CHAPTER 7
“The Axial Skeleton #2”
Course objectives:
Define and identify the bones of the
axial skeleton
Vertebral column

composed of 26 irregular bones.

These bones provide a solid support
structure, but are also remarkably flexible.
Regions of the Vertebral Column
–
–
–
–
Cervical − neck region 7 vertebrae
Thoracic – thorax region 12 vertebrae
Lumbar – lower back 5 vertebrae
Sacral – low, low back 1 vertebrae (5
fused)
– Coccygeal – tail bone 1 vertebrae (4
fused)
Spinal Curvature
Thoracic and sacral are concave (i.e. backward)
 Primary curves since they developed first.


Cervical and lumbar curves are convex (i.e.
forward) and secondary curves.
Vertebral column
Vertebrae

Individual vertebrae are found in the
cervical, thoracic and lumbar regions of
the vertebral column.

There are significant differences between
the vertebrae in each of these regions that
you should know.
Cervical vertebrae – C1- C7





Body is oval; spinous process is short (except C-7) and
sometimes split;
Large vertebral foramen
Transverse foramen for vertebral artery to brainstem.
C1 is Atlas articulates (atlanto-occipital joint) with
occipital bone of skull
-allows “yes” motion of head
C2 is Axis characterized by peg-like process called
“dens” or odontoid process which interlocks with atlas
(atlanto-axial joint)
-allows sideward rotation or “no” motion of head.
Cervical Vertebrae
Atlas
Axis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Atlanto/axial joint
Atlas
(C1vertebra)
Transverse
ligament
Axis C2
vertebrae)
(c) Axis and atlas, posterosuperior view
Articular facet of dens
Dens
Cervical Vertebrae
Thoracic vertebrae T1- T12
Body is roughly heart shaped
 Demifacets for rib articulation
 Vertebral foramen are circular
 Spinous process long and points inferiorly


The thoracic vertebra look like a giraffe’s
head when viewed from the lateral view!
Thoracic vertebrae T1- T12
Lumbar Vertebrae L1-L5
Pedicles and laminae are short and thicker
 Spinous processes are short, flat and hatchet
shaped
 Vertebral foramen is triangular
 Inferior and superior processes lock the
adlacent vertebrae together for strength and
stability.


The lumbar vertebra look like a Moose’s head!
Lumbar Vertebrae L1-L5
Sacral Vertebrae S1-S5

Sacral vertebrae consists of 5 fused vertebrae
fully fused by 30 years of age

Women sacrum is shorter, wider and more
curved

Connects the spine to the pelvic girdle at the
sacroiliac joint.

Sacral canal is continuation of vertebral canal.
Sacrum and Coccyx
Ant. View
Post view
Coccyx Vertebrae Co1-Co4
Coccyx is Greek for “cuckoo”
 Consists of 4 fused vertebrae
 Fuse between 20 and 30 years
 Tailbone is vestige of tail
- Men it points anteriorly
- Women it points inferiorly

Cervical and Thoracic vertebrae
Lumbar vertebrae
Additional structures of the vertebral column
Intervertebral discs




Present between all vertebrae C2- L5/S1;
Composed of fibro cartilage
Two regions of disc:
- nucleus pulposis – central core of disc
- annulus fibrosis - outer covering of fibro
cartilage
Function: -discs permit various movements
-provide shock absorbing functions for
vertebral column
Vertebra and vertebral disc
Herniated Intervertebral discs
Spinal cord
Dorsal root ganglion
Vertebral Ligaments
(1). Anterior and posterior longitudinal ligaments
hold vertebral column together along with trunk
skeletal muscles
-prevent hyper-extension and hyper-flexion of
the vertebral column.
(2). Shorter ligaments connect adjoining
vertebrae together.
-There are 3 of these ligaments the ligamentum
flavum, the supraspinous ligaments and the
interspinous ligaments.
Vertebral Ligaments
Bony Thorax
Consists of ribs attached to the vertebral
column and sternum
 True ribs R1-R7 attach directly to sternum
 False ribs R8-R10 attach indirectly
 Two floating ribs R11 & R12
 The Sternum consisting of:
- manubrium
- body
- Xiphoid process

Bony Thorax
Ribs
1. true ribs – the first (superiormost) seven pairs of
ribs R1-R7 are directly connected to the sternum via
costal cartilage.
- are called vertebrosternal ribs.
2. false ribs – the remaining five pairs of ribs.
There are two types of false ribs.
 vertebrochondral ribs -- rib pairs #8, #9, and
#10 are connected by a single band of costal
cartilage to the inferior portion of the sternum.
Unlike the first seven pairs of ribs they do not
have their own individual attachments.
 floating or vertebral ribs – rib pairs #11 and #12
are connected only to the vertebral column, they
have no anterior connection to the skeleton.
All ribs articulate with vertebral column. The head
of the rib articulates at a demifacet on the body
of the vertebrae, while the tubercle of the rib
articulates at a facet on the transverse process.
Sternum “breast plate”
Anterior central portion of thorax
 Only bony attachment of axial skeleton to
appendicular skeleton via clavicle.
 Consists of Manubrium, Body and Xiphoid
process
 Key landmarks: calvicular notches, jugular
notch “suprasternal notch”, sternal angle.

Sternum
The sternal foramen is an anomaly and occurs in ~ 4-10% of the population. It can be
mistaken for a bullet puncture in cases of traumatic death.
Hyoid bone
Lies inferior to the mandible
 Is not attached to skeleton by bony means
 Helps movement of base of tongue

Hyoid bone