Chapter 36, Problem 14STP

Summary Introduction

To write:

The name and describe the two divisions of the human skeleton. 

Introduction:

The skeleton system includes bones and cartilages that help to provide rigidity to the body so that it can against the force of gravity during movements. It provides support to the softer body parts and protection to delicate organs such as the brain, lungs, heart, etc. It also provides attachment for large muscles that help in the movement of the body parts. The skeletal system of an adult human consists of 206 bones. 

Explanation of Solution

The two divisions of the human skeleton are the axial skeleton and the appendicular skeleton. 

The division of the skeleton is based on the position of the skeletal structures in the body. The axial skeleton is present on the median longitudinal axis of the body and consists of the skull, vertebral column, sternum, and ribs. There are 80 bones in the axial skeleton. The appendicular skeleton is present at the lateral sides that extend outwards from the principal axis. It consists of pectoral and pelvic girdles and bones of arms and legs. There are 126 bones in the appendicular skeleton.

The axial skeleton system includes the bones of the head, neck, chest, and back. These bones help to protect the vital organs such as the brain, Spinal cord, heart and lungs, and sites of muscle attachment that help to move the head, neck, back, and the muscles that act across the pelvic and pectoral girdle as well.

The appendicular skeleton helps to attach the bones of the upper and lower limbs to the axial skeleton system through the pectoral (shoulder) and pelvic (hip) girdle, respectively. The bones of the pelvic region help to provide the stability during activities such as walking and running which include the movement of lower limbs. The bones of the pectoral region help to lift or carry the objects using upper limbs by providing a greater range of motion and mobility.

Conclusion

Thus, the two divisions of the skeletal system are the axial skeleton and the appendicular skeleton. The division is based on the position of the skeletal structures. The axial skeleton forms the vertical, central axis while the appendicular skeleton consists of the bones of limbs and pelvic and pectoral girdles.