and tangentially
137
Where do bones develop from
mesenchymal cells that arose from the sclerotome
138
What do mesenchymal cells develop into
fibroblasts
chondroblasts
osteoblasts
139
What does the somatic layer of lateral plate mesoderm give rise to
sternum, shoulder, and pelvic girdles
140
What do neural crest cells give rise to bone wise
the bones of the skull
141
Head somitomeres will form what bones
of the cranial vault and base of the skull
142
Bone first appears as condensations of what
mesenchyme cells that form bone models
143
Bone develops from two types of what
connective tissue
144
What are the two types of connective tissue bone develops from
cartilage and mesenchyme
145
What are the two methods of bone development
Intramembraneous ossification
| Endochondral ossification
146
What is Intramembraneous ossification
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
Intramembraneous ossification makes what types of bones
flat bones of the skull and most of clavicle
148
What is endochondral ossification from
hyaline cartilage
149
What is endochondral ossification
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
What do invading cells of endochondral ossification become
hemopoietic cells
151
What bones develop via endochondral ossification
most limb bones develop in this manner
152
Active movement of an axon toward a target is called what
pathfinding
153
What two types of cells arise from the ventricular zone of neuroepithelial cells
neuroblasts
| glia cells
154
What does the mantle layer contain
cell bodies and astrocytes
155
What does the marginal layer contain
nerve fibers and oligodendrocytes
156
What are the two ways that neural crest cells migrate
passively
| actively
157
What is passive movement of neural crest cells
differential growth
158
What is active movement of neural crest cells
crawling movements of the cell
159
Cells that remain close to the neural tube form what
ganglia
160
Cells that migrate away from the neural tube leave in what 3 waves
1. to the head and pharyngeal arches
2. autonomic ganglia in torso
3. melanocytes
161
Associated with neural crest cells is what
population of cells that stay within the surface ectoderm during neural folding and form ectodermal placodes
162
Axons in the spinal nerve grow to specific sites
epimere
| hypomere
163
In embryo, how long does the spinal cord run
the entire length of the vertebral column
164
In adults, the spinal cord ends at what level
L2
165
Where does the pia and arachnoid mater arise from
neural crest cells
166
Where does the dura mater arise from
mesoderm
167
What are neural tube defects
improper closing of the neural tube
168
How can neural tube defects be detected
elevated alpha fetoprotein in amniocentesis
169
What is tethered cord syndrome
defect in secondary neurulation; the conus medullaris and filum terminale are abnormally fixed to vertebral column
170
What is tethered cord syndrome associated with
lower limb and bladder control
171
How frequently does Hirschsprung's disease occur
1 in 5000 births
172
How frequently does Neurofibromatosis (type 1) occur
1 in 4000 births
