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95 Cards in this Set
- Front
- Back
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Which precursors give rise to skeletal tissue forming mesenchyme
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1. Paraxial mesoderm scleratomes of somites in the trunk, head mesoderm in the head
2. Lateral plate mesoderm-trunk 3. Neural Crest ectoderm (head) |
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Which transcription factor mediates the differentiation of STFM inot cartilage
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SOX-9
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Which transcription factor mediates the differentiation of STFM into bone
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Runx-2 (Cbfa-1)
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Describe how cartilage is formed
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1.The STFM cells in the preskeletal condensation express SOX-9 and differentiate into chondroblasts
2. The chondroblasts secrete Type II collagen and components of cartilage matrix 3.THis forms the cartilage element and surronding perichondrium |
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Describe the processes of intramembranous ossification
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Bone is formed diretly from a preskeletal condensation
1.The cells in the STFM condensation express Runx-2 which transforms them into osteoblasts 2. THe osteoblasts secrete type I collagen, osteocalcin, and osteopontin 3. The spcules radiate and form bone |
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Which precursors give rise to skeletal tissue forming mesenchyme
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1. Paraxial mesoderm scleratomes of somites in the trunk, head mesoderm in the head
2. Lateral plate mesoderm-trunk 3. Neural Crest ectoderm (head) |
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Which transcription factor mediates the differentiation of STFM inot cartilage
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SOX-9
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Which transcription factor mediates the differentiation of STFM into bone
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Runx-2 (Cbfa-1)
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Describe how cartilage is formed
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1.The STFM cells in the preskeletal condensation express SOX-9 and differentiate into chondroblasts
2. The chondroblasts secrete Type II collagen and components of cartilage matrix 3.THis forms the cartilage element and surronding perichondrium |
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Describe the processes of intramembranous ossification
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Bone is formed diretly from a preskeletal condensation
1.The cells in the STFM condensation express Runx-2 which transforms them into osteoblasts 2. THe osteoblasts secrete type I collagen, osteocalcin, and osteopontin 3. The spcules radiate and form bone |
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in general, which bones are formed by intramembranous ossification
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Superfical bones like flat skull bones
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How do bones formed by intramembranous ossification grow
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addition of new bone to the outer suface accompanied by removal of bone at the inner surface
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How is bone formed by endochondrial ossification
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1. the cells in the STFM condense and form a cartialge model of the bone
2. Runx-2, Shh, and BMP-6 cause chondrocyte hypertrophy and secretion of type X collagen, bone specific proteins, and angiogneic factors 3. Osetoblasts invade and replace the hypertrophic collagen with bone |
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Which type of ossification allows bones to grown in length
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Endochondral ossification because there is a cartilage growth plate (epiphysela plate) at the end. New cartilage is continually produced and then replaced by bone
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In which type of structure is each of the following types of cartiagle invovled
Type I Type II Type X |
Type I=intramembranous ossification
Type II=Cartilage formation Type X-Endochondrial Ossification |
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How does the position of the primary ossification center differ in long bones and flat bones
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long-shaft region
flat-center |
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What is the difference between primary and secondary ossifcation centers
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primary-initial ossification center for form in a developing bone
Secondary-additional centers of bone formation in prenatal, postnatal, and postpuberal period |
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WHere are secondary ossification centers usually located
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Ends of long bones, heads of ribs, surface of vertebrae
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Where is the epiphyseal plate of long bones usually located in relation to ossification centers
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Between the secondary and primary centers
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Secondary ossification centers can disappera during of after puberty and as late as the early 20-30's. What this dissappearance result in?
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disappearance of the epiphyseal plate
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What is the progenitor tissue for the vertebrae
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Scleratome mesenchyme of the somites, begining with somite #5, the first cervical somite.
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Describe the first steop of vertebrae formation (what happens to the somite?)
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The ventral half of the someite undergoes an epithelial-mesenchymal transfomration to become the scleratome mesenchyme
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What signals mediate scleratome formation? Where do they come from?
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Shh and noggin, come from notochord and floor plate of neural tube
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Describe what happens to the scerlartome mesenchyme cells destined to from vertebrae after they micgrate to the notochord and neural tube
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The scleratome mesenchyme arragnges
-craial=loose -caudal-compact |
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Why is it important that the cranial half of the scleratome mesenchyme becomes loosely compacted but the caudal half is dense
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The cranial-caudal subdivision is necessary for patterning of neural crest cell migration and spinal nerve axon outgrowth. Note that crest cells and nerve axons are inhibited from crossing the caudal half of the scleratome
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vertebrae formation
After the scleratome mesenchyme cells separate cranially (loose) and caudally (compact) they must resegment. How does this proces occur and what is the result? |
The cranial half of one somite fuses with the caudal half of the next adjeacent one. THis resutls in vertebrae that are intersegmental with respect to the original somite pattern which allos muscles from the dermatomes to span adjacent vertebrae.Intersegmental arteries now pass across the body of the vertebrae and the spinal nereves lie near the IV disks
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What are the vertebrae derivatives of each of the follwoing scleratome Compartments?
Central Ventral Dorsal Lateral Somitocoel |
Central-pedicle, proxmial costal processs
Ventral-vertebral body, IV disc Dorsal-Dorsal neural arch, Spinous process Lateral-Distal rib Somitocoel-vetrebral joints, IV disc, proxmial ribs |
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WHere do the meninges and blood vessels of the spinal cord come from?
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Cells in the medial part of the scelratome adjacent to the forming neuraltube.
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WHere doe the tendons o fthe epiaxial muscles attaching the the vertebrae come from?
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Cells in the lateral edge of the central compartment of the scleratome
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Describe the structure of the primitive vertebrae and how it becomes ossified
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Primitive structures-pair of neural arches from which costal and transverse processes will arise. The neurocentral junction, a layer of cartilage between the base of the neural arch and the centrum allows for growth of the vertebrea. Ossification occurs ~adolescence and unites the centrum and neural arch
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Where does the IV disk develop
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The intersegmental boundary from cells of the posterior scleratome and the somatocel cells
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Which vertebral structures do cells from the posterior (Caudal) half of the scleratome form? Anterior (Cranial)?
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Posterior (caudal)=vetebral body, transverse process, proxomal rib, main part of distal rib, main part of neural arch
ANterior (cranial)=veterbral body, small parts of neural arch and distal rib |
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What is the eventual fate of the notochord
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becomes the nucleus pulposus
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What mediates regionalization of the vertebral column
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The nested expression of Hox genes along the cranial-caudal axis of the embryo. Hox expression is mediated by retinoic acid. Hox is expressed at low levels cranially and high levels caudally.
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Describe the effect of a null mutation of HOX expression in the vertebral colum. Gain of function?
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A null mutation would tend to cranialize vertebral segements because Hox is expressed at low levels cranially.
A gain of function mutation would tend to caudalize vetebrae because Hox is expressed at high levels caudally. |
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What type of ossification process to vertebrae undergo
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enxochondrial ossification
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Describe the distribution of primary and secondary ossification centers in the developing vertebrae
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Primary-Two in the centrum which may fuse, one in each arch
Secondary-Cranial and caudal surfaces of the body, tips of the spinous and transverse processs Note the prescence of the cartilagenous neural central junction between the centrum and neural arches to allow for growth. |
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Describe Klippel-Feil sequece (Brevicollis)
characterization? associations? cause? |
Rare recessive disorder charcterized by several fused cervical spine vertebrae. Short neck, low nucal hair line, limitied mobility. Associated with GU and CP defects and hearing loss. May also have undescended scapulla, cervical rib and scoliosis.
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Describe scaralized/ lumarized vertebrae. Cause? Result?
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Sacralization-5th lumbar vertebrae is incorporated into sacrum
Lumbarization-1st sacral vertebrae is not included in the sacrum. Note that the total number of vertebrae remains unchanged |
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Describe Dysraphism and the spectrum of defects it includes
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Refers to a falure of fusion of neural arches
worse=Rachischisis where many or all vertebrae are unfused Spina bifida refers to when only a couple are unfused. SB occulta is the mildest form and usually asymptomatic |
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What problems might result form malformed vertebrae (hemivertebrae, wedge shpaed, unsegmented bars)
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Create an asymmetry that leads to abnormal curvatures like scoliosis, kyphosis , and lordosis
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What is the cause of hemivertebrae
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Failure of primary ossification centers (2 in centrum, 1 in each arch)
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Which cells form the proximal and distal portions of the ribs
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The ribs form as the costal processes expand laterall. the proximal portion forms form the cells of the central sceleratome and somitocoel while the distal portion is derived from lateral scleratome cells.
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How does the sternum form?
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Somatic mesoderm from the ventral body wall forms two cartilage bars. After folding in the transverse plane, the bars fuse. After fusion a segmentation occurs to form sternebrae which refuse and form the different parts of the sternum.
Primary ossification centers appear in the 5th mo. expcept for the xiphoid process |
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Describe the formation of sternebrae and what they become
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Sternebrae form as the result of a secondary segementation that occurs after the cartilage bars fuse. The cranial most remains unfused and becomes the manubrium. The caudal sternebrae becomes the xiphoid process.
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List several possible anomalies of rib development and what affect they might have.
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Accessory ribs may form in the lumbar and cervical regions which may cause brachail plexus issue. Fused and forekd ribs may also occur but they are usally asymptomatic.
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Although the ribs and sternum are closely associated they come form different progenitor tissues. What are these tissues
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Ribs-proxmial from central scleratome and somitocoel, distal from lateral scleratome cells
Sternum-somatic mesoderm |
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Describe pectus excavatum
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Posterior depression of the sternum, results from abnormal development of the sternum and costal cartilage, note that heart may be pressed against spine and deviated to the left, surgey may be required
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Describe pectus carniatum
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Ventral protrusion of the sternum resulting from abnormal development of the sternum and costal cartilage primorida. Usually an isolated anomaly, more common in males
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The neurocranism consists of ___ and ___ which are derived from___ and ossify via
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Chondrocranium (floor)-mesoderm, endochondrial ossification (most bones)
Calvaria-skull cap frontal and temporal are from neural crest ectoderm Parietal and occipital are from paraxial mesoderm Form via intramembranous ossification (flat bones) |
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The Facial bones are jaw are derived from___ and ossify via___
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Facial bones and jaw are derived from neural crest ectoderm and undergo intramembranous ossification
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The ossicles and styloid process are formed via which type of ossification
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endochondrial
(as are the majority of bones) |
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The chondrocranium (floor) is derived from fusion of sevearal chondrogenic centers associated with forming sense organs. These centers include
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Nasal and trabeculae cranni-olfaction
alatemporalis and orbitalis- orbit otic-interna lera |
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The cartilages that contribute to the formation of the cranium are derived from...
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Cranial to pituitary=neural crest ectomesenchyme
remainder-occipital somite scleratome tissue |
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Describe the location of the cartilage growth plates within the skull that allow for longitudinal growth of the skull base
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1. Sphenoid ethmoidal
2. Sphenoid occipital |
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The float bones of the calvaria form the roof of the cranium but they have different progenitor tissue. what tissue gives rise to the fronta bonel and squamos parts of the temporal bone? Parietal and occipital bone?
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Temporal+Frontal=neural crest ectoderm (ectomesenchyme)
Occipital=head mesoderm |
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Intersections between cranial sutures the run perpendicular to each other create fontaneels that allow for molding of the skull. WHere are each of these? When do they close and what reference pont do they form?
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1. Anterior-bregma 1.5-2 yr
2. Posterior-lambda, 2-3 mo. 3. 2x anterolateral-pterion, 2-3 mo 4.2x Posteriorlateral -Asterion 1 year |
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THe bones that comprise the face and jaws are derived from which type of progenitor tissue from which structures
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Neural crest ectomesenchyme (ectoderm) within the maxillary and mandibular promineneces of the 1st PA and frontonasal promience.
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How are most facial bones ossified
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intramembranous ossification (note that ossicles and styloid processes are EC)
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Describe acrania (exencephaly)
-characteristics -cause |
All or part of the neurocranium is missing. Associated with complete but abnormal brain that is coverd by thin membrane. Mesenchyme that formally forms between the surface ectoderm nd neural tube fails to form or migrate. Abnormal brian is due to missing inductive signals normally given by this overlying mesoderm.
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Describe cranioschisis
-characterization -cause |
Skull bones are note closed, often associated with anencephaly. Remaining brain tissue exposed to amniotic fluid that causes damages
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Describe craniosynostosis
-cause -characterization |
One or more sutures closes prematurely, associated with many syndromes. Shape of skull depends on which sutures close.
Scaphocephaly=saggital, long and narrow Acrocephaly/Brachycephaly=cornoal, short and tall |
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Craniosynostosis is the premature closure of one or more of the cranial sutures. Describe each form that can occur including the shape of the skull, the suture involved, and the name givne.
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1. Saggital suture=long and narrow=Scaphocephaly
2. Coronal Suture=Short and Tall=acrocephaly or brachycephaly 3. Only part of 1 suture= Plagiocephaly |
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Cranisynostosis is associated with defects of which genes?
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The form associated with syndromes is the result of FGF 1 and 2 mutations
The non-syndromic form is associated with FGF3 mutations. |
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What is the difference between primary and secondary craniosynostosis?
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Primary-the defect is inherent to the skull bones
Secondary-dfect in growth of brain results in premature suture closure |
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Describe cloverleaf skull (kleeblattschadel)
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A form of craniosynostosis in which multiple sutures have fuse prematurely, multiple anomalies
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Describe microcephaly
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-normal sized face but small calvaria
-caused by defect or absence of brain growth -genetic and environmental causes -mental disability, other anomalies |
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Which signaling molecuels secreted by the interzone mesenchyme contribute to the formation of joints
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Gdf 5 and 6
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Describe the formation of synovial joints
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Mesenchyme interzones form between the bone primordia. The mesenchyme differentiates into fibrous tissue. The fibrous tissue adjacent to the ends of the bones forms articular carilage and that in the center form the synovial tissue, intra-articular disc and intenral ligaments. Vacuoles forming within the fibrous tissue combine to form the joint cavity. The capusle froms from mesenchyme surroinding the interzone
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Describe the formation of fiberous joints and cartilagenous joints
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1. Mesenchyme interzone forms between the bone primorida
2. mesenchyme differnetiates into fibrous connective tissue or cartilage |
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Describe achondroplasai (a chondrodystrophia, heterogenous group of disorders characterized by disproportionate growth)
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-autosomal dominant or spontaneous
-interference with epiphyseal palte development leads to short limbs but normal trunk size -enlarged cranium, normal inteligenec -short fingers, accentuated lordosis -mutation of FGFR-3 |
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Describe Marfan syndrome
-cause -characteristics |
Autosomal dominant problem with fibrillin production. Long fingers, messed up eyes, spine, hypermobile joints, aortic aneurysms,
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Describe mucopolysaccharidooses
-cause -characteristics |
Autosomal recessive lysomal storage disorder. Chronic, progressive multisystem deteroiration with distortions of face and skull
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Describe Osterogenesis imperfecta
-cause -characteristics |
Autosomal dominant type I collagen (IM oss) problem. Brittle bones, blue sclera, ears, joints, teeth
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Describe hyperpituitarism
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Overproduction of growth hormone
if prior to plate closure-gigantism if after-acromegaly (disproportionate enlargement of face, hands, and feet) |
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Describe hypothyroidism
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Short stature
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From which precursor tissue does each of the following types of muscles develop
Skeletal Smooth m./ Cardiac/ Visceral smooth Vascular smooth Pupil, mammary, sweat gland |
Skeletal=paraxial mesoderm
Smooth, Cardiac, Visceral= Splanchnic mesoderm Vascular smooth=local mesoderm Pupil, myoepithelial=ectoderm |
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Describe the formation of skeletal muscle
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1. Myoblasts in mytome kept in cell cycle, migrate and become postmitotic
2. Formation of premuscle mass and fusion to form multinucleated fibers (M-cadherin) 3. Signals from ectoderm or neural tube and notochord upregulate myogeneic factors, muscle proteins expressed and sarcomere forms |
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Describe the signaling that indcued the formation of muslce fiber. Which molecules? From where?
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From adjacent ectoderm or neural tube and notochord, myf-5, MyoD, myogenis, MRF-4
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What innervates muscles in the head and neck tha tare dreived from head mesoderm and occipital myotomes
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Cranial Nerves
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The abaxial/hypaxial muslces are innervated by
(these are the muscles formed form myoblasts from the ventrolateral mytome that moved into the somatic mesoderm to form muscles of the ventrolateral body wall) |
Ventral primary rami of spinal nerves
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The primaxial/ Expiaxial muscles are innervated by
(these are the muslces fomr myoblasts from the dorsolateral myotome) |
Dorsal primary rami of spinal nerves
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What is the precusor tissue of smooth muscle
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splanchnic mesoderm
(note that the great vessels are from somatic mesoderm and neural crest and the vascular smooth muscle is from local mesoderm) |
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Which molecule is the "master regulator" of smooth muslce gene expression
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myocardin
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The great vessels are derived from which precursor tissue
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somatic mesoderm+ neural crest
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Vacular smooth muscle is derived from
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local mesoderm
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Cardiac muscle is derived from
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splanchinic mesoderm, cardiogenic crescent and secondary heart field
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Describe the formatino of cardiac muscle
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Splanchnic mesoderm gives rise to cardiac myoblasts that divide while beating and maturing. The mature myocytes become postmitotic and form cardiac muscle
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Describe the Poland sequence
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-Abscence of the perctoralis minor and sternocostal head of pec major
-nipple displaced laterally -yndactyly and brachydactyly |
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Describe prune belly syndrome
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-parial or complete absence of abdominal wall muslces
-associated with urinary bladder/ tract defects, urethral obstruction |
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Describe congenital torticolis
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-fixed rotation and tilting of head
-birth trauma, plagiocephaly, infections |
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Describe musclar dystrophy-duchenne type
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-X linked recessive
-skeletal muscle weakness w/o CNS invovlement -myocytes lack dystrophin |
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Describe the differneces between embryonic and mature connective tissue
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In the embryo the cells are arranged in a mesenchyme and there is a high ratio of cells to ECM. In mature tissue, the number of cells vaires and there is a high ratio of ECM to cells.
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Describe the basic structure of each of the three main types of supporting CT. What do they do?
1. Fibrous 2. Cartilage 3. Bone |
1. Fibrous-dense and loose varieties, form organ capusles, tendons, and fascia
2. Cartilage-cells embedee in hydrated amorphous ECM, avascular, provides flexible support 3. Bone-fibers and cells embedded in mineralized ECM, richly vascular, provided rigid support |
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Describe the differences between each of the three types of muscles
1. Skeletal 2. Cardiac 3. Smooth |
Skeletal-striated, multiple nuclei, voluntary contraction
Cardiac-straited, 1-2 nuclei, involuntary Smooth-non-striated, single nuclei, involuntary |
