B6: Vertebral Column

vertebral column: definition and functions

DEFINITION: the

posterior portions of the trunk

FUNCTIONS:

Posture

Support of weight

Protection for the spinal cord and spinal nerves

Partial protection for thoracic and abdominal organs

What types of bones are in the vertebral column and how many in each?

There are three types of bones:

1. 24 moveable presacral vertebrae

7 cervical

12 thoracic

5 lumbar

2. Sacrum -

which is 5 fused vertebrae

3. Coccyx -

which is 4 fused vertebrae

Intervertebral disc

fibrocartilaginous structures found between the bodies of adjacent vertebrae

Total number of bones (BEFORE fusion of the sacrum and coccyx) is

33

Total number of bones (AFTER fusion of the sacrum and coccyx) is

26...

24 pre-sacral vertebrae

1 sacrum

1coccyx

Fetal Curvature

In the fetus, the vertebral column exhibits one curvature, which is concave anteriorly.

This curvature is referred to as the

PRIMARY CURVATURE.

This curve is a result of differences in the height between the anterior and posterior aspects of the vertebral bodies.

(IMAGE ON THE RIGHT)

adult curvature

In the adult, the vertebral column exhibits 4 curvatures

Cervical (secondary)

Thoracic (primary)

Lumbar

(secondary)

Sacral (primary)

primary curvatures

concave anterior

The spinal curvatures present at birth; thoracic and sacral curvatures

Result of differences in the height between the anterior and posterior aspects of the vertebral bodies

secondary curvatures

concave posterior and due to differences in the heights between the anterior and posterior aspects of the intervertebral discs.

The cervical and lumbar exhibit a curve which is not primary, but rather have a curve which is classified as a secondary curvature

kyphosis

increased curvature of the thoracic region of the vertebral column, leading to a humpback posture; also called hunchback

lordosis

abnormal anterior (secondary) curvature of the lumbar spine (sway-back condition)

scoliosis

abnormal lateral curvature of the spine

typical vertebrae: body

the large round mass of the vertebra. It forms the anterior aspect of the vertebra.

typical vertebrae: vertebral arch

posterior to the body lies an arch of bone which is formed by two pedicles and two laminae.

typical vertebrae: pedicle

a bridge of bone extending from the posterior aspect of the body

'LITTLE FEET'

typical vertebrae: lamina

a flat plate of bone extending from the pedicle. The two laminae fuse with each other in the median plane.

'THIN PLATE'

typical vertebrae: vertebral foramen

the hole in the center of the vertebra which houses the spinal cord.

boundaries of the vertebral foramen

anterior - body

posterior - laminae

lateral- pedicles

spina bifida cystica

Sometimes vertebral arch doesn't close and this happens - exposure of the nervous system tissue

How is this prevented? Folic acid taken before and during pregnancy

How many processes come off the vertebral arch?

7! (think of how many days there are in a week)

one spinous process (posteroinferior), two transverse processes (posterolateral), and four articular processes.

vertebral processes serve as attachment points for ligaments and back muscles.

typical vertebrae: spinous process

a single process the projects posteriorly from each vertebral arch at the junction of the two laminae.

typical vertebrae: transverse process

wo

processes that project laterally from the junction of a lamina and a pedicle

typical vertebrae: superior articular processes

two processes that project posterior to the transverse processes, which articulate with the superjacent vertebra.

typical vertebrae: inferior articular processes

two processes that project inferiorly, posterior to the transverse process, which articulate with the infrajacent vertebra

The inferior articular process of T3 would articles with _______

the superior articular process of T4

typical vertebrae: vertebral notches

notches on the superior and inferior surface of the pedicle.

When two vertebrae are articulated the notches form a foramen called the INTERVERTEBRAL FORAMEN. The intervertebral foramen transmits the SPINAL NERVE

Intervertebral foramen

Opening formed by the inferior and superior notches on the pedicles of adjacent vertebrae. Allows passage of spinal nerves and vessels.

Spinal Nerve

a nerve that emerges from the spinal cord and is located in the intervertebral foramen

Cervical vertebrae unique components

Has transverse foramen, bifid spinous process and bifid transverse processes

cervical vertebrae: transverse foramen

On the transverse process. The Vertebral artery passes through from C6-C1.

cervical vertebrae: bifid spinous process

divides into 2 smaller projections

cervical vertebrae: bifid transverse processes

divides into 2 projections:

anterior and posterior tubercles

cervical vertebrae bones and how many?

7

CV 1 - ATLAS

CV 2 - AXIS

CV 3 - CV 6

CV 7 - VERTEBRAL PROMINENS

ATLAS a.k.a

C1

AXIS a.k.a

C2

VERTEBRA PROMINENS a.k.a

C7

cervical vertebrae: CV1 ATLAS

from Gk. Atlao = endure or sustain; to bear, carry

there is no body. It is replaced by the dens of CV2

there are no lamina or spinous process. They are replaced by an arch of bone, the POSTERIOR ARCH

the superior articular processes are concave for articulation with the occipital condyles

cervical vertebrae: CV2 AXIS

from L. Axis = an axle or pivot

a prominent superior projection, the DENS PROCESS (or odontoid process ), extends to the atlas

CV7 (Vertebra prominens)

has the longest, most prominent spinous process which does not bifurcate. It is important in counting vertebrae.

Transverse foramen is smaller relative to other cervical vertebrae.

b. Only the vertebralvein passes through, not the vertebral artery.

cervical vertebrae, vertebral artery and vein

notice how only the vertebral vein goes through c7 and that is why it has a smaller transverse foramen

thoracic vertebrae

there are TRANSVERSE COSTAL FACETS on the transverse processes for articulation with the ribs (12 thoracic vertebrae, 12 pairs of ribs)

there are no foramina in the transverse processes

thoracic vertebrae and rib contacts include:

Costovertebral joint: head of rib

contacts the body of the vertebrae.

Costotransverse joint: tubercle of rib

contacts transverse process of vertebrae

costovertebral joint

head of rib articulates with demifacet on vertebral body

costotransverse joint

Tubercle of rib articulates with transverse process

lumbar vertebrae

there are no foramina in the transverse processes

there are no facets

on the transverse processes

largest size

the spinous processes are quadrangular

why is the lumbar vertebrae largest in size?

1. In general, the presacral vertebrae increase in size going superior to inferior.

2. The reason is that each successive vertebra must support all the structures superior to it.

3. After the weight has been transmitted to the pelvis and lower limbs in the lumbo - sacral region the vertebrae inferior to this region do not support the body weight.

4. The size of the sacrum and coccygeal vertebrae decreases going inferiorly.

The size of the sacrum and coccygeal vertebrae ___________ going inferiorly.

decreases

sacrum

5 fused vertebrae

sacrum superior articulation

the intervertebral disc inferior to LV5

sacrum lateral articulation

the ALA of the sacrum articulates with the ilium of the hip bone

ALA means wing .Auricular surface - a smooth surface on the lateral portion of the ala. it forms the sacro-iliac (SI) joint with the ilium

sacrum inferior articulation

the coccyx

the sacrum has two surfaces

pelvic and dorsal

pelvic surface of sacrum

concave anterior surface

PELVIC SACRAL

FORAMINA: four pairs of openings for

the ventral rami S1- S4

pelvic sacral foramina

four pairs of openings for

the ventral rami S1- S4

dorsal surface of sacrum

the posterior aspect of the bony sacrum

MEDIAN SACRAL CREST:

ridge representing the spinous processes of the superior 3 to SV.

DORSAL SACRAL

FORAMINA: four pairs of foramina for the dorsal rami S1 S4.

SACRAL HIATUS:an opening due to the absence of lamina on the 5th sacral segment

median sacral crest

ridge representing the spinous processes of the superior 3 to SV.

dorsal sacral foramina

four pairs of foramina for the dorsal rami S1 S4.

sacral hiatus

an opening due to the absence of lamina on the 5th sacral segment.

coccyx

4 fused vertebrae

auricular surface

region on the ilium for articulation with the sacrum