Transcript Skeletal – Part 4
Skeletal
PART 5
Vertebral Column (Spine)
Vertebral Column (Spine) – Serves as the axial support of the body Extends from the skull (which it supports) to the pelvis, where it transmits the weight of the body to the lower limbs. 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 separate bones called vertebrae.
But 9 of these eventually fuse, forming the two composite bones, the sacrum and the coccyx, which construct the inferior portion of the vertebral column.
Sacrum – Located below the lumbar vertebrae; Made up of five fused vertebrae.
Coccyx – Located below the sacrum; made up of 4 fused vertebrae.
Vertebrae
Of the 24 single bones: Cervical Vertebrae – 7 vertebrae of the neck. Thoracic Vertebrae – Next 12 vertebrae; midsection of the back.
Lumbar Vertebrae – Remaining 5 vertebrae supporting the lower back.
Remembering common meal times (7 a.m., 12 noon, and 5 p.m.) may help you recall the number of bones in these 3 regions!
Intervertebral Discs
Intervertebral Discs – Pads of flexible fibro cartilage that separate single vertebrae.
Cushion the vertebrae and absorb shock.
Change over age: In a young person, the discs have high water content (90%) and are spongy and compressible.
As a person ages, the water content of the discs decreases (as it does in other tissues throughout the body), and the discs become harder and less compressible.
Herniated Discs
Herniated Discs –
Slipped intervertebral discs.
Older people are more predisposed to herniated discs since the following occur: 1.
2.
Drying of the discs Weakening of the ligaments of the vertebral column If the protruding disc presses on the spinal cord or the spinal nerves exiting from the cord, numbness and excruciating pain can occur.
Spinal Curvature
The discs and the S shaped structure of the vertebral column work together to: 1.
2.
Prevent shock to the head when we walk or run. Make the body trunk flexible.
Abnormal Spinal Curvatures
There are three types of abnormal spinal curvatures: 1.
Scoliosis 2.
3.
Kyphosis Lordosis May be congenital or a result from disease, poor the spine.
posture, or unequal muscle pull on
Cervical Vertebrae
The 7 cervical vertebrae form the neck region of the spine. The first two vertebrae (atlas and axis) are different because they perform functions not shared by the other cervical vertebrae.
The Atlas (C
1
)
The Atlas (C
1
):
Has no body.
The superior surfaces of its transverse processes contain large depressions that receive the occipital condyles of the skull.
This joint allows you to nod “yes.”
The Axis (C
2
)
The Axis (C
2
):
Acts as a pivot for the rotation of the atlas and skull above.
It has a large, upright process, the odontoid process (or dens), which acts as the pivot point.
The joint between C 1 and C 2 allows you to rotate your head from side to side to indicate “no.”
“Typical” Cervical Vertebrae
Includes C 3 through C 7 .
They are the smallest, lightest vertebrae.
Spinous processes: Short and divided into two branches.
Transverse processes: Contain foramina (openings) through which the vertebral arteries pass on their way to the brain above. Any time you see these foramina in a vertebra, you should know immediately that it is a cervical vertebra.
Thoracic Vertebra
The 12 thoracic vertebrae (T 1 T 12 ) are all typical.
They are larger then cervical vertebrae.
The body: Somewhat heart-shaped. Has two costal demifacets (articulating surfaces) on each side, which receive the heads of the ribs.
The spinous process: Long and hooks sharply downward, causing the vertebra to look like a giraffe’s head viewed from the side.
Lumbar Vertebrae
The five lumbar vertebrae (L 1 -L 5 ) have massive, blocklike bodies.
Since most of the stress on the vertebral column occurs in the lumbar region, these are the sturdiest of the vertebrae.
Spinous processes: Short, hatchet-shaped, makes them look like a moose head from the lateral aspect.
The Sacrum
The sacrum is formed by the fusion of five vertebrae.
It lies between L 5 the coccyx. and The winglike alae articulate laterally with the hip bones, forming the sacroiliac joints.
The Sacrum
The sacrum forms the posterior wall of the pelvis. The vertebral canal continues inside the sacrum as the
sacral canal.
Coccyx
The coccyx is formed from the fusion of 3-5 tiny, irregularly shaped vertebrae.
It is the human “tailbone,” a remnant of the tail that other vertebrate animals have.