Question

Name the keystone bone of the cranium. Where is it located?

Answer 1

Hint: The butterfly-shaped bone of the cranium holds all the cranial bones together. This cranial bone is also characterized by a saddle-shaped bony structure in its center called sella turcica. The pituitary gland of the endocrine system lies in the sella turcica.

Complete answer:
Axial and appendicular skeleton together make the skeletal system of the human body. The adult human body consists of 206 bones. The axial skeleton includes 80 bones and the appendicular skeleton is made up of 126 bones. The appendicular skeleton includes the bones of the upper and lower limbs and the girdles. Therefore, the bones of pectoral and pelvic girdles are included in the appendicular skeleton.

The axial skeleton includes the bones present along the imaginary vertical axis of the body. It includes the bones of the skull, ribs, sternum, and the vertebrae of the spine. Skull is composed of a total of 22 bones and includes the bones of the cranium and face.

Cranium is the bony structure whose bones are joined by immovable joints and protects the brain. The sphenoid bone is located in the middle part of the floor of the cranium and makes the posterior walls of the orbits. Orbits are the eye-sockets. The sphenoid is a single bone with the shape of a bat or a butterfly with outstretched wings. It articulates with other bones of the cranium. Since it holds the bones of the cranium together, it is called the keystone bone.

Note: Cranium is composed of a total of eight bones. It includes frontal bone, parietal bones, occipital bone, temporal bones, sphenoid bone, and ethmoid bone. Frontal, occipital, sphenoid, and ethmoid bones are present as the single bones while the rest are paired.