Axial SkeletonIncludes: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

Atlas (C1) – superior articular facets articulate with occipital condyles of skull and allow nodding motion of head

Characteristics of Cervical Vertebrae

Axis (C2) – 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

Thoracic – have a mid-sized body and a long,

narrow spinous process which slants inferiorly at a sharp

angle; facets on transverse processes

articulate with ribs

Characteristics of Thoracic Vertebrae

Lumbar – have largest bodies to support the most

weight; thick, moose-head

shaped spinous processes

Characteristics of Lumbar Vertebrae

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:Manubrium- articulates

with clavicles and 1st and 2nd ribs

Body – articulates with 2nd – 10th ribs (directly or indirectly)

Xiphoid process – doesn’t ossify until about age 40.

Ribs• True Ribs – 1st – 7th

pairs; have direct attachment to sternum by hyaline cartilage

• False Ribs – 8th – 12th pairs; attach indirectly to sternum or not at all– 11th and 12th pair of ribs

are also called floating ribs because they do not attach to sternum at all.