Class notes

Chapter 7 - Axial Skeleton

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HLSC 120 - Anatomy (HLSC120)

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University Of Alberta (UofA)

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HLSC 120 – Human Anatomy
Chapter 7: Axial Skeleton

▪ There are 206 bones in an adult skeleton Nasal septum – thin ridge of bone that subdivides the nasal cavity into left and right
Skeletal system is divided into 2 parts: halves
Axial skeleton – composed of bones along the central axis of the body (3 regions: Inferior nasal conchae – found along the lateral walls of the nasal cavity; 2 scroll-
skull, vertebral column, thoracic cage); create a framework that supports and shaped bones
protects the organs; houses special sense organs; provides areas for the attachment SUPERIOR VIEW – shows 4 of the cranial bones
of skeletal muscles Coronal suture – articulation b/w the frontal and the parietal bones
Hemopoietic tissue – found in spongy bone of most axial skeleton; Sagittal suture – connects the left and right parietal bones almost exactly in the
responsible for blood cell formation midline of the skull
Appendicular skeleton – consists of bones of the appendages (upper and lower Parietal foramen (single) / foramina (paired) – found along the posterior one-third
limbs, as well as the bones that hold the limbs to the trunk of the body) of the saggital suture; conducts tiny emissary veins from the veins of the brain to
SKULL the veins of the scalp; number can vary b/w individuals
composed of both cranial and facial bones Lambdoid suture – its superior part represents the articulation of the occipiral bone
Cranial bones – form the rounded cranium w/ both parietal bones
cranium – completely surrounds and encloses the brain; made up of 8 POSTERIOR VIEW – shows the occipital bone, lambdoid structure, and portions of
bones (unpaired ethmoid, frontal, occipital, sphenoid bones, paired parietal and temporal bones
parietal and temporal bones) w/c provide attachment sites for several jaw, External occipital protuberance – bump on the back of the head; males have a
head, and neck muscles prominent, pointed one while females have a more subtle, rounded one
Facial bones – form the face; protect the entrances to the digestive and respiratory Sutural (wormian) bone – found within the lambdoid suture
systems; provide attachment sites for facial muscles LATERAL VIEW – shows 1 parietal bone, 1 temporal bone, 1 zygomatic bone, 1
Cranial cavity – encloses, cushions, and supports the brain maxilla, frontal bone, mandible, and portions of the occipital bone
ANTERIOR VIEW – shows the major bones of the skull Lacrimal bone – articulates w/ the nasal bone anteriorly and w/ the ethmoid bone
Frontal bone – forms the forehead posteriorly
Orbital cavity – eye sockets; Sphenoid bone- articulates w/ the frontal, parietal, and temporal bones
Superior and Inferior orbital fissure - 2 large openings Pterion – region that represents the H-shaped set of sutures of these 4 articulating
Superciliary arches – brow ridges; superior to the orbits bones
Nasal bones – left and right; form the bony bridge of the nose Zygomatic bone – cheekbone; forms the zygomatic arch
Glabella – superior to the nasal bones, found b/w the orbits Zygomatic arch – bones posterior to your ears; terminates superior to the point
Maxillae – left and right fuse to form most of the upper jaw and the lateral where the mandible articulates w/ the mandibular fossa of the temporal bone
boundaries of the nasal cavity; help form the floor of each orbit Mastoid process – posterior to the external auditory canal; the bump you feel
Infraorbital foramen – inferior to each orbit, within each maxilla; conducts blood posterior and inferior to your external ear opening
vessels and nerves to the face SAGGITAL VIEW – reveals bones that form the nasal cavity and the endocranium;
Mandible –forms the lower jaw shows bones that form the nasal septum more clearly
Mental protuberance – prominent chin of the mandible Frontal sinus – space in the frontal bone
Anterior nasal spine – found on the inferior border Sphenoidal sinus – open space in the sphenoid bone

,Perpendicular plate – forms the superior portion of the nasal septum Occipitomastoid suture – connects the occipital bone w/ the portion of the
Vomer – forms the inferior portion temporal bone that houses the mastoid process
Ethmoid bone – serves as a “wall” b/w the anterior floor of the cranial cavity and Coronal suture – extends across the superior surface of the skull along a coronal or
the roof of the nasal cavity frontal plane; represents the articulation b/w the anterior frontal bone and the
Maxillae and palatine bones – form the hard palate; acts as both the floor of the more posterior frontal bone
nasal cavity and part of the roof of the mouth Lamdboid suture – extends like an arc across the posterior surface of the skull,
INFERIOR (BASAL) VIEW - shows that the skull is a bit complex bec of its foramina articulating w/ the parietal bones and the occipital bone; named for the Greek
and weird-shaped bone features letter lambda, w/c its shape resembles (λ)
Hard palate – most anterior structure Saggital suture – extends b/w the superior midlines of the coronal and the lambdoid
Pterygoid processes of the sphenoid bone – found on either side of the palate sutures; in the midline of the cranium (along the midsaggital plane) and articulates
Internal nares – adjacent to these openings; internal openings of the nasal cavity the right and left parietal bones
Foramina – found b/w the mandibular fossa and pterygoid processes Squamosal suture – found on each side of the skull; articulates the temporal bone
Foramen ovale – closest to the pterygoid processes and the parietal bone of that side; squamous part of the temporal bone typically
Foramen spinosum – lateral to the pterygoid processes overlaps the parietal bone
Jugular foramen – posterior and lateral to these foramina; space b/w the temporal Sutural bones – wormian bones; small; ranging in size from a tiny pebble to a
and the occipital bones; anteromedial to this is the entrance to the carotid canal quarter but can also be larger; any suture may have sutural bones but are most
Foramen lacerum – extends b/w the occipital and temporal bones; this opening is common in lambdoid suture; represent independent bone ossification centers
closed off by connective tissue in a living individual BONES OF THE CRANIUM (8 bones)
Foramen magnum – largest foramen of all; means big hole; through this opening, form a rigid protective structure for the brain
spinal cord enters the cranial cavity and becomes continuous with the brain stem; CRANIUM – consists of a roof and a base
on either side are the rounded occipital condyles Calvaria – skullcap; roof of the cranium; composed of the squamous part of
INTERNAL VIEW OF CRANIAL BASE – reveals the following: the frontal bone, the parietal bones , squamous part of the occipital bone
Frontal bone – most anteriorly located bone Base – composed of portions of the ethmoid, sphenoid, occipital, temporal
Cribriform plate of the ethmoid bone – surrounded by the frtonal bone Cranial Bones – form as a result of the fusion of separate ossification
Lesser & greater wings of the sphenoid – found posterior to the frontal bone centers, an event that may not occur until after birth
Temporal bones – form the lateral regions of the cranial base FRONTAL BONES – form part of the calvaria, the forehead, roof of the orbits;
Occipital bone – form the posterior aspect formed from 2 major separate ossification centers; orbital surface is relatively
SUTURES smooth
immovable fibrous joints that form the boundaries b/w the cranial bones; dense ▪ Metopic suture – unites the left and right sides of the developing frontal bone;
regular connective tissue seals cranial bones firmly together at a suture; different this suture usually fuses and disappears by age 2
types of sutures are distinguished by the margins b/w the bones, w/c often have ▪ Frontal squama – vertical flattened region of the frontal bone; ends at the
intricate interlocking forms, like puzzle pieces, and form a strong union, or supraorbital margins
articulation; typically disappear as the adjoining bones fuse ▪ Superciliary arches – superior to the supraorbital margins; brow ridges; male
Endocranially – when fusion of bones starts internally skulls have more pronounced arches than female skulls
Ectocranially – fusion of the skull’s external surface ▪ Supraorbital foramen / notch – found at the midpoint of each supraorbital
Osteologists can estimate the approximate age at death of an individual skull by margin
examining the extent of suture closure. ▪ Glabella – smooth part of the frontal bone sandwiched b/w the superciliary
arches

, ▪ Frontal sinuses – found within the frontal bone; start to appear after age 6 and o Stylomastoid foramen- lies b/w the mastoid process and the styloid
develops fully at age 10 process; facial nerve extends through here to innervate the facial
▪ Frontal crest – found on the internal surface of the frontal bone; a midline muscles
elevation of bone; serves as a point of attachment for the falx cerebri o Carotid canal – medial to the styloid process; transmits the internal
▪ Falx cerebri – protective connective tissue sheet that helps support the brain carotid artery
PARIETAL BONES – form the lateral walls and roof of the cranium; its internal ▪ Squamous region – lateral flat surface of the temporal bone immediately
surfaces exhibit many grooves that accommodate some of the blood vessels w/n inferior to the squamosal suture
the cranium; each parietal bone is bordered by 4 sutures that unite it to the o Zygomatic process – inferior to the squama; curves laterally and
neighboring bones anteriorly to unite w/ the temporal process of the zygomatic bone;
▪ Parietal foramen – occurs in the posterior 1/3 of the parietal bone, adjacent to this union forms the zygomatic arch
the saggital suture; a tiny emissary vein travels through this opening, o Mandibular fossa – a depression where each temporal bone
connecting the venous sinuses w/ the veins of the scalp articulates w/ the mandible inferior to the base of both zygomatic
▪ Superior & inferior temporal lines – found on the lateral surface; a pair of faint processes
ridges exhibited on each parietal bone; arc cross the surface of the parietal and o Articular tubercle – a bump anterior to the mandibular fossa
frontal bones; mark the attachment site of the large, fan-shaped temporalis o Tympanic region – immediately posteriolateral to the mandibular
muscle that closes the mouth fossa; small bony ring surrounding the entrance to the external
▪ Parietal eminence – superior to the temporal lines; rounded, smooth parietal auditory canal
surface OCCIPITAL BONES – its concave internal surface closely follows the
TEMPORAL BONES – form the inferior lateral walls and part of the floor of the contours of the brainsubdivided into:
cranium; each temporal bone is composed of 3 regions: ▪ Squamous region – forms the posterior region of the skull
▪ Petrous region – means rock; thick region; houses sensory structures of the ▪ Basilar region – forms part of the base of the cranium
inner ear that provide info about hearing and balance o Foramen magnum – large, circular opening
o Internal auditory canal – also called auditory meatus or acoustic o Occipital condyles – found lateral to this foramen; smooth
meatus; provides a passageway for nerves and blood vessels to the knobs; where the skull articulates w/ the first cervical
inner ear vertebra (i.e. when you nod yes, you are moving the occipital
o Groove for the sigmoid sinus – runs along the inferior surface of the condyles against the vertebra)
petrous region o Hypoglossal canal – found at the anteromedial edge of each
o Sigmoid sinus - venous sinus (vein) that drains blood from the brain condyle; where the hypoglossal nerve extends to supply
o Mastoid process – prominent bulge on the inferior surface of the tongue muscles
temporal bone; anchoring site for muscles that flex or rotate the head; o Condylar canal – found posterior to each occipital condyle;
filled w/ many small, interconnected air cells that communicate w/ the transmits a vein
middle ear ▪ Prominent ridges that appear on the external surface of the occipital
o Mastoid foramen – found on the inferior surface of the temporal bone:
bone; opens near the mastoid process; tiny emissary veins travel o External occipital crest – projects in a posterior direction from
through this foramen to connect the venous sinuses inside the the foramen magnum, ending in the external occipital
cranium w/ the veins on the scalp protuberance
o Styloid process – serves as an attachment site for several hyoid and
tongue muscles

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