axial skeleton

Axial skeleton consists of

Skull, hyoid bone, spinal column, the ribs, and the sternum. All of the axial skeleton lie on or are near the median plane of the body.

Skull

37 to 38 separate bones united by immovable, fibrous joints called sutures. The mandible is connected to the rest of the skull by the only freely movable, synovial joint.

Skull regions

Cranium, ear, and face bones

External bones of the cranium

Caudal to rostral, occipital bone, interparietal bones, parietal bones, temporal bones, and the frontal bones.

Internal bones of the cranium

Hidden, sphenoid bone and more rostral ethmoid bone

Occipital bone

Forms the caudo-ventral portion of the base of the skull. It is the most caudal skull bone, it is where the spinal cord exits the skull, it articulates with the first cervical vertebra. The foramen magnum is located in the center.

Occipital condyles

On either side of the foreman magnum, articular surfaces that join with the atlas to form the atlantoociputal joint.

Interparietal bones

2 small bones located on the dorsal midline between the occipital bone and the parietal bones.

Parietal bones

Form the dorsolateral walls of the cranium

Articular surfaces

Joint surfaces, smooth areas of compact bone come in contact with each other to form joints. Each articular surface is covered by a layer of hyaline cartilage called articular cartilage

Condyle

Large, round, articular surface, somewhat cylindrical shape

Facet

Flat, articular surface

Process

Includes all the lumps, bumps, and other projections on a bone. Some processes such as heads and condyles have joint forming functions while others are not parts of joints, they have irregular, rough surfaces

Fossa

Depressed or sunken area on the surface of a bone

Temporal bones

Located below or ventral to the parietal bones, form the lateral walls of the cranium, contain the middle and inner ear structures, and are the skull bones that form the temporomandibular joints (tmj) with the mandible.

External acoustic meatus

Only ear structures visible from the outside, the bony canal that leads into the middle and inner ear cavities.

Frontal bones

Form the forehead region of the skull

Paranasal sinus, the frontal sinus

Contained within the frontal bone

Sphenoid bone

Hidden bone of the cranium that forms the ventral part of the cranium and contains a depression (the petuitary fossa) that houses the petuitary gland, an endocrine gland.

Ethmoid bone

Hidden cranium bone that contains the cribriform plate through which many branches of the olifactory (sense of smell) nerve pass from the upper portion of the nasal cavity to the olfactory bulbs of the brain

Bones of the ear

Ossicles, starting from the outside; the malleus (hammer), the incus (anvil), and the stapes (stirrup). They transmit vibrations from the tympanic membrane (eardrum) across the inner ear cavity to the cochlea (inner ear structure)

Face bones

External (landmark bones); incicisive, nasal, maxillary, lacrimal, zygomatic, and mandible bones. internal (hidden bones); Palatine, pterygoid, vomer, and turbinates bones.

Incisive bones (premaxillary)

Most rostral skull bones, house the upper incisor teeth

Nasal bones

Form the bridge of the nose

Maxillary bones

Make up most of the upper jaw, house upper canine teeth, upper cheek, and maxillary sinuses, form the hard palate with the Palatine bones

Lacrimal bones

Two small bones that form part of the medial portion or the orbit of the eye, houses lacrimal sac (tear drainage)

Zygomatic bones (malar)

Two bones that form a portion of the orbit of the eye And join with a process from the temporal bones to form the zygomatic arches on either side of the skull

Madible

Lower jaw, only movable skull bone

Mandibular symphysis

Cartilaginous joint that join the mandible

Shaft of the mandible

Horizontal portion that houses all the teeth

Ramus of the mandible

Powerful jaw muscles attach and where the condyles that form the tmj are located

Palatine bones

Make up the caudal portion of the hard palate

Pterygoid bones

Support part of the lateral walls of the pharynx (throat)

Vomer bone

Located on the midline of the skull and forms part of the nasal septum

Turbinates

Nasal conchae, four thin scroll like bones that fill most of the space of the nasal cavity.

Hyoid bone

Hyoid apparatus, U shaped structure, located on the high in the neck, just above the larynx, between the caudal ends of the mandible, helps the animal swallow

Spinal column

Cervical, thoracic, lumbar, sacral, and coccygeal vertebra

Vertebra

Irregular bones consisting of a body, arch, and a group of processes

Intervertebral discs

Separate vertebra, made of fibrocartilage

Spinal canal

Houses and protects the spinal cord, arches of all vertebra lined up

Vertebra processes

Spinous, transverse and articular

Cervical vertebra

7, first two names atlas and axis

Dens

Peglike that fit into the caudal end of the axis to help form the atlantoaxil joint

Thoracic vertebra

House the ribs, typically 13

Lumbar vertebra

6-7

Sacral vertebra

Fuse to form a single solid structure called the sacrum. Forms a joint with the pelvis on each side called the sacroiliac joint

Coccygeal vertebra

Bones of the tail

Ribs

Flat bones, # usually = number of thoracic vertebra. Connects to costal cartilage at the costochondral junction. Sternal ribs make up cranial part of thorax, asternal ribs make up caudal part, unattached ribs are floating ribs.

Sternum

Breastbone, forms the floor of the thorax, contains sternebra (rod-like) most cranial sternebra is the manubrium, most caudal sternebra is the xiphoid process.

Cornual (horn)

Process of frontal bone

Ramus

The vertical part at the caudal end that forms the temporomandibular joints with the temporal bone, it is where powerful jaw muscles attach

Tympanic bullae (egg shaped)

Swellings on the ventral surface, contain middle ear structures

Dorsal vertebra process (1)

Spinous process

2 lateral processes in vertebra

Transverse processes

Cranial and caudal (2) ends of vertebra

Articular