Chapter 6: The Skeletal System - Axial Division

Flashcards based on Chapter 6 lecture notes covering the skeletal system: axial division, including skull anatomy, vertebral column structure, and the thoracic cage.

What are the main functions of the axial skeleton?

It functions as a framework supporting and protecting organs in the dorsal and ventral body cavities, contains special sense organs, and provides attachment sites for muscles that adjust posture, move the thoracic cage for respiration, and stabilize the appendicular skeleton.

How many total bones make up the axial skeleton, and how are they divided among its three major component groups?

The axial skeleton contains $80$ total bones, divided into the skull and associated bones ($29$), the thoracic cage ($25$), and the vertebral column ($26$).

Which $8$ bones form the cranium?

The occipital bone ($1$), parietal bones ($2$), frontal bone ($1$), temporal bones ($2$), sphenoid bone ($1$), and ethmoid bone ($1$).

What are the $14$ facial bones of the skull?

Paired bones: maxillae ($2$), palatine bones ($2$), nasal bones ($2$), zygomatic bones ($2$), lacrimal bones ($2$), and inferior nasal conchae ($2$). Single bones: vomer ($1$) and mandible ($1$).

Which skull bones contain paranasal sinuses, and what functions do these sinuses serve?

Paranasal sinuses are located in the frontal, ethmoid, sphenoid, and maxillary bones. They reduce skull weight, produce mucus, and allow air to resonate for voice production.

What unique bony structure is created when the body of the atlas fuses with the body of the axis during development?

The dens (odontoid process).

What head movement is permitted by the joint between the atlas ($C_1$) and the occipital condyles?

It allows a person to shake their head "yes."

What head movement is permitted by the articulation between the atlas ($C_1$) and the axis ($C_2$)?

It allows a person to shake their head "no."

What is the vertebra prominens ($C_7$) and what elastic ligament attaches to it?

It is the seventh cervical vertebra ($C_7$) which resembles a thoracic vertebra, featuring a long, slender spinous process and enlarged transverse processes; the ligamentum nuchae attaches to its spinous process and extends cranially to the occipital crest.

What key features distinguish typical cervical vertebrae from other vertebrae?

They are the smallest vertebrae, feature a split or bifid tip on the spinous process, and have costal processes attached to transverse processes that form transverse foramina.

What anatomical features characterize thoracic vertebrae?

Heart-shaped bodies, long slender spinous processes pointing at a posterocaudal angle, dorsolateral transverse processes, and extra costal facets for articulation with ribs.

What anatomical features characterize lumbar vertebrae?

Very thick oval-shaped bodies, small triangular vertebral foramina, laterally pointing transverse processes, and stumpy, flattened spinous processes resembling a fish tail fin.

What is the functional difference between primary curves and secondary curves of the vertebral column?

Primary (accommodation) curves in the thoracic and sacral regions sweep posteriorly and develop before birth to accommodate abdominopelvic viscera. Secondary (compensation) curves in the cervical and lumbar regions sweep anteriorly and develop after birth as infants learn to hold up their heads (cervical) and walk (lumbar).

Based on the provided diagram, identify the three abnormal spinal curvatures labeled (a), (b), and (c).

(a) Kyphosis, (b) Lordosis, and (c) Scoliosis.

Based on the provided figure, what bone is shown and what are its main structures?

The hyoid bone, consisting of a body, greater horns, and lesser horns.

How are the $12$ pairs of ribs categorized based on their attachments?

Ribs $1\text{–}7$ are true ribs. Ribs $8\text{–}12$ are false ribs, which include vertebrochondral ribs (ribs $8\text{–}10$) and floating ribs (ribs $11\text{–}12$).

What total number of individual bones make up the adult vertebral column across its regions?

The adult vertebral column consists of $26$ bones: $7$ cervical vertebrae, $12$ thoracic vertebrae, $5$ lumbar vertebrae, $1$ sacrum (composed of $5$ fused vertebrae), and $1$ coccyx (composed of $3\text{–}5$ fused vertebrae).