Axial Skeleton Includes 80 bones Skull 22 bones

Axial Skeleton Includes: 80 bones • Skull (22 bones) • Hyoid bone • Auditory ossicles (6) • Vertebral Column (26 vertebrae in adults) • Thorax (12 pair of ribs/sternum)

Skull • 8 cranial bones which enclose and protect the brain – Two parietal, two temporal, frontal, occipital, sphenoid and ethmoid • 14 facial bones – two nasal, two maxillae, two zygomatic, two palatine, two lacrimal, two inferior nasal conchae, mandible, vomer

Function • Besides protection of the brain, cranial bones function to: – Stabilize the position of the brain, blood vessels and nerves (by attachment to inner surfaces of bones) – Provide large areas of attachment for muscles that move the head (by attachment to outer surfaces of bones) – Facial bones protect and provide support for entrances to the digestive and respiratory systems; also provide attachment for some muscles involved in facial expressions.

Details on Temporal bone markings • External auditory meatus = canal in the temporal bone that leads to the middle ear. • Mastoid process = rounded projection on temporal bone that serves as attachment site for neck muscles. • Styloid process = projects downward from undersurface of temporal bone and serves as attachment site for muscles of tongue and neck • Mandibular fossa = forms a joint with condylar process of mandible

• Carotid foramen – hole in temporal bone through which carotid artery passes.

Details on Occipital bone markings • Foramen magnum= largest foramen in skull; medulla oblongata of the brain connects to spinal cord through this foramen • Occipital condyles= oval processes on either side of foramen magnum that articulate with the first cervical vertebra.

Details on Sphenoid bone markings • Articulates with all the other cranial bones, holding them together • Sella turcica = depression on superior surface of sphenoid bone which surrounds the pituitary gland • Foramen ovale = mandibular nerve passes through • Optic foramen= optic nerve passes through

Details on Ethmoid bone markings • Ethmoid bone contains 3 -18 air spaces that form the ethmoidal sinuses • Perpendicular plate= forms upper part of nasal septum • Cribriform plate = forms roof of nasal cavity • Olfactory foramina= fibers of the olfactory nerve pass through • Crista galli= serves as point of attachment for the meninges. • Superior nasal concha and Middle nasal concha = cause turbulence in inhaled air which cleanses air before it passes into the rest of the respiratory tract.

Details on Facial bone markings: • Mandible= largest, strongest facial bone; only movable skull bone; contains the condylar process which articulates with the manidibular fossa of temporal bone to form the Temporomandibular Joint (TMJ). • Mental foramen = holes in mandible that dentists use to reach the mental nerve when injecting anesthetics

Temporomandibular Joint syndrome • TMJ syndrome is characterized by dull pain around ear, tenderness of jaw muscles, clicking or popping noise when opening or closing mouth. • Caused by improperly aligned teeth, trauma to head/neck, or arthritis

• Vomer = triangular bone on floor of nasal cavity; one of the components of nasal septum (divides the nasal cavity into right and left sides) • Nasal Septum = formed by vomer, septal cartilage and perpendicular plate of ethmoid bone

Paranasal Sinuses • Hollow portions of bones surrounding the nasal cavity • Named for their locations in bones of the same name · Functions : · Lighten the skull · Give resonance and amplification to voice

The Hyoid Bone · The only bone that does not articulate with another bone · Serves as a moveable base for the tongue

The Fetal Skull · The fetal skull is large compared to the infants total body length · Fontanelles – fibrous membranes connecting the cranial bones · Allow the brain to grow · Convert to bone within 24 months after birth

The Vertebral Column · Consists of 7 cervical, 12 thoracic, 5 lumbar vertebrae; sacrum and coccyx · Vertebrae separated by intervertebral discs · Each vertebrae is given a name according to its location

Structure of a Typical Vertebrae • Body= weight bearing part • Vertebral arch= formed by lamina and pedicles • Vertebral foramen= spaced between the vertebral arch and the body; contains the spinal cord • Seven processes serve as points of muscle attachment or form joints with other vertebrae – Know Spinous process and Transverse process

Characteristics of Cervical Vertebrae Atlas (C 1) – superior articular facets articulate with occipital condyles of skull and allow nodding motion of head

Axis (C 2) – Dens (odontoid process) extends superiorly into vertebral foramen of atlas and allows the atlas to pivot in a “no” type movement. . Dens can get shoved into the medulla oblongata (brain stem) during head trauma.

All cervical vertebrae have 3 foramen: vertebral and two transverse foramen which allow passage of arteries, veins and nerves to and from brain

Characteristics of Thoracic Vertebrae Thoracic – have a midsized body and a long, narrow spinous process which slants inferiorly at a sharp angle; facets on transverse processes articulate with ribs

Characteristics of Lumbar Vertebrae Lumbar – have largest bodies to support the most weight; thick, moose-head shaped spinous processes

Abnormal Spinal Curvatures

Thoracic Cage • Forms a cage to protect major organs · Made-up of three parts · Sternum · Ribs · Thoracic vertebrae

Sternum • Narrow flat bone consisting of 3 parts: q. Manubrium- articulates with clavicles and 1 st and 2 nd ribs q. Body – articulates with 2 nd – 10 th ribs (directly or indirectly) q. Xiphoid process – doesn’t ossify until about age 40.

Ribs • True Ribs – 1 st – 7 th pairs; have direct attachment to sternum by hyaline cartilage • False Ribs – 8 th – 12 th pairs; attach indirectly to sternum or not at all – 11 th and 12 th pair of ribs are also called floating ribs because they do not attach to sternum at all.