Spine Anatomy Flashcards
(42 cards)
The Back and Beyond
Bones are four times stronger than concrete. The minerals calcium and phosphorus make bones (and teeth) hard and strong. Eating foods that contain these minerals, such as yogurt and spinach, helps keep your bones healthy.
Living Structures
Bones are living, breathing structures. They don’t exactly inhale and exhale, but bones do make red (and white) blood cells. Red cells deliver oxygen, whereas the white ones rush like battlefront nurses to fight germs and diseases. If bones weren’t alive, a broken bone would remain broken forever. Instead, they remarkably repair themselves(often with a little help from our medical friends). This natural ability for self-repair is the same for a broken finger as it is for a fractured backbone.
More Bones at Birth
Bones come in many shapes and sizes, each designed for a particular function. The bones of the spine, called vertebrae, are like cylindrical building blocks. They stack on top of each other like small cans separated by little cushions called discs. The spinal column (also known as the vertebral column) is held together mainly by discs and facet joints with support from ligaments and muscles.
Definition
The place where two bones come together is a called a joint. In the spine, the joint formed at meeting of two vertebrae is called a facet joint. Like joints anywhere in the body, they can swell and pinch nerves. Many people focus on the discs as a source of back pain although the facet joints are often to blame.
Cervical Spine
This is your neck, which contains seven vertebrae(C1–C7). The last, C7 is the bone that generally sticks out the most. You can easily feel it at the base of your neck, especially when you bend your head forward. Go ahead, see if you can find it.
The cervical vertebrae’s main job
The cervical vertebrae’s main job is to support your head. This is no small feat given that the head can weigh as much as 11 pounds! That’s why how you hold your head matters so much. For many computer workers, a small but constant forward jut of the head is not uncommon. The result can transmit forces deep into the neck and shoulders. Stress to your neck muscles can lead to joint misalignment, which can pinch nerves. The result? Ouch! A sore neck with pain possibly radiating down into your arms.
Think about how many directions you can move your head
Think about how many directions you can move your head. There’s up, down, side to side, forward and back, and around. It can tilt like a bobble head. Thank the cervical vertebrae—in particular, the pivoting action of C1—for all those marvelous movements. And that’s a good thing most of the time. On the downside, the highly flexible neck makes it especially vulnerable to injury—such as whiplash when your head is thrust forward due to impact from a rear-end auto crash.
Thoracic Spine
This is your rib-cage/midback area and it has 12 vertebrae (T1–T12). Unlike your other vertebrae, these attach to your ribs. The thoracic spine can move forward relatively easily, though it’s much more limited bending backward. This part of your back is not typically a huge problem when it comes to back pain(most problems occur in the lower back). The midback can, however, be overly curved in some individuals, a condition called kyphosis. It often results from bad posture—think of slouching teenagers. But it can also be caused by disease. Either way, the excessive curve makes a person appear hunchbacked.
kyphosis
There can be some discomfort with kyphosis caused by disease, but postural kyphosis doesn’t generally cause much pain. However, excessively rounding your thoracic spine may also lead to the head being positioned forward, which, as we mentioned earlier, causes problems in your neck. The forward slumping also shortens the muscles in front of your torso and overstretches some back muscles. This can lead to discomfort when you try to sit up straight. The good news is that you can correct this with good posture and proper exercise.
Meet your lower back
the part that causes pain for the vast majority of people. But before you curse the day you were born with it, know that those five lumbar vertebrae (L1–L5) have a mighty big job to do: they support most of the weight of your body. As you can see in the illustration, being the largest of the vertebrae, they’re highly qualified for the job. These bones are indeed made for walking, running, sitting, and lifting. All these activities, of course, have a potential injury risk—which you can reduce by keeping your back and abdominal muscles strong and maintaining proper flexibility throughout your back and body. Good muscle conditioning lends support to your lower back (and other parts of the spine), and with proper stretching, you can keep the area flexible as well.
Lumbar Lordosis or “Swayback”
An excessive curve in the lower back is called lordosis, also known as swayback. This curve puts way too much pressure on your lumbar vertebrae. Lordosis can be caused by disease, a movement of the spine such as bending the back, or bad posture. Think of the final pose of gymnasts when they dismount from the parallel bars. The chest is thrust forward, shoulders back, and the lower back arches. This is what extreme lordosis in the lower back can look like. Of course, gymnasts do it on purpose. Although it’s not a disease when they perform these contortions, they can end up with back problems because of it.
For the rest of us mortals, simply sitting incorrectly can cause too much pressure on the lumbar spine. That’s why knowing how your vertebrae should be aligned and taking appropriate steps to make that happen can go a long way toward relieving back issues.
Sacrum and Coccyx
You might think that spinal fusion is something only surgeons do, but nature actually does this too and if you’re over 30 years old, it’s already happened to you. Your sacrum (from the Medieval Latin os sacrum, meaning holy bone), the flat triangular bone situated between your hips, is actually five fused vertebrae. This fusion isn’t complete until you’re about 25 or 30. This part is the lowest and last curve in your spine. The curve, called the lumbosacral curve, helps support body weight.
Below the sacrum is the tail end of your spine, called the coccyx or tailbone. Again, several fused vertebrae (generally 3–5) form the coccyx. Injury to this area can lead to coccydynia, which is a real pain in the you-know-what.
Coccydynia
Coccydynia is a painful condition involving swelling around your tailbone. When the ligaments and tendons in this area become inflamed, it hurts to sit. You can also get this pain from a fracture of the coccyx, which can happen if you fall and land on your tailbone.
facet joints
Like other joints in the body, facet joints are subject to repetitive stress injuries and degenerative diseases such as osteoarthritis. Also, the joint capsule can rupture and form cysts that pinch nerves, but most of the time, they just flare up.
Cartilage
Cartilage is basically smooth, rubbery tissue. Your nose is composed of it, as are your ears. Cartilage caps the ends of bones, providing cushion and slipperiness, enabling bones to move easily. When cartilage wears away, bone grinds on bone, causing pain and deterioration. Osteoarthritis and rheumatoid arthritis are two common diseases that damage joint cartilage. In the spine, facet joints are covered with cartilage.
Ligaments
Ligaments are strong fibrous bands that connect bone-to-bone. Their main job is to stabilize bones, holding them in place. They do, however, have a little flexibility.
Joint capsules
Joint capsules lie between the joints. A fluid, called synovial fluid, is produced in the capsule. Because there is a lot of sliding at these joints, the lubricating fluid is very important in helping prevent grinding. (Cartilage also helps.)
Sacroiliac (SI) Joints
The sacroiliac (SI) joints link your sacrum to your pelvis, specifically to your iliac bones. You can easily feel your iliac bones; they're the bones at the top of your hips. Strong ligaments stabilize and attach your sacrum to your hip bones. Some motion is possible through these joints, but it's very limited. Pregnancy, for example, can loosen these joints, and if they don't return to normal, they can cause instability issues later in life. The SI joint can be an overlooked source of back pain; it's subject to the same things that can happen to other joints, such as osteoarthritis. Also keep in mind the weight this lowest part of your spine bears. Excessive body weight and lifting injuries can negatively affect these joints. Because lots of muscles attach to the sacrum, muscular weakness or imbalances can misalign joints and be possible sources of pain.
discs sit between each vertebra.
Tough on the outside with a softer, gel-like fluid inside, discs sit between each vertebra. Think of them as car tires on their sides, filled with a thick gel. When your car drives over a bump, the rubber tire ‘gives’ a little, to absorb the bump. Similarly, each time we move the spine, the discs change shape in relation to the movement. Like so many structures in the body, discs are multifunctional. They are shock absorbers, and they connect and protect vertebral bones. Without discs, bone would touch bone with each movement and eventually grind away.
Discs are made from collagen; technically speaking, they are fibrocartilage, which means they consist of strong fibers with some elasticity.
herniated disc
Also know that the shocks absorbed are usually small and not a problem generally speaking, especially because these discs are quite tough. They do, however, have their limits, just like tires. When the shock is too extreme, something has to give and a tire will blow. In the case of our intervertebral discs, the gel on the inside can burst out (causing a herniated disc) or the outside can protrude (a bulging disc); the discs can also dry out and get thinner (due to disease or sometimes from aging).
The outer layer of the disc
The outer layer of the disc is called the annulus fibrosis. Its main job is to attach to the vertebra above and below, although it also provides some cushion. The fibers are crisscrossed, making the connections super strong. Repetitive stress can sometimes cause this outer layer to bulge. If the bulge pushes on a nerve, the result is pain.
The nucleus pulposus
The nucleus pulposus is the gel-like center of the disc designed to absorb shock and provide lubrication. It’s mostly made of water. As we age, it can dry up a bit, making the discs thinner and less shock absorbent. There is some evidence that inversion therapy or lumbar traction can help the discs rehydrate, but the long-term benefits have yet to be demonstrated.
ligaments, tendons, and muscles
Skeletal bones form the framework of our bodies, and in the previous section we talked about the joints and discs that link the bones. But something has to secure all these pieces in place. These are mainly ligaments, tendons, and muscles, all types of connective tissue. Each provides both stability and mobility to a greater or lesser degree.
Connective tissue
Connective tissue is a broad term referring to various types of tissue that connect and support structures literally everywhere in the body. Collagen, tendons, and even muscles are types of connective tissue. Fascia, a type connective tissue that lies just under the surface of the skin, can tighten and cause pain in various parts of the body, including the back. Some diseases such as rheumatoid arthritis are considered connective tissue disorders.
