Development of the Bone
A. All the bones are mesodermal in origin.
B. All are formed from preformed cartilaginous models
C. Bones are formed by either cartilaginous or membranous ossifications
D. Cartilages are classified into three types: fibrocartilage, hyaline cartilage, and elastic cartilage.
All are formed from preformed cartilaginous models
All the bones are mesodermal in origin. Mostly they are formed from preformed cartilaginous structure. They can directly form from the mesenchyme as well by membranous ossifications. The bones of the cranial vault and face are formed by membranous ossification.
A. Also called endochondral ossification
B. The cartilage cells enlarge in this process
C. The cartilage cells convert into osteoclasts engulfing surrounding mesenchyme and leaving behind the empty spaces (primary areolae).
D. The bones of base of skull and long bones of limbs are formed by cartilaginous (endochondral) ossification.
The cartilage cells convert into osteoclasts engulfing surrounding mesenchyme and leaving behind the empty spaces (primary areolae).
The cartilage cells enlarge and the matrix surrounding them gets calcified under the influence of an enzyme (alkaline phosphatase) secreted by cartilage cells. Then the cartilage cells die and disappear, leaving behind the empty spaces (primary areolae).
A.It is formed by membrano-cartilaginous ossification
B.The cleidocranial dysostosis is the congenital abnormality in which there is complete or partial absence of the clavicles.
C.Cleidocranial dysostosis occurs due to defective cartilaginous ossification.
D.Large fontanelles and delayed closing of sutures are seen in Cleidocranial dysostosis
Cleidocranial dysostosis occurs due to defective cartilaginous ossification.
This condition occurs due to defective intramembranous ossification. In contrast, in achondroplasia/dwarf the mutation in FGFR 3 gene leads to abnormal endochondral ossification. It is an inherited autosomal dominant trait.
C. Pedicles and articular processes
D. Costal process
The vertebral arches form the pedicles, laminae, spine, articular processes, and transverse processes. The Costal processes form the costal elements of the transverse processes.
A. Spinal nerves & ribs
B. Vertebra & myotomes
C. The intervertebral disc & spinal nerves
D. Muscles and intervertebral disc
Ans. C. The intervertebral disc & spinal nerves
Vertebrae are intersegmental structures because each vertebra is derived from portions of two adjacent somites. The transverse processes and ribs are also intersegmental, and hence separate the muscles derived from two adjoining myotomes. The spinal nerves & the intervertebral disc develop from a single somite and hence are segmental structures.
A. The most severe form of spina bifida is called Spina bifida aperta
B. Hairy patches on skin indicates Spina bifida occulta
C. Spondylolisthesis occurs when the pedicles of the vertebral arch fail to fuse with the vertebral body.
D. Spondylolisthesis commonly affects L4 vertebrae where it slips forward over the body of L5.
Spondylolisthesis commonly affects L4 vertebrae where it slips forward over the body of L5.
Spondylolisthesis commonly affects the L5 vertebra. As a result, the body of the fifth lumbar vertebra slips forward over the sacrum.
- Occipitalization of atlas vertebra occurs due to fusion of atlas vertebra with occipital bone.
- Sacralization of the fifth lumbar vertebra occurs due to partial or complete fusion of the fifth lumbar vertebra with the sacrum.
- Congenital scoliosis can occur due to hemivertebra.
- Spina bifida is a large gap in vertebrae dorsally that occurs when two embryonic neural arches fail to fuse with each other.