Biomech unit 4 Upper limb & Spine - deck 5 Flashcards
What does the thoracic (or dorsal) spine consist of and where is it located in the body?
It consists of the twelve vertebrae located in the posterior part of the thoracic region of the trunk (the chest).
What is each thoracic vertebrae attached to ?
A pair of ribs (Left and right side of the vertebrae)
How does each rib articulate with each thoracic vertebrae?
The head of each rib articulates with the body and the tubercle of each rib articulates with the transverse process
What 3rd articulation do the 2nd to the 9th ribs have with the thoracic vertebrae?
They also articulate with the body of the vertebrae above
What do the articulations between the ribs and thoracic vertebrae allow?
The ribs to move up and down as we breathe.
What does the articulations of the ribs with the thoracic vertebrae do in terms of the movement allowed in the thoracic region ?
The ribs give added rigidity to the thoracic spine which effectively limits its mobility to only a very limited degree of flexion and extension and little rotation.
What does the lumbar spine consist of ?
5 vertebrae
How do the vertebrae in the lumbar spine differ from vertebrae in other regions of the spine ?
- The vertebrae in the lumbar spine have larger bodies
- This is because the lumbar vertebrae are subjected to significantly greater loads than the vertebrae in the rest of the spine.
What part of the spine do the sacrum and coccyx form ?
They form the distal portion of the spine, they lie below the lumbar vertebrae
Describe the shape and what forms the sacrum
It is a single triangular-shaped bone that has resulted from the fusion of five separate vertebrae
What is the coccyx and what forms it ?
It is a single bone that has resulted from the fusion of four or five vertebra.
What is the sacrum the link between ?
The lumbar spine and the pelvic girdle
(The pelvic girdle consists of paired hipbones, connected in front at the pubic symphysis and behind by the sacrum; each is made up of three bones—the blade-shaped ilium, above and to either side, which accounts for the width of the hips; the ischium, behind and below, on which the weight falls in sitting; and the pubis, in front.)
The junction between the lumbar spine and the sacrum is very mobile - T or F?
True
Other than the lumbar spine what is the sacrum joined to?
It is also joined to the 2 inominate bones of the pelvis (R and L inominate bones)
State what the inominate bones of the pelvis are
The bone formed from the fusion of the ilium, ischium, and pubis; the hip bone.
State what flexion and extension of the spine is
- Flexion occurs when bending forwards
- Extension occurs when bending backwards
Describe how during actual movements the motion of the spine is complex and often combined with motion in other parts of the skeletal system.
For example, during forward bending the first 50 to 60 degrees of flexion occurs in the lumbar spine with any further flexion being achieved by the tilting of the pelvis forward.
Describe the distribution of lateral bending permitted in the different segments of the spine
It has a similar distribution to that of flexion and extension, with the cervical spine being the most mobile and the thoracic spine the least
Between what 2 bones of the spine is there no lateral bending permitted?
Between C1 & C2
Describe how the distribution of rotation of the spine permitted in each segment of the spine varies
The amount of rotation about the longitudinal axis of the spine generally decreases down the spine
Between what 2 bones is there no rotation permitted ?
Between the atlas (C1) and the occipital (OC) bone of the skull
What do bad postures do to loadings on the spine? give examples
Bad postures increase loadings on the spine
e.g. pic shows a bar chart of the comparative loads on the third lumbar intervertebral disc for different postures. The load during standing is defined as 100% during upright standing. Note that during sitting the loading is actually larger than during upright standing and how slumping (bad posture) forwards can almost double the load.
Explain specifically why bad posture increases the loading on the lumbar spine?
Consider the position of the upper body relative to the lumbar spine
In Pic the vertical arrow shows the direction of the weight of the upper body in two cases:
- The moment arm of the upper body mass about the lumbar spine is increased in the case of relaxed sitting (bad posture) due to the backward tilt of the pelvis.
- The flexion moment produced by the upper body weight and the moment arm must be counterbalanced by an extension moment produced by the posterior back muscles. The larger the moment arm is the greater the muscle forces need to be.
- The muscles produce a compressive load on the spine which increases with increasing muscle force. Thus any change in posture that causes the upper body to be in a position offset from the lumbar spine effectively increases the load that it must carry.
Describe how lifting technique of a weight affects loading on the lumbar spine
The load on the lumbar spine is increased in accordance with the increase in the moment arm produced by weight of the object being lifted.
Illustrated in the difference in loading between good and bad lifting techniques:
The moment arms of the weight of both upper body and the object are greater with bad lifting technique (not bending the knees and not having the object close to the body) this means the centre of mass is acting further away and therefore the moment arms of the weight of the upper body and object are increased
