Friday, 4 December 2015

Bones of the Skull.




In October I posted a blog about the anatomy of bones but I thought it would be interesting to find out more about the individual bones, starting with the skull.


The skull is made up of many different bones, often paired,  and its main function is to protect the brain.  In addition, the skull supports the facial muscles and provides points for the veins, arteries and nervous systems to enter and exit.  The skull bones are mostly flat and until adulthood are separated by cartilage or fibrous tissue, as the horse develops this changes to bone.  


Occipital Bone: Found at the back of the skull it is relatively strong and thick.  These bones also form the foramen magnum which is the passage for the spinal cord from the brain. At the top of the occipital bone is the nuchal crest, which is the highest point of the cranium.  This is the part that is protected by a poll guard when travelling.  The occipital bone forms the roof of the cranium with the interparietal, parietal and frontal bones (these are thinner than the occipital).  

Parietal Bones: These are found at the front, between the Frontal Bones, Squamous Temporal Bones and the Occipital Bone.

The Frontal Bone: Is made up of a pair of bones.  As mentioned above these are thinner than the occipital bone, however, the brain is protected by the frontal sinuses.  This is an air space between two thin layers of bone.  The cerebellum section of the brain is found at the back of the skull (just above the foramen magnum)and the cerebrum section at the front. 

Squamous Temporal Bones: Are the flat bones just in front of the ear!
The Supraorbital Process:  This is a bony arch which reaches over the top of the orbit (the eye socket) and joins the Frontal Bone to the Zygomatic Bone.

Zygomatic Arch: Is another curved bar of bone which joins the Maxilla to the Squamous Temporal Bone.

The Zygomatic Bone: Is the section just below the eye.

The Lachrymal Bone: Is found between the Zygomatic Bone and Nasal Bone, in front of the eye.


The Nasal Bone : Covers the nasal and oral passages.  The nasal passages are where the air flows into the pharynx - see my Respiratory System blog.  Each passage is separated by the nasal septum and has small bones (ethmoid bones) at the back which are covered in the membrane which is where the olfactory nerves are found  (see my blog).

The Turbinate Bones: These are also small bones which project into the nasal cavity near the front.  They provide an increased surface area which in turn provides support for the membranes which warm the incoming air.

The Maxilla:  Together with the Pre-Maxillary Bone they make up the upper jaw.  The Maxilla holds the molars and helps to form the walls to the nasal passages.

Pre-maxillary Bone:  Holds the incisor teeth and again forms the walls of the nasal passages. 

Mandible: Is the lower jaw and is very large, holding all the lower teeth. 

The Sinuses: These are not bones but are large air filled cavities enabling the skull to be large to accommodate the jaws (of a grazer) but not too heavy.  There are several sinuses in each half of the skull - the frontal, superior maxillary, inferior maxillary and sphenopalatine. 

The Temporal Fossa: Is an important space located below the Zygomatic Arch, which is where the top part (coronoid process) of the lower jaw fits.

Next week the blog will be about the spine. 



There are lots of great books which will go into lots more detail about all the different parts of each bone - if you are interested in finding out more



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Until next time!
Jo

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