The Skeletal System

Professor Dave again, let’s look at the human skeleton.

Now that we’ve learned about the structure of bones, we are ready to take a look at how

they are assembled in the body.

The skeletal system is comprised mainly of bones, around two hundred and six of them

in an adult to be specific, but there is also a good amount of cartilage, joints, and ligaments,

which all together make up around twenty percent of a person’s body mass.

We will get to joints a little bit later, first let’s check out all the different

bones in the body.

As we recall, there are two sections to the human skeleton, those being the axial skeleton,

made of the skull, vertebral column, and thoracic cage, and the appendicular skeleton, made

more or less of just the limbs.

Let’s go through the axial skeleton first, starting at the top with the skull.

The skull is a fascinating structure, made of twenty two different bones.

Cranial bones are the ones that protect the brain, and facial bones are the ones that

give structure to the face.

Most of the bones in the skull are flat bones, and in the cranium these are connected at

serrated lines called sutures.

The cranium is made of a vault, as well as a base, and we should note that the base is

divided into the anterior, middle, and posterior cranial fossae.

Together, these produce the cranial cavity, where the brain sits.

There are also ear cavities and nasal cavities, as well as orbits, which house the eyes.

All together there are eight cranial bones.

There is the frontal bone, two large parietal bones, the occipital bone, two temporal bones,

the sphenoid bone, and the ethmoid bone.

The cranial bones are connected, as we said, by sutures, and those have specific names

as well.

These are the coronal, sagittal, lambdoid, squamous, and occipitomastoid sutures.

We should also mention the foramina, which are holes that nerves and arteries and veins

pass through, most notably the foramen magnum at the base of the skull through which the