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36 Cards in this Set

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What embryonic progenitor tissues are used to form the skeleton? What are progenitor skeletal cells?
Mesoderm. Mensenchyme
Skeletal progenitor mesenchyme is derived from different tissues based on where it is. In the Trunk progenitors are derived from two sources: (2) In the Head, they're derived from: (2) p.3
Trunk: Paraxial and Somatic Mesoderm
Head: Neural Crest Ectomesenchyme, Head Mesoderm
Define Preskeletal Condensation
It's the site of future bone/cartilage formation.
STFM (skeletal tissue forming mesenchyme) produce two important TFs. What are they what do they induce?
STFM producing Sox-9 induces cartilage formation
STFM producing Runx-2 produces bone
What happens to mice with RunX Null Mutation?
They become cyanotic and die bc they do not from bone, they're ribs are flexible cartilage that compress lungs.
Describe how cartilage forms.
preskeletal condensation of STFM (under influence of signals from nearby tissue) --> Sox9 is produced --> condroblasts --> secrete cartilage matrix, no chondrocytes --> cartilage.
What is the primary ossification center?
Initial ossification center in a developing bone. Long bone = shaft. Flat bone = center. Controlled by hormones.
What is bone age?
Amount of epiphyseal cartilage that's retained.
Cells from which half of the sclerotome contributes to the formation of the vertebral body, small parts of the neural arch and distal rib? (p7):
Anterior half
What is the sclerotome?
See your notes, p1b. They are the cells that arise from the somatocoel when the epithelial mesenchym of the somite reverts back to scleratome mesenchyme.
Cells from which half of the sclerotome contributes to the formation of the ventral body, transverse process, proximal rib, main part of distal rib and main part of neural arch?
Posterior half
What controls regionalization of the vertebral column (e.g. cervical, lumbar, etc)? (p.7)
Nested expression of Hox genes along the cranial-caudal axis of the embryo
What controls Hox expression?
Retinoic acid
Null mutation of Hox expression causes what? What about gain of function?
Null mutation = cranialization of vertebral segments.
Gain of function = caudalizes vertebral segments.
What structure allows for growth in the vertebra? (p8)
Neural Central Junction
Describe Klippel-Feil Sequence:
1. Frequency/Genetics
2. Characteristics (4)
3. Associated with:
4. % have (3)
1. 1/40,000; Recessive
2. Several fused cervical vertebrae, shortened neck, low nuchal hair line, limited cervical spine motility
3. Associated with Genitourinary, cardiopulmonary, hearing defects
4. 20-30% have undescended scapulae, cervical rib, scoliosis (60%)
Describe Sacralization

(BTW: How many Lumbars and Sacrum vertebrae are there?)
Sacralization: Fusion of 5th lumbar vertebrae to sacrum. Thus it appears that there are 4 lumbar vertebrae and 6 fused sacral vertebrae.
(5 Lumbar and 5 Sacral)
Describe Lumbarization. Is this better or worse than Sacralization?
1st sacral verebrae is not fused to the sacrum. Thus it appears that there are 6 lumbar vertebrae and 4 sacral vertebrae. This causes hypermobility and that tends to cause more problems than lumbarization.
Failure of fusion of the neural arches of vertebra:
Dysraphism
Condition where one or a few adjacent vertebrae have unfused spinous processes:
1. What is the major classification of this?
2. What is the mild asymptomatic form of this?
Spina Bifida
1. Dyraphism
2. Spina bifida occulta
What is the primordial tissue for:
1. Proximal Rib
2. Distal Rib
3. Sternum
1. Scleratome and Somatocoel
2. Lateral scleratome
3. Somatic mesoderm
Posterior depression of sternum:
Ventral protrusion of sternum:
Pectus Excavatum
Pectus Carniatum
Classify these skull bones as cranial or viscerocranium and endochondrial or intramembranous ossification.
1. Chondrocranium (Cranium/Endo)
2. Fascial Bones (Viscero/Intra)
3. Jaws (Viscero/Intra)
4. Calvaria (Cranium/Intra)
5. Ossicles (Viscero/Endo)
6. Styloid process (Viscero/Endo)
The skull is derived from two germ layers:
Paraxial Mesoderm and Neural Crest Ectomesenchyme
The Chondrocranium is composed of four bones:
1. Petrous portion of temporal bone. (paired)
2. Base of occipital bone (unpaired)
3. Spenoid (unpaired)
4. Ethmoid (unpaired)
In the chondrocranium, cartilages forming above the pituitary are derived from:
Cartilages forming below pituitary:
Above: Neural crest ectomesenchyme
Below: Occipital somite (1-4) sclaratome tissue
Where are the growth plates in the cranium?
Between the Sphenoid and Ethmoid and between the Sphenoid and Occipital.
Intersections between cranial sutures that run perpendicular to each other are called:
What is they're function?
Fontanelles.
Function is to allow bones to interlock as pass through birth canal.
Saggital sutures fusing prematurely cause:
Coronal sutures fusing prematurely cause:
Saggital: Scaphocephaly
Coronal: Acrocephaly (tall) or Brachycephaly (wide, short) skull
Craniosynostosis is associated with mutations in:
FGF receptor
Microcephaly?
Normal face size but calvaria is small due to defect or absence of brain growth.
Vertebrae are derived from:
Intervertebral discs are derived from:
Vert: Sclerotome portion of somites
IV discs: scleratome (and perhaps notochord)
What is Generalized Tissue Dysplasia?
a defect in Extracellular Matrix (ECM) affecting growth in one part or all of the skeleton.
What Generalized Skeletal Tissue Dysplasia is an example of Germ Line Mosaicism?
Achondroplasia
What is the primary precursor for muscle tissue?
Mesoderm
What are the derivatives of:
1. Skeletal m
2. Smooth, visceral smooth and cardiac muscle
3. Vascular smooth m.
4. Smooth m of constrictor and dilator pupilae m; myoepithelia cells of mammary and sweat glands:
1. Paraxial mesoderm
2. Splanchnic mesoderm
3. Local mesoderm
4. Ectoderm