Transcript Slide 1

• Additional vertebrae may be
present.
• The sacrum may show six
segmernts.
• Part of a vertebra may be
missing.
• (a) The two halves of the neural
arch may fail to fuse in the
midline, condition is called spina
bifida.
• The gap between the neural arch may
not be obvious (spina bifida occulta),
or may be large enough for meninges
and neural elements to bulge out of it.
• Spina bifida in a fetus can be
recognized by ultrasound
examination( Examination of amniotic
fluid shows increased levels of alpha
feto proteins (AFP) in a case with
spina bifida.
• The vertebral body may ossify from two primary
centres which so fuse. One of these parts may
fail to develop, resulting in only half I the body
being present. This is called hemivertebra. It is
usually associated with absence of the
corresponding rib.
• The two halves of the vertebral body may be
formed normally but may fail to fuse. The
vertebral body then consists of two
hemivertebrae.
• Sometimes the gap between the two halves is
large enough for meninges and nerves to bulge
forward between them (anterior spina bifida).
• Two or more vertebrae that are
normally separate may be fused
to each other.
• Such fusion may occur in the
cervical region (Klippel-Feil
syndrome.
• The atlas vertebra may be fused
to the occipital bone
(occipitilization atlas).
• The fifth lumbar vertebra may be
partially or completely fused the
sacrum (sacralization of fifth lumbar
vertebra).
• Parts of the vertebral column that are
normally fused to each other may
separate.
• The first sacral vertebra may be
separate from the rest of the sacrum
(lumbarization of the first sacral
vertebra).
• The odontoid process may be
separate from the rest of the axis
vertebra.
• The articular facets may be
abnormal in orientation, or may be
deficient. When this happens in the
lower lumbar region, the body of the
fifth lumbar vertebra may slip
forwards over the sacrum. This is
called spondylolisthesis.
• Diastematomylia.
• The vertebral canal may be
divided into two lateral halves by
a projecting shelf of bone, which
splits the spinal cord longitudinally
into two halves
chondro-osteo-dystrophy
• Ossification of the vertebral
bodies may be defective thus
reducing the total length of the
spine.
• This can lead to the formation of
dwarfs who have a short trunk but
have limbs of normal length.
sacrococcygeal teratoma.
• A peculiar tumour arising from
cells of the primitive knot may
be seen attached to the lower
end of the spine. Various
tissues may be seen in it.
• (a) They may cause deformities of the
spine. The spine may be bent on itself
(congenital scoliosis).
• Deformities of cervical vertebrae may
lead to tilting of the head to one side
and its rotation to the opposite side
(congenital torticolis).
• This deformity may be secondary to a
contracture of the
sternocleidomastoid muscle.
• (b) The spinal'nerves, or even the
spinal cord, may be implicated.
They may be subjected to
abnormal pressure leading to
paralysis.
• (c) They are frequently the cause
of backache.
• Anomalies of the Sternum and
Ribs
• Some ribs that are normally
present may be missing.
Unilateral absence of a rib is often
associated with hemivertebra.
• Accessory ribs may be present.
Such a rib may be attached to the
seventh cervical vertebra (cervical
rib), or to the first lumbar vertebra
• When the fusion of the two sternal
bars is faulty, the body of the sternum
shows a partial or even a complete
midline cleft.
• Minor degrees of nonfusion may
result in a bifid xiphoid process or in
midline foramina.
• Transverse clefts may also occur.
• In the condition called funnel chest,
the lower part of the sternum and the
attached ribs are drawn inwards into
the thorax. The primary defect is that
the central tendon of the diaphragm is
abnormally short.
• The upper part of the sternum (and
related costal cartilages) may project
forwards (pigeon breast).
• Bones that are Completely Formed in
Membrane
(a) The frontal and parietal bones are formed in
relation to mesenchyme covering the developing
brain.
(b) The maxilla (excluding the premaxilla),
zygomatic and palatine bones, and part of the
temporal bones, are formed by
intramembranous ossification of the
mesenchyme of the maxillary process.
(c) The nasal, lacrimal and vomer bones are
ossified in the membrane covering the nasal
capsule.
• Completely Formed in Cartilage
ethmoid bone and the inferior nasal concha
are derived from the cartilage
of nasal capsule.
The septal and alar cartilages of the nose
represent parts of the capsule that do not
undergo ossification.
• Bones that are Partly Formed in Cartilage
and Partly in Membrane
(a) Occipital: The interparietal part is formed
in membrane; the rest of the bone is
formed by endochondral ossification.
(b) Sphenoid: The lateral part of the greater
wing, and the pterygoid laminae, are
formed in membrane; the rest is cartilage
bone.
• (c) Temporal: The squamous and tympanic
parts are formed in membrane.
• The petrous and mastoid parts are formed
by ossification of the cartilage of the otic
capsule. The styloid process is derived
from the cartilage of the second branchial
arch.
• (d) Mandible: Most of the bone is
formed in membrane in the
mesenchyme of the mandibular
process.
• The ventral part of Meckel's cartilage
gets embedded in the bone. The
condylar and coronoid processes are
ossified from secondary cartilages
that appear in these situations.
• The greater part of the vault of the
skull is missing in cases of
anencephaly.
• In one syndrome, deformities of the
skull are associated with absence of
the clavicle (cleidocranial
dysostosis ).
• Premature union of the sagittal
suture gives rise to a boat-shaped
skull (scaphocephaly).
• Early union of the coronal suture
results in a pointed skull
(acrocephaly).
• Asymmetrical union of sutures results in a twisted skull
(plagiocephaly).
• When the brain fails to grow the
skull remains small
(microcephaly).
• The bones of the vault of the skull
may be widely separated by
expansion of the cranial cavity in
congenital hydrocephalus.
• In a rare congenital condition called
Hand-Schulter-Christian disease,
large defects are seen in the skull
bones.
• The occipital bone may be fused to
the atlas vertebra.
• Anomalies of Limbs
• One or more limbs of the body may
be partially, or completely, absent
(phocomelia, amelia). These
conditions may be produced by
harmful drugs.
• Part of a limb may be deformed.
Deformities are most frequently seen
in the region of the ankle and foot,
and are of various types.
• In the most common variety of
deformity, the foot shows marked
plantar flexion (equinus: like the
horse), and inversion (varus). Hence
this condition is called talipes
equinovarus, or club foot.
• Congenital strictures, congenital
amputations or congenital
contractures may be present.
• There may be abnormal fusion (bony or
fibrous) between different bones of the
limb.
• Adjoining digits may be fused (syndactyly).
• The phalanges of a digit may be fused to
one another (synphalangia).
• A digit may be abnormally large
(macrodactyly), or
• abnormally short (brachydactyly).
• In arachnodactyly, the fingers are long and
thin (spider fingers).
• Supernumerary digits may be
present (polydactyly). A digit
(most commonly the thumb) may
have an extra phalanx.
• The palm or sole may show a
deep longitudinal cleft (lobster
claw).
• The limbs may remain short in
achondroplasia .
• Sometimes the bone ends
forming a joint are imperfectly
formed (congenital dysplasia).
This can lead to congenital
dislocation.
• The hip joint is most
commonly affected.