Block II develop of MSK Flashcards
(160 cards)
1
Q
What does the paraxial mesoderm separate into?
A
into blocks called somites
2
Q
What are the functions of somites? (general)
A
Determines the migration path of the neural crest cells and spinal nerves axons
3
Q
What structures do somites give rise to?
A
Gives rise to vertebrae, ribs, skeletal muscle of the body walls and limbs
4
Q
What dies the lateral plate mesoderm (lpm) do?
A
- Forms all connective tissue (i.e., Cartilages, ligaments, etc.)
- Blood vessels, and bones of the appendicular skeleton (i.e., Limb bones and bones of limb girdles) and sternum
5
Q
At what week does the skeletal system start to develop?
A
4th week
6
Q
How does the skeletal system start to develop?
A
Develops from paraxial, lateral plate mesoderm and neural crest cells
7
Q
In the paraxial mesoderm, what do somites differentiate into?
A
differentiate into: Sclerotome & Dermomyotome
8
Q
What type of cells do the sclerotome give rise to?
A
Cells form the vertebrae and ribs
(ventromedial part)
9
Q
What type of cells do the dermomyotome give rise to?
A
Cells from its myotome region form myoblasts (primordial muscle cells);
those from its dermatome region form the dermis. (dorsolateral part)
10
Q
By the end of week 4, what does the sclerotome turn into?
A
Sclerotome becomes mesenchyme
11
Q
The mssenchymal cells from the sclerotome differentiate into what 3 primary bone strcutures?
A
Mesenchymal cells migrate and differentiate in fibroblast, chondroblasts or osteoblasts. (End of week 4)
12
Q
What happens with cell in the head region by the end of week 4?
A
Messenchyme are present for head region and they are derived from neural crest cells
13
Q
Where do messenchyme from head region migrate to?
A
Migrate into the pharyngeal arches and
form the bones and connective tissue of
craniofacial structures
14
Q
identify
A
sclerotome, dermatome, myotome
15
Q
What are the two types of bone ossification?
A
Intramembranous & endochondrial
16
Q
What is intramembranous ossification?
A
Mesenchymal condensation in the dermis differentiates into bone
-ex. flat bones of skull
17
Q
What is endochondrial ossification?
A
Mesenchymal cells first gives rise to a hyaline cartilage models
-ex. long bones, skull base bones
18
Q
What is the major type of protein present in cartilage and bone extracellular matrix?
A
Collagen type I fibers embedded in amorphous component
19
Q
Explain intamembranous ossification
A
-Mesenchymal cells condensate
-Osteoblasts secrete the organic matrix
(osteoid)
-Calcium phosphate is then deposited and
the matrix reorganized into compact bone
-Osteoblasts in the osteoid become
osteocytes.
-Continuous remodeling of bone occurs at
fetal and postnatal life due to the activity of osteoblasts and osteoclasts
20
Q
What are examples of flat bones?
A
sternum/calvaria
21
Q
What is an ostioid?
A
Matrix of bone
22
Q
In the process of intramembranous ossification, what do messenchymal cells turn into?
A
osteoblasts
23
Q
What structure gives flat bones its structure?
A
Trabeculae
24
Q
What is the “old” version of osteoblasts?
A
osteocytes
25
What type of bones does endochondrial ossification work?
long bones
26
Explain endochondrial ossification
-Ossification of the limbs
-Mesenchyme cells begin to condense and differentiate into chondrocytes
-Chondrocytes form a cartilaginous model of the prospective bone
-Primary Ossification Center
-Secondary Ossification Center
27
Where does primary ossification occur?
body of bone; where blood vessels invade the center of the cartilaginous model, bringing osteoblasts at the diaphysis
28
Where does secondary ossification occur?
blood vessels invade the epiphyses
29
By what is the Growth of the bones maintained?
by proliferation of chondrocytes in
the growth plates
30
Where does the cranium develop from?
develops from mesenchyme around the developing brain
31
What does the cranium consists of?
-Neurocranium
-Viscerocranium
32
What are the divisions of the neurocranium?
membranous part and cartilaginous part
33
What does the membranous part of the neurocranium do?
Forms a protective case around the brain
via intramembrabous ossification
34
What does the cartilaginous part of the neurocranium do?
-AKA chondrocranium
-Endochondral ossification forms the bones of the base of the cranium
35
What does the viscerocranium do?
* Forms the skeleton of the face
* Mainly form by the first two pharyngeal
arches
36
What are other structures of the cranium?
calvaria
sutures
fontanellas
37
What is the calvaria?
the cranial vault
38
how does the calvaria form?
formed by intramembranous ossification in the mesenchyme at the sides and top of the brain
39
What are the sutures?
Fibrous joints composed of dense connective tissue that joins the flat bones
40
what are the fontanellas?
-6 large fibrous areas where several sutures meet
* The softness of the bones and their loose connections at the sutures enable the calvaria to undergo changes in shape (“molding”) during birth
41
identify
42
identify
43
what tissue does the fontanellas have?
cartilage
44
What is acrania?
Absent calvaria (no parietal bones, temporal bones or frontal bones) without defects of the vertebral column.
45
identify
acrania
46
what is acrania associated with?
anencephaly (partial absence of the brain)
47
What is the cause of acrania?
results from failure of the cranial end of the neural tube to close during the 4th week of development
48
identify
craniosynostosis
49
What is craniosynostosis
Most cranial deformities that result from premature closure of the cranial sutures; more common in males than in females;
prenatal closure results in the most severe abnormalities.
50
What are the causes of craniosynostosis?
Mutations of the transcription factors MSX2, TWIST1 and fibroblast growth factor receptors (FGFR1, FGFR2 and FGFR3)
have been implicated in cases of craniosynostosis and other cranial deformities [closure of notochord]
51
What is scaphocephaly?
type of crabiosynostosis, Premature closure of the sagittal suture (skull becomes long and narrow); constitutes 57% of all cases. compatible with life.
52
What is brachychephaly?
type of craniosynostosis; premature closure of the coronal suture results in a short skull.
53
What is plagiocephaly?
type of craniosynostosis; the coronal or lambdoid suture closes prematurely on one side only (cranium is twisted and asymmetric).
54
Causes of plagiochephaly?
Regulation of suture closure involves secretion of various isoforms of transforming growth factor-β
55
identify
plagiocephaly
56
identify
brachycephaly
57
identify
plagiocephaly
58
Where does vertebral column originate from?
from the sclerotome portions of the somite
59
What takes place during the 4th week regArding vertebral column development?
Sclerotomes migrate around the spinal cord and notochord to contribute with the vertebrae formation.
60
What constitutes the future vertebral body?
Mesenchymal tissue formed by the fusion of the remaining densely packed cells with the loosely arranged cells of the immediately caudal sclerotome
61
What constitutes the future intervertebral discs?
formed by densely packed cells which move cranially, opposite the center of the myotome
62
What does the condensation of sclerotome result in?
sale la vertebra
63
How does the nucleus pulpous form?
* the gelatinous center of the IV disc formed by the expansion of the notochord between the vertebrae
* It emerges when the notochord degenerates and disappears where it is surrounded by the developing vertebral bodies.
64
How does the anulus fibrous form?
formed by circularly-arranged fibers that surround the nucleus pulposus;
IV disc = nucleus pulposus + anulus fibrosus
65
What are chondrification centers?
appear in each mesenchymal vertebra during 6th week.
two chondrifications centers fuse to form a cartilaginous central region
66
what are primary ossification centers of vertebral body?
when the centers in the vertebral arches fuse with each other
67
When does vertebral ossification begin?
during 8th week
68
What are the vertebral body ossifications centers?
Two primary ossification centers (ventral and dorsal) for the vertebral body which then fuse to form one center
69
What are the vertebral arch ossifications centers?
Two primary ossification centers one in each half of the vertebral arch.
70
What the ossification centers end up with?
3 primary ossification centers
- 1 in the vertebral body or centrum
-2 in the vertebral arches (one in each half of the vertebral arch)
71
what is the neurocentral joint?
cartilaginous articulation betweeb the vertebral arch and the centrum that allows bone to grow; these arches fuse with the body durin ages 3-6
72
When does Bony halves of the vertebral arch and where does fusion starts?
ages 3-5 approx;
Fusion starts in the lumbar region and then progresses cranially
73
what happens to vertebral column development during puberty?
Five second ossification centers appear
74
What are the 5 second ossification centers
* one at the tip of the spinous process
* one at the tip of each transverse process
* two anular epiphyses (superior and inferior rim of the vertebral body)
* All secondary centers fuse around age 25
75
Where do ribs develop from?
from the mesenchymal costal processes of the thoracic vertebrae [transverse process]
76
how do ribs ossify?
They become cartilaginous during
the embryonic period and ossify during the fetal period.
77
What happens to the original site of union of costal process with vertebrae?
is replaced by costovertebral joints.
78
What are the sternal bars?
the begin to chondrify and fuse as ribs become connected and fuse with sternum
79
What is hemivertebra?
-Failure of one of the chondrification centers to appear as a consequence there is failure of half of the vertebra to form
-Scoliosis produced by this vertebral defect
80
What is rachischisis?
Vertebral abnormality produced by the failure of the neural folds to fuse (doesnt close, spinal cord exposed)
Etiology: lack of proper induction by notochord or exposure to teratogenic agents
81
identify
Cranioschisis (orange)
Rachischis (blue)
82
identify
Rachischis
83
Where does the muscular system develop from?
mesodermal germ layer
84
What are te types of muscles that emerge from the mesodermal germ layer?
Skeletal muscle
Smooth muscle
Cardiac muscle
85
Where does the skeletal muscle derive from?
* Derived from paraxial mesoderm
* Form somites from occipital to the sacral region and somitomeres head
86
Where does the smooth muscle derive from?
* Derived from visceral splanchnic mesoderm
* Pupil, mammary glands and sweat gland muscles
87
Where does the cardiac muscle derive from?
Derived from visceral splanchnic mesoderm
88
In what does the myotome divide into?
Dorsal epaxial
Ventral hypaxial
89
What does the ventral hypaxial give rise to?
* Gives rise to body wall muscles( abdomen and thorax)
* Upper and lower limb muscles [flexors and extensors]
90
What does the dorsal epaxial give rise to?
Gives rise to back muscles
91
What genes are important for development of hypaxial muscles?
MyoD
92
What genes are important for development of epaxial muscles?
MYF-5
93
What are MyoD and MYF-5 important for?
Both genes are involved in the
development of the abdominal and intercostal muscles.
94
WHat is myogenesis?
muscle formation; Starts with the elongation of the nuclei and cell bodies of
mesenchymal cells as they differentiate into myoblasts (primordial muscle cells).
95
What are myotubes?
Elongated, multinucleated, cylindrical structures formed by the fusion of myoblasts
96
WHat regulates the beginning of myogenesis an induction of myotome?
Signaling molecules from the ventral tube (SHH), notochord (Noggin), dorsal neural tube (WNTs, NT-3), and the overlying ectoderm (BMP-4, WNT)
97
What are myoblasts?
embryonic muscle cells derived from mesenchyme
98
How does muscle growth occur?
Muscle growth during development results
from the ongoing fusion of myoblasts and
myotubes.
99
What are myofilaments?
develop in the cytoplasm of the myotubes during or after fusion of the myoblasts; soon after that, myofibrils and other organelles characteristic of striated muscle
cells develop.
100
When do most skeletal muscles develop?
Most skeletal muscle develops before birth, and almost all remaining muscles are
formed by the end of the 1st year
101
Where does smooth muscles differentiate from?
splanchnic mesenchyme surrounding the endoderm of the primordial gut and its derivatives [autonomic system]
102
What is the serum response factor (SRF)
Activates the genetic cascade responsible for smooth muscle development
103
Where do vessels from smooth muscles derive?
arises from somatic mesoderm
104
When do smooth muscles receive autonomic innervation?
As smooth muscle fibers develop into sheets or bundles
105
Where do cardiac muscle develops from?
Develops from the lateral splanchnic mesoderm, which gives rise to the mesenchyme surrounding the developing heart tube
106
Which cells form first in the cardiac muscle development and from where do they differentiate?
cardiac myoblasts; differentiate from this primordial myocardium
107
Where do cardiac muscle fibers come from?
arise by differentiation and growth of single cells, unlike striated muscle fibers, which develop by fusion of cells
108
Growth of cardiac muscle fibers result from?
the formation of new myofilaments
109
What are intercalated discs?
areas of adhesion between myoblasts in which the intervening cell membrane does not disintegrate
110
Where do purkinje cells come from?
form the conducting system of the heart
111
What are purkinje cells?
atypical cardiac muscle cells which develop less myofibrils and are larger in diameter than typical cardiac muscle fibers
112
identify
intercalated discs
113
When do limbs become visible?
4th week
114
What is the emergence of the limbs?
1. Parietal (somatic) layer of lateral plate mesoderm
2. Apical ectodermal ridge (AER)
115
What does the Parietal (somatic) layer of lateral plate mesoderm form?
-bones and connective tissues of the limbs
-Covered by a layer of cuboidal ectoderm
116
What is the AER?
-Ectoderm at the distal border of the limb thickens
-Also known as undifferentiated zone
-As the limb grows cells begin to differentiate Into cartilage and muscle
117
Identify
118
119
identify
upper limb 5th week
120
identify
upper limb 6th week
121
identify
upper limb 8th week
122
identify
lower limb 8th week
123
how does development of limbs proceed?
proximo-distally into its three components:
-stylopod
-zeugopod
-autopod
124
What does Stylopod develop?
humerus and femur
125
What does zeugopod develop?
radius/ulna and tibia/fibula
126
What does autopod develop?
carpels, metacarpals, digits/tarsals, digits/metatarsals
127
What happens to the upper limb during week 6?
1. Limb buds becomes flattened to form the hand and footplates
2. Separated from the proximal segment by a circular constriction
3.First hyaline cartilage models, foreshadowing the bones of the extremities
4. Joints are formed in the cartilaginous condensations
128
What happens to the upper limb during the 8th week?
1. By this time a second constriction [elbow] divides the proximal portion into two segments
2. Fingers and toes are formed when cell
death in the AER separates this ridge into five parts
129
When does morphogenesis of lower limb occur?
lower limb is approximately 1 to 2 days behind
130
What happens with the position of the upper limb?
Upper limb rotates 90° laterally [anatomical position]
* Extensor muscles lie on the lateral and posterior surface
* The thumbs lie laterally
131
What happens with the position of the lower limb?
Lower limb rotates approximately 90° medially [queda pa dentro]
* Placing the extensor muscles on the anterior surface
* The big toe lies medially
132
Where do muscle cells for the limbs derived from somites come from in the upper limb?
Segments C5-T2
133
Where do muscle cells for the limbs derived from somites come from in the lower limb?
Segments L2-S2
134
What is the function of the lateral plate mesoderm?
1. Determines the elongation of the limb buds
2. The muscle tissue first splits into flexor and extensor components
135
Muscles of the limbs are innervated by?
ventral primary rami
136
how does the ventral primary rami divide and what does it give rise to?
-Initially divide to form dorsal and ventral branches to these compartments
* Eventually they will give rise to:
1. Radial n. (Dorsal segmental branches)
2. Ulnar n. (Ventral branches)
3. Median n. (Ventral branches)
137
Where does brachial plexus surge from?
ventral primary ramus
138
Mention the functions of the spinal nerves
1. Provide motor innervation for the muscles
2. Provide sensory innervation through the dermatomes
3. Reflect the original segmental pattern of the somites and demonstrate the early association of individual spinal nerves with
the derivatives of each dermomyotome
139
Which are the molecular regulators of the limbs FOR DIFFERENTIATION?
Retinoic acid
HOXA11
HOXA13
140
What does retinoic acid do?
Acts as morphogen to initiate the genetic cascade that differentiation of the stylopod [proximal bones]
141
What is MEIS1?
transcription factor involved with retinoic acid
142
What does HOXA11 do?
Differentiation gene of the zeugopod [radio/ulna; tibia/fibula]
143
What does HOXA13 do?
Differentiation gene of the autopod [distal]
144
What happens to AER?
It degenerates to expose the digits of the hand
145
Which are the molecular regulators of the limbs FOR Growth factors?
1. Fibroblast growth factor 10 (FGF10)
2. FGF4 & FGF8
146
What does Fibroblast growth factor 10 (FGF10) do and by what is it secreted?
* Secreted by lateral plate mesoderm cells
* Initiates limbs outgrowth
147
What does FGF4 & FGF8 do and by what are they secreted?
* Secreted by the ridge
* Maintain the undifferentiated zone
148
What does factor SHH do?
-Contributes to specification of the antero-posterior axis
-Digits appear in the proper order
149
Whta do BMPs do?
regulate dorsoventral axis (posterior part)
150
What do HOX genes do?
Regulate the types and shapes of the bones of the limb
151
What is the most critical period for limb development?
4th and 5th weeks
152
What is Amelia?
Complete absence of one or more of the extremities
153
What is phacomelia?
Absent long bones, and rudimentary hands or feet are attached to the trunk by small, irregularly shaped bones
154
What is Syndactyly?
Two or more fingers or toes are fused
155
What is polydactyly?
* Presence of extra fingers or toes
* Extra digits frequently lack proper muscle connections
156
identify
Amelia
157
identify
Phacomelia
158
identify
Syndactyly
159
identify
Polydactyly
160
