1
Q
how many bones are found in the axial skeleton?
A
80
2
Q
how many bones are found in the appendicular skeleton?
A
126
3
Q
part of the skeleton that contains the skull, vertebral column, ribs, and sternum
A
axial skeleton
4
Q
formation of the axial skeleton is directed by:
A
the formation of the soft tissues (forms a protective casing around them)
5
Q
part of the skeleton that contains the bones of the limbs and limb girdles
A
appendicular skeleton
6
Q
morphogenesis of the limb bones is inherent to:
A
limb mesoderm
7
Q
endochondral bone is formed by:
A
endochondral ossification
8
Q
dermal bone is formed by:
A
intramembranous ossification
9
Q
bones formed by endochondral ossification are formed from a:
A
cartilage template
10
Q
which bones are formed via endochondral ossification?
A
- all bones of the trunk and limbs (except the clavicle)
- bones derived from pharyngeal arch cartilages
- bones of the cranial base and sensory capsules
11
Q
involves ossification of the mesenchyme without a cartilage intermediate
A
intramembranous ossification
12
Q
which bones are formed by intramembranous ossification?
A
- flat bones
- most bones of the face and skull
13
Q
what are the two sections of the skull?
A
the neurocranium and viscerocranium
14
Q
the part of the skull housing the brain
A
the neurocranium
15
Q
the part of the skull made of the bones of the face (around the eyes, ears, mouth, and nose)
A
the viscerocranium
16
Q
both the neurocranium and viscerocranium are made mainly by:
A
dermal bone (but they are derived from different tissues)
17
Q
which tissues are the neurocranium derived from?
A
mostly paraxial mesoderm (unsegmented + somites) and some neural crest
18
Q
which tissues are the viscerocranium derived from?
A
mostly neural crest
19
Q
at birth, the calvaria (top portion of the neurocranium) consists of:
A
~7 individual flat bones separated by fibrous sutures and soft sports (fontanelles) where the sutures intersect
20
Q
what is the purpose of the fibrous sutures and soft fontanelles?
A
allows for flexibility of the skill during birth and for postnatal growth of the brain
21
Q
fontanelles are soft spots of the skull and can indicate:
A
dehydration/increased intracranial pressure
22
Q
the major fontanelles of the cranium are:
A
- anterior fontanelle where the sagittal and coronal sutures meet
- posterior fontanelle where the lambdoid and sagittal sutures meet
- four lateral fontanelles
23
Q
the major sutures of the cranium are:
A
- sagittal suture between the parietal bones
- coronal suture between the frontal and parietal bones
- squamous suture between the temporal and parietal bones
- lambdoid sutures between the occipital bone and parietal bones
24
Q
how much does a newborn’s brain expand in volume per day?
A
1%
25
true or false: a newborn's brain doubles in size by 4 months
true
26
the sutures and fontanelles of the cranium will eventually ossify through:
intramembranous ossification
27
when do the cranial fontanelles close/ossify?
from the first few months to the first few years
28
when do the cranial sutures close/ossify?
timing is variable but extends into adulthood
29
true or false: the skull grows in thickness as well as volume
true
30
premature closure of 1 or more sutures
craniostynosis
31
in a newborn with craniostynosis, as growth continues in other regions of the skull, this will lead to:
deformation of the skull
32
true or false: the neurocranium includes the calvaria and skull base
true
33
the calvaria is mostly made from:
dermal bone (dermatocranium)
34
the skull base is mostly made from:
endochondral bone (chondrocranium)
35
during formation of the chondrocranium, cartilage forms around the cranial nerves, leaving:
holes in the skull base
36
most of the cartilage of the chondrocranium is ossified by:
birth (but there are joints between bones at which growth can still occur postnatally)
37
what kind of joints are found at the base of the skull?
synchondroses (joints where cartilage joins two bones together and act like the growth plates of long bones)
38
a major site of skull base growth
spheno-occipital joint
39
when does the spheno-occipital joint start to ossify?
at puberty
40
develop as diverticula off the walls of the nasal cavity and become air-filled extensions into the adjacent bone
paranasal sinuses
41
when do the maxillary sinuses develop?
in late fetal life
42
when do the non-maxillary paranasal sinuses develop?
postnatally
43
over the early postnatal years, growth of the viscerocranium is largely due to:
growth of the paranasal sinuses and alveolar bone supporting teeth
44
the sclerotome (of the somites) will resegment to form:
the vertebrae and ribs
45
the caudal portion of the sclerotome is inhibitory for:
motorneuron axon growth
46
what portion of the sclerotome do developing spinal nerve axons pass through?
the cranial portion
47
division between the cranial and caudal portions of the sclerotome is marked by:
von Ebner's fissure
48
true or false: neural crest cell migration follows the same path to form sensory neurons
true
49
as the sclerotomes reorganize, the caudal portion of each sclerotome merges with:
the cranial portion of the next sclerotome
50
do myotomes resegment themselves alongside the sclerotomes?
no, therefore they can connect to two adjacent vertebrae
51
what is the major purpose of sclerotome resegmentation?
a shift in alignment between the sclerotomes and myotomes to facilitate muscle attachment to vertebrae
52
spinal nerves travel through ______ to reach muscles
intervertebral foramina
53
how many portions of sclerotome does it take to make one vertebra?
4
54
the occipital sclerotomes (1-4) plus the cranial part of the sclerotome C1 fuse to form:
the base of the occipital bone
55
the caudal C1 sclerotome fuses with cranial C2 to form the:
C1 vertebra
56
the caudal C8 sclerotome fuses with the cranial T1 sclerotome to make:
the T1 vertebra
57
how many cervical vertebrae are made from eight cervical somites?
seven
58
how many pairs of cervical spinal nerves are there?
eight
59
spinal nerves C1-C7 exit the spinal cord ______ the vertebra
above
60
spinal nerves T1-S4 exit the spinal nerve ______ the vertebra
below
61
where does spinal nerve C8 exit the spinal cord?
between the C7 and T1 vertebra
62
what happens to the notochord within the vertebra?
it disappears
63
what happens to the notochord of the intervertebral disc?
expands to become the gelatinous nucleus pulposus
64
the sclerotome cells remaining between vertebrae following resegmentation will become arranged in:
circular fibers of the annulus fibrosus, a collagen-rich fibrocartilage
65
see slides 812-814
vertebral formation
66
during vertebral formation, the cartilage model develops as:
five pieces, each with its own ossification centre
67
if the cartilaginous vertebral arches fail to fuse, it results in a condition called:
spinal bifida occulta
68
the vertebrae are mainly ossified by birth, but certain areas remain cartilaginous and act as:
growth plates
69
when do the neural arches of the vertebrae fuse?
in years 3-5
70
when do the neural arches fuse with the vertebral body?
at about age 6
71
secondary ossification centres for the spinous processes, transverse processes, and heads of the ribs appear at:
puberty, but ossification isn't fully complete until about 25 years
72
ossification of the vertebral body starts in the ______ and spreads ______
centre, outward
73
cartilaginous growth plates on the superior and inferior surfaces of the vertebral body, and provide growth in the cranial-caudal axis
epiphyseal plates
74
ossification of the epiphyseal plates in the vertebral body will be complete by ______ and only a thin layer of ______ will remain
~18 years, hyaline cartilage
75
extend from the outer edge of the annulus fibrosis to anchor the intervertebral disc to the vertebra
Sharpey's fibres
76
Sharpey's fibres are initially anchored to:
cartilage at the end of the growth plate
77
a secondary ossification centre that develops in the rim of the epiphyseal plate (superior and inferior), where Sharpey's fibres anchor
ring apophysis
78
ring apophysis starts to ossify at _______ and fuses with the vertebral body at ______
~5-10 years, ~18 years
79
ring apophysis forms the rim of the ______, which is not a major site for ______
vertebral body, growth in height
80
see slides 820-822
pictures of vertebrae enjoy them
81
true or false: each segment of the vertebral column has a distinct morphology
true
82
the cranial-caudal patterning of the vertebra is established early within the sclerotome by the expression of:
hox genes (a family of transcription factors)
83
what is a homeobox?
a conserved 180bp region coding for a DNA-binding domain
84
each hox gene contains a:
homeobox
85
how are hox genes arranged?
in 4 paralagous clusters within the genome
86
hox genes are expressed in specific, but overlapping, regions along the:
cranial-caudal axis of the embryo
87
does hox patterning cause the limbs to arise at specific places?
yes (upper limbs at the cervical/thoracic boundary, and lower limbs at the lumbar/sacral boundary)
88
what causes vertebral and rib anomalies?
- changes to cranial-caudal patterning (ex: hox genes)
- changes to genes important for segmentation
- changes to genes important for vertebral formation
89
a condition where cervical or lumbar vertebrae develop ribs
accessory rib anomalies
90
lateral curvature of the spine which can result from a failure of one half of the vertebra to form
scoliosis
91
what are the two different types of scoliosis?
congenital and idiopathic
92
what is the difference between congenital and idiopathic scoliosis?
congenital is present from birth (a developmental defect), while idiopathic arises during childhood due to a defect in growth
93
what are the true ribs?
the first seven pairs of ribs that connect to the sternum via the costal cartilages
94
what are the false ribs?
the lower five pairs of ribs that do not connect directly to the sternum
95
what is the clavicle derived from?
from neural crest cells
96
what type of ossification creates the clavicle?
intramembranous ossification
97
the sternum develops initially as mesenchymal condensations called ______, which are derived from ______
sternal bars, lateral plate mesoderm
98
where do the sternal bars converge?
at the midline, and fuse from cranial to caudal
99
what happens to the sternal bars during fusion?
they chondrify, then the sternum segments and forms multiple ossification centers
100
where do the ossification centers of the ribs form?
beside where the ribs connect to the sternum
101
during development, you start with many ossification centers that fuse together, and you end up with:
- one in the manubrium
- four in the body
- one in the xiphoid process
102
true or false: all six major ossification centres of the sternum are all present at the same time
false, they are not
103
when does the xiphoid ossification centre appear?
not until adulthood
104
are there differences between males and females with the appearance of ossification centres and fusing of segments?
yes
105
by year 25, sternal segments have mainly fused, leaving the final organization of:
the manubrium, the body, and the xiphoid process
106
when does the xiphoid body ossify and fuse with the body?
in mid-life
107
what do chondrocytes do?
make cartilage
108
what do osteoblasts do?
make bone
109
both chondrocytes and osteoblasts originate from:
mesenchymal stem cells
- paraxial mesoderm (axial skeleton and occipital bone)
- lateral plate mesoderm (appendicular skeleton and sternum)
- neural crest cells (cartilage of the face and neck)
110
what do osteoclasts do?
resorb bone
111
where do osteoclasts originate?
the hemotopoietic system (ie: are a form of immune cell)
112
where does dermal bone originate from?
neural crest cells or paraxial mesoderm
113
list the seven major steps of intramembranous ossification
1) small clusters of mesenchymal cells differentiate as osteoblasts
2) osteoblasts secrete osteoid, which calcify over a few days, forming a bone spicule
3) osteoblasts trapped on the bone become quiescent osteocytes
4) spicules of bone grow through secretion of osteoid by surrounding osteoblasts
5) spicules join to form trabeculae, which grow around blood vessels
6) surrounding mesenchyme condenses to form a sheath (the periosteum)
7) trabeculae under the periosteum are replaced by lamellar bone, creating 2 plates sandwiching the woven bone
114
what is woven bone?
the trabeculae which grow around blood vessels
115
the organic component of bone
osteoid
116
during endochondral ossification of the long bones, ______ turns on in mesenchymal condensations and induces the differentiation of chondrocytes
sox 9 (transcription factor)
117
in endochondral ossification, chondrocytes secrete extracellular matrix proteins, creating:
a small cartilage model of the bone
118
chondrocytes pass through four different stages:
resting, proliferating, prehypertrophic, and hypertrophic
119
the cells in the centre of the developing long bones are the first to hypertrophy, and these cells secrete:
an attractant for blood vessels
120
hypertrophic chondrocytes can either undergo _____ or _____
apoptosis, osteoblasts
121
during endochondral ossification, invading blood vessels also bring osteoblasts and osteoclasts, which will:
make and remodel bone in the primary ossification centre
122
while blood vessels invade the endochondral bone, osteoblasts differentiate in the perichondrium (now called the periosteum) and create:
a bony collar
123
in the endochondral bones, the primary osssification centre is in the:
middle of the diaphysis (shaft) of a long bone
124
at birth, the diaphysis is mostly ______, and the epiphyses (ends) are ______
ossified, cartilage
125
after birth, ______ appear in the epiphyses
secondary ossification centres
126
once a secondary ossification center forms, it expands radially to ossify most of:
the epiphyses
127
where is the growth plate found?
between the epiphysis and diaphysis
128
when do the growth plates of the long bones close?
usually by 20 years of age
129
is it possible for bones to grow after the growth plates close?
not in length, but they can grow appositionally in response to exercise
130
true or false: each stage of bone development has a specific genetic signature, and the effect of a mutation in any of these genes depends on the particular role for that gene in bone development
true
Anat 400
flashcards
Decks in class (19)
# Cards
-
Intro to Embryology61
-
Fertilization and the First Week88
-
Week Two - Implantation and Formation of the Bilaminar Disc70
-
Week Three - Gastrulation and Neural Induction78
-
Week Four - Neurulation, Somite Formation, and Folding of the Embryo85
-
Placenta and Fetal Membranes96
-
The Respiratory Sysyem75
-
The Cardiovascular System Part 174
-
The Cardiovascular System Part 280
-
Skin, Hair, and Teeth92
-
The Urogenital System Part 175
-
The Urogenital System Part 282
-
The Skeletal System130
-
Limb Development87
-
The Nervous System153
-
Sensory Systems65
-
Head and Neck Part 175
-
Head and Neck Part 272
