Module 3: Bones, Features, ID And Siding-Axial Skeleton

Question 1

Cranium

Answer 1

Fuse in many species and rarely found in isolation

Question 2

Frontal bone

Answer 2

“Forehead”; encloses portion of eye orbitsl; articulates with maxilla and nasal bones rostrally, lacrimals and palatines, and sphenoid laterally, parietal bones posteriorly/caudally
Articulates with zygomatics in species with full postorbital closure/bar

Question 3

Eye orbits

Answer 3

Delineated by postorbital processes on posterior-lateral aspect of bone

Question 4

Frontal sinuses

Answer 4

Area between orbitals

Question 5

Sinuses

Answer 5

Midline

Question 6

Zygomatic process

Answer 6

Lateral

Question 7

Coronal suture

Answer 7

Caudal

Question 8

Temporal lines

Answer 8

Towards midline and caudal

Question 9

Orbits

Answer 9

Size, orientation and completeness provide insight into reliance on vision for hunting/survival.
Large and semi-complete orbits (felines)-visual acuity in hunting
Large, well protected orbits (owls)-nocturnal vision
Anterior orbit creates visual field overlap and stereoscopic vision/depth perception
Smaller, less protected orbits (rodents)-less reliance on vision
Large, laterally places orbits (ungulates-horses, deer, cow)-see nearly 360 degrees for watching predators; monocular vision-no depth perception

Question 10

Nasal bones

Answer 10

Concave on internal surface and meet at midline
Form superior surface of the nose
Length of nose: reliance on smell

Question 11

Nasal conchae

Answer 11

Snail-like; act as turbines in sense of smell, larger in animals that rely more heavily on sense of smell

Question 12

Lacrimals

Answer 12

Concave on external surface, contain tear ducts/lacrimal fossae
Size/shape vary
Location can be species diagnostic

Question 13

Maxillae

Answer 13

Form the bulk of the face
Have infraorbital foramen-facial nerve passes
Incisive foramen-intramural surface of maxilla
Form lower margin of orbits, lateral margins of nasal opening, and contain most/all upper dentition
Infraorbital foramen vary among species

Question 14

Siding maxilla

Answer 14

Teeth are lateral, canines and incisive foramen anterior
Exterior convex, interior concave

Question 15

Premaxillae

Answer 15

Forms lower margin of nasal opening, contains anterior dentition (incisors, typically)
Some mammals have edentulous premaxilla (horse)

Question 16

Siding premaxilla

Answer 16

Pointy projection caudally, incisors anterior/rostral
Midline concave

Question 17

Palatines

Answer 17

Back part of roof of mouth
Each have large palatine foramen, plus often smaller accessory foramen
Canids-palatine foramen (major palatine foramen) at maxilla-palatine suture & posterior palatine foramen (minor palatine foramen) in actual palatine bone

Question 18

Zygomatics/jugals/Malars

Answer 18

Cheek bones
Concave on internal surface
Temporal process-posterior projection; articulates with zygomatic process of temporal bone to form cheek bone
Superior projection-frontal process, smaller in canids, larger in felines, non-existent in rodents

Question 19

Siding zygomatic

Answer 19

Anterior/rostral aspect wider for articulation with maxilla and caudal portion converges to a point inferiorly, point curves back towards midline

Question 20

Temporals

Answer 20

Auditory structures
Posterior to zygomatic process-mandibular fossa, for articulation with mandibular condyle. Often a well-defined retro articulate process on posterior aspect of mandibular fossa
Auditory bulla-posterior to process ^, as well as external auditory meatus (ear hole); slightly inferior on the temporal and inflated and thin-walled
Internal to bulla-peatrus portion of temporal, very sturdy.
Temporal articulate with the parietals at squamosal suture-superiorly projecting fan shaped wing of bone that overlaps parietal striae or ridges on inferior aspect of parietals

Question 21

Siding temporal

Answer 21

Auditory bulla inferior and caudal. Mandibular fossa at base of zygomatic process and tends to be more open anteriorly/rostrally with a “wall” on the caudal aspect. Zygomatic process sweeps anteriorly and converges to a point superiorly

Question 22

Parietals

Answer 22

Form superior aspect of the brain case, internally concave
External bone is smooth or has temporal ridges for attachment of temporal muscles
Internal surface undulating or grooved to accommodate ridges and furrows of brain and blood vessels on surface of brain. Crest can form to accommodate muscle attachments

Question 23

Siding the parietal

Answer 23

Straie inferior and sagittal suture/crest is superior and midline
Muscle markings sweep superiorly and caudally (fingers through hair)

Question 24

Occipital

Answer 24

Forms the posterior aspect of the cranium
Foramen magnum-large hole through which spinal cord passes
Occipital condyles-on either side of the foramen for articulation with first cervical vertebra
Paracondylar or jugular processes-lateral to occipital condyles
Paired condylar, jugular, and hypoglossal canals for nerves and blood vessels are on the occipital bones
Nuchal ridge-superior to the foramen magnum, increases in size with increased neck muscles
Basioccipital-basilar portion of the occipital, dense and projects rostrally to articulate with the sphenoid

Question 25

Siding the occipital

Answer 25

Occipital condyles are caudal and inferior; point up and out/lateral Nuchal ridge is superior Paracondylar processes point down, thinner at top and curve medial and thicker at bottom, can start to curve medically

Question 26

Sphenoid

Answer 26

Bat-like, mostly appreciated from the internal aspect of the cranium, has several wings and foramen Optic nerves through the large optic canal Often divided into several parts-presphenoid (smaller, more rostral), basisphenoid (larger, caudal), and pterygoid (inferiorly projecting wings) Hypophysis (pituitary gland) sits in sella turcica

Question 27

Ethmoid

Answer 27

Anterior to the sphenoid Delicate, pierced by the olfactory nerves, and can be quite large

Question 28

Vomer

Answer 28

Very thin, plow-shaped usually Ruins down the midline of the nasal passage and articulates with the maxillae, palatines, and sphenoid

Question 29

Mandible

Answer 29

Formed by 2 horizontal rami that join anteriorly at mandibular symphysis, which fuses in some species Contains lower dentition Ascending ramus-posterior aspect of the mandible Coronoid process-anterior bony projection on the ramus Mandibular condyle-more posterior projection, articulates with the mandibular fossa of the temporal bone Posterio-inferior projection-angular process, extension of the gonial angle Single/multiple mental foramina found on horizontal ramus near canine or premolars-rostral, middle, and caudal mental foramen Singular mandibular foramen on each horizontal ramus internal surface, posterior to molar at base of ascending ramus

Question 30

Mandible cont…

Answer 30

Dietary habits dictate shape Grazing animals-looser articulations with the cranium for more lateral movement Shearing animals-tighter articulations including larger retroarticular process or more sculpted mandibular fossa on temporal Condyle in line with tooth row, arc of maxilla and mandible direct opposite-teeth meet more effectively (slicing, shearing, grinding) Condyle well above tooth row allows teeth to approach at more oblique angle (rolling or milling)

Question 31

Siding mandible

Answer 31

Mandibular symphasis towards midline Mental foramen lateral Mandibular foramen medial Looking at posterior aspect, coronoid process, mandibular condyle, and gonial angle all curve/point laterally

Question 32

Vertebra

Answer 32

Similar length neck to pelvis, cylindrical Similar structures with some modifications Ventral portion dominated by vertebral body which is sandwiched by intervertebral discs

Question 33

Amphiplatyan/aceolous vertebra

Answer 33

Flat on both surfaces, handle compressive forces

Question 34

Procoelous vertebra

Answer 34

Concave on cranial surface, convex on caudal surface, flexibility of the spine without excessive stretching of spinal cord Reptiles/amphibians

Question 35

Opisthocoelous vertebra

Answer 35

Convex on cranial surface, concave on caudal, flexibility reptiles/amphibians

Question 36

Amphicoelus vertebra

Answer 36

Concave on both surfaces, wide range of motion, cartilaginous and bony fish

Question 37

Heterocoelus vertebra

Answer 37

Saddle-shaped and allow retraction of neck and restrict twisting reducing SCI Birds and turtles

Question 38

Vertebral arch

Answer 38

Dorsal aspect of vertebra

Question 39

Pedicle

Answer 39

Short segments of arch closest to the body

Question 40

Lamina

Answer 40

Plate-like segment closest to spinous process

Question 41

Spinous process

Answer 41

Dorsal projection of bone at the midline

Question 42

Transverse processes

Answer 42

Lateral projections at the intersection of the pedicle and lamina

Question 43

Superior/cranial and inferior/caudal articular facets

Answer 43

Allow for articulation between the vertebra and also located at the intersection of the pedicle and lamina Cranial face dorsally, caudal ventrally

Question 44

Cervical vertebrae

Answer 44

7 usually Transverse foramen in transverse processes to allow vertebral arteries to pass Superior/cranial and inferior/caudal articular facets flat and horizontal Spinous processes shorter than thoracic vertebra, increase from cranial to caudal Ventral crest on ventral surface

Question 45

C-1

Answer 45

Atlas Articulates with cranium Flattened ventrodorsally and has large wings caudally projecting Superior articular facets are cupped while caudal are flattened Cranial joint allows flexion and extension of head

Question 46

C-2

Answer 46

Axis Allows pivoting of atlas and rotation of head Cranially has dens projection (body of c-1 transferred) Shape of dens can suggest rotation degree allowed Elongated and spinous process is sail-like

Question 47

C-7

Answer 47

Transitional vertebra, last cervical vertebra Has characteristics of cervical and thoracic Lacks transverse foramen often and spinous process is elongated and looks like thoracic Some caudal articular facets curved Caudal costal fovea present for first rib articulation

Question 48

Thoracic vertebrae

Answer 48

11-16 Ribs articulate with these at the cranial and caudal costal fovea (demifacets) and at transverse processes (which are longer than cervical vertebra and have articular facet or transverse fovea on ventro-lateral aspect) 1-10 have 2 costal fovea, while 11+ often have 1 Enlarged spinous processes, decreasing from cranial to caudal (t-2 or t-3 largest)-area of insertion for muscles Facets (sup/inf) are flat, but slightly sloped Head of rib articulates with 2 thoracic bodies, cranial and caudal, tubercle of rib articulates with transverse fovea Spinous processes point caudally, but decrease at t7 or t8. T9 and t10 shorten and t11 almost perpendicular to body. T12 to lumbar, point slightly cranial and increase in size Middle through lower lumbar have accessory process projecting caudally T11 cranial and caudal articular facets curve medially and laterally, respectively for flexion and extension; still have articular facets of ribs

Question 49

Lumbar vertebrae

Answer 49

4-7 Longer bodies than thoracic vertebra, elongated transverse processes with no articular facets Increase in size descending, project cranially, some accessory processes that project caudally Sup/inf. Facets curved Sup towards midline/concave, inf convex Spinous processes point slightly cranially and increase in size from cranial to caudal

Question 50

Sacral vertebrae

Answer 50

3-6 that fuse 1st sacral element articulates with most posterior/inferior lumbar vertebra Articular surface-promontory Alae-wings of sacrum, articulate with os coxa at auricular surface 1st sacral element also has curved superior/anterior facets for articulation with last lumbar vertebra Sacrum fused to os coxa usually

Question 51

Coccygeal/caudal vertebrae

Answer 51

Variable on whether or not there is a tail First few have transverse and spinous processes and cranial and caudal facets in reduced form, eventually lost Transverse processes project caudally

Question 52

Sternum

Answer 52

Articulates with clavicle if present, and ribs Directly articulates with more anterior ribs (true ribs) via cartilaginous attachments, indirectly via common cartilage with lower/false ribs Several segments: manubrium (most cranial with cranial projection), xiphoid process (caudal segment, flattened) Body of sternum can be several sternebra joined by cartilage or fused into one element