The Axial Skeleton

• Eighty bones segregated into three regions
• Axial skeleton

• Skull 
• Vertebral column 

• Bony thorax 

• Upper limb

• pectoral girdle

• scapula
• clavicle

• humerous
• radius & ulna
• carpals
• phalanges

• pelvic girdle

• Sacrum
• Ilium, ischium, pubis

• femur
• tibia
• fibula
• tarsals
• phalanges

• Eight cranial bones

•  two parietal, two temporal, frontal, occipital, sphenoid, and ethmoid (say ‘em)
• Enclose and protect the brain and furnish attachment sites for the head and neck muscles.
• All are flat bones
• Curved skull adds strength for the weight

• only the mandible and vomer are unpaired. The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae.  (say ‘em)

Selected Bones of the Skull (cranial are red)

• Temporal X 2
• Parietal X 2
• Frontal bone
• Occipital bone
• Temples above ear
• Top and sides of head
• Forehead & sinuses
• Back of the skull
• Mandible
• Maxillary
• Zygomatic
• Lower jaw
• Upper jaw
• Cheekbones

• Four sutures mark the articulations of the parietal bones 

• Coronal suture – articulation between parietal bones and frontal bone anteriorly
• Sagittal suture – where right and left parietal bones meet superiorly
• Lambdoid suture – where parietal bones meet the occipital bone posteriorly
• Squamosal or squamous suture – where parietal and temporal bones meet 

Sphenoid Bone

Wedge-shaped bone that spans the width of the middle cranial fossa

Forms the central wedge that articulates with all other cranial bones

Ethmoid Bone

Most deep of the skull bones; lies between the sphenoid and 

nasal bones; forms most of the bony area between the nasal 

cavity and the orbits

Facial Bones

• Fourteen bones of which only the mandible and vomer are unpaired

• The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae

Mandible and Its Markings

• The mandible (lower jawbone) is the largest, strongest bone of the face

Maxillary Bone

Medially fused bones that make up the upper jaw and the central portion of the facial skeleton; facial keystone bones that articulate with all other facial bones except the mandible

Zygomatic Bones

• Irregularly shaped bones (cheekbones) that form the prominences of the cheeks and the inferolateral margins of the orbits

• Nasal bones

• thin medially fused bones that form the bridge of the nose

• Lacrimal bones

• contribute to the medial walls of the orbit and contain a deep groove called the lacrimal fossa that houses the lacrimal sac

• Vomer 

• plow-shaped bone that forms part of the nasal septum

• Palatine bones 

• two bone plates that form portions of the hard palate, the posterolateral walls of the nasal cavity, and a small part of the orbits

• Inferior nasal conchae

• paired, curved bones in the nasal cavity that form part of the lateral walls of the nasal cavity

• Bony cavities for the eyes (cushioned by fatty tissues)

• Formed by parts of seven bones – frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid

Paranasal Sinuses

• Mucosa-lined, air-filled sacs found in five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones
• Air enters the paranasal sinuses from the nasal cavity and mucus drains into the nasal cavity from the sinuses
• Lighten the skull and enhance the resonance of the voice

Hyoid Bone

• Not actually part of the skull, but lies just inferior to the mandible in the anterior neck
• Only bone of the body that does not articulate directly with another bone (oooh, good test ?)

• Attachment point for neck muscles that raise and lower the larynx during swallowing
  and speech

Vertebral Column

• Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results

• Cervical vertebrae – 7 bones of the neck
• Thoracic vertebrae – 12 bones of the torso
• Lumbar vertebrae – 5 bones of the lower back
• Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones

Vertebral Column: Curvatures

• Posteriorly convex curvatures –                       thoracic and sacral
• Posteriorly concave curvatures –                      cervical and lumbar

• Primary curvatures - thoracic and sacral

  Secondary curvatures - cervical and lumbar

  • Abnormal spine curvatures include scoliosis (abnormal lateral curve), kyphosis (hunchback), and lordosis (swayback)

Vertebral Column: Intervertebral Discs

• Cushion-like pad composed of two parts

• Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility
• Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

• Body or centrum

• disc-shaped, weight-bearing region

• Vertebral arch

• composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen

• Vertebral foramina

• make up the vertebral canal through which the spinal cord passes

• Spinous processes

• project posteriorly, and transverse processes project laterally

• Superior and inferior articular processes

• protrude superiorly and inferiorly from the pedicle-lamina junctions

• Intervertebral foramina

• lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

Cervical Vertebrae (in general, there are some odd ones)

• Seven vertebrae (C₁-C₇) are the smallest, lightest vertebrae
• C₃-C₇ are distinguished with an oval body, short spinous processes, and large, triangular vertebral foramina

• Each transverse process contains a transverse foramen
• Most notable spinous is C-7 = vertebra prominens

Cervical Vertebrae: The Atlas (C₁)

• The atlas has no body and no spinous process
• It consists of anterior and posterior arches, and two lateral masses
• The superior surfaces of lateral masses articulate with the occipital condyles = carries the skull

Cervical Vertebrae: The Axis (C₂)

• The axis has a body, spine, and vertebral arches as do other cervical vertebrae
• Unique to the axis is the dens, or odontoid process, which projects superiorly from the body and is cradled in the anterior arch of the atlas
• The dens is a pivot for the rotation of the atlas

Thoracic Vertebrae

• There are twelve vertebrae (T₁-T₁₂) all of which articulate with ribs

• Major markings include two facets and two demifacets on the heart-shaped body, the circular vertebral foramen, transverse processes, and a long spinous process

• The location of the articulate facets prevents flexion and extension, but allows rotation of this area of the spine

Lumbar Vertebrae

• The five lumbar vertebrae (L₁-L₅) are located in the small of the back and have an enhanced weight-bearing function

• They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen
• Orientation of articular facets locks the lumbar vertebrae together to provide stability

Bony Thorax (Thoracic Cage)

• The thoracic cage is composed of the thoracic vertebrae dorsally, the ribs laterally, and the sternum and costal cartilages anteriorly
• Intercostal spaces are occupied by intercostal muscles which help with breathing.  The muscles look like this……..

Sternum (Breastbone)

• A dagger-shaped, flat bone that lies in the anterior midline of the thorax

• Results from the fusion of three bones – the superior manubrium, the body, and the inferior xiphoid process

• Anatomical landmarks include the jugular (suprasternal) notch, the sternal angle, and the xiphisternal joint

Ribs

• There are twelve pair of ribs forming the flaring sides of the thoracic cage
• All ribs attach posteriorly to the thoracic vertebrae
• The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages
• Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage  
• Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment

Structure of a Typical True Rib

• Bowed, flat bone consisting of a head, neck, tubercle, and shaft

Appendicular Skeleton

• The appendicular skeleton is made up of the bones of the limbs and their girdles
• Pectoral girdles attach the upper limbs to the body trunk
• Pelvic girdle secures the lower limbs

Pectoral Girdles (Shoulder Girdles)

• The pectoral girdles consist of the anterior clavicles and the posterior scapulae
• They attach the upper limbs to the axial skeleton in a manner that allows for maximum movement
• They provide attachment points for muscles that move the upper limbs

Clavicles (Collarbones)

• Slender, doubly curved long bones lying across the superior thorax
• The acromial (lateral) end articulates with the scapula, and the sternal (medial) end articulates with the ????    

• Provide attachment points for numerous muscles, and act as braces to hold the scapulae and arms out laterally away from the body

Scapulae (Shoulder Blades)

• Triangular, flat bones lying on the dorsal surface of the rib cage, between the second and seventh ribs

• Scapulae have three borders and three angles
• Major markings include the suprascapular notch, the supraspinous and infraspinous fossae, the spine, the acromion, and the coracoid process

The Upper Limb

• The upper limb consists of the arm (brachium), forearm (antebrachium), and hand (manus)
• Thirty-seven bones form the skeletal framework of each upper limb

Arm

• The humerus is the sole bone of the arm
• It articulates with the scapula at the shoulder, and the radius and ulna at the elbow

• Proximal humerus includes the head, anatomical and surgical necks, greater and lesser tubercles, and the intertubercular groove
• Distal humerus includes the capitulum, trochlea, medial and lateral epicondyles, and the coronoid and olecranon fossae
• Medial portion includes the radial groove and the deltoid process

Hand

• Skeleton of the hand contains wrist bones (carpals), bones of the palm (metacarpals), and bones of the fingers (phalanges)

Carpus (Wrist)

• Consists of eight bones

• Scaphoid, lunate, triquetral, and pisiform proximally
• Trapezium, trapezoid, capitate, and hamate distally
• Some Lovers Try Positions That They Can't Handle
• She Looks Too Pretty. Try To Catch Her

Pelvic Girdle 

• The pelvic girdle consists of the two coxal bones and the sacrum (sacrum does double duty)
• Attaches the lower limbs to the axial skeleton 
• Provide attachment points for muscles that move the lower limbs

The Lower Limb

• The three segments of the lower limb are the thigh, leg, and foot
• They carry the weight of the erect body, and are subjected to exceptional forces when one jumps or runs

Femur

• The sole bone of the thigh is the femur, the largest and strongest bone in the body
• It articulates proximally with the hip and distally with the tibia and fibula
• Major markings include the head, fovea capitis, greater and lesser trochanters, gluteal tuberosity, lateral and medial condyles and epicondyles, linea aspera, patellar surface, and the intercondylar notch

Tibia

• Receives the weight of the body from the femur and transmits it to the foot
• Major markings include medial and lateral condyles, intercondylar eminence, the tibial tuberosity, anterior crest, medial malleolus, and fibular notch

Fibula

• Sticklike bone with slightly expanded ends located laterally to the tibia
• Major markings include the head and lateral malleolus