Examville.com - Anatomy - Functions Of Skull

Examville is a global education community where users like you can connect and interact with other students and teachers from around the world. Share, seek, download and discuss everything inside and outside the classroom. All you need is an email address and a password to get started.

JOIN US FOR FREE: http://www.examville.com

© Examville.com, LLC June 2009

FUNCTIONS OF SKULL (i) (ii) (iii) (iv) (v)

Cranium protects and houses the brain. It contains and supports the eyes. Skull contains nasal chambers where sense of small is perceived. It has respiratory passages. Maxillae and mandible form upper and lower jaws having teeth. They help in cutting and mastication of food. (vi) Mandible being mobile plays a major role in mastication and speech. (vii) Hyoid apparatus supports the throat and tongue. (viii) Ear bones are mobile. They are helpful in amplification of sound. (ix) Facial bones support the upper portion of digestive tract and respiratory tract. (x) Muscles attached to facial bones are meant for the facial expression. Vertebral Column (33/26, bones) It is also called back bone. Length of vertebral column in males is 71 cm, in females 61 cm. Vertebral column lies in the mid-dorsal region of neck and trunk. It is a string of 26 vertebrae which have two forward and two backward curves. Discs or pads of fibrocartilage occur in between adjacent vertebrae. They are called intervertebral discs. They provide flexibility to vertebral column. A ligament supports the vertebrae against dislocation. Vertebrae are of five types – cervical, thoracic, lumber, sacral and coccygeal with a vertebral formula of C7T12L5S5C4. Each vertebra has a large disc-like flattened body called centrum in front and neural arch behind. A neural canal or neural foramen occurs between the two. Spinal cord passes through it. Neural arch is formed of two rounded pedicles infront and two flattened laminae on the back side. Pedicles of adjacent vertebrae enclose intervertebral foramen for passage of spinal nerves. A neural spine occurs at the tip of neural arch. Transverse processes occur on the sides. Articular facets occur at the bases of tranverse processes. There are two superior articular factes or prezygapohyses. (sing. Prezygapophysis) and two inferior articular facets occur or post-zygapophyses. Superior and inferior articular facets of adjacent vertebrae form gliding type of joints.

(i) Cervical Vertebrae (7). They are small sized vertebrae of the neck region. All humans have 7 cervical vertebrae. The first cervical vertebra is called atlas. It has reduced centrum, rudimentary neural spine and concave superior articular facets for fitting over two occipital condyles to provide for nodding movement of head. Inferior articular facets are circular. A median facet is also present for odontoid process of axis. Second cervical vertebra or vertebra or axis has a strong odontoid process or dens that fits into odontoid canal of atlas to provide sideways rotation of the head. Spines are bifid upto fifth cervical vertebrae. Third to seven cervical vertebrae are typical. At the lower portion of transverse processes of cervical vertebrae there is present an aperture called foramen transversarium. It forms a channel known as vertebrarterial canal for the passage of blood vessels from heart to the brain and back. (ii) Thoracic Vertebrae (12). Thoracic vertebrae are larger than cervical vertebrae. Transverse processes are stout. Spines are long and downwardly directed. Thoracic vertebrae have sites for attachment to ribs. They are twelve in number and form thoracic basket with the ribs for the protection of the lungs and heart. Tip of the transverse process has a facet for attachment with tubercle of rib. Head part of rib attaches to a facet formed jointly by two adjacent vertebrae near the pedicle. The first and the last thoracic vertebrae have complete facet for rib heads. The last three thoracic vertebrae do not have facets for rib tubercles.

(iii) Lumbar Vertebrae (5). They are five in number. Lumbar vertebrae occur in the abdomen. They are the largest, thickest and strongest of all vertebrae as they bear part of the weight of the trunk. Lumbar vertebrae possess long but narrow transverse processes. Neural spines are horizontal. (iv) Sacrum (5 sacral vertebrae). It is a triangular bony complex formed by the fusion of five vertebrae. Sacrum is concave in front and convex behind. It is attached to pelvic girdle by sacroiliac joints. The attachment transfers weight of the body to legs through pelvic girdle. Sacrum bears transverse lines indicating position of different sacral vertebrae. It also possesses foramina for exit of spinal nerves. (v) Coccyx (4-5 coccygeal vertebrae). It is a small vestigial tail bone which is formed by the union of 4 (or 5) nodule-like coccygeal bones. Coccyx is attached to base of sacrum.