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Monday, June 28, 2010

CRANIAL BONES OR SKULL BONES - LESSON 209

Cranial bones are of six in types. They are as follows:

Cranial bones:
1. Frontal bone
2. Sphenoid bone
3. Occipital bone
4. Temporal bone
5. Parietal bone
6. Ethmoid bone

Now we will see about each bone one by one.

1.  Frontal Bone:  This cranial bone forms the forehead, and the hollow openings that enclose the eyes.
frontal bone

2. Sphenoid Bone: This bone is structurally resembles a bat. This bat shaped bone widens behind the eyes such that it forms the base part of the cranium. Sphenoid bone attaches frontal bone, ethmoid bone and occipital bone. And so this bone is called as sphenoid bone. Sphenoid means wedge or anchor. There is a small hollow depression in the sphenoid bone in which the pituitary gland is located. This depression is called sella turtica which means Turkish saddle.

3. Occipital Bone: This bone outlines the base of the cranium or skull and the back portion of the skull, as well as it joins the temporal bones and the parietal bones. The joint of this bone with other bones forms a stitch or suture. The foramen magnum is an opening located in the inferior or lower portion of the occipital bone. Only through this foramen magnum the spinal cord goes by.

4. Temporal Bone: The temporal bones are two in number and these two bones form the base of the lower portion of the cranium. Each of these two bones covers the ears. Each of the temporal bone contains a fossa which attaches the lower jaw bone or mandible. The area of attachment between the lower jaw bone and each of the temporal bones is called temporomandibular joint or in short TMJ. The temporal bone contains a round process called mastoid process behind each ear. Mast/o means breast.  The other process called styloid process is a descending projection from the temporal bone.  Styloid means pledge.
               
5. Parietal Bone:  These are two in number.  Parietal bones form the top portion or upper part of the sides of the skull.

6.  Ethmoid Bone:  This is a slender bone in structure, but spongy in texture.  This bone holds up or supports the nasal cavity, as well as eye orbits.  This bone is riddle or sieve in shape and so it is called ethmoid bone.  Ethm/o means sieve.

In the next lesson we will learn aboout Facial Bones.  Okay.

Come on...

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