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82 Cards in this Set
- Front
- Back
Located at the tip of each limb bud and induces the mesenchyme beneath it to elongate
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Apical Ectodermal Ridge
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Limb buds are made up of (2 things):
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Mesenchyme (somatic mesoderm) covered by surface ectoderm
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Which Spinal Roots supply the upper limb
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C5-T1
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Which Spinal Roots supply the lower limb bud
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L2-S3
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Cartilaginous bones begin to develop from ----- early in week ------
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Chondrification Centers, week 5
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During what time do limb buds descend to their adult height
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Weeks 6-8
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Ossification of long bones
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osteogenesis
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osteogenesis begins from
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primary ossification centers in the middle of the long bone
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When does osteogenesis begin?
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Week 7
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The skeletal muscle of the limb is derived from ------------- that migrates into the limbs
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myotomal cells
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The complete absence of one or more limbs
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amelia
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Defect where the upper portion of a limb is absent or poorly developed
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Phocomelia
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Congenital anomaly characterized by two or more fused together fingers or toes
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Syndactyly
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Enlargement of one or more digits
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Macrodactyly
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Condition in which one has extra digits
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Polydactyly
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Condition in which one has fewer than normal digits
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Ectrodactyly
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Malformation characterized by abnormal positions of the foot
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Clubfoot (talipes equinovarus)
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One form of congenital dwarfism resulting from improper development of cartilage at the end of long bones
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Achondroplasia
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Segmented series of tissue blocks adjacent to the neural tube
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Somites
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Somites are made from:
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paraxial mesoderm
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Somites develop into two segments:
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Sclerotome & Dermomyotome
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Three layers contributing to skeletal system formation
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Paraxial mesoderm, lateral plate mesoderm, and neural crest
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Ventromedial portion of the somite gives rise to
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Sclerotome cells
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These cells become polymorphous and and form loosely woven tissue (mesenchyme)
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Sclerotome cells
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Cells that migrate and give rise to fibroblasts, chondroblasts, and osteoblasts
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Mesenchymal cells (from sclerotome)
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Dorsolateral portion of the somites gives rise to:
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Dermomyotome cells
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Cells that give rise to the dermis and mucle
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Dermomyotome cells
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The somatic mesoderm layer comes from
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Lateral plate mesoderm
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Gives rise to appendicular skeletal bones (pelvic, shoulder girdles, long bones, sternum)
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Somatic mesoderm layer (lateral plate mesoderm)
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Cells in the head that give rise to mesenchyme participating in the formation of the bones of the face and skull
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Neural Crest
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Contributes to the formation of the cranial vault and the base of the skull
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Occipital Somites (paraxial mesoderm)
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Mesenchyme in the dermis differentiates directly into bone
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intramembranous ossification
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Flat bones of the skull are formed through (mandible, skull, clavicle)
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intramembranous ossification
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Part of the skull encasing the brain, made up of membranous vault and cartilaginous base
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Neurocranium
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Mesenchymal cells give rise to hyaline cartilage models which are then ossified
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Endochondral ossification (most bones)
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Mesenchyme in the membranous neurocranium comes from ---------&---------
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Neural Crest and Paraxial mesoderm
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The membranous neurocranium undergoes what type of ossification?
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Intramembranous
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In intramembranous ossification --------- appears and radiates from primary ossification centers toward the periphery
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bone spicules
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Flat bones are separated by seams of connective tissue known as
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Sutures
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Sagittal Suture derived from
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Neural Crest
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Coronal Suture is derived from
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paraxial mesoderm
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Points where more than two bones meet in the cranium
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fontanelles
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Gives rise to the base of the skull
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Cartilaginous neurocranium
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Bones arising anterior to the anterior half of the sella turcica are from:
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Neural Crest
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The bones arising from neural crest in the skull make up the
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prochordal chondrocranium
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Bones arising posterior to the posterior 1/2 of the sella turcica are from:
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paraxial mesoderm (occipital sclerotomes)
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Paraxial mesoderm in the cranium forms:
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Chordal Chondrocranium
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Bones of the face are primarily derived from
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The first two branchial arches (nerual crest)
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Forms the maxilla, zygomatic bone, and the squamous part of the temporal bone
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Dorsal portion of first branchial arch
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Forms the mandibular process containing meckel's cartilage
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Ventral portion of the 1st branchial arch
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Meckel's Cartilage condenses and ossifies by ----------- to give rise to the --------------
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intramembranous ossification, mandible
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Gives rise to the sphenomandibular ligament
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Meckel's Cartilage
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Induces mandibular development and then disappears
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Meckel's Cartilage
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First Bones to be ossified
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bones of the inner ear (4th month)
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Gives rise to the incus, malleus, and stapes
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The second branchial arch (& dorsal end of 1st arch)
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Mesenchymal core of the limb bud is formed from:
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somatic layer of lateral plate mesoderm
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Gives rise to the bones and CT of the limbs
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mesenchymal core
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The mesenchymal core of the limb bud is covered by
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cuboidal ectoderm
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Ectoderm at the distal border of the limbs thickens to give:
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Apical Ectodermal Ridge (AER)
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Terminal portions of the limb bud flatten to form hand and foot plates when?
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6th week
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Mesenchyme in the limb buds condenses and the cells differentiate to give rise to (2 things)
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Chondrocytes and the first hyaline cartilage models
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When do the limbs rotate in opposite directions
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7th week
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Exerts inductive influence on adjacent mesenchyme causing cells to remain undifferentiated but rapidly proliferating
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Apical Ectodermal Ridge
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Which limb rotates 90 degrees laterally
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Upper limb
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After rotation, which direction does the thumb lie?
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Laterally
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Which limb rotates 90 degrees medially
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Lower limb
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Cell death in the joint interzone gives rise to
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joint cavities
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What is formed in the cartilaginous condensations when chondrogenesis is arrested?
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joints
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ossification of the bones of the extremities occurs via what mechanism?
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endochondral ossification
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When do primary ossification centers appear in the shaft of the long bone?
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week 12
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Vertebrae form from what part of the somite?
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Sclerotome
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When do vertebrae start to form?
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4th week
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Mesenchyme between developing vertebral bodies does not proliferate but gives rise to:
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intervertebral disks
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Ribs are derived from what tissue?
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sclerotome portions of paraxial mesoderm (costal processes of thoracic vertebrae)
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The sternum is formed independent of the ribs by:
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somatic mesoderm (ventral body wall)
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Gives rise to skeletal muscle of the axial skeleton, body walls, limbs, and head
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Paraxial mesoderm
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Destined to contribute to myotome progenitor cells or limb and body wall muscles
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Ventrolateral lip (VLL)
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Destined to contribute to dermatome and myotome progenitor cells of back mm
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Dorsomedial lip (DML)
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Gives rise to smooth muslce surrounding the gut and its derivatives
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somatic mesoderm
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gives rise to cardiac muscles surrounding the endothelial heart tube
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somatic mesoderm
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gives rise to smooth muscle in pupillary regions, mammallary glads and sweat glands
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ectoderm
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Gives rise to dorsal aorta, large arteries and coronary artery muscles
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Neural crest and lateral plate mesoderm
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