Anatomy & Physiology

Anatomy & Physiology

 

How Your Back Works

A healthy back allows you to bend and stretch without pain. The spine has three natural curves, which keep your body balanced. Strong, flexible muscles support your spine. Soft, cushioning disks separate the hard bones of your spine, allowing it to bend and move.

The Parts of the Spine

  • The vertebrae are the 24 bones that make up the spine.

  • The spinous process is the part of each vertebra you can feel through your skin.

  • Each of these bones has a canal that runs top to bottom. Together these canals form a tunnel called the spinal canal.

  • The lamina of each vertebra forms the back of the spinal canal.

  • Running through the canal are nerves.

  • A foramen is a small opening where a nerve leaves the spinal canal.

  • Disks serve as cushions between vertebrae. A disk's soft center absorbs shock during movement.

The Supporting  Muscles

Strong, flexible muscles help maintain your three natural curves. They hold your spine in proper alignment. This helps support your upper body. Strong stomach, buttock, and thigh muscles help take the strain off your back.

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How Your Hip Works

The hip joint is one of the body's largest weight-bearing joints. It's a ball-and-socket joint. This helps the hip remain stable even during twisting and extreme ranges of motion. A healthy hip joint allows you to walk, squat, and turn without pain.

A Healthy Hip

The hip joint is formed where the rounded head of the thighbone (femur) joins the pelvic bone. The joint is covered with tissue and powered by large muscles. When all of the parts listed below are healthy, a hip should move easily.

  • Cartilage is a layer of smooth tissue. It covers the ball of the thighbone, and lines the socket of the pelvic bone. Healthy cartilage absorbs stress and allows the ball to glide easily in the socket.

  • Muscles power the hip and leg for movement.

  • Tendons attach the muscles to the bones.

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How Your Knee Works

A healthy knee bends easily and rotates slightly. The joint absorbs stress and moves smoothly. This allows you to walk, squat, and turn without pain.

A Healthy Knee

The knee is a hinge joint, formed where the thighbone (femur) and the shinbone (tibia) meet. The joint is covered with smooth tissue and powered by large muscles. When all the parts listed below are healthy, a knee should move easily.

  • Cartilage is a layer of smooth tissue. It covers the ends of the thighbone and shinbone. It also lines the back side of the kneecap. Healthy cartilage absorbs stress and allows the knee to bend easily.

  • Muscles power the knee and leg for movement.

  • Tendons attach the muscles to the bones.

  • Ligaments are bands of tissue that connect bones and brace the joint.

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Parts of a Hand

Hands are made up of more bones and moving parts than most other areas of your body. When they're healthy, all of these parts work together to perform an amazing array of tasks-from very delicate movements to feats of strength.

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Parts of the Shoulder

The shoulder is the most flexible part of the body. The main joint in the shoulder is called the glenohumeral joint.This is where the arm bone (humerus) rests in a shallow socket called the glenoid. The bones in the shoulder are connected by ligaments, muscles, and other strong tissues. When the shoulder is healthy, you can move your arm in almost any direction (a full range of motion).

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Parts of a Foot

Your foot is made up of soft tissue and bones that work together to form a healthy, functioning, and pain-free foot.

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Anatomy of a Normal Spine

The spinal column is a stack of bones (vertebrae) that are separated by soft pads of tissue (disks).Each of these bones has a canal that runs top to bottom. Together these canals form a tunnel called the spinal canal. Running through this canal are nerves. These nerves carry signals between the brain and body.

The spine has three natural curves: the cervical, the thoracic, and the lumbar.

The Parts of the Spine

  • The vertebrae are the 24 bones that connect like puzzle pieces to make up the spine.

  • The lamina of each vertebra forms the back of the spinal canal.

  • A foramen is a small opening. This is where a nerve leaves the spinal canal.

  • The transverse process is the wing of bone on either side of each vertebra.

  • The spinous process is the part of each vertebra you can feel through your skin.

  • A disk lies between each of the vertebrae.

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Back Basics: A Healthy Spine

A healthy spine supports the body while letting it move freely. It does this with the help of three natural curves. Strong, flexible muscles help, too. They support the spine by keeping its curves properly aligned. The disks that cushion the bones of your spine also play a role in back fitness.

Three Natural Curves

The spine is made of bones (vertebrae) and pads of soft tissue (disks). These parts are arranged in three curves:cervical, thoracic, and lumbar. When properly aligned, these curves keep your body balanced. They also support your body when you move. By distributing your weight throughout your spine, the curves make back injuries less likely.

Strong, Flexible Muscles

Strong, flexible back muscles help support the three curves of the spine. They do so by holding the vertebrae and disks in proper alignment. Strong, flexible abdominal, hip, and leg muscles also reduce strain on the back.

The Lumbar Curve

The lumbar curve is the hardest-working part of the spine. It carries more weight and moves the most. Aligning this curve helps prevent damage to vertebrae, disks, and other parts of the spine.

Cushioning Disks

Disks are the soft pads of tissue between the vertebrae. The disks absorb shock caused by movement. Each disk has a spongy center (nucleus) and a tougher outer ring (annulus). Movement within the nucleus allows the vertebrae to rock back and forth on the disks. This provides the flexibility needed to bend and move.

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The Kneecap (Patella) & Knee Joint

The kneecap (patella) is a small triangular bone. It is just one of the many parts that make up the knee joint. Some of the other parts are muscles, ligaments, and leg bones. The kneecap provides leverage for your muscles as they bend and straighten the leg. It also protects the knee joint.

The Kneecap Up Close

Take a closer look at this small bone to see how it works.

From the front, you can see the kneecap's slightly rounded, shield-like shape.

From the back, you can see cartilage. This is tough tissue that covers the bone. It helps the kneecap slide easily against the thighbone.

From the top, you can see that the kneecap sits in a groove or "track" in the thighbone.

A closer view of the kneecap shows the difference between the smooth cartilage and the rougher bone beneath.

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The Kneecap (Patella) In Action

As the leg moves, the kneecap moves, too. It slides up and down its track on the thighbone. But if the kneecap slides "off track"-even a little-pain and damage can result.

When the Kneecap is "On Track"

The kneecap is controlled by muscles and ligaments that work like a system of pulleys. This system includes the quadriceps muscles, retinacula, and patellar tendon. If all these parts pull in just the right way, the kneecap stays in place and glides easily in its track. Pressure is spread evenly on the back of the kneecap.

 

When the Kneecap Gets "Off Track"

An injury can cause some muscles or ligaments to pull too hard or not hard enough. When that happens, the kneecap no longer glides easily against the thighbone. Pressure may be spread unevenly on the back of the kneecap, causing wear and tear on the cartilage.

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The Shoulder Joint

The shoulder is made up of bones, muscles, ligaments, and tendons. They work together so you can reach, swing, and lift in comfort. Learning about the parts of the shoulder and joint will help you to understand your shoulder problem.

The Parts of the Joint

The shoulder joint is where the humerus (upper arm bone) meets the scapula (shoulder blade).

  • Muscles and ligaments help make up the joint. They attach to the shoulder blade and upper arm bone.

  • At the top of the shoulder blade are two bony knobs called the acromion and coracoid process.

  • The subacromial space is between the top of the humerus and the acromion. This space is filled with tendons and muscles.

  • The bursa is a sac of fluid that cushions shoulder parts as they move.

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Know Your Neck: The Cervical Spine

By learning about the parts of the neck, you can better understand your neck problem. The bones of the neck are calledcervical vertebrae. Together, they form a bony column called the spine. Vertebrae also protect the spinal cord, a pathway for messages to reach the brain. Surrounding the spine are soft tissues such as muscles, tendons, and nerves.

Flexibility Is Key

For the neck to function normally, it has to be flexible enough to move without discomfort. A healthy neck can move easily in six different directions.

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Your Neck Muscles

The muscles in the neck and shoulders need to be strong to hold the neck and head in place. These muscles also help move the neck and shoulders. Your healthcare provider can recommend exercises to help stretch and strengthen your neck muscles.