Textbook Notes (362,815)
Canada (158,059)
ANP1106 (77)
Chapter 7

Chapter 7 the skeleton.doc

28 Pages
Unlock Document

University of Ottawa
Anatomy and Physiology
Jacqueline Carnegie

Chapter 7: The Skeleton -there are 206 named bones in the body and account for 20% of body mass The Axial Skeleton -structure from 80 bones segregated into 3 major regions: the skull, vertebral column, and thoracic cage -the axial skeleton: 1) forms the longitudinal axis of the body 2) supports the head, neck, and trunk 3) protects the brain, spinal cord, and the organs in the thorax The Skull -the most complex bony structure in the body -formed by cranial and facial bones -cranial bones (cranium) enclose and protect the brain and furnish attachment sites for head and neck muscles -facial bones: 1) form the framework of the face 2) contain cavities for the special sense organs of sight, taste, and smell 3) provide openings for air and food passage 4) secure the teeth 5) anchor the facial muscles of expression -most skull bones are flat bones -all adult skull bones are united by interlocking joints called sutures (except the mandible) -sutures have a saw-toothed, serated appearance -the major skull sutures are the coronal, sagittal, squamous, and lambdoid sutures -the cranium can be divided into a vault and a base -cranial vault (calvaria) forms the superior, lateral, and posterior aspects of the skull as well as the forehead -cranial base (floor) forms the skull's inferior aspect -bony ridges divide the base into 3 distinct fossae; the anterior, middle, and posterior cranial fossae -the brain sits in the fossae and is enclosed by the cranial vault; the brain occupies the cranial cavity -smaller cavities in the skull include the middle and internal ear cavities, the nasal cavity, and the orbits which house the eyeballs -the skull has 85 named openings that provide passageways for the spinal cord, blood vessels serving the brain, and cranial nerves Cranium -made up of 8 cranial bones: the paired parietal and temporal bones, and the unpaired frontal, occipital, sphenoid, and ethmoid bones 1) Frontal Bone -forms the anterior cranium -articulates posteriorly with the paired parietal bones via the coronal suture -the most anterior part is the vertical squamous part (forehead) -frontal squamous regions ends inferiorly at the supraorbital margins (the thickened superior margins of the orbits that lie under the eyebrows) -the frontal bone extends posteriorly from the supraorbital margins to form the superior wall of the orbits and the anterior cranial fossa -this fossa supports the frontal lobes of the bone -each supraorbital margin is pierced by a supraorbital foramen (notch) which allows the supraorbital artery and nerve to pass to the forehead -the glabella makes up the smooth portion of the frontal bone between the orbits -nasal bones meet at the frontonasal suture which lies inferior to the glabella -the area lateral to the glabella has internal sinuses known as frontal sinuses 2) Parietal Bones and the Major Sutures -large, rectangular bones that form most of the superior and lateral aspects of the skull -they form the bulk of the cranial vault -the 4 largest sutures occur where the parietal bones articulate (form a joint) with other crania bones a) Coronal Suture -found where the parietal bones meet the frontal bone anteriorly b) Sagittal Suture -found where the parietal bones meet superiorly at the cranial midline c) Lambdoid Suture -found where the parietal bones meet the occipital bone posteriorly d) Squamous Suture -found where a parietal and temporal bone meet on the lateral aspect of the skull -one on each side 3) Occipital Bone -forms most of the skull's posterior wall and base -articulates anteriorly with the paired parietal and temporal bones via the lambdoid suture and the occipitomastoid suture respectively -joins with the sphenoid bone in the cranial floor via its basilar region which has a midline projection called the pharyngeal tubercle -internally, the occipital bone forms the walls of the posterior cranial fossa which supports the cerebellum -the foramen magnum is found at the base of the occipital bone and allows the inferior part of the brain to connect with the spinal cord -foramen magnum surrounded by 2 occipital condyles which articulate with the first vertebra of the spinal column -occipital condyles and its articulation allows for the "yes" nodding motion -the hypoglossal canal is hidden medially and superiorly to each occipital condyle -the external occipital protuberance is a median protrusion that is superior to the foramen magnum -this is the knoblike projection just below the bulging part of the posterior skill 4) Temporal bones -there are 2 temporal bones -found on the lateral skull surface on each side -inferior to the parietal bones and meet them at the squamous sutures -form the inferolateral aspects of the skull and parts of the cranial floor -has 4 major areas: a) Squamous Region -abuts the squamous sutures -has a barlike zygomatic process that meets the zygomatic bone of the face anteriorly -the zygomatic process and the zygomatic bone meet to form the zygomatic arch -these are the projects on your cheek -small, oval mandibular fossa on the interior surface of the zygomatic process receives the condyle of the mandible, forming the freely movable temporamandibular joint b) Tympanic Region -surrounds the external acoustic meatus (external ear canal) where sound enters the ear -the external acoustic meatus and the eardrum at its deep end are part of the external ear -the styloid process is the attachment point for tongue and neck muscles and for a ligament that secures the hyoid bone of the neck to the skull c) Mastoid Region -contains the mastoid process which acts as an anchoring site for some neck muscles -this is felt as the lump posterior to the ear -full of air cavities (mastoid sinuses / mastoid air cells) -the stylomastoid foramen found between the styloid and mastoid processes allow the facial nerve to leave the skull d) Petrous Region -contributes to the cranial base -found between the occipital bone posteriorly and the sphenoid bone anteriorly -the sphenoid bone and the petrous portions make up the middle cranial fossa which support the temporal lobes of the brain -the middle and internal ear cavities are found in the petrous region and contain sensory receptors for hearing and balance -the jugular foramen (at the junction of the occipital petrous temporal bones), 3 cranial nerves, the carotid canal (anterior to the jugular foramen; transmits the internal carotid artery into the cranial cavity), the foramen lacerum (between the petrous temporal bone and the sphenoid bone), and the internal acoustic meatus (superolateral to the jugular foramen) all penetrate the bone of the petrous region 5) Sphenoid Bone -bat shaped -spans the width of the middle cranial fossa -forms the central wedge that articulates with all other cranial bones -consists of a central body and 3 pairs of processes: 1) the greater wings 2) the lesser wings 3) pterygoid processes -the paired sphenoid sinuses are found within the body of the sphenoid -the superior surface of the body resembles a saddle -the greater wings project laterally from the sphenoid body forming parts of: 1) the middle cranial fossa 2) the dorsal walls of the orbits 3) the external wall of the skull -the lesser wings form part of the floor of the anterior cranial fossa and part of the medial walls of the orbits -the pterygoid process projects inferiorly from the junction of the body and greater wings -they anchor pterygoid muscles which are used for chewing -the optic canals allow the optic nerves to pass to the eyes -there are 4 crescent-shaped openings on each side of the sphenoid body -the anteriormost is the superior orbital fissure which is a long slit between the greater and lesser wings -the superior orbital fissure allows cranial nerves that control eye movements to enter the orbit -foramen rotundum and foramen ovale provide passageways for branches of cranial nerves (maxillary and mandibular nerves) to reach the face -the foramen rotundum is in the medial part of the greater wing and is oval -the foramen ovale is large and oval and is posterior to the foramen rotundum -the foramen spinosum is posterlateral to the foramen ovale; this transmits the middle meningeal artery which serves the internal faces of some cranial bones 6) Ethmoid Bone -lies between the sphenoid and nasal bone of the face -most deeply situated bone of the skull -forms most of the bony area between the nasal cavity and the skull -superior surface formed by the paired horizontal cribriform plates -helps form the roof of the nasal cavities and the floor of the anterior cranial fossa -punctured by tiny holes called olfactory foramina which allow olfactory nerves to pass -the crista galli (rooster's comb) is a triangular process projecting superiorly between the cribriform plates -the dura mater (outer covering of the brain) attaches to the crista galli and helps secure the brain in the cranial cavity -the perpendicular plate projects inferiorly in the median of the plane and forms the superior part of the nasal septum which divides the nasal cavity into right and left halves -a lateral mass on each side of the perpendicular plate is riddled with ethmoid sinuses or ethmoid air cells -the superior and middle nasal conchae extend medially from the lateral masses -the lateral surfaces of the ethmoid's lateral masses are called orbital plates -they contribute to the medial walls of the orbits Sutural bones -tiny, irregular shaped bones or bone clusters that occur within sutures -most often found in the lambdoid suture -not structurally significant -not constant in all skulls Facial Bones -made up of 14 bones -only the mandible and vomer are unpaired -facial skeleton of men is more elongated than women 1) Mandible -U-shaped -lower jawbone -largest and strongest bone in the face -the body forms the chin -2 upright rami (branches) meet the body posteriorly at a mandibular angle -the mandibular notch separates 2 processes (the coronoid processes) from the superior margin of each ramus -the coronoid process is an insertion point for the large temporalis muscle which elevates the lower jaw during chewing -the mandibular condyle lies posterior to the coronoid process and articulates with the mandibular fossa of the temporal bone to form the temporomandublar joint on the same side -the mandibular body anchors the lower teeth -the alveolar margin makes up the superior border of the mandibular body and contains the sockets / alveoli where teeth are embedded -the mandibular symphysis is a slight depression midline of the mandibular body which indicates where the 2 mandibular bones fused during infancy -there is one mandibular foramen on each medial surface of the ramus which permits the nerves responsible for tooth sensation to pass to the teeth in the lower jaw -site of lidocaine injection -the mental foramina are openings on the lateral aspects of the mandibular body which allow blood vessels and nerves to pass to the skin of the chin and lower lip -"ment" = chin 2) Maxillary Bones -maxillary bones (maxillae) are fused medially -form up upper jaw and central position of the facial skeleton -all facial bones articulate with the maxilla (except for the mandible) -carry the upper teeth in their alveolar margins -the maxillae meet medially and inferior to the nose to form the anterior nasal spine -the palatine processes of the maxillae project posteriorly from the alveolar margins and fuse medially at the intermaxillary suture to form the anterior two-thirds of the hard palate -posterior to the teeth is a midline foramen called the incisive fossa which is a passageway for blood vessels and nerves -frontal processes extend superiorly to the frontal bone to form the lateral aspects of the bridge of the nose -the regions that flank the nasal cavity laterally contain the maxillary sinuses (largest paranasal sinus) -the maxillae articulate with the zygomatic bones via the zygomatic processes -the inferior orbital fissure is located deep within the orbit at the junction of the maxilla with the greater wing of the sphenoid -this allows the zygomatic nerve, the maxillary nerve, and blood vessels to pass to the face -the infraorbital foramen lies below the eye socket on each side and allows the infraorbital nerve and artery to reach the face 3) Zygomatic Bones -irregularly shaped -articulate with the zygomatic processes of the temporal bones posteriorly, the zygomatic processes of the frontal bone superiorly, and the zygomatic processes of the maxillae anteriorly -form the prominences of the cheek bones and part of the inferolateral margins of the orbits 4) Nasal Bones -thin and rectangular -fused medially -form the bridge of the nose -articulate with the frontal bone superiorly, maxillary bones laterally, and the perpendicular plate of the ethmoid bone posteriorly -inferiorly attach to the cartilages that form the skeleton of the external nose 5) Lacrimal Bones -finger-nail shaped -contribute to the medial walls of each orbit -articulate with the frontal bone superiorly, ethmoid bone posteriorly, and the maxillae anteriorly -each bone contains a deep groove that helps form the lacrimal fossa -houses the lacrimal sac which is part of the passageway that allows tears to drain from the eye surface into the nasal cavity 6) Palatine Bones -L-shaped -made from 2 bony plates (horizontal and perpendicular bony plates) -has 3 articular processes: 1) pyramidal articular process 2) sphenoidal articular process 3) orbital articular process -horizontal plates complete the posterior portion of the hard palate -perpendicular (vertical) plates form part of the posterlateral walls of the nasal cavity and a small part of the orbits 7) Vomer -plow-shaped -lies in the nasal cavity -forms part of the nasal septum 8) Inferior Nasal Conchae -paired -thin, curved bones in the nasal cavity -project medially from the lateral walls of the nasal cavity, inferior to the middle nasal conchae of the ethmoid bone -largest part of the 3 pairs of conchae -form part of the lateral walls of the nasal conchae (as with the other conchae) Hyoid Bone -inferior to the mandible in the anterior neck -only bone of the body that does not articulate directly with any other bone -anchored by the narrow stylohyoid ligaments to the styloid processes of the temoral bones -consists of a body and 2 pairs of horns which are attachment points for neck muscles which raise and lower the larynx during swallowing and speech -acts as a moveable base for the tongue The Orbits -cone-shaped -bone cavities in which the eyes are encased and cushioned -the walls of the orbit are formed by parts of seven bones (i.e.: frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal and ethmoid bones) Nasal Cavity -made up of bone and hyaline cartilage -roof of the nasal cavity formed by the cribriform plates of the ethmoid bone -lateral walls shaped by the superior and middle conchae of the ethmoid bone, perpendicular plates of the palatine bone, and the inferior nasal conchae -depressions on the conchae are known as meatuses (i.e.: superior, middle, and inferior meatus) -floor of nasal cavity is formed by the paltien processes of the maxillae and the palatine bones -nasal cavity is divided into right and left parts by the nasal septum -bony portion of the septum is formed by the comer inferiorly and the perpendicular plate of the ethmoid bone superiorly -septal cartilage completes the septum anteriorly -mucous in nasal septum and chonchae moisten and warms enering air and cleanses debris -conchae increases the turbulence of air and forces more air into contact with mucosa Paranasal Sinuses -mucosa lined -air filled -cluster around the nasal cavity -found in 5 skull bones (i.e.: frontal, sphenoid, ethmoid, and paired maxillary bones) -small openings connect the sinuses to the nasal cavity -air enters the sinuses from the nasal cavity -mucus formed by the sinus mucosae drains into the nasal cavity -sinuses help lighten the skull and enhance the resonance of the voice The Vertebral Column -known as the spine or spinal column -made up of 26 irregular bones -serves as the axial support of the trunk -extends from the skull to the pelvis -surrounds and protects the spinal cord -provides attachment for the ribs -in the fetus, the column consists of 33 separate bones or vertebrae -inferiorly, 9 separate bones will fuse to form 2 composite bones; the sacrum and the coccyx -the 24 remaining bones remain as individual vertebrae separated by intervertebral discs Regions and Curvatures -about 70 cm long -has 5 major regions -7 vertebrae of the neck make up the cervical vertebrae -the next 12 vertebrae make up the thoracic vertebrae -the 5 vertebrae supporting the lower back are the lumbar vertebrae -remember the common meal times (7 am, 12 pm, 5 pm) -vertebrae become progressively larger from the cervical to the lumbar region; they must support greater weight as it goes down -the sacrum is inferior to the lumbar vertebrae -articulates with the hip bones of the pelvis -convex -5 fused vertebrae -the end up of vertebral column is the coccyx -4 fused vertebrae -vertebrae has an S (sinusoid) shape in the lateral view -the cervical and lumbar curvatures are concave posteriorly -the thoracic and sacral curvatures are convex posteriorly -curvature increases resilience and flexibility Ligaments -ligaments support the vertebral column -strap-like -anterior and posterior longitudinal ligaments are the major supporting ligaments -run as continuous bands down the front and back surfaces of the vertebrae from the neck to the sacrum -broad anterior ligament is strongly attached to both the bony vertebrae and the discs -ligaments prevent hyperextension of the spine -posterior ligament is narrow and weaker than the anterior ligaments and attaches only to the discs; it helps resist hyperflexion (bending too far forward) -ligamentum flavum connects adjacent vertebrae -contains elastic connective tissue and is strong -stretches when we bend forward and recoils when we become erect Intervertebral Discs -a cushionlike pad composed of 2 parts: -an inner gelatinous nucleus pulposus that gives the disc its elasticity and compressibility -the anulus fibrosus which surrounds the nucleus pulpous; acts as a strong collar composed of collagen fibres superficially and fibrocartilage internally -limits expansion of the nucleus pulposus when the spine is compressed -binds successive vertebrae together -withstands twisting forces -resists tension in the spine -intervertebral discs act as shock absorbers during vertical movement -allows the spine to flex and extend -at compression points, discs flatten and bulge out between the vertebrae -discs are thickest in the lumbar and cervical regions; this enhances flexibility in the regions -intervertebral discs account for 25% of the height of the vertebral column -herniated (prolapsed) discs involve the rupture of the anulus fibrosus and the protrusion of the spongy nucleus pulposus through the anulus -the protrusion may press on the spinal cord or on spinal nerves exiting from the cord, resulting in numbness or pain Structure of Vertebrae -every vertebrae consists of a body (centrum) anteriorly and a vertebral arch posteriorly -the body is disc-shaped and is weight-bearing -the body and vertebra arch enclose an opening called the vertebral foramen -successive vertebral foramina of connected / articulated vertebrae form the vertebral canal which the spinal cord passes -the vertebral arch is formed by 2 pedicles and 2 laminae -the pedicles are short, bony pillars that project posteriorly from the vertebral body and form the sides of the arch -pedicles have notches on their superior and inferior borders, providing lateral openings between adjacent vertebrae (intervertebral foramina) -the spinal nerves from the spinal cord pass through the intervertebral foramina -the laminae are flattened plates that fuse in the median plane and complete the arch posteriorly -7 processes project from the vertebral arch: 1) Spinous Process -not paired -median posterior projection arising from the junction between the 2 laminae -site of muscle attachment that move the vertebral column and for ligaments that stabilize the vertebral column 2) Transverse Process -paired -extends laterally from each side of the vertebral arch -site of muscle attachment that move the vertebral column and for ligaments that stabilize the vertebral column 3) Superior and Inferior Articular Process -both sets are paired -protrude superiorly and inferiorly from the pedicle-lamina junctions, respectively -facets are smooth joint surfaces of the articular processes; covered in hyaline cartilage -inferior articular processes of each vertebra form movable joints with the superior articular processes of the vertebra below -successive vertebrae join at their bodies and at their articular processes Cervical Vertebrae -7 cervical vertebrae (C1-C7) -smallest and lightest vertebrae -C3-C7 represent the typical cervical vertebrae: -the body is oval; wider from side to side than in the anterposterior dimension -except for C7, the spinous process is short, projects directly up, and is bifid (split at the tip) -the vertebral foramen is large and triangular -each transverse process contains a transverse foramen where the vertebral arteries pass to service the brain -at C7, the spinous process is not bifid and is larger than the other cervical vertebrae -palpable (obvious) through the skin -used as a landmark; known as vertebra prominens -C1 and C2 have no intervertebral disc between them; they are highly modified and reflect their special function Atlas (C1) -has no body and no spinous process -is a ring of bone consisting of anterior and posterior arches and a lateral mass on each side -each lateral mass has articular facets on both its superior and interior surfaces -suprior articular facets receive the occipital condyles of the skull and carry the skull -allows the "yes" head nodding movement -inferior articular facets form joints with the axis (C2) below it Axis (C2) -has a body and other typical vertebral processes -not as specialed as the atlas -has a knoblike dens projecting superiorly from its body -fuses with the axis during embryonic development -acts as a pivot for the rotation of the atlas -allows for the "no" rotational / side to side head movement Thoracic Vertebrae -12 thoracic vertebrae (T1-T12) -articulate with the ribs -increase in size from the first to the last -unique characteristics include: -body is heart shaped -has 2 small facets (demifacets) on each side and 1 at the superior edge (superior costal facet) and another at the inferior edge (inferior costal facet) -demifacets receive the heads of the ribs -T10 - T12 have only 1 facet to receive
More Less

Related notes for ANP1106

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.