Vertebral Column

Vertebral Column (Spine)

• Extends from the skull, which it supports, to the pelvis, where it transmits the weight of the body to the lower limbs

• The spine is formed from 26 irregular bones connected and reinforced by ligaments in such a way that a flexible curved structure results

Vertebrae• Before birth, the spine consists of

33 separated bones called vertebrae, but 9 of these eventually fuse in to 2 composite bones

• Of the remaining 24 single bones:7 vertebrae of the neck

(cervical vertebrae) 12 thoracic vertebrae5 lumbar vertebrae

supporting the lower back

Intervertebral disks• Cushion the vertebrae and absorb shocks- In a young person, the disks have a high water

content- As a person ages, the water content of the

disks decreases, and the disks become harder and less compressible

- Drying of the disks, along with a weakening of the ligaments of the vertebral column predisposes older people to herniated (slipped) disks

Spinal Curvatures

Functions:1. The disks and the S-shaped structure of the vertebral column work together to prevent shock to the head when we walk or run2. They also make the body trunk flexible

Spinal Curvatures

• Primary curvatures: The curvatures that are present when we are born.

e.g. The spinal curvatures in the thoracic and sacral

(lower spine) regions • Secondary curvatures: The

curvatures that are present after we are born.

e.g. The cervical (neck) curvature

Abnormal Spinal Curvatures

Vertebrae Structure

• Body or Centrum:Disk like, weight-bearing part of the vertebra facing

anteriorly in the vertebral column• Vertebra Foremen:

Canal through which the spinal cord passes

Vertebrae Structure

• Spinous process: Single projection arising from the posterior aspect of the vertebrae

• Transverse processes: Two lateral projections from the body

Vertebrae Structure

• Superior and inferior articular processes:

Paired projections lateral to the

vertebral foramen, allowing a vertebra to form joints with adjacent vertebrae

Cervical Vertebrae

• The 7 cervical vertebrae (C1-C7) form the neck region of the spine.

• The first 2 vertebrae are different because they perform functions not shared by the other cervical vertebrae

Cervical Vertebrae C1• The 7 cervical vertebrae

(C1-C7) form the neck region of the spine.

• C1 is called the atlas. It has no body, and large depressions on the surface where the skull sits. It articulates with the occipital condyles, and allows you to nod “yes”

Cervical Vertebrae C2• C2 is called the axis, and

acts as a pivot point for rotation of the atlas and the skull.

• It has a large process called the odontoid process, which sticks into the atlas.

• The joint between C1 and C2 allows us to rotate the head from side to side “no”

Cervical Vertebrae C3-C7

• The C3 through C7 vertebrae are typical vertebrae with some features that will identify them as cervical vertebrae:

• They are the smallest and lightest vertebrae

• They have short spinous processes that are divided in two

Cervical Vertebrae C3-C7• They have foramen in

their transverse processes – this is what one can use to identify these vertebrae as cervical vertebrae;

• The foramina are where the vertebral arteries run through

Superior and lateral views

of the cervical vertebrae

Thoracic Vertebrae

• The 12 thoracic vertebrae (T1-T12) are all typical

Thoracic Vertebrae T1-T12• Their bodies are heart-

shaped• They have long spinous

processes that point sharply downward

• From the side, thoracic vertebrae look like giraffe’s head, this is what one can use to identify these vertebrae as thoracic vertebrae

Lumbar Vertebrae

• The 5 lumbar vertebrae are the sturdiest of the vertebrae since most of the stress on the vertebral column occurs in the lumbar region

Lumbar vertebrae L1-L5• Their bodies are

massive and block like

• From the side, a lumbar vertebrae look like a moose head – this is what one can use to identify these vertebrae as lumbar vertebrae

Sacrum

• The sacrum is formed by the fusion of 5 vertebrae

• Superiorly, it articulates with L5

• Inferiorly, it articulates with the coccyx (tail bone)

Sacrum• The sacrum forms

the posterior wall of the pelvis

• The vertebrae canal continues inside the sacrum as the sacral canal

Coccyx

• The coccyx is formed by the fusion of 3 to 5 small, irregularly shaped vertebrae

• It is the human “tailbone”, a remnant of the tail that other vertebrate animals have

Identify the following vertebrae