Tag: our skeletal system and the skin

• The cervical spine is made up of 7 vertebrae. The first 2, C1 and C2, are highly specialized and are given unique names: atlas and axis, respectively. C3-C7 are more classic vertebrae, having a body, pedicles, laminae, spinous processes, and facet joints.
• The typical cervical vertebrae are $C3, C4, C5, and C6$. The atypical cervical vertebrae are C1 – Atlas, C2 – Axis, and C7 – vertebra. The key difference between typical and atypical vertebrae is that typical vertebrae consist of all basic components of a vertebra while atypical vertebrae are the vertebrae that have modified structure due to their position and function.
  
• Hence 3, 4, 5, 6 are typical cervical vertebrae.
• So,the correct answer is '3,4,5,6'.

• Urostyle is a long bone formed from fused vertebrae at the base of the vertebral column in some lower vertebrates, especially frogs and toads.
• In frog Eighth vertebra is amphicoelous and the 9th vertebra is biconvex and is attached to urostyle on the posterior side.
• Hence the Last vertebra of the frog is Urosyyle.
• So, the correct answer is 'Urostyle'.

• Bone is the rigid part that constitutes the vertebral skeleton. It is a connective tissue largely composed of organic protein collagen and the inorganic mineral hydroxyapatite.
• Mineral hydroxyapatite is chemically Calcium phosphate.
  
• Hence the major constituent of vertebrate bone is calcium phosphate.
• So, the correct answer is 'Calcium phosphate'.

• Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, bones become weak and may break from a fall or, in serious cases, from sneezing or minor bumps. Osteoporosis means “porous bone.”
  
• Osteoporosis can be caused due to deficiency of vitamin D, while osteomalacia is caused by a deficiency in calcium and phosphorus. 
• Hence Osteoporosis is characterized by deterioration of the bone due to deficiency of phosphorous is an incorrect statement.
• So, the correct answer is 'III alone is incorrect'.

• The spinous process extends posteriorly, or rearward, from the laminae of the vertebra, and is a point of attachment for several muscles, ligaments, and fasciae. 
  
• In cervical vertebrae C2 through C6, there exists a common variation of bifurcation. A spinous process is considered bifurcated when a small 'split' occurs at the distal end.
• ​The bifurcation allows for the nuchal ligament to fall centrally which allows the cervical musculature to attach jointly to this strong ligament, as well as the spinous process without interference at the bony insertion.
  
• Hence the Bifurcated spinous process is present in second and Sixth cervical vertebrae.
• So, the correct answer is 'Second and Sixth cervical vertebrae'.

The opisthocoelous vertebra is concave at the posterior end but not the anterior end. Mostly fish and salamanders are of the opisthocoelous type.

Sternum or breastbone is a flat, narrow and long bone which forms the base for attachment of ribs and is made up of one bone; there are 24 bones or 12 pairs consisting of the rib cage; pelvis consists of 3 bones and face is composed of facial bones which are 14 in number.

Thus, the correct answer is option A.

Articulation between the occipital condyles and the atlas vertebra forms a hinge joint, it permits the head movement in one plane.

The joint of the femur with pelvic girdle is a synovial - ball and socket joint. Where the ball like projection of the femur fits into the cup like acetabulum of the pelvic bone, with the movement being 360$^0$ and the gap between the joint filled by synovial fluid.