Development: trunk Flashcards
what week of development: gastrulation
third week
gastrulation: features
- embryo axial orientation
- bilaminar-> trilaminar disc:
- ectoderm
- mesoderm
- endoderm
primitive streak should disappear by what week?
- end of 4th week
- if not, benign tumour- sacrococcygeal teratoma
notochord: function
- basis of development of axial skeleton
- indicator for future sites of vertebral bodies
- induce thickening of ectoderm and formation of neural plate
development of neural tube:
- neural plate and neural crest - neural groove - neural tube with neural crest merged - crest becomes spiral ganglion
somites: formed by
- mesoderm and neural tube form columns of paraxial mesoderm
- segment into cube structures
somites differentiates into:
- myotome
- dermatome
- sclerotome
myotomes: contribute to
- development of skeletal muscles of neck, trunk and limbs
dermatomes: contribute to
connective tissue
- dermis of the skin
sclerotomes: contribute to
- vertebrae and ribs
development of vertebral column: 4th week
- each mesenchymal (sclerotome) segment (somite) differentiates into cephalic (less condensed) and caudal part (more condensed cells)
- notochord in middle (nucleus pulposus)
- sclerotome forms annulus fibrosus
synovial joint development: what week?
- 6th week
- by 8th week resemble adult joints
synovial joint development: how
- interzonal mesenchyme differentiate to form capsule and ligaments (peripheral)
- form joint capsule (centrally)
how does spinous and transverse processes develop?
- extensions of chondrification centres in vertebral arches
ossification of vertebra: begins
- during embryonic period, primary ossification centres
ossification of vertebra: at birth
- 3 bony parts connected by cartilage
- for growth of spinal cord
ossification of vertebra: secondary ossification centre
- after puberty
- unite at around 25yrs
muscle differentiation: pathway
- myoblasts migrate to muscle location
- fuse to form myotubules - begin to express contractile proteins - formation of sarcomeres leads to maturation in myofibrils
development of muscles: myotome somite divides into
- dorsal (epiaxial) division
- ventral (hypaxial) division
development of muscles: genes
- MyoD
- Myf5
- initiate and regulate muscle development
development of vertebral column: genes
- Pax-1
- regulates development
what muscles arise: epaxial division
- extensors of neck/ vertebral column
intrinsic
- superficial (splenius)
- intermediate (erector spinae)
- deep (transversospinalis)
sacral/ coccygeal region:
- myotomes form sacrococcygeal lig
what muscles arise: hypaxial division- cervical region
- scalenes
- longus capitis
- longus colli
what muscles arise: hypaxial division- thoracic region
- intercostals
- transversus thoracis
- subcostals
- diaphragm
what muscles arise: hypaxial division- abdomino-pelvic region
- internal/ ext obliques
- transversus abdominus
- psoas
- quadratus lumborum
- obturator ext/ int
what nerves supply: epaxial division
- posterior rami of spinal nerves
what nerves arise: hypaxial division
- anterior rami of spinal nerves
vertebra T10 corresponds to which spinal cord segments:
L1, L2
vertebra T11 corresponds to which spinal cord segments:
L3, L4
vertebra L1 corresponds to which spinal cord segments:
sacral and coccygeal cord segments
list 3 main developmental abnormalities:
- variation in no. of vertebrae
- variation in normal architecture of vertebra
- tumours of embryological remnants
eg. brevicollis
- short neck
- low hairline
- restricted head movements
- from undeveloped vertebral body/ defect in vertebral segmentation
eg. accessory rib
- in lumbar/ cervical region
- if cervical, could present some neurovascular symptoms (numbness of upper limb)
- extra rib
anomalies of ribs: eg.
- pliable ribs
- pectus excavatum (sunk in ribcage)
- pectus carinatum (pigeon chest)
eg. sacralisation of L5:
- L5 incorporated into sacrum
- back pain
eg. lumbarisation of S1
- S1 separated,
- not many symptoms
eg. hemivertebra
- failure of one chondrification centre
- failure of half vertebra undeveloped
- hemivertebra (wedge)
- butterfly (2 hemivertebra)
- changes posture, scoliosis
eg. block vertebra:
- failure of segmentation of two or more vertebrae
distortion: scoliosis eg.
- spinous process deviated to one side
- rib pushed posteriorly, thoracic cage narrowed
- other rib laterally and anteriorly
eg. kyphosis
- anteriorly
- failure of formation of v. body,
- failure of segmentation
- spinal osteoporosis (elderly)
eg. schmorl’s node
- protrusion of cartilage of IV disc
- through vertebral body endplate into adjacent vertebra
eg. spina bifida oculta
- vertebral arches must fuse completely
- lamina of L5/ S1 fail to develop and fuse normally
- everything normal
- extra hair
- asympotomatic
eg. spina bifida cystica
- 1+ vertebral arches fail to develop
- protrude out of lumbar region
meningocele:
- herniation of meninges (only space, but everything ok)
meningomyelocele:
- herniation of meninges and spinal cord
eg. spina bifida cystica symptoms
- severe meningomyelocele
- paralysis of limbs
- loss of bladder control
- loss of bowel control
- recurrent CNS infections
can you prevent spina bifida?
prenatal screening:
- ultrasound
- aminocentesis
- blood test
prevent:
- folic acid supplements
eg. teratoma
- benign tumour
- from primitive streak
- develops from independent cells from any of 3 embryonic germ layers
- any type of tissue (bone, hair, skin, muscle)
eg. chordoma
- from persistent notochord
- slow growing malignant tumour
- common at base skull
- difficult to remove-> infiltrates bone
- once detected, too late
- can develop in lumbosacral region
