Human Osteology

Focuses on the bones of the cranium, face, ribcage, vertebral column and the teeth.

supraorbital notch or foramen (frontal bone)

located on the medial half of the superior orbital rim

temporal lines (frontal bone)

found on the lateral ectocranial surface

frontal sinuses (frontal bone)

located anteriorly and occasionally penetrate the orbital plates

frontal eminences (frontal bone)

prominent bumps on ectocranial surface, superior to orbits

sagittal sulcus (frontal bone)

prominent vertical groove that runs down midline of endocranial surface

frontal crest (frontal bone)

midline crest that merges with anterior end of sagittal sulcus

foramen caecum

foramen of varying size, found endocranially at the base of frontal crest

parietal eminence (parietal bones)

large, rounded bump centered on ectocranial surface of parietal

parietal foramen (parietal bones)

located superiorly, close to sagittal suture

sagittal sulcus (parietal bones)

found endocranially where left and right parietals articulate and is a posterior continuation from sagittal sulcus of frontal

sigmoid sulcus (parietal bones)

crosses the mastoid angle and cuts a groove on endocranial surface

arachnoid fovae (parietal bones)

concentrated endocranially along anterior extent of sagittal edge of each parietal

meningeal grooves (parietal bones)

dominate the endocranial surface of parietal

siding the parietal bones?

thickest corners are mastoid and occipital angles, meningeal grooves orient vertically along coronal suture and more horizontally near squamosal suture

basilar part (occipital bone)

thick square projection anterior to foramen magnum

superior nuchal lines (occipital bone)

lie to either side of midline on ectocranial surface

inferior nuchal lines (occipital bone)

parallel the superior lines but lie lower on ectocranial surface

external occipital crest (occipital bone)

highly variable median line that runs along ectocranial surface

external occipital protuberance (occipital bone)

lies on ectocranial midline, highly variable appearance but more prominent in biological males

condylar fossa (occipital bone)

ectocranial depressions immediately posterior to the condyles

occipital condyles (occipital bone)

raised oval structures on either side of foramen magnum

hypoglossal canals (occipital bone)

tunnels through anterior part of the base of each condyle

jugular processes (occipital bone)

laterally directed corners placed lateral to the occipital condyles

internal occipital protuberance (occipital bone)

lies at the center of the cross-like shape endocranially

groove for the transverse sinus (occipital bone)

transverse arms of cross-like shape endocranially

internal occipital crest (occipital bone)

inferior crest originating from internal occipital protuberance

petrous pyramid (temporal bones)

massive dense bony portion that dominates endocranial surface of the bone

mastoid process (temporal bones)

inferior projection of temporal bone, bears roughened external surface for muscle attachment

articular eminence (temporal bones)

bump located on inferior border of zygomatic process near where it connects to the squamous portion of the temporal

mandibular fossa (temporal bones)

lies posterosuperior to the articular eminence

postglenoid process (temporal bones)

projection found just anterosuperior to the external auditory meatus, found between tympanic part and mandibular fossa

carotid canal (temporal bones)

large circular canal located medially to styloid process and anterior to jugular fossa

jugular fossa (temporal bones)

deep fossa located just medial to the base of the styloid process

how to side temporal bones?

petrous pyramid tapers anteromedially, mastoid process angles anteriorly, articular eminence is posterior, zygomatic process stretches anteriorly

describe the auditory ossicles

malleus is hammer shaped, incus is anvil shaped and stapes is stirrup shaped. Malleus is most lateral, incus is in the middle and the stapes is the most medial

orbital surface (sphenoid bone)

found on greater wings, form the lateral walls of each orbit and are smooth and flat

optic canal (sphenoid bone)

paired openings that pass anterioinferiorly to lesser wings; medial and superior to superior orbital fissure

superior orbital fissure (sphenoid bone)

open spaces between the inferior surfaces of lesser wings and anterior surface of greater wings

lateral pterygoid plate (sphenoid bone)

thin lateral plate of bone seen in lateral view of cranium

medial pterygoid plate (sphenoid bone)

roughly parallels the lateral plate and is set closer to the midline

pterygoid hamulus (sphenoid bone)

hook-like process forming the posterolateral bottom corners of each medial pterygoid plate

foramen rotundum (sphenoid bone)

round foramen situated medially, visible from posterior view, found at junction between greater wings and body

foramen ovale (sphenoid bone)

larger foramen located posterior to foramen rotundum on each side

sella turcica (sphenoid bone)

saddle-shaped depression on endocranial surface of sphenoid, located on superior surface of the spehnoidal body

foramen spinosum (sphenoid bone)

located on each greater wing just posterolateral to the foramen ovale, set in the posteroinferior spines of the sphenoid

cribriform plate (ethmoid bone)

best observed endocranially, where it fills ethmoid notch of the frontal bone; perforated by many small foramina

crista galli (ethmoid bone)

perpendicular projection of cribiform plate that projects endocranially

lateral masses (ethmoid bone)

lie to either side of midline, thin walled ethmoid cells

perpendicular plate (ethmoid bone)

flattened lamina placed at midline between the lateral masses, projects inferiorly

alveolar processes (maxilla bones)

horizontal portion of maxilla; holds tooth roots

anterior nasal spine (maxilla bones)

thin projection of bone at midline in nasal aperture

maxillary sinuses (maxilla bones)

large void in body superior to alveolar process

anterior lacrimal crest (maxilla bones)

vertical crest located on lateral aspect of frontal process

incisive foramen (maxilla bones)

perforates anterior hard palate at midline

how to side maxilla?

the alveoli are helpful in determining, in fragments of frontal process the thinner edge is anterior and medial while the anterior lacrimal crest is found laterally

horizontal plate (palatine bones)

forms the posterior third of the hard palate

perpendicular plate (palatine bones)

appressed tightly to posteromedial wall of maxilla opposite the maxillary sinus

posterior nasal spine (palatine bones)

located on superior surface of horizontal plate; the superior or nasal cavity side of the plate is smoother

greater palatine foramen (palatine bones)

perforates the rear corner of hard palate and is formed as alveolar process of maxilla meets the horizontal plate

how to side the nasal bones?

the inferior border is slightly notched, the superior border (that articulates with the frontal bone) is narrow and thick

nasal foramen (nasal bone)

located approximately in the middle of the nasal bone on the facial surface

zygomaticofacial foramen (zygomatic bones)

perforates the convex lateral surface of the zygomatic bone

masseteric origin (zygomatic bones)

the roughened, expanded inferior edge of the bone

zygomaticoorbital foramina (zygomatic bones)

perforate the inferolateral corner of the orbital cavity

posterior lacrimal crest (lacrimal bones)

a vertical crest on the medial orbital wall that bounds the posterior half of the lacrimal groove

lacrimal sulcus (lacrimal bones)

forms the lacrimal groove when articulated with the maxilla

how to side the lacrimals?

orient the posterior lacrimal crest vertically, the crest sweeps forwards and the lacrimal groove will be anterior

alae or wings (vomer)

located on either side of deep midline furrow on superior surface

perpendicular plate (vomer)

thin, vertical sheet of bone on the midline below the wings

posterior border (vomer)

nonarticular surface that divides the nasal aperture in two halves

nasopalatine grooves (vomer)

mark both sides of perpendicular plate and run anteroinferiorly from wings

mental foramen (mandible)

large foramen located laterally on body, below the premolars

mental eminence (mandible)

the chin, a triangular protuberance on the midline at the base of the body

mandibular condyle (mandible)

the large rounded articular prominence on the posterosuperior corner of the ramus

coronoid process (mandible)

thin triangular section of ramus anterior to mandibular condyle

oblique line (mandible)

weak eminence that passes from root of the ramus to the area at the rear of mental foramen

gonial angle (mandible)

the rounded posteroinferior corner of the mandible

mandibular foramen (mandible)

enters the bone obliquely, centered in the medial surface of the ramus

mylohyoid line (mandible)

obliquely crosses the medial surface of the corpus, begins near the last molar and diminishes as it runs anteroinferiorly

mylohyoid groove (mandible)

crosses the medial surface of the ramus and runs anteroinferiorly from the edge of the mandibular foramen

pterygoid tuberosity (mandible)

interrupts the medial surface of the gonial angle posteroinferior to the mylohyoid groove

head (rib)

the swollen proximal part of the rib that bears 2 demifacets (articular surfaces) for contact with the bodies of the thoracic vertebrae

neck (rib)

the short segment between the head and the rib’s articulation with the transverse process of the thoracic vertebrae

tubercle (rib)

located on the posteroinferior corner of each rib and is the articulation point for the transverse process of the thoracic vertebrae

angle (rib)

the sharp curve in the bone lateral to the tubercle, marked by prominent line on the external surface of the shaft immediately distal (lateral) to the tubercle

shaft (rib)

the curved tapering segment between the tubercle and the rib’s distal end, the shafts of ribs 3-6 are thicker and rounder than the shafts of ribs 7-12

costal groove (rib)

the groove along the medial side of the inferior edge of the shaft, most prominent in ribs 5-7

sternal end (rib)

the anterior end of the shaft; roughened cupped surface for cartilage attachment

cranial edge (rib)

the blunt, smooth and convex upper surface of most ribs

caudal edge (rib)

the sharp lower surface of most ribs, the costal groove gives this edge a concave appearance

describe the first rib

broad, superoinferiorly flattened, short and tightly curved with only one articular facet, cranial surface is roughened and there is no true inferior costal groove

describe the second rib

intermediate between the unusual first rib and more typical ribs 3-9, large tuberosity near external midshaft portion

describe the tenth rib

like ribs 3-9 but only has one articular facet on the head

describe the eleventh rib

single articular facet, lacks a tubercle, narrow and often pointed sternal end, shaft has slight angle and shallow costal groove

describe the twelfth rib

shorter than the eleventh, may even be shorter than the first, lacks angle and costal groove, sternal end tapers to a point

how to side the ribs?

for first rib: the head and neck point inferiorly and the superior surface bears grooves when in correct anatomical position

for other ribs: head points towards midline; tubercles are inferior; cranial edge is thicker and blunter than the grooved, sharp inferior edge

for the twelfth rib: the inner surface faces superiorly

manubrium (sternum)

the most massive, thickest and squarest part of the sternum

clavicular notches (sternum)

occupy the superior corners of the sternum where the manubrium articulates with the left and right clavicles

jugular notch (sternum)

the midline notch on the superior border of the manubrium

costal notches- manubrium (sternum)

occupy both sides of manubrium inferior to the clavicular notches, represent articulation with costal cartilage of first ribs