Axial Skeletom (pt.1)

introduction & cranial bones

Skeletal System: Functions

• creates a framework for our body

• supports weight

• esential for movement (supports structures and attachments for muscles/tendons)

• protection of soft tissues/organs

Musculoskeletal System: made up of

bones, joints, muscles

Orthopedics

branch of medical science dealing with prevention and correction of disorders of the musculoskeletal system

Axial Skeleton

• longitudinal axis of the body

• ~80 bones

  • Skull

  • Auditory ossicles

  • Hyoid bone

  • Vertebral column (vertebrae, sacrum)

  • Thorax (ribs, sternum)

Appendic-

-to hang on to

Appendicular Skeleton

• ~126 bones

  • Pectoral girdle

  • Upper extremities

  • Pelvic girdle

  • Lower extremities

Long bones

bones that are longer than they are wide; consists of a shaft and two ends (epiphysis)

ex: humerus

Short bones

cube-shaped bones roughly equal in length and width

ex: trapezoid, wrist bone

Flat bones

thin, flattened, and typically slightly curved bones

ex: sternum

Irregular bones

bones with complex shapes that do not fit into other categories

ex: vertebrae

Sesamoid bones

small, round bones embedded within tendon

ex: patella

Sutural bones

tiny, irregularly shaped bones found within the sutures of cranial bones

Skull: Cranial Cavity Bones

• 8 bones form the cranial cavity

  • Frontal (single)

  • 2 Parietal (paired)

  • 2 Temporal (paired)

  • Occipital (single)

  • Sphenoid (single)

  • Ethmoid (single)

• floor of cavity = cranial base

Skull: Facial Bones

bones that surround the mouth, nose, nasal cavity, most of the orbits

14 facial bones

• 2 Nasal (paired)

• 2 Maxillae (paired)

• 2 zygomatic bones (paired)

• Mandible (single)

• 2 Lacrimal bones (paired)

• 2 Palatine bones (paired)

• 2 Inferior nasal concha (paired)

• Vomer (single)

Cranial cavity - Skull

houses the brain

Nasal cavity

large, air-filled space above and behind the nose that warms, moistens, and filters inhaled air

Orbits

the bony cavities in the skull that house and protect the eyes and their associated structures

Paranasal cavities

sinuses — frontal, maxillary, sphenoid, ethmoid

Middle-ear cavities

located within temporal bones that house auditory ossicles that function in hearing

Inner-ear cavities

located within temporal bones that house structures for sensing sound and equilibrium

Cranial cavity - Bones

• movable bones of the skull

  • auditory ossicles

  • mandible

• all other bones are fixed (joints = sutures)

• skull = many surface markings

Functions - Skull

• protect and stabilize the brain

• stabilize blood vessels, lymphatic vessels, nerves, etc

• attachment point for muscles

Meninges

membrane that lines the inner surface of the cranial cavity

Where do meninges attach?

attach above structures as they enter the cranial cavity and stabilize them

Purpose of outer surface of cranium and facial bones:

serve as attachment points for muscle for movement of the head, mastication, and for facial expression

What do cranial and facial bones protect?

special sense organs

ex: vision, taste, smell, hearing, equilibrium

Frontal bone

• anterior portion of skull

• anterior portion of cranial base

• Supraorbital foramen/notch

Supraorbital foramen/notch

Frontal bone;

supraorbital nerve and blood vessels run within the foramen/notch

Parietal bones

• two

• forms the majority of the roof and sides of the cranial cavity

Temporal bone

forms in inferior/lateral cranium and cranial base

• Zygomatic arch

• Madibular fossa

• Ear structures

• Internal acoustic meatus

• Styloid process

• Stylomastoid foramen

• Carotid canal

• Jugular foramen

Zygomatic arch

Temporal bone;

formed partly by the temporal bone

Mandibular fossa

Temporal bone;

forms the superior component of the temporomandibular joint (TMJ)

Ear structures

Temporal bone;

houses middle and internal ear (hearing/equilibrium)

contains external acoustic meatus (ear canal)

Internal acoustic meatus

Temporal bone;

passageway for CN VII (facial) and CN VIII (vestibulocochlear) nerves

Styloid process

Temporal bone;

muscle attachment site for tongue and neck

Stylomastoid foramen

Temporal bone;

passageway for CN VII and stylomastoid blood vessels

Carotid canal

Temporal bone;

passageway for the internal carotid artery

Jugular foramen

Temporal bone;

forms the anterior aspect

passageway for the jugular vein

Occipital bone

posterior cranial cavity and large portion of the cranial base

• Foramen magnum

• Occipital condyles

• Hypoglossal canal

• Posterior external portion

Foramen magnum

Occipital bone;

passageway for medulla/spinal cord transition, vertebral/spinal arteries, and CN XI

Occipital condyles

Occipital bone;

articulate with C1 (atlas) to form the atlanto-occipital joint (allows nodding)

Hypoglossal canal

Occipital bone;

passageway for CN XII

Posterior external portion

Occipital bone;

attachment site for neck ligaments and muscles

Sphenoid bone

bat and butterfly-shaped; centrally located in the cranial base

forms part of the orbital cavity wall; articulates with/holds together all other cranial base bones

• Sphenoid sinus

• Sella turcica/superior aspect

• Pterygoid processes/inferior

• Optic canal

• Superior orbital fissure

• Foramen rotundum

• Foramen ovale

• Foramen spinosum

• Foramen lacerum

Sphenoid sinus

Sphenoid bone;

located in the middle portion of the bone

Sella turcica/superior aspect

Sphenoid bone;

houses the pituitary gland

Pterygoid processes/inferior aspect

Sphenoid bone;

muscle attachment sites for the mandible

Optic canal

Sphenoid bone;

passageway for CN II (optic nerve) and optic blood vessels into the orbit

Superior orbital fissure

Sphenoid bone;

passageway for blood vessels and multiple cranial nerves

Foramen rotundum

Sphenoid bone;

passageway for the maxillary branch of CN V (trigeminal nerve)

Foramen ovale

Sphenoid bone;

passageway for the mandibular branch of CN V and blood vessels

Foramen spinosum

Sphenoid bone;

passageway for blood vessels

Foramen lacerum

Sphenoid bone;

passageway for the ascending pharyngeal artery

Ethmoid bone

delicate, sponge-like bone

forms anterior cranial base, medial orbital walls, superior nasal cavity sidewalls, and superior nasal septum

• Ethmoid labyrinth (air cells)

• Superior & middle nasal conchae (turbinates)

• Cribriform plate

• Cribriform foramina

• Crista galli

• Perpendicular plate

Ethmoid labyrinth

Ethmoid bone;

function as paranasal sinuses

Superior & middle nasal conchae (turbinates)

Ethmoid bone;

swirl inhaled air to trap foreign particles in mucus and warm/moisten the air

the superior concha also increases surface area for olfactory/smell nerve endings

Cribiform plate

Ethmoid bone;

forms the roof of the nasal cavity and the anterior cranial base

Cribriform foramina

Ethmoid bone;

multiple openings within the cribiform plate for olfactory nerves (CN I) to pass through

Crista galli

Ethmoid bone;

attachment point for the falx cerebri (meningeal membrane that separates the two brain hemispheres)

Perpendicular plate

Ethmoid bone;

forms the superior portion of the nasal septum