Changes

==Introduction==

==Introduction==

The shape and size of the skull varies widely, not only between species but also with age, breed and sex of similar species. The skull is divided into three components- the neurocranium, the dermatocranium and the viscerocranium. The skull also includes the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]], mandible, ossicles of the middle [[Ear - Anatomy & Physiology|ear]] and the cartilage of the [[Larynx - Anatomy & Physiology|larynx]], nose and [[Ear - Anatomy & Physiology|ear]]. The skull protects the brain and head against injury and supports the structures of the face. In some animals the skull is also used for defensive actions, for example in [[Horn - Anatomy & Physiology|horned]] ungulates such as red deer stags.  

The shape and size of the skull varies widely, not only between species but also with age, breed and sex of similar species. The skull is divided into three components- the '''neurocranium''', the '''dermatocranium''' and the '''viscerocranium'''. The skull also includes the '''[[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]]''', '''mandible''', '''ossicles of the middle [[Ear - Anatomy & Physiology|ear]]''' and the cartilage of the '''[[Larynx - Anatomy & Physiology|larynx]]''', '''nose''' and '''[[Ear - Anatomy & Physiology|ear]]'''. The skull protects the brain and head against injury and supports the structures of the face. In some animals the skull is also used for defensive actions, for example in [[Horn - Anatomy & Physiology|horned]] ungulates such as red deer stags. The '''neurocranium''' develops from the neural crest and mesoderm and undergoes endochondral ossification. It lies ventral to the brain. The '''dermatocranium''' lies dorsal to the brain and develops from the neural crest and mesoderm. It undergoes [[Bone & Cartilage Development - Anatomy & Physiology#1. Intramembranous Ossification|intramembranous ossification]]. The '''viscerocranium''' is the pharyngeal skeleton. It is derived only from the neural crest and undergoes [[Bone & Cartilage Development - Anatomy & Physiology|endochondral and intramembranous ossification]]. The various facial muscles attach onto the skull in different places depending on their function. Movement of the external apendages, [[Mastication|mastication]] and facial expressions all rely on the movement of the facial muscles.

 

The neurocranium develops from the neural crest and mesoderm and undergoes endochondral ossification. It lies ventral to the brain.

 

The dermatocranium lies dorsal to the brain and develops from the neural crest and mesoderm. It undergoes [[Bone & Cartilage Development - Anatomy & Physiology#1. Intramembranous Ossification|intramembranous ossification]].

 

The viscerocranium is the pharyngeal skeleton. It is derived only from the neural crest and undergoes [[Bone & Cartilage Development - Anatomy & Physiology|endochondral and intramembranous ossification]].

 

The various facial muscles attach onto the skull in different places depending on their function. Movement of the external apendages, [[Mastication|mastication]] and facial expressions all rely on the movement of the facial muscles.

==Structure==

==Structure==