Anatomy axial skeleton

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What is the axial skeleton?


The axial skeleton consists of those bones that lie in the longitudinal axis of the body, running through its center of gravity


Name the axial bones


The bones of the axial skeleton include the bones of the skull, the hyoid, the ribs, sternum, and vertebrae


What is the appendicular skeleton?


The appendicular skeleton contains the bones of the upper and lower extremities, including the pectoral (shoulder) girdle and pelvic girdle


Identify the cranial bones


The cranial bones are the: 1 frontal, 2 parietal, 2 temporal, 1occipital,

1 sphenoid, and 1 ethmoid.


identify the facial bones


The facial bones are the: 2 nasal, 2 maxillae, 2 zygomatics ( zygomas),

1 mandible, 2 lacrimal, 2 palatine, 2 inferior nasal conchae, and 1 vomer.


What is a suture of the skull?


A suture is an immovable fibrous joint in the skull where bone surfaces are closely united by connective tissue.




The coronal suture is located between the frontal bone

and the 2 parietal bone




The sagittal suture is located between the 2 parietal





The lambdoidal sutures are found between the right

and left parietal bones and the occipital bone




The squamosal sutures are located between the

parietal bone and the temporal bone of each side


What are Wormian bones?


Wormian bones are small fragments of bones found in the sutures, particularly in the sagittal and lambdoidal sutures


What are the fontanels and what are their functions?


Fontanels are membrane-filled spaces between the bones of the cranium seen at birth. These “soft spot” areas of dense fibrous connective tissue bridge the incompletely formed cranial bones. They close as the bones, and the brain, complete their develop-ment.

Fontanels have two functions:

(1) allow head to change shape while passing through

the birth canal

(2) allow for rapid growth of brain during the first two



anterior fontanel


The anterior (frontal) fontanel is found between the two

parietal bones and the two segments of the frontal bone; closes between 18 - 24 months


posterior fontanels


The posterior (occipital) fontanel is found between the

two parietal bones and the occiput; closes at 2 months.


sphenoidal fontanel


The anterolateral (sphenoidal) fontanel is located at

the junction of the frontal, parietal, temporal, and sphenoid bones; closes at 3 months


mastoidal fontanel


The posterolateral (mastoidal) fontanel is found at the

junction of the parietal, occipital, and temporal bones; closes at 12 months.


Describe the hyoid bone. What are its functions?


The hyoid bone is unique in the body because it articulates with no other bone. It is suspended by ligaments and tendons from the temporal bone in the anterior neck, between the mandible and the larynx. It supports the tongue and provides attachment for some of its muscles, as well as other muscles of the neck and pharynx


Name the bones of the thorax


The vertebral column (spine), together with the ribs and the sternum, forms the skeleton of the thorax.


Describe the vertebral column


The vertebral column is composed of a series of individual bones called vertebrae (a single one is called a vertebra). Together, the vertebrae form a strong, flexible rod that bends anteriorly, posteriorly, and laterally, and rotates


What are the functions of the vertebral column?


Functions of the vertebral column:

1. Enclose and protect the spinal cord.

2. Support and allow for movement of the head.

3. Give points of attachment for ribs and muscles of the back


What are intervertebral foramina?


Between individual vertebrae are openings called intervertebral foramina through which pass the spinal nerves


Identify the five different types of vertebrae


The 26 vertebrae of the adult are distributed as:

7 cervical, 12 thoracic, 5 lumbar, 1 sacrum, 1 coccyx


What are intervertebral discs?


Between each adjacent vertebra from level C-1 to the sacrum are pads of connective tissue called intervertebral discs


What are the two parts of a disc?


Each disc is composed of two parts. The outer portion, formed of fibrocartilage, is the annulus fibrosus. The inner portion is a soft, pulpy tissue rich in hyaluronic acid, elastin, and water. It is called the nucleus pulposus.


How do the discs function?


The discs form strong, slightly movable joints between the adjacent vertebrae, permitting the movements of the spine and absorbing vertical shock. When they are compressed, the discs bulge outward, particularly in the lumbar region where the weight of the upper body is brought to bear on the pelvis


Describe the vertebral curves


When viewed from the side the vertebral column shows four normal curves. The cervical and lumbar curves are anteriorly convex. The thoracic and sacral curves are anteriorly concave


What are there functions of the vertebral curves?


These curves, like those in long bones, give the spine strength and absorb vertical shock, acting like a spring


What are the primary curves


The thoracic and sacral curves are said to be primary curves because they retain the original curvature of the embryo/fetus


What are the secondary curves?


The cervical and lumbar curves are said to be secondary curves since they are modifications of the original curve related to assuming and erect posture by holding up the head and walking


Describe the bony thorax


The term thorax refers to the entire chest. The skeletal portion of the thorax is a bony cage formed by the sternum, ribs, costal cartilages, and bodies of the thoracic vertebrae. The cage is cone-shaped with the narrow end superior and the broad end posterior. It is flattened front-to-back.


What are the functions of the bony thorax?


The bones give partial protection to thoracic organs, support and attach the upper extremities to the axial skeleton, and give sites for muscle attachment


Describe the sternum


The sternum (breastbone) is a flat narrow bone lying in the midline of the anterior thoracic wall.

The sternum is formed by fusion of three parts:

1. Manubrium

2. Body (gladiolus)

3. Xiphoid process.


What is the sternoclavicular notch?


The superior- most portion of the sternum, where the two clavicles join the sternum at the manubrium, forms the sternoclavicular notch. This is an important clinical landmark.


Describe the posterior articulation of the ribs


Each rib articulates posteriorly with its corresponding thoracic vertebra and the vertebra directly below it. Ex. Rib 1 articulates with both thoracic vertebrae 1 and 2


What are the true ribs?


Ribs 1-7 have a direct attachment to the sternum via the costal cartilages. Therefore, they are called true ribs


What are the false ribs?


Ribs 8-10 have a single cartilaginous union with the sternum because their costal cartilages fuse into one. Along with ribs 11-12, these are the false ribs. Ribs 11-12 are also known as floating ribs because they have only a posterior attachment. They have no costal cartilages


Describe an intercostal space


Between the ribs are the intercostal spaces, each containing intercostal muscles, blood vessels, and nerves