MS devo Flashcards
What does paraxial mesoderm form in skeletal development?
vertebral columns, ribs, neurocranium
What does lateral plate mesoderm form in skeletal development?
pectoral girdle, limbs, sternum
What do neural crest cells form in skeletal development?
viscerocranium (bones on the front of your face), hyoid bone
Why do bones form through intramembranous ossification?
more rapid formation in areas urgently needed by fetus
ex: mandible, need for sucking on boobs
What makes up the axial skeleton?
vertebrae
ribs
sternum
skull
What makes up the appendicular skeleton?
pectoral girdle
pelvic girdle
limb bones
What does the viscerocranium (anterolateral facial bones) form from?
neural crest cells
What does the neurocranium form from?
paraxial mesoderm
occipital somites
What makes up the chondrocranium and how is it formed?
base of the skull (sphenoid, petrous temporal, portion of occipital)
form by endochondral ossification
What is the membranous neurocranium and how is it formed?
everything except the chondrocranium
form by intramembranous ossification
At what age do your skull sutures fuse?
5-7 yrs
What are the different fontanelles?
fontanelles: enlarged membranous spaces where more than 2 bones form
anterior fontanelle (largest on top of head)
anterolateral/sphenoidal fontanelle
posteriorlateral/mastoid fontanelle
posterior fontanelle
What is craniosynostosis?
premature closure of sutures
What happens if your saggital suture closes too early?
You have scaphocephaly.
your head is really long and skinny (like your face gets squished on either side
What happens if you coronal suture closes too early?
You have brachycephaly.
your head looks like a really wide and ugly football
In relation to the axial skeleton, what is NOT formed by paraxial mesoderm?
sternum
part of the skull
In relation to axial skeleton formation, what structures are derived from paraxial mesoderm?
vertebrae
annulus fibrosis of intervertebral discs
ribs
neurocranium
When do vertebrae start to develop?
4th week: sclerotome cells surround neural tube and notochord
What happens during vertebral resegmentation?
sclerotomes are devided in half: a less dense cranial portion, and a more dense caudal portion.
resegmentation: a cranial (less dense) and a caudal (more dense) segment FROM NEIGHBORING SCLEROTOMES meet up and join
What forms the annulus fibrosus of IV discs?
Dense (caudal) portion of sclerotome
How do the ribs develop?
they grow out as costal processes from developing thoracic vertebrae
How and when is the sternum induced to form?
induced to form by ribs growing anteriorly towards midline
10th week
sternum develops as two sternal bars from LATERAL plate somatic mesoderm
What does the appendicular skeleton develop from?
lateral plate somatic mesoderm
When does endochondral ossification take place?
5th week: mesenchyme buds start to form
6th week: hyaline cartilage models start to form (finished by 8th week)
When does ossification begin in long bones?
primary ossification centers appear around 7/8th week
What is achondroplasia?
disturbance of endochondral ossification
makes you really short
like aleah from teen mom
What is skeletal muscle derived from?
paraxial mesoderm
What is cardiac muscle derived from?
intraembryonic splanchnic mesoderm
What is smooth muscle derived from?
intraembryonic splanchnic mesoderm
When do myoblasts actively contract?
7th week
Where are progenitor cells for muscle tissues located on the dermomyotome?
vertrolateral lips (VLL) dorsalmedial lips (DML)
What does the lateral somatic frontier separate?
paraxial mesoderm from lateral plate mesoderm
primaxial domain and abaxial domain
Where is the primaxial domain and what does it contain?
surrounds neural tube
contains only somite derived cells from DML, VLL
Where is the abaxial domain and what does it contain?
located laterally to primaxial domain
parietal layer of lateral plate mesoderm with a few somite derived cells (some VLL cells migrate across lateral somatic frontier)
What does the primaxial domain form?
back m.
shoulder girdle m.
intercostal m.
What does the abaxial domain form?
infrahyoid m.
pec major and minor m.
abdominal wall mm.
limb m.
What are epaxial muscles and what innervates them?
back muscles
dorsal primary rami
What are hypaxial muscles and what innervates them/
muscles of limb and body wall
ventral primary rami
What smooth muscles are derived from ectoderm?
neuroectoderm: dialate eyes
surface ectoderm: my epithelial cells of mammary, salivary, sweat glands
In general, what germ layer is muscle from?
mesoderm
When do limb buds emerge?
end of week 4
upper before lower
What is the structure of a limb bud?
mesenchymal core surrounded by surface ectoderm
What does the apical ectodermal ridge (AER) do?
signals nearby mesenchyme to keep being undiffentiated and dividing (called the progress zone)
What are cells further away from AER doing?
differentiating into cartilage, muscle
In what direction do limbs grow?
proximal to distal
How do the limbs rotate?
UL: rotates 90 deg laterally (so that thumb faces laterally)
LL: rotates 90 deg medially (big toe faces medial)
How and when do your hands/feet form?
6th week: cute little paddles
end of 6th week: mesechyme grows into paddles forming digital rays (outline of future digits)
cells inbetween fingers/toes in AER die
end of 8th week: mesenchyme differentiates into hyaline cartilage models
meromelia
absence of part of a limb
amelia
absence of whole limb
polydactyly
extra digits
syndactyly
fewer digits
What drug fucked up kid’s limbs?
thalidomide
