The Skeletal System Ch 6: Axial Division

Flashcards testing concepts, bone structures, classifications, and diagrams from the Skeletal System: Axial Division chapter.

How many total bones make up the human skeletal system, and how many are in the axial versus appendicular divisions?

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

What are the primary functions of the axial skeleton?

It serves as a framework supporting and protecting organs in the dorsal and ventral body cavities, contains special sense organs (taste, smell, hearing, balance, 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 comprise the skull and its associated bones, and how are they categorized?

There are 29 total bones: 8 cranial bones, 14 facial bones, 6 auditory ossicles enclosed in temporal bones, and 1 hyoid bone.

Which 8 bones form the cranium?

The cranium is formed by 1 Occipital bone, 2 Parietal bones, 1 Frontal bone, 2 Temporal bones, 1 Sphenoid bone, and 1 Ethmoid bone.

What are the 14 facial bones of the skull?

Paired bones: 2 Maxillae, 2 Palatine bones, 2 Nasal bones, 2 Zygomatic bones, 2 Lacrimal bones, and 2 Inferior nasal conchae. Single bones: 1 Vomer and 1 Mandible.

What anatomical structures are labeled (a), (b), and (c) in this diagram of abnormal vertebral column curves?

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

What are the paranasal sinuses, and what functions do they perform?

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

What is the ligamentum nuchae, and where is it attached?

It is an elastic ligament extending cranially from the spinous process of $C_7$ (vertebra prominens) to the occipital crest.

How many bones form the adult vertebral column, and how are they divided by region?

The adult vertebral column consists of 26 bones: 7 Cervical, 12 Thoracic, 5 Lumbar, 1 Sacrum (5 fused vertebrae), and 1 Coccyx (3–5 fused vertebrae).

What is the 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 the infant learns to hold up its head (cervical) and walk (lumbar).

What structural features distinguish the atlas ($C_1$) from other cervical vertebrae, and what movement does it permit?

The atlas has no body and consists of anterior and posterior vertebral arches. Its articulation with the occipital condyles allows one to shake their head "yes."

What anatomical structure forms on the axis ($C_2$) during development, and what movement does it allow?

The body of the atlas fuses with the body of the axis to form the dens (odontoid process). The articulation between the atlas and axis allows one to shake their head "no."

What structure holds the dens in place in the articulated atlas and axis complex shown?

The transverse ligament.

What are the distinguishing anatomical features of typical thoracic vertebrae?

They feature heart-shaped vertebral bodies, long slender spinous processes pointing posterocaudally, dorsolateral transverse processes, and specialized costal facets for rib articulation.

What are the distinguishing anatomical features of typical lumbar vertebrae?

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

What bone is depicted in this figure, and what are its major structural components?

The hyoid bone; its main components are the body, the greater horns, and the lesser horns.

What are the two primary functions of the thoracic cage?

1. Protecting the heart, lungs, thymus, and other organs within the thoracic cavity. 2. Serving as an attachment site for muscles involved in respiration, positioning the vertebral column, and moving the pectoral girdle and upper limb.

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

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