The Axial Skeleton

I highly recommend Professor Wissman’s sites For bones: http://homepage.smc.edu/wissmann_paul/bones/EBbonestutorial.html Check out all his links: http://homepage.smc.edu/wissmann_paul/anatomy1/ Also check out: Site for xrays & other diagnostic procedures: http://www.radiologyinfo.org/en/sitemap/category.cfm?category=diag

Prof Wissman’s bone site; this doesn’t show the roll-over answers This is an example of Prof Wissman’s bone site; this doesn’t show the roll-over answers http://homepage.smc.edu/wissmann_paul/bones/EBbonestutorial.html

THE SKELETAL SYSTEM The Axial Skeleton The skeleton consists of Bones (206) Cartilages Joints – also called articulations, are the junctions between skeletal elements Ligaments – connect bones Divided into axial and appendicular

Axial skeleton - forms long axis of body Skull Vertebral column Thoracic cage Appendicular skeleton – appendages and what they attach to Upper limbs (arms) Pectoral girdle (shoulder) Lower limbs (legs) Pelvic girdle

Axial skeleton Vertebral column Thoracic cage Skull Vertebral column Thoracic cage Axial skeleton is shown in green

The Skull Cranial bones (or cranium) Enclose the cranial cavity, which supports and protects the brain Attachment sites for some head and neck muscles Facial bones (anterior aspect of skull) Form framework of face Form cavities for sense organs of sight, taste and smell Provides openings for passage of air and food Hold the teeth Anchor the muscles of the face

Cranium Vault – “calvaria” = skullcap Base or floor: inferior part Forms superior, lateral and posterior aspects of skull, and forehead Base or floor: inferior part Prominent bony ridges divide cranial base into 3 “fossae” (steps) – anterior, middle and posterior Anterior cranial fossa Middle cranial fossa Posterior cranial fossa (looking down on the floor of the skull)

Cranial bones Frontal bone Parietal bones (paired) Occipital bone Temporal bones (paired) Sphenoid bone Ethmoid bone

Cranial bones frontal parietal parietal parietal _______sphenoid temporal _____ethmoid occipital occipital

Temporal bones this is the right temporal bone looking at it from the right side

Small cranial bones… Ethmoid Sphenoid

Sutures Immovable, interlocking joints of flat bones of skull Irregular, saw-toothed appearance Largest 4 skull sutures: where bones articulate with parietal bones Coronal Sagittal Squamous Lambdoid (FIND THEM)

Find: coronal, squamous and lamboid sutures

Find: sagittal and lambdoid sutures

Cranial “cavity” – houses brain Smaller cavities Housing middle and inner ear Nasal cavity Orbits Sinuses Openings (foramina, canals, fissures) for: Spinal cord Blood vessels Twelve cranial nerves: I-XII

Remember, the skull is composed of: Cranial bones (or cranium) [these were just reviewed] and Facial bones (anterior aspect of skull) Form framework of face Form cavities for sense organs of sight, taste and smell Provides openings for passage of air and food Hold the teeth Anchor the muscles of the face

Facial bones Mandible Vomer Maxillae (paired) Zygomatics (paired) Nasal (paired) Lacrimal (paired) Palatines (paired) Inferior nasal conchae (paired)

Facial bones: Mandible Vomer Maxillae (paired) Zygomatics (paired) Nasal (paired) Lacrimal (paired) Palatines (paired) Inferior nasal conchae (paired)

Maxilla (there are 2 which fuse, forming the upper jaw) Mandible (lower jaw)

Nasal cavity Of bone and cartilage Roof is ethmoid’s cribriform plate (part of slide 18) nasal bone Nasal cavity ethmoid Of bone and cartilage Roof is ethmoid’s cribriform plate Floor formed by palatine processes of the 2 maxillae and horizontal plates of palatine bones These nasal-floor structures form roof of the mouth, called the hard palate inf nasal concha maxilla___________ vomer

Nasal cavity To left, bones forming the left lateral wall of the nasal cavity (nasal septum removed) To right, nasal cavity with nasal septum in place, showing how the ethmoid bone, septal cartilage, and vomer make up the septum

Orbit Cone-shaped bony cavities holding the eyes, muscles that move the eyes, some fat and tear-producing glands; you don’t need to know all these bones that form it, just realize how complex it is and recognize the optic canal (optic nerve passes out through it) (right orbit shown)

Paranasal sinuses Air-filled sacs in the bones “Paranasal” because they cluster around and connect to the nasal cavity

Hyoid bone Only bone which does not articulate with any other bone Moveable base for the tongue Points of attachment for neck muscles that raise and lower the larynx during swallowing

Remember that the Axial skeleton includes: Skull Vertebral column Thoracic cage Axial skeleton is shown in green

The Vertebral Column Fetus and infant: 33 separate bones, or vertebrae Adult: 24 vertebrae Inferior 9 have fused forming The sacrum (5) and The coccyx (4)

Vertebrae Cervical – 7 Thoracic - 12 Lumbar - 5 Sacrum (5 fused) Coccyx (4 fused)

Spinal curvatures Cervical and lumbar are concave posteriorly* (lordosis) Thoracic and sacral are convex posteriorly* (kyphosis) Abnormal (see lab book p120): Too much of either Scoliosis (more than 10 degrees of lateral curvature) *when viewed from the side

Abnormal curvatures

Non-bony parts Intervertebral discs Anterior longitudinal ligament anulus fibrosis and nucleus pulposus) Anterior longitudinal ligament Posterior longitudinal ligament Ligamentum flavum

Anterior longitudinal ligament: wide, strong and attaches to vertebrae as well as discs (prevents hyperextension) Posterior longitudinal ligament: narrow and relatively weak, attaching only to discs * Note “intervertebral foramen” vs “vertebral foramen” on next slides

Structure of a typical vertebra

Cervical vertebrae (C1-C7) C1 (atlas) C2 (axis)

Cervical Vertebrae Smallest Lightest Most flexible Triangular vertebral foramen Transverse processes have foramina (transverse foramen) Spinous process bifid (forked) except for C7

Thoracic Vertebrae T1-T12 Heart shaped body Additional small costal facets (costal=ribs) Round or oval vertebral foramen Form posterior part of rib cage

Lumbar Vertebrae L1-L5 Massive blocklike bodies Short, thick hatchet-shaped spinous processes Limited mobility

The Sacrum Coccyx Shapes posterior wall of pelvis Composite bone of 5 fused vertebrae Sacral foramina allow passage of vessels & nerves Coccyx (the tailbone)

Remember that the Axial skeleton includes: Skull Vertebral column Thoracic cage Axial skeleton is shown in green

The Thoracic Cage

Sternum Ribs Manubrium Body Xiphoid process True ribs 1-7 False ribs 8-12 Floating ribs 11,12

Vertebral and Sternal Articulations

Typical rib

Disorders of the axial skeleton Scoliosis (over 10% curvature) Kyphosis Lordosis Vertebral compression fractures Spinal stenosis

Fontanels Unossified remnants of membranes Present at birth Anterior fontanel largest Called “soft spots” Ossify by 1 ½ - 2 years Continue to ossify into adulthood; the sutures can become fused in old age

Some abnormalities (early fusion) of sutures: “craniosynostosis” Metopic Synostosis and trigonocephaly A: Preop B: 2 years after       frontal orbital      advancement Sagittal synostosis and scaphocephaly The most common suture to fuse is the middle or sagittal suture. Often the back or front of the skull will be worse but the overall shape is a long skull with a shortened distance from ear to ear. Pre-op CAT scan Diagram of surgery 2 years post-op From - http://www.ppsca.com/skull.htm