Axial Skeleton (pt.2)

facial bones, vertebrae, etc.

Nasal bones (2)

• form the bridge of the nose

• protect the upper entry to the nasal canal

• structure of the tip of the nose is cartilage and not bone

Lacrimal bones (2)

• smallest facial bones

• part of the medial wall of the orbit

  • Lacrimal fossa

Lacrimal fossa

Lacrimal bones;

houses the lacrimal sac where tears collect and pass into the nasal cavity

Palatine bones (2)

• Posterior hard palate

• Posterior lateral wall of nasal cavity

• Part of orbit floor

Inferior nasal concha (2)

• Inferior lateral wall of the nasal cavity

• Increases surface area of the nasal cavity and swirls the air

Vomer

• Inferior portion of the nasal septum

Zygomatic bones (2)

• “cheek bones”

• Lateral wall and floor of the orbit

• Temporal processes form part of the zygomatic arch

  • Zygomaticofacial foramen

Zygomaticofacial foramen

Zygomatic bones;

maxillary division of the trigeminal nerve CN V and blood vessels

Maxillae (2)

• Articulates with all other facial bones except the mandible

• Forms part of the floor of the orbit, lateral walls, floor of nasal cavity and most of the hard palate

• Separate the nasal cavity from the oral cavity

  • Maxillary sinus

  • Alveolar processes

  • Dental alveoli

  • Infraorbital foramen

  • Incisive foramen

  • Inferior orbital fissure

Maxillary sinus

Alveolar processes

Maxillae;

ridgelike arches that contain dental alveoli

Dental alveoli

Maxillae;

sockets for teeth

Infraorbital foramen

Maxillae;

blood vessels and maxillary division of the trigeminal nerve CN V pass through

Incisive foramen

Maxillae;

greater palatine blood vessels and nasopalatine nerve pass through

Inferior orbital fissure

Maxillae;

located between the sphenoid bone and maxilla

contains infraorbital nerve branch of trigeminal CN V and blood vessels

Mandible

• Largest, strongest facial bone

• One of the only movable skull bone

  • Anterior coronoid process

  • Mental foramen

  • Mandibular foramen

Anterior coronoid process

Mandible;

area where muscles attach

Mental foramen

Mandible;

mental nerve passes through

Mandibular foramen

Mandible;

inferior alveolar nerve, a branch of the trigeminal nerve CN V and blood vessels pass through

Nasal septum

• divides the nasal cavity into right and left sides

• made of the vomer, perpendicular plate of the ethmoid bone, and septal nasal cartilage

• Anterior portion = hyaline cartilage

• Posterior articulation = perpendicular plate of ethmoid bone

• Posterior-inferior articulation = formed by vomer

Orbits

• pyramid-shaped cavities housing the eyes

• formed by: frontal, sphenoid, ethmoid, palatine, zygomatic, lacrimal maxilla

  • Superior orbital fissure

  • Supraorbital foramen/notch

Superior orbital fissure

Orbits;

located at the superior lateral angle of the apex

Supraorbital foramen/notch

Orbits;

located at the supraorbital margin

Foramens and canals

structures passing through these openings are important for bloods vessels, nerves, or ligaments

Sutures

• immovable fibrous joint in adults

• moveable in young children and act as growth centers

• holds most bones of the cranium and face together

• most sutures are named for the bones they unite

  • Coronal

  • Saggital

  • Lambdoid

  • Squamous

Coronal suture

Sutures;

joint of frontal and 2 parietal bones

Sagittal suture

Sutures;

unite the two parietal bones superiorly

Lambdoid suture

Sutures;

unites the 2 parietal bones to the occipital bone

Squamous suture

Sutures;

unite the parietal bones to the temporal bones laterally

Paranasal sinuses

• cavities within certain skull bones (frontal, sphenoid, ethmoid, maxillae)

• lined by mucous membranes continuous with the nasal cavity

• secrete mucous which drains into the lateral wall of the nasal cavity

• very small at birth and when young

• allows skull to increase in size with little change to mass

• increase surface area of nasal mucosa

• resonating chambers that improve voice quality

Fontanels

• Areas of unossified mesenchyme (dense connective tissue) located between incompletely ossified cranial bones at birth

• Skull initially consists of thin sheets of mesenchyme surrounding the developing brain

• Undergo intramembranous ossification over time and are eventually completely replaced by bone

• Provide flexibility to the fetal skull and allow space for rapid brain and skull growth

Anterior fontanel

Fontanels;

largest, located midline between the parietal bones and frontal bones

closes at 18-24 months

Posterior fontanel

Fontanels;

midline between the parietal and occipital bones

closes at about 2 months

Anterolateral fontanels

Fontanels;

between the frontal, parietal, temporal, and sphenoid bones

close at about 3 months

Posterolateral fontanels

Fontanels;

between the occipital, parietal, and temporal bones

close at about 12 months

Hyoid bone

• does not articulate with any other bone

• located between mandible and larynx

• suspended from styloid process of the temporal bone by ligaments and muscles

• provides attachments for some tongue, neck and pharynx muscles

• consist of a body and paired lesser horns and greater horns

• often fracture due to strangulation

Vertebral column

• flexible rod that can move forward, backward, sideways, and rotate

• encloses and protects spinal cord

• supports the head

• attachment points for ribs, pelvic girdle, muscle of back and upper limbs

  • 7 cervical

  • 12 thoracic

  • 5 lumbar

  • sacrum

  • coccyx

Primary curves

Vertebral column;

thoracic and sacral

retain the original curve of the fetus

Secondary curves

Vertebral column;

cervical and lumbar

develop after birth

Abnormal curves

Kyphosis

Lordosis

Scoliosis

Kyphosis

Lordosis

Scoliosis

Spinal column: Intervertebral discs

• adjacent vertebral bodies from inferior to the 2nd vertebra to the sacrum

• form strong joints, permit movement of the vertebral column, absorb shock

• can compress

• avascular

• rely of blood flow of the adjacent vertebrae for oxygen, nutrients, and waste removal

• with age, the nucleus pulposus hardens and becomes less elastic

• Superior and inferior surfaces of thin layers of hyaline cartilage

Annulus fibrosus

Spinal column: Intervertebral discs;

outer ring of fibrous cartilage

Nucleus pulposus

Spinal column: Intervertebral discs;

inner soft, pulpy, highly elastic substance

Sacrum

• Composed of five “sacral vertebrae”

• Begins fusing between 16-18 years old.

• Completed by age 30.

• Serves as a strong foundation for the pelvic girdle

• The sacral canal is a continuation of the vertebral canal

• The adult female sacrum is wider and shorter than the male sacrum

Coccyx

• Four “Coccygeal vertebrae” fuse between ages 20-30

• Female coccyx points inferiorly

• Male coccyx points more anteriorly

Thorax

• Made up of the sternum, costal cartilage, ribs, and thoracic vertebrae

• Encloses and protects the organs of the thoracic and superior abdominal cavities

• Support for the bones of the upper limb

• Plays a role in breathing

Ribs

• 12 pairs of ribs

• Numbered 1-12 from superior to inferior

• Articulates with the corresponding thoracic vertebra

• First-seventh ribs have direct anterior attachment to the sternum by costal cartilage

• Eighth-tenth ribs attach indirectly to the sternum by the costal cartilage of the seventh rib

• Eleventh and twelfth ribs do not attach (floating ribs)

• Blood vessels and nerves follow the inferior aspect of the ribs

• Costal cartilage contributes to the elasticity of the thoracic cage