Chapter 7, Problem 1CYR

Which of the following are considered parts of the axial skeleton? (Circle all that apply.)

a. Pectoral girdle

b. Lower limb

c. Skull

d. Vertebral column

e. Pelvic girdle

f. Thoracic cage

Summary Introduction

Introduction:

The skeletal system provides the framework for the body. The human skeletonconsists of 270 bones at the time of birth, but the number decreases to 206 inadulthood because of the fusion of some bones. The human skeletal system is dividedinto two parts: axial skeleton, whichmaintainsan upright posture of the human body, and appendicular skeleton, whichconsists of limbs and girdles. Appendicular skeleton helps in the movement of the body.

Answer to Problem 1CYR

Correct answer:

The parts of the axial skeleton are skull, vertebral column, andthoracic cage.

Explanation of Solution

Justification/explanationfor the correct answer:

Options (c), (d), and (f) areskull, vertebral column, as well as thoracic cage, respectively. The axialskeleton consists of 80 bones. The skull is composed of 22 bones, out of which eightare cranial bones and 14 are facial bones, whichmake the framework for the face. The vertebral column is composed of 33 bones, out of which 24 bonessurround the spinal cord, and two inferior bones, namely, the sacrum (5 fused vertebrae) and coccyx (4 fused vertebrae), are fused with each other. The thoracic cage has 12 pairs of ribs, whichprotect the lungs and heart. Hence, options (c), (d), and (f) are correct.

Explanation for the incorrect answers:

Option (a) is pectoral girdle. Pectoral girdle surrounds and supports the upper limbs. Itcontains two bones: clavicle and scapula, and is not a part of the axial skeleton. So, it is an incorrect option.

Option (b) is lower limb. The lower limb consists of three parts, which are femur(thigh), tibia, and fibula (leg), and foot bone comprising tarsals, metatarsals, and phalanges. Theselimbs hold the upper part of the body. Theyhelp in locomotion and are not a part of the axial skeleton. So, it is an incorrect option.

Option (e) is pelvic girdle. Pelvic girdle consists of two pelvic bones and the sacrum. It supports the pectoral girdle. The pelvic bone consists of three fused bones, namely, ilium, ischium, and pubis. It is also not apart of the axial skeleton. So, it is an incorrect option.

Hence, options (a), (b), and (e) are incorrect.

Conclusion

Thus, it can be concluded that the skeletal system of a humancomprisestwo parts. The parts of the axial skeletonare skull, vertebral column, and thoracic cage. So, options (c), (d), and (f) are correct.