The Living Back
Clavicle
The human back has both the flexibility we need to perform complex and precise movements and sufficient strength to anchor our limbs and enable us to stand upright. Even so, many of us suffer from back pain, which is usually the result of misuse or neglect owing to our busy lifestyles. Of all the elements that comprise our backs, the spine is the most elegant in term of its design. It consists of 33 individual bones called vertebrae.
Elements of flexibilty As a whole, the spine allows sufficient flexibility to make twisting and bending possible, even though the movement permitted between individual vertebrae is often small. In fact, the sacral vertebrae and some of the coccygeal ones allow no movement at all. The movement of the spine also allows the ribs to rise and fall when we breathe in and out. But the flexibility does not come at the expense of strength: the spine is still strong enough to support the head and anchor the muscles that move the lower limbs. It also contains and protects the spinal cord, which carries the nerves that connect the brain to the nerves that serve the rest of the body. The most numerous of the vertebrae are those from the base of the neck to the middle of the chest: the thoracic vertebrae. Each one is separated from the vertebrae above and below it by an intervertebral disc of cartilage that makes up about a quarter of the spine’s length; the discs act both as shock absorbers and ball bearings, allowing the Spinous process spine to twist and bend.
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Back to Basics
Cervical vertebrae
Scapula
Humerus
The spine There are five groups of vertebrae: cervical, in the neck; thoracic, in the chest; lumbar, in the lower back; sacral, between the buttocks; and the coccyx (tailbone).
The shoulder The joints between the collarbone (clavicle), upper arm (humerus) and shoulder blade (scapula) allow movement but give the shoulder strength.
Each vertebra also has a number of joints – not just the intervertebral ones, but synovial joints (that is, lubricated by synovial fluid, which, rather like a car’s engine oil, helps to reduce wear and tear when bone moves against bone). The most important are the facet joints (page 16). They are bony catches that prevent each vertebra from slipping off the next one, making the spine into a bony chain that, again, is flexible yet strong. But the facet joints can also be vulnerable to both accidents and the strains
Thoracic vertebrae
A vertebra A vertebra of the thoracic spine is illustrated below. The body of the vertebra faces inwards towards the abdominal cavity and the processes face outwards.
Transverse process
A protective basin While the back and shoulders anchor the arms, the pelvis anchors the legs. In Latin, pelvis means ‘basin’, which is a fitting term for the protective housing of so many vital organs. But it can also be thought of as part of the lower back, not just because its upper rim is part of the back, but because of the strength and stability it provides as the anchoring point for the legs. These are joined to the pelvis at the hip sockets.
Taller in the Morning!
The pelvis The pelvis anchors the legs to the spine.
The centre of the cartilaginous discs between the vertebrae is classically likened to the chewy centre of a hard sweet, and is 85 per cent water. During the day our upright stance means that the weight of the bones in the spinal column compresses each disc by as much as 10 per cent. But during sleep the pressure is reduced and the discs reabsorb water, with the result that you can wake up as much as 2 cm (1 in) taller than when you went to bed.
Sacrum
talk about the shoulder in a book about the back, but the two are not only linked anatomically but through their working relationship. This means that many problems in the spine can make themselves felt in the shoulder and vice versa. The shoulder joint (see left and page 88) comprises the associated back bones, the collarbone (clavicle) and the shoulder blade (scapula), and the upper arm bone (humerus). Most of the muscles that anchor the joint originate in the back and, in particular, in the scapula. Therefore the joint’s performance and the movements of the arm are inextricably linked with those of the back.
caused by poor posture, making a catch slip off and so disrupt the chain.
Lumbar vertebrae
Body of vertebra
Shouldering the strain It may seem strange to
Sacroiliac joint
Ilium
Sacral vertebrae
Hip joint
Pubic symphysis
Coccyx
The Living Back
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