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77 Cards in this Set

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Along trunk hypomere gives rise to _
lateral and ventral segments
Lateral segments
Cervical - scalenes, geniohyoid, prevertebral
Thoracic - intercostals + transversus thoracis
Abdominal - obliques
Lumbar - quadratus lumborum
Sacral - pelvic diaphragm
Ventral segments
Infrahyoid + rectus abdominis
Arthrogryposis multiplex congenita
- Failure of normal muscle around joint
- Results in stiffness of joint
Congenital torticollis
- Shortening of SCM
- Commonly results from tearing of muscle during birth
Poland anomaly
- Congenital absence of pectoralis major
- Associated also with syndactyly
Prune belly
- Abdominal muscles do not support guts
Sclerotome is segmental T/F
TRUE - but associated with intersegmental arteries
Myotomes and arteries remain segmental- T/F
FALSE - MYOTOMES AND NERVES
Describe intersegmental position of vertebrae
As mesodermal cells from sclerotome migrate towards notochord and neural tube, they split into CRANIAL PORTION AND CAUDAL PORTION.
Caudal portion of each sclerotome fuses with cranial portion of succeeding sclerotome which results in intersegmental position of vertebra. Splitting of sclerotome is important because it allows developing spinal nerve a route of access to myotome which it must innervate
How does occipital bone forms
In cervical region caudal portion of 4th occipital sclerotome (O4) fuses with cranial portion of first cervical sclerotome (C1) to form the base of occipital bone. This allows C1 spinal nerve to exit between base of occipital bone and C1 vertebrae
Nucleus pulposus develops from _
Notochord
Annulus fibrosus develops from _
Mesenchyme
Congenital scoliosis
- Asymmetric fusion of vertebra
- Appears that half of vertebra is missing
- Abnormal curvature of vertebral column
Klippel Feil anomaly (Brevicollis)
Short neck because of absence of cervical vertebra
Spina bifida occulta
- Failure of vertebral arch to close
- Asymptomatic but accompanied by tuft of hair over defect
Upper limb buds appear _

Lower limb buds appear _
Uppper - day 26

Lower - day 28
Mesenchyme from lateral plate mesoderm contributes following to limb
- bones
- tendons
- ligaments
- cartilage
- fascia
- joints
- vessels
- dermis
Epidermis comes from _
AER - apical ectodermal ridge
Muscles come from _
somites
Motor nerves come from _
neuroectoderm inside spinal cord cell bodies
Sensory nerves and melanocytes come from _
Neural crest (cell bodies in DRG)
How do limb buds grow
Grow mainly by proliferation of mesenchyme
Homeobox containing genes (HOX) genes regulate _
- Axes
- Patterning
AER
Apical ectodermal ridge - apex of each limb bud thickens to form multilayered AER
AER has inductive effect of underlying mesenchyme
- AER causes adjacent cells to remain undifferentiated
AER is essential for _
PROXIMAL-DISTAL AXIS
Zone of polarizing activity
Mesenchymal cells aggregate at POSTERIOR margin of limb bud to form ZONE OF POLARIZING ACTIVITY
ZPA is responsible for patterning of _
ANTERIOR-POSTERIOR AXIS
What can interfere with ZPA and lead to limb deffects
Retinoic acid (vit A) - prescribed for acne should not be given to pregnant women
How does upper limb rotate
Laterally through 90 degrees on their long axis
How does lower limb rotate
Lower limb rotates medially almost 90 degrees on their long axis
Upper limb innervation
C5-T2
Lower limb innervation
L2-S2
Which axons grow first - motor or sensory
MOTOR - sensory axons use the motor axons as guide to their target
Axial artery of upper limb becomes _ and continues as _
BRACHIAL

COMMON INTEROCEOUS
_ arise as secondary branches of brachial artery
Radial and ulnar arteries
Which artery present in embryo typically degenerates in upper limb of adult
MEDIAN
Axial artery in lower limb continues as _
INFERIOR GLUTEAL

ARTERY TO SCIATIC NERVE

POPLITEAL

FIBULAR
Which arteries in lower limb arise as secondary
Anterior and posterior tibial
Critical time for limb development
4th and 5th weeks
Cause of many limb defects from 1957 to 1961
THALIDOMIDE
Achondroplasia
- Cause of dwarfism
- 1/15000
- limbs are bowed and short
- disturbance of endochondral ossification at epiphyseal plates
Thanatophoric dysplasia
- Lethal skeletal dysplasia
- 1/20000
- Death of respiratory failure
- Fibroblast growth factor receptor defficiency
Limb defects are classified as _
AMELIA - absence of entire limb

MEROMELIA - absence of part of limb
Congenital absence of radius
- Radius is completely absent
- Hand deviates laterally
Brachydactyly
- Shortness of digits
- often associated with short stature
Polydactyly
- Supernumerary digits
- Extra digit is usually useless
- Extra digit is medial or lateral
Syndactyly
1/2200
- can be cutaneous (webbing of digits)
- osseous - fusion of bones
Congenital clubfoot
- Any defect involving talus
- 1/1000
- Abnormal orientation of the foot that prevents normal weight bearing
- Inconclusive evidence for restricted movement in utero as cause
- Caused by environmental factors
Congenital dislocation of hip
1/1500
Results from laxity of joint capsule or underdevelopment of acetabulum
During week 3 developing embryo consists of _
Trophoblast - forms placenta
Embryoblast
Embryoblast consists of
Epiblast and hypoblast
Gastrulation occurs when
Day 16
Process of gastrulation results in formation of 3 germ layers - ?
Ectoderm - CNS, skin
Endoderm - GI, visceral tubes
Mesoderm
By 17th day intraembryonic mesoderm has developed into 3 distinct regions - what are they
- PARAXIAL MESODERM - will develop into somites
- INTERMEDIATE MESODERM - will form urinary system
- LATERAL PLATE - somatic + visceral
By the end of third week paraxial mesoderm begins to form _
SOMITOMERES - rostral to caudal sequence
Somitomere consists of _
Mesoderm cells arranged in concentric whirls around center
Numbers of somites
4 occipital
8 cervical
12 thoracic
5 lumbar
5 sacral
8-10 coccygeal
In the head somitomeres form _
Neuromeres
Which somites will disappear
First occipital and last 7 coccygeal
Ventral and medial parts of somite dissociate and shift position and are known as _
SCLEROTOME
Cells of sclerotome surround _ and migrate _
- Surround notochord and neural tube and migrate laterally to form limb precursors
Remaining part of somite except sclerotome is _
DERMATOMYOTOME
SCLEROTOME gives rise to _
CARTILAGE + BONE
DERMATOME gives rise to _
DERMIS + SUBCUTANEOUS TISSUE
MYOTOME gives rise to _
MUSCLE
Mesenchyme of sclerotome develops into _
- Fibroblasts
- Chondroblasts
- Osteoblasts
CT comes from _
LATERAL PLATE
Intramembranous ossification vs endochondral ossification
Intramembranous - FROM MESENCHYME

Endochondral - FROM CARTILAGE
Intramembranous ossification forms _
most flat bones
Somatic layer of lateral plate mesoderm forms
Sternum and limb bones
Neural crest forms _
bones of skull
Head somitomeres form _
Cranial vault and base of skull
Skeletal muscle arises mainly from _
MESODERM specifically paraxial mesoderm (from somites and somitomeres in head)
Myotome develops into 2 distinct regions _
Epimere

Hypomere
Epimere is innervated by _ while hypomere is innervated by _
EPIMERE - dorsal rami

HYPOMERE - ventral rami
Which muscles come from epimere
Intrinsic muscles of the back like erector spinae

Hypomere - everything else