An Introduction to the Axial Skeleton Copyright 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Terms: Structures of Bones Articulations: Contacts with other bones Landmarks (Bone Markings; Marks): Areas of muscle and ligament attachment Foramina: Openings for nerves and blood vessels
All bones possess distinctive landmarks that are designed for specific functions, e.g. certain landmarks are used as articulating surfaces to form a joint (an articulation) with another bone on the skeleton. Examples of these include condyles, heads, and facets. A complete list of bony landmarks is shown in your activities packet pg 89 Table 7.1 In your lab activities study sheet, it is suggested that you create online study cards using Quizlet
The Axial Skeleton
The axial skeleton Has 80 bones & forms the vertical axis of the body. It can be divided into three parts: the skull, the vertebral column, & the bony thorax. The skull: 8 cranial bones & 14 facial bones Bones associated with skull: 6 auditory ossicles & hyoid bone The vertebral column: 24 vertebrae (singular = vertebra), The sacrum, & The coccyx The thoracic cage: 24 ribs & The sternum
The axial skeleton forms the vertical axis of the body
Functions of the Axial Skeleton Supports and protects organs in body cavities Attaches to muscles of: Head, neck, & trunk Respiration Appendicular skeleton
The Skull
The skull is composed of two sets of bones: 8 cranial bones: Forms the walls and floor of the cranial cavity Most of the bones are flat or slightly curved 14 facial bones: Have irregular shapes. These bones form the face & the walls of orbital and nasal cavities and provide bony sockets for the teeth.
Learning the bones of the skull can be challenging, thus you must examine it s 3-D. In addition to your drawings, note your 3-D paper skull and the ipad App. All but one of the bones of the skull are joined by interlocking joints called sutures. Only the mandible, or lower jawbone, is attached to the rest of the skull by a freely moveable joint.
The Skull Figure 7 2 Cranial and Facial Subdivisions of the Skull. Copyright 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Terminology Aids
Sinuses Cavities that decrease the weight of the skull Sutures Lined with mucous membranes Protect the entrances of the respiratory system The immovable joints of the skull The four major sutures Lambdoid suture Coronal suture Sagittal suture Squamous suture
For a suture, compare the uniting of two skull bones with fibrous connective tissue to the sewing together of two pieces of fabric with a zigzag stitch. The word suture comes from sutura, Latin for seam.
imagine the ethmoid as a capital letter T. (Make a T with your hands, as you would if signaling a time-out.)
The knuckles of the hand that form the cross bar of the T are analogous to the crista galli, which can only be viewed from inside the cranial cavity. Crista galli = rooster s comb
The term ethmoid derives from sieve-like and numerous ethmoid sinuses of the ethmoid bone. Cribriform may remind students of a corncrib.
Functions of the ethmoid Forms floor of the cranium Roof of the nasal cavity Part of the nasal septum and medial orbital wall Contains ethmoidal air cells (network of sinuses)
Three Parts of the Ethmoid The cribriform plate Roof of the nasal cavity Contains the crista galli The two lateral masses Ethmoidal labyrinth (ethmoidal air cells) The perpendicular plate Part of the nasal septum
Foramina of the Ethmoid Olfactory foramina In the cribriform plate For olfactory nerves
If the perpendicular plate of the ethmoid bone is displaced from its medial position narrowing the nasal cavity (deviated septum), the result can be chronic sinus problems
Associate the Latin adjective magnum with the word magnify to indicate that this foramen is BIG.
The parietal bones get their name because they form the wall of the cranium, just as a parietal membrane covers the wall of a body cavity.
The squamous portion of a bone refers to the flattened region, just as squamous epithelium refers to flattened cells.
Sphenoid means wedge-shaped. The sphenoid bone is wedged between the cranial and facial bones. Trace the outline of the bat with wings that the sphenoid resembles.
The pituitary gland rides protected in its sella turcica, literally, Turkish saddle.
Marks of Temporal Bones Mandibular fossa: articulates with the mandible Zygomatic process Articulates with temporal process of zygomatic bone Forms zygomatic arch (cheekbone)
Marks of Temporal Bones Mastoid process: For muscle attachment Contains mastoid air cells connected to middle ear the word mastoid (mastos), referring to a breast-like shape (recall mastectomy, removal of the breast).
Marks of the Temporal Bones Styloid (stylo = stake) process attach tendons and ligaments of the hyoid, tongue, and pharynx Auditory ossicles Three tiny bones in tympanic cavity (middle ear) Transfer sound from tympanic membrane (eardrum) to inner ear
Coronoid comes from the word corona, a crown. Imagine this process as the point in a king s crown. The word coronation is related.
The word mental pertains to the chin. Recall Rodin s The Thinker.
Functions of the hyoid bone Supports the larynx Attaches muscles of the larynx, pharynx, and tongue Articulations of the hyoid bone Connects lesser horns to styloid processes of temporal bones
The hyoid bone hides behind the mandible. Not really counted as a skull bone, located in throat.
The hyoid bone is the only bone in the body that doesn t articulate with another bone. The space between the muscular base of the tongue and the soft tissue above the thyroid cartilage (hyoid bone).
The vomer is probably the least famous skull bone. It means plowshare (from its shape).
the zygomatic process is on the zygomatic bone. Note the color coded diagram, that demonstrates that this feature also belongs to the temporal bone.
The maxilla holds the upper teeth, but it also composes much of the face, including the floor of the orbit and the roof of the mouth.
Andre the Giant (Andre Rene Roussimoff), world-renowned professional wrestler and actor, suffered from pituitary gigantism and acromegaly. Acromegaly develops in those for whom hypersecretion of growth hormone continues past epiphyseal closure. After closure, elongation of endochondral bones is over, but appositional growth of these bones and intramembranous bones continues. This leads to deformity of the face, skull, and mandible; a coarsening of facial features; and thickening of fingers and toes.
The Infant Skull
The Infant Skull Grows rapidly, Is large compared to the body It Has many ossification centers Fusion is not complete at birth
Fontanel (fountain or spring) Are areas of fibrous connective tissue (soft spots pulse can be felt, especially anterior) Cover unfused sutures in the infant skull Allows the skull to flex during birth