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Axial Skeleton

Introduction

Anatomists divide the skeletal system into axial skeleton and appendicular skeleton. The axial skeleton is the central part of our body and includes image descriptionthe skull, image descriptionthe hyoid bone, image descriptionthe vertebral column, the sternum, and image descriptionthe ribs. The appendicular skeleton includes the bones of the limbs (e.g., the upper and lower limbs) and the girdles (e.g., the shoulder girdle and the pelvic girdle).

In this tutorial, we will dive into the anatomy of the axial skeletal system.

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Skull

The human skull is a protective vault, for our most critical organ, the brain. It consists of 22 bones divided between the image descriptionneurocranium (braincase) and image descriptionviscerocranium (facial skeleton).

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Make sure to check our tutorials covering both the cranial bones and the facial bones.

Hyoid bone

The hyoid bone is a small u-shaped bone that does not articulate with any other bone, connecting to its neighboring structures by muscles and ligaments.

It is image descriptionlocated at the midline at the level of C3, providing stability to the adjacent structures and playing a critical role in the movement of the upper airway.

Vertebral column

Also called the spine or backbone, the vertebral column is a continuous series of vertebrae separated by intervertebral discs. There are usually 33 vertebrae named according to their region as follows:

  1. image descriptionCervical vertebrae (7)
  2. image descriptionThoracic vertebrae (12)
  3. image descriptionLumbar vertebrae (5)
  4. image descriptionSacrum (5 fused) & coccyx (4 fused).
An image showing the whole vertebral column
An image showing the whole vertebral column with the cervical part highlighted with green
An image showing the whole vertebral column with the thoracic part highlighted with green
An image showing the whole vertebral column with the lumbar part highlighted with green
An image showing the whole vertebral column with the sacrum and coccyx highlighted with green
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The vertebral column houses and thus protects the spinal cord, supports the upper body’s weight, and plays a vital role in a wide range of movements.

Rib cage (thoracic cage)

The rib cage consists of the thoracic vertebrae, twelve pairs of ribs (and their corresponding costal cartilages), and the sternum.

It is an essential component of the respiratory system, protecting the lungs and the heart, and helping with breathing.

Sternum

Also called the breastbone, the image descriptionsternum is located at the midline anteriorly articulating with the clavicles and costal cartilages of the ribs.

Sternum Bone - Overview
Sternum Bone - Labeled
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Ribs

The image descriptionribs are further divided into true ribs (1-7), false ribs (8-10), and floating ribs (11-12).

Unlabelled image of the anterior view of the rib cage
Anterior view of the true ribs of the rib cage
Anterior view of the false ribs of the rib cage
Anterior view of the floating ribs
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