BONE DEVELOPMENT ACH Flashcards
when is the critical period for the development of skeleton, muscles and limbs
week 4
when does neural tube begin to close
week 4
where are somitomeres derived from
paraxial mesoderm
what induces formation of the somitomeres
neural tube
how does somitomere development progress and what regulates it
rostal to caudal
what do somitomeres become when they are compacted and bound by epithelium
somites
how many pairs of somites
42-44
pairs 1-7 of somites
do not compact
what do the 1-7 somites contribute to
head and neck structures
what do mesodermal cells from somites give rise to
dermomyotome
what does dermomyotome give rise to
dermatomes
dermatomes
skin, dermis, subcutaneous tissue
myotomes
skeletal muscle of trunk and limbs
sclerotome
bone
what makes up mesenchyme
multipotent cells
where is mesenchyme derived from
mesoderm or neural crest
notochord leads to..
neural plate and neural tube development
neural tube develops to..
somites
intramembranous ossification
mesenchymal cells differentiate directly into osteoblasts
where does intramembranous ossification occur?
flat skull bones
endochondral ossification
mesenchymal cells are transformed into chondroblasts that lay down hyaline cartilage
what causes primary ossification centers to form?
periosteal capillaries bring in osteogenic cells into the diaphysis
what do osteoblasts do?
lay down minearlized matrix that replaces cartilage
what continues to lay down cartilage until we’re about 20
growth (epiphyseal) plate
which direction do growth plates grow
diaphysis toward epiphysis
where do secondary ossification centers form?
ephiphyses (ends)
when do most secondary ossification centers form?
postnatally
abnormality of conversion of cartilage into bone. Most common form of dwarfism.
achondroplasia
what bones does achondroplasia affect?
long bones
enlargement of head, hands, and feet due to excess growth hormone secreted by pituitary after closure of epihyseal plates
acromegaly
excess growth hormone before growth plates close (during childhood)
gigantism
autosomal dominant disorder due to mutation in gene for fibrillin that affects connective tissue - results in long thin limbs
marfan syndrome
extreme bone fragility, spontaneous fracture may even occur in utero, defect in type I collagen gene
osteogenesis imperfecta
hip joint gets flattened due to misgrowing of cartilage in the hip - head of femur can slip out
congenital hip dysplasia/dislocation
mesenchyme between hyaline cartilage models is replaced by fibrous tissue or fibrocartilage
fibrocartilaginous joints
where are fibrocartilaginous joints
sutures in the skull
where chondroblasts condense around ends of bones and across space to form articular surfaces and joint capsules
synovial joints
what can cartilage between epiphyses remodel into?
menisci
where does myotome originate from?
paraxial mesoderm
what do myoblasts give rise to
myotubes
what do myotubes develop
myofilaments
what do the myofilaments do for skeletal muscle
give skeletal muscle fibers their striation
what cells reside in the muscle and can make new myocytes in response to exercise
satellite cells
where does smooth muscle of the gut, respiratory and mesenteries originate from?
splanchnic mesoderm of lateral plate
what gives rise to smooth muscle in the walls of the vascular system of the head, limbs and body wall
somatic mesoderm
what gives rise to myoepithelial cells of the mammary and sweat glands and smooth muscle of the iris
ectoderm
where does cardiac muscle originate from
splanchnic mesoderm
T/F. cardiac myblasts fuse.
False. They develop into individual cells.
type of ossification that forms the vertebral column
endochondral
what do sclerotomes split into?
dense-caudal
what separates the two parts
intersclerotomic (von Ebner’s) fissure
what is resegmentation
caudal part of one segment fuses with the rostral part of segment below so each vertebra is intersegmental
what fuse to form the spinous processes
sclerotome forms vertebral arch. left and right arches fuse
what is nucleus pulposis derived from/
notochord
what is annulus fibrosis derived from
sclerotome
where do arteries exit
loose cephalic (at the level of the body)
where do spinal nerves exit
at the level of the disc
condition that results from failure of the neural tube to close
spina bifida
least severe form of spina bifida. often marked by tuft of hair but no obvious symptoms.
spina bifida occulta
spina bifida form in which meninges protrudes through defect in spinal cord or skull
meningocele
spina bifida form in which meninges and spinal cord protrude through the defect
meningomyelocele
form of occult spinal dysraphia in which neural ectoderm fails to completely separate from the surface ectoderm. spinal cord may be tethered.
Congenital dermal sinus
caused by failure of ossification center on one side of vertebral body.
congenital scoliosis
shortened neck due to non-segmentation of cervical vertebrae. limited movement of neck and low hairline.
congenital brevicollis (Klipper-Feil sequence)
concave chest caused by issues with sternal bars fusing and forming cartilage models of manubrium, sternum, and xiphoid
pectus excavatum
chest pushes outward
pectus carinatum
what do ribs develop from
costal processes of thoracic vertebrae
what forms from rib development?
costovertebral synovial joints
rib that can compress neurovascular structures supplying upper limb.
cervical rib C7 - occurs in thoracic outlet syndrome
what do myotomes divide into?
epimere and hypomere
what do myoblasts in the epimere form?
deep back muscles (erector spinae)
what innervates epimere muscles
dorsal primary rami
what do myoblasts in the hypomere form
intercostal muscles
what supplies the hypomere muscles
ventral primary rami
underdevelopment or absense of pectoralis muscles, usually unilateral
poland syndrome
poor development of abdominal muscle wall causing skin to wrinkle, often accompanied by urinary tract abnormalities, delays in sitting and walking
prune belly syndrome
spasm or shortening of one side of sternocleidomastoid muscle so head is twisted to one side
congenital torticollis
when do limbs between to develop
week 4
what limb develops first
upper limbs
what genes control positioning of limbs
homeobox genes
what mesoderm contributes to limb components
somatic and somititc mesoderm
somites for upper limbs
C5-T1
somites for lower limb
L2-S2
core of limb bud is..
mesoderm
outside of limb bud is..
ectoderm
when the ectoderm thickens what’s formed?
apical ectodermal ridge (AER)
what does the AER secrete
FGF
what does FGF do?
stimulates growth and development of mesenchyme
what do cells further from AER become
cartilage and muscle
what happens to form the digits
apoptosis in certain areas of AER
specialized mesenchymal cell that responds to FGFs from AER
zone of polarizing activity (ZPA)
what does ZPA do
secretes factors that determine axis…like sonic hedgehog gene
what does the sonic hedgehog protein do?
determines anterior and posterior axis (thumb vs. little finger, great toe vs baby toe)
when do limbs rotate
week 8
which way do the thumbs rotate
90 degrees laterally
which way do the toes rotate
90 degrees medially
absence or malformation of one or more limbs
amelia
partial absence of one or more limbs, shortened limb with/without hand or foot attached, limbs resemble flippers
meromelia or phocomelia
drug that was teratogenic that was prescribed for morning sickness
thalidomide
duplication of digits, most common is little finger
polydactyly
failure of apoptosis that results in webbed fingers and or toes
syndactyly
fusion of adjacent digits but nothing in the middle.. leads to unusual positioning of the foot
clubfoot