Name the 3 regions of the axial skeleton

• skull
• vertebral column
• thoracic cage

what does the cranial bone consist of?

frontal bone, (2) parietal bone, occipital bone, (2) temporal bones, sphenoid bone and ethmoid bone

Describe the Frontal bone

• anterior portion of the cranium
• most of anterior cranial fossa
• superior walls of orbits
• contains air-filled frontal sinus

Describe Parietal Bones and major associate sutures

superior and lateral aspect of cranial vault

4 sutures mark the articulations of parietal bones w/frontal, occipital, and temporal bones:

1. Coronal suture- btw parietal bones and frontal bone
2. sagittal suture- btw right and left parietal bones
3. lambdoid suture- btw parietal bones and occipital bone
4. squamous (squamosal) sutures- btw parietal and temporal bones on each side of skull

Describe Occipital bone

• most of skull's posterior wall and posterior cranial fossa
• articulates w/1st vertebrae
• sites of attachment for the ligamentum nuchae and many neck and back muscles

Temporal Bone

• paired
• inferolateral aspects of skull and parts of cranial floor
• 4 major regions- 1. squamous 2. tympanic 3. mastoid 4. petrous

Sphenoid Bone

• complex, bat-shaped bone
• keystone bone- articulates w/all other cranial bones
• 3 pairs of processes- greater wings, lesser wings, and pterygoid processes

Ethmoid Bone

• deepest skull bone
• superior part of nasal septum, roof of nasal cavities
• contributes to medial wall or orbits (eyes)

Sutural Bones

thin irregularly shaped bones that appear within sutures

What are the Facial Bones

• mandible, (2- maxillae) maxillary bones, (2) Zygomatic bones, (2) nasal bones, (2) lacrimal bones, (2) palatine bones, vomer, and (2) inferior nasal conchae.

Mandible

• lower jaw
• largest, strongest bone of the face
• temporomandibular joint; only freely movable joint in skull
• Articulated w/zygomatic bones

Zygomatic Bones

• cheekbones
• inferolateral margins of orbits
• articulates w/lower part of the frontal and orbitals

Maxillary bones

• medially fused to form upper jaw and central portion of facial skeleton
• keystone bones articulate with all other facial bones except mandible

Nasal and Lacrimal Bones

nasal bnes- form bridge of nose

Lacrimal bones

• In medical walls of orbits
• lacrimal fossa houses lacrimal sac

Palatine and Vomer Bones

Palatine Bones

• posterior 1/3 of hard plate
• posterolateral walls of the nasal cavity
• small portion of the orbits

Vomer

• plow shaped
• lower part of nasal septum

Inferior Nasal conchae

form part of lateral walls of nasal cavity

Orbits

• eyes
• encase eyes and lacrimal glands
• sites of attached for eye muscles
• formed by part of 7 bones

Paranasal sinuses

• mucosa-lines, air filled spaces
• lighten the skill
• enhance resonance of voice

Hyoid Bone

• not a bone of the skull
• does not articulate directly with another bone
• site of attachment for muscles of swallowing and speech

Vertebral Column

• transmits weight of trunk to lower limbs
• surrounds and protects spinal cord
• flexible curved structure containing 26 irregular bones

1. Cervical vertebrae (7)- neck
2. Thoracic (12) thoracic cage
3. Lumbar (5)- lower back
4. Sacrum- bone inferior to the lumbar vertebrae
5. Coccyx- terminus of vertebrae column (4 or 5)

Scoliosis

abnormal lateral curve

Kyphosis

hunchback

Lordosis

swayback

Intervertebral discs are composed of 2 cushionlike pads.

1. Nucleus pulposus- inner gelatinous nucleus that gives the disc its elasticity and compressibility
2. Anulus fibrous- outer collar composed of collagen and fibrocartilage

General structure of the 7 processes per vertebrae

• Spinal process- projects posteriorly
• Transverse processes (2)- project laterally
• Superior articular processes (2)- protrude superiorly inferiorly
• Inferior articular processes (2)- protrude inferiorly

Describe Atlas (C₁)

• no body or spinous process
• consists of anterior and posterior arches, and 2 lateral masses
• superior surfaces of lateral masses articulate w/the occipital condyles

Describe Axis (C₂)

• Dens projects superiorly into the anterior arch of the atlas
• Dens is a pivot for the rotation of the atlas

Thoracic vertebrae

• T₁ to T₁₂
• _{all articulate w/ribs at facets and demifacets}
• _{long spinous process}
• location of articular facets allows rotation of this area of spine

Lumbar Vertebrae

• L₁ to L₅
• short, thick pedicles and laminae
• flat hatchet-shaped spinous processes
• orientation of articular facets locks lumbar vertebrae together so as to prevent rotation

Sacrum

• 5 fused vertebrae (S₁ to S₅)
• forms posterior walls of pelvis
• Articulates with L₅ superiorly, and with auricular surfaces

Coccyx

• tailbone
• 3-5 fused vertebrae
• Articulates superiorly with sacrum

Thoracic Cage

• composed of thoracic vertebrae (posteriorlly)
• sternum (anteriorlly)
• ribs and their costal cartilages (laterally)

What are the functions of the thoracic cage?

• protects vital organs of thoracic cavity
• supports shoulder girdle and upper limbs
• provides attachment sites for many muscles, including intercostal muscles used during breathing

Sternum

• aka breastbone
• articulates with costal cartilages

Name the 3 fused bones and their articulations

1. Manubrium- articulates w/clavicle and ribs 1 & 2
2. Body- articulates w/costal cartilages of ribs 2 through 7
3. Xiphoid process- site of muscle attachment. Not ossified until ~age 40

Ribs and their attachments

12 pairs

all attach posteriorly to thoracic vertebrae

pairs 1-7- true (vertebrosternal) ribs

• 1-7 attach directly to the sternum by individual costal cartilages

pairs 8-10 also called vertebrochondral ribs.

• attach indirectly to sternum by joining costal cartilage of rib above

Pairs 11-12 are also called vertebral (floating) ribs

• no attachment to sternum

Appendicular skeleton

bones of the limbs and their girdles

• pectoral girdle attaches the upper limb to the body trunk
• pelvic girdle secures the lower limbs

Pectoral girdle

aka shoulder girdle

• inferior to clavicle and posterior to scapulae
• attach the upper limbs to the axial skeleton
• provide attachment sites for muscles that move the upper limbs

Clavicle

aka collarbone

• flattened acromial (lateral) end articulates w/scapula
• cone-shaped sternal (medial) end articulates w/sternum
• acts as braces to hold the scapulae and arms out laterally

Scapula (shoulder blades)

• situated on the dorsal surface of rib cage, btw 2 and 7
• flat and triangular, with 3 borders and 3 angles
• 7 large fossae
• posteriorly it is not articulated w/the rib cage but with muscle (this allows the arm to move up and down)

Arm

aka Humerus

• longest bond of upper limb
• articulates superiorly w/glenoid cavity of scapula
• articulates inferiorly w/radius and ulna

Ulna

• medial bone in forearm.
• forms the major portion o the elbow with the humerus
• proximally articulates w/humerus, distally w/carpal

Radius

• lateral bone in forearm
• head articulates w/capitulum of humerus and w/radial notch of ulna
• interosseous membrane connects the radius and ulna along their entire length

Pelvic (Hip) girdle

• 2 hip bones (each called coxal bone or os coxae)
• attach the lower limbs to the axial skeleton w/stronger ligaments
• transmit weight of upper body to lower limbs
• support pelvic organs

Each hip bone consists of 3 fused bones

• ilium (superior)
• ischium (posteroinferior)
• pubis (anterior, form pubic symphysis)

together with the sacrum and the coccyx, these bones form the bony pelvis

Female pelvis

adapted to childbearing (fibrocartilage)

true pelvis (inferior to pelvi brim) defines birth canal

cavity of the true pelvis is broad, shallow and has greater capacity (wider)

Male pelvis

tilted less forward

adapted for support for heavier build and stronger muscles

cavity of true pelvis (narrow but deep)

What are the 3 segments of the lower limb?

Thigh: femur

Leg- tibia and fibula

Foot- 2 tarsals in the ankle, 5 metatarsals an 14 phalanges

Femur

largest and strongest bone in the body

articulates proximally with the acetabulum of hip and distally with the tibia and patella

Tibia

medial leg bone

receives the weight of the body from the femur and transmits it to the foot

Fibula

not weight bearing; no articulation with femur

site of muscle attachment

connected to tibia by interosseous membrane

articulates with tibia via proximal and distal tibiofibular joints

Calcaneous

heal of the foot bone

3 arches of the foot

• lateral longitudinal
• medial longitudinal
• transverse

Fontanelles

at birth, skull bones are connected to this.

unossified remnants of fibrous membranes between fetal skull bones

anterior, posterior, mastoid and sphenoid