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Embryology - Development of Skeletal System
Cole 2/14/11
116
Medical
Undergraduate 4
02/09/2011

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Term
sclerotome of somite
Definition
where does the axial skeleton(ribs, vertebrae, sternum) come from?
Term
somatic lateral plate mesoderm
Definition
where does appendicular skeleton(pectoral and pelvic girdle, limb bones) come from?
Term
hypaxial mesoderm
Definition
where do limbs muscles come from?
Term
intersegmental
Definition
vertebrae form as _______ structures derived from adjacent sclerotomes
Term
cranial and caudal sections
Definition
what do sclerotomes split into?
Term
cranial
Definition
caudal portion of sclerotome fuses with _____ portion of the sclerotome caudal to it
Term
above the same # vertebra until C8, which comes out the bottom of C7 vertebrae(no C8 vertebrae) from there on, out the bottom
Definition
where do spinal nerves come out the vertebrae?
Term
hox genes
Definition
what determines what kind of vertebrae each one is?
Term
initially 8, but the upper part of C1 fuses with the base of the skull making 7
Definition
how many cervical somites are there?
Term
neural arches, and centrum(vertebral bodies)
Definition
sclerotomes form what parts of vertebrae at first?
Term
it regresses except where it is incorporated into the vertebral discs
Definition
what happens to the notochord?
Term
kinda varies on where it is and how bad-so they cause a range of pain/disability
Definition
what do herniations cause?
Term
congenital scoliosis
Definition
abnormal LATERAL curvature of the spine resulting from normal vertebral development
Term
1)failure of formation
b)failure of segementation
3)mixed (1 & 2)
Definition
there are many types of defects in congenital scoliosis, but the are all the result of abnormal formation/segmentation of vertebral precursors(somites) what are the 3 varieties?
Term
hemivertebrae(semisegmented, full segmented, or wedge vertebrae)
Definition
what bone formation/structure is seen when there is failure of formation in congenital scoliosis?
Term
block(like 2 normal fused)
unsegmented bar(fused on 1 side but not other)
Definition
what bone formation/structure is seen when there is failure of segmentation in congenital scoliosis?
Term
mesenchymal cells lateral to the body of vertebra->develop into costal processes, grow into ribs in thoracic region only
Definition
what do ribs come from?
Term
cervical or lumbar ribs can form -> thoracic outlet syndrome, nerve or arteries can be compressed
Definition
what happens when accessory ribs form?
Term
cartilagenous sternal bars in ventral body wall
Definition
what structure does the sternum come from?
Term
the sternal bars fuse in cranial caudal direction and form the manubrium, body, and xiphoid process
Definition
how does the sternum develop?
Term
hole in the body of the sternum, less than 10% of population has it
Definition
what is the sternal foramen, how common is it?
Term
it is apparently mistaken for bullet wounds, but more importantly a dumb acupuncture person stabbed someone there causing 3-4 deaths
Definition
what is significant about the sternal foramen?
Term
inductive
Definition
development of the appendicular skeleton involves ____ interaction between the mesoderm and ectoderm(epithelia)
Term
late in week 4, there is an outgrowth of the body wall, and lateral plate mesoderm is activated
Definition
when does limb development initiate, how?
Term
upper
Definition
what forms first, upper or lower limb?
Term
lateral plate mesoderm
Definition
what forms the core of a limb bud
Term
forms vasculature and skeletal components
Definition
what does lateral plate mesoderm become in a limb?
Term
inductive signal from the main body axis acts on adjacent cells at specific regions along the flank of the main body
Definition
what is the first step in limb bud positioning?
Term
an inducer (FGF-1) secreted by axial mesoderm
Definition
initial stimulus for development of limbs is likely cause by what?
Term
overlapping
Definition
Hox(homeobox) genes are expressed in ______ patterns along the trunk(craniocaudal axis) of the developing embryo
Term
expression of hox genes in overlapping patterns
Definition
what distribution controls the position of the limbs on the body wall?
Term
ectoderm
Definition
what covers the limb(becomes skin)?
Term
overlying ectoderm on the limb bud-drives the limb from proximal to distal
Definition
what forms the Apical Ectodermal Ridge (AER)
Term
AER (Apical ectodermal ridge) and Zone of Polarizing activity
Definition
what 2 regions control limb tissue differentiation?
Term
AER
Definition
thickened ectoderm on the apex of the limb bud
Term
produces FGF which interacts with underlying mesoderm
Definition
what does the AER do to stimulate mitosis and promote growth?
Term
AER
Definition
what directs limb bud organization along the proximo-distal axis (dorsal/ventral axis)
Term
anterior (preaxial/thumb) to posterior (postaxial)
Definition
what direction does the Zone of Polarizing Activity direct limb development?
Term
Zone of Polarizing Activity
Definition
consists of mesodermal cells located at the base of the limb bud that produce retinoic acid (Vitamin A)
Term
Retinoic acid
Definition
what initiates the expression of Sonic Hedge Hog?
Term
Sonic Hedge Hog?
Definition
directs organization of limb bud and patterning of digits
Term
Sonic Hedge Hog and Retinoic acid
Definition
misexpresion of _____ or _____ results in a mirror image duplication of the limb structures
Term
Tbx5
Definition
what is expressed in forelimb, but not hindlimb?
Term
Tbx4 and Pitx1
Definition
what is expressed in the hindlimb, but not the forelimb?
Term
the Tbx5, Tbx4, and Pitx1 (homeobox genes)
Definition
what are the possible "master control genes" of the arms and legs?
Term
proximo-distal
Definition
in the developing limb bud _________ growth precedes differentiation
Term
zone of cell division (progress zone)
Definition
region of actively dividing cells in the limb bud
Term
Zone of differentiation
Definition
region of cell specialization in the limb bud
Term
zone of cell division
Definition
which is more distal? (zone of proliferation or zone of differentiation?)
Term
Hox genes
Definition
necessary for the proper sequence and timing of tissue differentiation
Term
proximal to distal
Definition
which direction does limb development proceed?
Term
Hox genes
Definition
what regulates the type/size of bones?
Term
Progress Zone
Definition
AER secretes FGF that influences the closest cells ( ____ ____) to develop into distal structures
Term
proximal
Definition
cells no longer within range of AER remain ____ in nature
Term
1)mesenchymal condensation
2)joint specification
3)joint interzone formation
4) cavitation
...
5) mature joint
Definition
what are the steps in joint formation?
Term
programmed cell death gets rid of the webbing, if it doesn't, there can be syndactyly with skin/bone fused.
Definition
what happens to make the fingers and toes?
Term
about 4 days (day 44-48)
Definition
how long does it take to dissolve finger webs?
Term
1) skeleton + vasculature
2) muscles
3) Schwann cells
4) motor axons(dermatome map)
Definition
what does each thing make in the limb?
1)LP mesoderm:
2)Hypaxial mesoderm:
3) Neural crest
4) Neural tube
Term
aorta, cardinal veins, endogenous mesodermal cells
Definition
earliest vasculature arises from cells budding off the _____ and ____ as well as from _____ _____ cells
Term
central artery that drains into a peripheral marginal sinus, then into peripheral venous channels
Definition
what does the early vascular pattern consist of ?
Term
beneath the ectoderm or in the central cartilage
Definition
Where do blood vessels not form?
Term
anterior or posterior divisions of VENTRAL primary RAMI (to hypomeres)

-in upper limb (brachial plexus)
posterior division = posterior cord, anterior division forms medial and lateral cords
Definition
where does the innervation of limbs come from?
Term
90 degrees laterally

some dorsal musculature lags behind and comes to lie on the anterior pre-axial border
Definition
which direction does the upper limb rotate?
Term
unknown
Definition
what is the etiology of most limb defects?
Term
reduction, duplication, malformations
Definition
what are the 3 types of limb defects
Term
limb-6.8%
other 17.5%
Definition
what percent of congenital formations are limb? other musculoskeletal?
Term
meromelia
Definition
part of a limb is missing
Term
amelia
Definition
all of a limb is missing
Term
reduction defect
Definition
arrest or failure of a limb to develop
Term
mesomelia
Definition
shortened forearm or leg elements
Term
Radial club hand
Definition
congential absesence or hyoplasia of the radial structures of the forearm and hand.
Hypoplastic or absent muscular structures and radial nerve
Term
early passive stretching excercises and corrective casting
Definition
what is best for treatment of radial club hand?
Term
morning sickness/Hansen's disease(leprosy) drug, causes tetromelia and all kinds of stuff->disrupts the signal between AER and Progress Zone
Definition
What is thalidomide and how does it relate to embreyo?
Term
duplication defect
Definition
defect with duplication of components
Term
polydactyly
Definition
extra digits
Term
whole extra limb
Definition
what does duplication of AER cause?
Term
Parasitic twins
Definition
what should you not get confused with duplication defects?
Term
it is considered common
Definition
How rare is polydactyly?
Term
it is often ioncompletely formed and useless
Definition
what happens with the extra digit in polydactyly?
Term
Supernumerary digits
Definition
soft-tissue duplications without a skeletal component that typically arise from the lateral surface of a normal digit, most often the ulnar side of the fifth finger
Term
medial or lateral rather than central
in the foot usu. lateral
Definition
where is the extra digit more commonly found in polydactyly?
Term
dominant
Definition
is polydactyly dominant or recessive?
Term
yes, yes
Definition
is polydactyly seen in ultrasounds? in Ernest Hemmingway's cats?
Term
overgrowth, undergrowth, focal defects, association with other general/syndromic skeletal abnormalities
Definition
4 causes of malformation defects
Term
Syndactyly
Definition
most common limb abnormality
Term
Syndactyly
Definition
webbed fingers/toes resulting from failure of programmed apoptosis in digital ray
Term
between fingers 3 & 4 and toes 2 & 3
Definition
where is syndactyly more frequent?
Term
yes

(it is simple dominant or simple recessive)
Definition
is syndactyly dominant or recessive?
Term
uncommon
Definition
how common is brachydactyly?
Term
brachydactyly
Definition
reduction in the length of phalanges, also associated with short stature
Term
dominant
Definition
is brachydactyly a dominant or recessive trait?
Term
cleft hand/foot (lobster claw)
Definition
absence of one or more central digits or between digits 2 & 4
Term
uncommon
Definition
how common is cleft hand/foot?
Term
lobster claw deformity (aka cleft hand/foot)
Definition
hand/foot is divided into 2 parts that oppose each other usually missing the third digit.

the remaining digits are partioally or completely fused
Term
sirenomelia
Definition
mermaid syndrome
Term
depends on presence or absence of bones in the lower limb

type 1: all bones present
type 2: fused fibula
type 3: fibula absent
type 4: partially fused femur, fused fibula
type 5: partially fused femur
type 6: fused femur, fused tibia
type 7: fused femur, tibia absent
Definition
how is sirenomelia classified?
Term
1) (start)legs are fused together by skin and feet splayed in a V-shape
2) saline sacks are inserted and gradually filled to stretch the skin
3) 2 operations 3months apart separated the legs using the stretched skin to cover the wounds
4) a later operation will rotate splayed feet foreward
Definition
what are the steps in a separation surgery for sirenomelia?
Term
achondroplasia
Definition
most prevalent form of dwarfism
Term
caused by a mutation of FGF-R3
Definition
what mutation causes achrondroplasia
Term
pathologic changes at epiphyseal plate; zone of proliferation and hypertrophy are narrow and disorganized
Definition
what does the mutation cause resulting in dwarfism in achondroplasia?
Term
achondroplasia dwarfism
Definition
failure of proliferation and column formation of epiphyseal cartilage cells (a defect in endochondral bone formation) which impairs longitudinal growth of tubular bones
Term
autosomal dominant
Definition
what is the inheritance pattern of achondroplasia? (recessive/dominant?)
Term
Brittle bone disease (osteogenesis imperfecta)
Definition
bone fragility that predisposes to fractures and deformities related to connective tissue abnormalities
Term
blue sclera
Definition
what is a tell-tale sign of brittle bone disease(osteogenesis imperfecta?)
Term
no
Definition
is brittle bone disease always evident at birth?
Term
check for brittle bone disease-osteogenesis imperfecta (blue sclera)
Definition
if a child comes to the ER with repeat fractures, before calling the PoPo for abusive parents, what should you check?
Term
talipes equinovarus
Definition
what is the most common type of club foot?
Term
1/1000 births, twice as frequent in males
Definition
how frequent is talipes equinovaris?
Term
club foot
Definition
disease where the sole of the foot is turned medially and the foot is inverted
Term
abnormal positioning or restricted movement of the lower limbs in utero, feet are structurally normal
Definition
what is the cause of flexible club foot?
Term
usually resolves spontaneously
Definition
how is flexible club foot treated?
Term
abnormal development of the ankle and foot joints during the 6th and 7th week of pregnancy
Definition
what causes rigid club foot?
Term
talus
Definition
where are bony deformities found in rigid club foot?
Term
flexible and rigid
Definition
what are the 2 types of club foot?
Term
pieces of the amnion tear off and wrap around appendages (fingers or whole arm even) causes skeletal malformations, but it's not a skeletal developmental disorder
Definition
what is amniotic band syndrome?
Term
yes, some German farmer got a double arm transplant and is recovering well.
Definition
are arm transplants legit?
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