The Skeletal System: Axial Division

Comprehensive question and answer review flashcards for the skeletal system's axial division, covering the skull, cranial and facial bones, vertebral column regions, spinal curves, vertebral anatomy, and thoracic cage structures.

What are the primary functions of the axial skeleton?

It forms a framework that supports and protects organs in the dorsal and ventral cavities, houses special sense organs for taste, smell, hearing, balance, and vision, and provides attachment sites for muscles that adjust posture, move the thoracic cage for respiration, and stabilize the appendicular skeleton.

How many total bones are in the human skeletal system, and how are they divided between the axial and appendicular divisions?

There are 206 total bones in the human skeletal system, divided into 80 bones in the axial skeleton and 126 bones in the appendicular skeleton.

What is the detailed anatomical breakdown of the 80 bones in the axial skeleton shown in this chart?

The 80 axial bones consist of 29 skull and associated bones (8 cranial, 14 facial, 6 auditory ossicles, 1 hyoid), 25 thoracic cage bones (1 sternum, 24 ribs), and 26 vertebral column bones (24 vertebrae, 1 sacrum, 1 coccyx).

Which 8 bones form the cranium?

The 8 cranial bones are the Occipital (1), Parietal (2), Frontal (1), Temporal (2), Sphenoid (1), and Ethmoid (1).

Which 14 bones make up the facial skeleton?

The 14 facial bones include the paired Maxillae (2), Palatine bones (2), Nasal bones (2), Zygomatic bones (2), Lacrimal bones (2), and Inferior nasal conchae (2), along with the single Vomer (1) and Mandible (1).

What are the four paranasal sinuses, and what are their primary functions?

The four paranasal sinuses are the frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal air cells; they lighten skull weight, produce mucus, and resonate air for voice production.

How many bones form the adult vertebral column, and what are its major functions?

The adult vertebral column consists of 26 bones (24 vertebrae, 1 sacrum, 1 coccyx). It encloses and protects the spinal cord, supports the skull, supports head, neck, and trunk weight, transfers weight to lower limbs, and maintains upright posture.

How many vertebrae are in each region of the adult vertebral column?

The vertebral column contains 7 Cervical, 12 Thoracic, 5 Lumbar, 1 Sacral (5 fused vertebrae), and 1 Coccygeal (3–5 fused vertebrae).

What is the functional and developmental difference between primary and secondary spinal curves?

Primary curves (thoracic and sacral) sweep posteriorly and develop before birth to accommodate abdominopelvic viscera; secondary curves (cervical and lumbar) sweep anteriorly and develop after birth as infants learn to hold up their head (cervical) and walk (lumbar).

What three abnormal spinal curvatures are illustrated in this image?

(a) Kyphosis (exaggerated thoracic curvature), (b) Lordosis (exaggerated lumbar curvature), and (c) Scoliosis (abnormal lateral curvature of the spine).

What are the key structural features of a typical cervical vertebra?

Cervical vertebrae are the smallest, have a stumpy spinous process often with a bifid tip, costal processes extending ventrolaterally, and transverse foramina located between the costal and transverse processes.

What are the unique anatomical characteristics of the atlas (C1)?

The atlas lacks a vertebral body, possesses anterior and posterior vertebral arches, and articulates superiorly with the occipital condyles to permit nodding 'yes'.

How is the dens of the axis (C2) formed, and what movement does the atlas-axis joint allow?

The body of the atlas fuses with the body of the axis during development to form the dens (odontoid process); articulation between the atlas and axis allows rotation of the head to signal 'no'.

What is the vertebra prominens (C7), and what structure attaches to its spinous process?

C7 is the seventh cervical 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 are the defining structural characteristics of typical thoracic vertebrae?

Thoracic vertebrae feature a heart-shaped body, long slender spinous process pointing posterocaudally, dorsolateral transverse processes, and costal facets for rib articulations.

What are the characteristic structural features of typical lumbar vertebrae?

Lumbar vertebrae are the largest, having a thick oval-shaped body, a small triangular vertebral foramen, stumpy flattened spinous process resembling a fish tail fin, and laterally pointing transverse processes.

How are the 12 pairs of ribs categorized in the thoracic cage?

Ribs 1–7 are true ribs (vertebrosternal ribs); Ribs 8–12 are false ribs, which include Ribs 8–10 (vertebrochondral ribs) and Ribs 11–12 (floating ribs with no anterior connection).

What are the two primary functions of the thoracic cage?

It protects thoracic cavity organs (heart, lungs, thymus) and serves as an attachment site for muscles involved in respiration, positioning the vertebral column, and moving the pectoral girdle/upper limbs.

Which three structures form the sternum?

The sternum is composed of the manubrium, the body, and the xiphoid process.