At birth the human body has about 350 bones; in
adulthood, we have 206-why?
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Axial Skeleton
• Consists of 80 bones
• Forms longitudinal axis of body
• Three major regions
– Skull
– Vertebral column
– Thoracic cage
• Supports head, neck and trunk
• Protects brain, spinal cord, and thoracic organs
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The Skull—formed by cranial and facial bones
1. Cranial bones
• Enclose the brain in the cranial cavity
• Provide sites of attachment for head and neck
muscles
2. Facial bones
• Framework of face and the sense organs
• Openings for air and food passage
• Sites of attachment for teeth and muscles of
facial expression
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Temporal Bones
• Major markings: zygomatic process, mandibular fossa
external auditory (or acoustic) meatus, mastoid process,
mastoid sinus, styloid process
External acoustic
meatus
Mastoid region
Zygomatic process
Mandibular fossa
Mastoid
process
Tympanic region
Styloid process
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Figure 7.8
Occipital Bone
• Most of skull’s posterior wall and base
• Articulates with 1st vertebra
• Sites of attachment for the ligaments which attach
the neck to the skull and the neck and back muscles
• Major markings: foramen magnum, occipital
condyles, external occipital protuberance and crest
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Zygomatic Bones:
Cheekbones and lateral and inferior margins of
orbits
Ethmoid Bone- don’t need to know markings
• Deepest skull bone; lies between the sphenoid
and nasal bones
• Forms most of the bony area between the
nasal cavity and the orbits
• Contributes to medial wall of orbits
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Sphenoid Bone--Butterfly or bat-shaped bone that
spreads across the middle of the skull
• Articulates with all other cranial bones-holds other
bones of the skull together
• Made up of the following areas:
– Body
--Lesser wings
– Greater wings
--Pterygoid processes
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Maxilla Bones
• Medially fused to form upper jaw and central portion
of facial bones
• Keystone bonearticulates with all other facial
bones except mandible
• Major markings: palantine process, alveoli,
infraorbital fissure, maxillary sinus
Sinuses: Mucosa-lined, air-filled spaces found in
frontal, sphenoid, ethmoid, and maxillary bones
Air enters from the nasal cavity and mucus drains into
the nasal cavity from the sinuses
Lighten the skull , Enhance resonance of voice
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• Nasal bones —thin, medially fused bones that
form bridge of nose
• Lacrimal bones —contribute to the medial
walls of orbits and has a deep groove called
the lacrimal fossa that houses the lacrimal sac
• Vomer--plow shaped bone that forms part of
nasal septum
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Mandible or lower jaw
• Largest, strongest bone of face
• Temporomandibular joint: only freely movable joint
in skull
• Major markings: coronoid process, mandibular
condyle (also called condyloid process), body, mental
foramina (nerves for tooth sensation travel through
these), ramus, and alveoli
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Nasal Cavity
• Constructed of bone and hyaline cartilage
• Roof formed by ethmoid
• Lateral walls formed by part of ethmoid and palantine bones, and inferior
nasal conchae
• Floor formed by palantine process of the maxilla and palantine bone
Orbits
• Bony cavities in which eyes are enclosed (and cushioned by adipose tissue)
and also contains the lacrimal glands
• Sites of attachment for eye muscles
• Formed by parts of seven bones: frontal, sphenoid, zygomatic, maxilla,
palantine, lacrimal and ethmoid
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Greater horn
Lesser horn
Body
Hyoid Bone: Not actually bone of the skull; lies inferior to the
mandible in the anterior neck
• Only bone in the body that does not articulate directly with
another bone;
• Is a movable base for the tongue, attachment point for the
muscles of swallowing and speech which raise and lower the
larynx while swallowing and
BIOLtalking
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Vertebral Column
• Flexible, curved structure containing 26 irregular
bones (vertebrae)
• Transmits weight of trunk to lower limbs
• Surrounds and protects spinal cord
• Vertebrae get larger (moving from cervical to lumbar)
because they have to support more weight
– Cervical vertebrae (7)—vertebrae of the neck
– Thoracic vertebrae (12)—vertebrae of thoracic
cavity
– Lumbar vertebrae (5)—vertebra of lower back
– Sacrum—bone inferior to lumbar vertebrae and
articulates with hip bones
– Coccyx—end of vertebral column
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Curves of the Vertebral Column
• Increase resilience and flexibility of spine
• Allow us to stay in upright position
• Shock absorber—prevents lower extremity shock from
easily reaching brain
– Cervical and lumbar areas are concave curves
(posteriorly)
• Thoracic and sacral areas are convex curves
(posteriorly)
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Ligaments
• Hold vertebral column in place along with trunk muscles
• Anterior and posterior longitudinal ligaments major supports
– From neck to sacrum
• Short ligaments- ligamentum flavum
– Connect each vertebra to those above and below
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Intervertebral Discs
•
Cushionlike pad composed of two parts
1. Nucleus pulposus
• Inner gelatinous nucleus that gives disc
elasticity and compressibility
2. Anulus fibrosus
• Surrounds nucleus pulposus; composed of
collagen and fibrocartilage
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General Structure of Vertebrae
• Body or centrum: anterior weight-bearing region
• Vertebral arch: posterior: composed of pedicles and
laminae that, along with centrum, enclose vertebral
foramen
• Vertebral foramina: compose vertebral canal
through which spinal cord runs
• Pedicles (little feet):project posteriorly from
vertebral body, form sides of arch
• Laminae: flat plates, complete arch posteriorly
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• Spinous process —projects posteriorly
• Transverse processes —project laterally
• Both of these are attachment sites for muscles
and ligaments that move and stabilize vertebrae
• Superior articular processes —protrude superiorly
• Inferior articular processes —protrude inferiorly
• Intervertebral foramina
– Lateral openings formed by notched areas on
superior and inferior borders of adjacent
vertebrae for spinal nerves
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Cervical Vertebrae
• C1 to C7: smallest, lightest vertebrae
• C3 to C7 have an oval body, short spinous processes which are often
bifurcated, and large, triangular shaped vertebral foramen
• C1 (atlas) and C2 (axis) have unique features
Atlas (C1)
• No body or spinous process (doesn’t need a body because it
supports the weight of the head vs the entire body)
• “Yes” vertebra
Atlas (C1)
• No body or spinous process (doesn’t need a body because it supports the
weight of the head vs the entire body)
• “Yes” vertebra
• c1 and c2 are differ from the rest of the vertebrae in that there is no
intervertebral disc between them
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Thoracic Vertebrae--T1 to T12.
**All articulate with ribs
**Location of articular facets prevent flexion and extension but allow rotation of
this area of spine; have facets for articulation with head of ribs
**Have long spinous process, a heart shaped body, circular vertebral foramen
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Table 7.2
Lumbar Vertebrae: L1 to L5, located in the small of the back
• Flat hatchet-shaped spinous processes
• Orientation of articular facets locks lumbar vertebrae together to prevent rotation
and provide added stability; Body is thick and massive to support the weight of the
body
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Table 7.2
Sacrum
– 5 fused vertebrae (S1–S5) which make the
posterior wall of pelvis
– Articulates with L5 superiorly, and with auricular
surfaces of the hip bones laterally
– Markings: Sacral foramina, sacral canal
Coccyx
– Tailbone
– 3–5 fused vertebrae
– Articulates superiorly with sacrum
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Thoracic or Rib Cage
• Composed of thoracic vertebrae, sternum, ribs and
costal cartilage (cartilage which attach ribs to sternum)
• Functions
– Forms protective cage around heart, lungs, and great
blood vessels
– Supports shoulder girdle and upper limbs
– Provides attachment sites for many neck, back, chest
and shoulder muscles
– Intercostal muscles used during breathing lift and
lower the thorax
– some flexibility in rib cage due to cartilage so we can
breathe
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Ribs and Their Attachments
• 12 pairs make up the sides of the thoracic cavity
• All attach posteriorly to body and transverse
processes of the thoracic vertebrae
• Pairs 1 through 7
– True ribs because attach directly to sternum by costal
cartilages
• Pairs 8 through12 : False ribs—
– Pairs 8–10; attach indirectly to sternum by joining
costal cartilage of rib above
– Pairs 11–12--floating ribs; no attachment to sternum
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Developmental Aspects: Fetal Skull
• Infant skull has more bones than adult skull because skull
bones are unfused and are connected by fontanelles
– Fontanelles: Unossified remnants of fibrous
membranes between fetal skull bones
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LABWORK
1. Identify and describe the bones and bone markings
listed in the handout.
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