Classification of the Bones

Which of the following is part of the axial skeleton?

• Shoulder girdle

• Pelvic girdle

• Vertebral column

• Lower extremities

Answer explanation

The axial skeleton consists of the long axis of the body, including the skull, vertebral column, and bony thorax. The appendicular skeleton comprises the bones of the limbs and girdles.

Which of the following is true about lamellar bones?

• They are mature bones with a highly organized structure.

• They contain randomly oriented collagen fibers.

• They are primarily found in the fetal period.

• They have a spongy appearance.

Answer explanation

Lamellar bones are mature bones with an organized structure, consisting of parallel layers of bone tissue. They contrast with woven bones, which contain randomly oriented collagen fibers.

Which process of bone development involves the direct ossification of mesenchyme during the fetal period?

• Endochondral ossification

• Intramembranous ossification

• Cartilaginous ossification

• Osteogenesis

Answer explanation

Intramembranous ossification involves the direct ossification of mesenchyme during the fetal period, leading to the formation of membranous bones. It contrasts with endochondral ossification, where cartilage models are replaced by bone.

Which type of bone has a cuboidal shape and is found in the ankle and wrist?

• Long bone

• Short bone

• Irregular bone

• Pneumatic bone

Answer explanation

Short bones are cuboidal and are primarily found in the ankle (tarsus) and wrist (carpus). Long bones are tubular, flat bones serve protective functions, and irregular bones have various shapes.

What is the total number of bones in the appendicular skeleton?

• 80

• 206

• 126

• 112

Answer explanation

The appendicular skeleton contains 126 bones, which include the bones of the upper and lower extremities, along with the girdles (shoulder girdle and pelvic girdle).

Which term describes bones that contain empty spaces within them, like the frontal and maxillary bones?

• Long bones

• Pneumatic bones

• Short bones

• Flat bones

Answer explanation

Pneumatic bones contain empty spaces or air-filled cavities within them, like the frontal and maxillary bones. This feature helps to lighten the weight of the bones.

Which of the following is NOT part of the bony thorax?

• Sternum

• Ribs

• Vertebral column

• Clavicle

Answer explanation

The bony thorax includes the sternum, ribs, and vertebral column. The clavicle is part of the appendicular skeleton, specifically the shoulder girdle.

Which type of bone formation involves cartilage models forming from mesenchyme during the fetal period?

• Intramembranous ossification

• Endochondral ossification

• Cartilaginous ossification

• Osteogenesis

Answer explanation

Endochondral ossification involves the formation of cartilage models from mesenchyme during the fetal period, which are later replaced by bone.

Compact bone is the outer dense layer, while spongy bone is the inner layer with a spongy appearance.

• True

• False

Answer explanation

Compact bone is the outer dense layer that appears smooth and homogeneous, while spongy bone has a spongy appearance due to small needle-like spicules and numerous openings.

Short bones are found only in the ankle and wrist.

• True

• False

Answer explanation

Short bones have a cuboidal shape and are primarily found in the ankle (tarsus) and wrist (carpus).