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Skeleton

Skeleton

Description:

This lesson will identify the structure and function of the appendicular skeleton.

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Tutorial

What's Covered

In this lesson today we're going to discuss the two divisions of the skeletal system:

  1. Appendicular Skeleton
  2. The Axial Skeleton

1. The Appendicular Skeleton

The appendicular skeleton are bones of the limbs, hips, and shoulders. If you think of any body part that is a hanging body part, that is part of your appendicular skeleton. Your appendicular skeleton is broken down into two sections as well:

  • Pectoral girdle- includes bones of the upper body that are part of the appendicular skeleton such as scapulae, clavicles, and our upper limbs.
  • Pelvic girdle- includes the bones of the lower body that hang such as pelvis and our lower limb

Everything that's highlighted in purple here on our skeleton is an example of bones of the appendicular skeleton.

Terms to Know

    • Appendicular skeleton
    • The division of the skeletal system that includes the bones of the hips, shoulders and the limbs.
    • Pelvic Girdle
    • The bones associated with the lower part of the appendicular skeleton including the pelvis and legs.
    • Pectoral Girdle
    • The bones associated with the upper part of the appendicular skeleton including the scapulas, clavicles and arms.

2. Axial Skeleton

The other division of our skeletal system is our axial skeleton. The axial skeleton includes the bones of the skeleton that compose your vertical axis. If you think of a person standing up, your vertical axis is the up and down axis. The bones that compose that axis are your skull, vertebral column, ribs, and sternum.

The axial skeleton highlighted in green

Term to Know

    • Axial Skeleton
    • The division of the skeletal system that composes the body's vertical axis and includes the skull, backbone, ribs and sternum.

To look more in depth at the parts of the axial skeleton, let's begin with vertebral column. This is your backbone, and it is made up of 33 individual bones called vertebra (plural is vertebrae); these are broken up into a couple different segment:

  • Cervical vertebra- the first 7 bones of the spine; the bones that make up our neck.
  • Thoracic vertebrae- the 12 bones that make up most of your spine
  • Lumbar vertebrae- your lower back would be this section, and that's made up of a total of 5 vertebrae.
  • Sacrum- made up of 5 bones all fused together.
  • Coccyx- made up of 4 bones, again, like the sacrum, all of which are fused together.

In between each of the bones of your spine, you have these disks that are made of cartilage, making a cartilaginous joint in between each of these bones. That cartilage helps provide cushion between the bones so there's not friction when those bones are rubbing together. The main purpose of your spine is to give your body that structure and support, and to protect your spinal cord.

Term to Know

    • Vertebral Column
    • A part of the axial skeleton that protects the spinal cord and gives shape and structure to the body.

Let's take a look at another type of bone found in our axial skeleton, which is the skull. The skull is actually made up of over two dozen bones. All of these bones are fused together by something called sutures. This is type of joint that forms between the bones; it's not a type of joint that generally allows for movement, but holds those bones of the skull together. And the purpose of the bones of your skull is to protect your brain and also to shape your face

The last group of bones to look at in the axial skeleton are the ribs and the sternum. Their purpose is to protect your internal organs. You actually have 12 pairs of ribs that all attach to the spine, and form a cage to protect your internal organs. They're all fused to the spine, and then you have some that attach to the sternum in the front.

Terms to Know

    • Ribs
    • Bones of the axial skeleton that attach to the sternum and backbone to compose a "cage" that protects internal organs.
    • Sternum
    • A bone of the axial skeleton that serves as an attachment point on the front of the body for the ribs.

Summary

The skeleton is broken down into two main sections: the appendicular and axial skeletons. The appendicular skeleton comprises the bone of the limbs and is broken down further into the pectoral girdle (limbs of the upper body) and the pelvic girdle (limbs of the lower body. The axial skeleton includes the bones that make up your vertical axis and include your skull, vertebral column, ribs and sternum.


Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Sternum

    ​A bone of the axial skeleton that serves as an attachment point on the front of the body for the ribs.

  • ​Ribs

    Bones of the axial skeleton that attach to the sternum and backbone to compose a "cage" that protects internal organs.

  • ​Vertebral Column

    ​A part of the axial skeleton that protects the spinal cord and gives shape and structure to the body.

  • Skull

    A part of the axial skeleton that acts to protect the brain.

  • Axial Skeleton

    ​The division of the skeletal system that composes the body's vertical axis and includes the skull, backbone, ribs and sternum.

  • ​Pectoral Girdle

    ​The bones associated with the upper part of the appendicular skeleton including the scapulas, clavicles and arms.

  • ​Pelvic Girdle

    ​The bones associated with the lower part of the appendicular skeleton including the pelvis and legs.

  • Appendicular skeleton

    The division of the skeletal system that includes the bones of the hips, shoulders and the limbs.