Overview of Bones:

What do Bones do?

Bones serve numerous vital functions in the human body and contribute to our overall health and well-being. The major functions of bones include:

- Support and Structure: Bones provide the structural framework that supports the entire body. They form the skeleton, which gives the body its shape and provides support for muscles, organs and tissues.

- Protection: Bones act as protective shields for vital organs. For example, the skull protects the brain, the rib cage protects the heart and lungs and the spinal vertebrae protect the spinal cord

- Movement: Bones in conjunction with muscles, joints and ligaments enable movement. Muscles attach to bones via tendons and when muscles contract they exert force on the bones, enabling movement at the joints.

- Detoxification: Bones have the ability to take in heavy metals like lead, mercury, and arsenic from the bloodstream as part of the detoxification process.

- Mineral Storage: Bones serve as a reservoir for essential minerals such as calcium and phosphorus. Bones are also referred to as calcium banks. The minerals stored in our bones are crucial for bone strength, nerve & muscle function and enzyme activity.These minerals are deposited and stored in the bones and can be released into our bloodstream as and when needed to maintain proper levels in the body.

- Blood Cell Production: Within the bone marrow, specialized cells called hematopoietic stem cells produce red blood cells, white blood cells and platelets through a process called hematopoiesis. This synthesis of blood cells is crucial for oxygen transport, immune function and blood clotting

- Endocrine Function: Bones produce hormones such as osteocalcin which regulates blood sugar levels and metabolism and osteocalcin which influences energy metabolism and fertility.

- Metabolic Regulation: Bones play a role in regulating mineral balance and metabolism. They release minerals into the bloodstream when needed for various physiological functions and can also absorb minerals from the bloodstream when levels are found to be excessive.

- Maintaining Acid-Base Balance: Bone tissue helps maintain acid-base balance in our body by acting as a buffer. Bones absorb or release alkaline salts as needed to regulate pH levels in the blood and tissues.

- Fat Storage: Yellow bone marrow stores fat and serves as an energy reserve during periods of low calorie intake.

- Sound Transmission: Skull bones help transmit sound vibrations to the inner ear, enabling hearing.

- Impact Absorption and Pressure Regulation: Bones absorb the impact of falls and bumps, minimizing damage to underlying tissues. Certain bones such as the patella in the knee help distribute pressure evenly across joints thus preventing wear and tear. Bones bear the weight of our body and distribute it efficiently across joints, enabling activities such as standing, running and jumping.

Types of bone

Bones in the human body can be classified into five main types based on their shape and function:

1. Long Bones: Long bones are characterized by their elongated shape and serve as levers for movement. They consist of a shaft (diaphysis) and two expanded ends (epiphyses) and are found in the arms, legs, fingers, and toes. Examples of long bones include the femur (thigh bone), humerus (upper arm bone), and phalanges (finger and toe bones).

2. Short Bones: Short bones are roughly cube-shaped and provide support and stability in joints with limited movement. They are found primarily in the wrists (carpals) and ankles (tarsals). Examples of short bones include the carpals (wrist bones) and tarsals (ankle bones).

3. Flat Bones: Flat bones are thin, flattened, and often curved, They provide protection for internal organs and serve as sites for muscle attachment. They consist of two layers of compact bone with a layer of spongy bone in between. Examples of flat bones are the skull bones (parietal, frontal, occipital), sternum (breastbone), ribs and scapula (shoulder blades).

4. Irregular Bones: Irregular bones as the name suggests have complex shapes that do not fit into the categories of long, short or flat bones. They often have unique functions and serve various purposes in the body. Some examples are the vertebrae (spinal bones), pelvic bones and some facial bones such as the maxilla and mandible.

5. Sesamoid Bones: Sesamoid bones are small, round bones embedded within tendons or joint capsules. They reduce friction, modify pressure and provide mechanical advantage to muscles. The most well-known sesamoid bone is the patella (kneecap), found in the tendon of the quadriceps muscle at the front of the knee.

Bone Diseases and Disorders

Common types of diseases related to the bone include:

Osteoporosis: It is a bone disorder characterized by low bone density and deterioration of bone tissue. It leads to an increased risk of fractures, particularly in the hip, spine and wrist. Osteoporosis can be caused by a number of factors, including low levels of calcium and vitamin D, hormonal changes and certain medications.

Osteoarthritis: It is a degenerative joint disease that occurs when the protective cartilage that cushions the ends of bones wears down over time, causing pain, stiffness, and loss of mobility in the affected joints. Osteoarthritis can be caused by a number of factors, including age, injury, overweight and obesity, and joint overuse. There is no cure for osteoarthritis but treatment can help manage the symptoms. This may include pain medication, physical therapy and joint replacement surgery.

Rheumatoid Arthritis: An autoimmune bone disease that causes chronic inflammation of the joints. It leads to damage to the joint tissue, cartilage and bone, resulting in pain, swelling and deformation of the joints

Paget's Disease of Bone: It is a chronic bone disease marked by abnormal bone remodeling, leading to weakened, enlarged and deformed bones. Paget's disease often has no symptoms but some people may experience bone pain, deformity, fractures and other complications.

Osteogenesis Imperfecta: This genetic disorder is also known as brittle bone disease. It causes fragile bones that are prone to fractures. Other symptoms include short stature, weak muscles and hearing loss.

Bone Cancer: Various types of cancer can originate in the bones (primary bone cancer) or spread to the bones from other parts of the body (secondary bone cancer), leading to bone pain, fractures and other symptoms. Treatment for bone cancer depends on the type and stage of the cancer. Options may include surgery, chemotherapy and radiation therapy.

Bone Infections: Conditions such as osteomyelitis, a bacterial infection of the bone, can cause inflammation, pain and bone damage if left untreated.

Scoliosis: Scoliosis is marked by an abnormal sideways curvature of the spine which can lead to uneven shoulders, waist asymmetry and back pain, among other symptoms.

Rickets and osteomalacia: These conditions cause soft and weak bones. Rickets affects children while osteomalacia affects adults. Rickets and osteomalacia are caused by a lack of vitamin D, which is needed for the body to absorb calcium from food.

How are bone disorders diagnosed? What are the tests used to detect bone problems?

Diagnosing bone diseases involves a multi-pronged approach, combining diagnostic tests with medical history, physical examination, symptoms, risk factors (age, family history & medications) and lifestyle choices such as diet and exercise

Common bone tests and bone scans include:

Imaging tests:

• X-rays: X-rays can detect changes in bone density, structure and alignment. They are often the first imaging modality used to assess for bone abnormalities and screen for bone fractures, arthritis & Paget's disease.
• DEXA scan: DEXA scans are used to measure bone mineral density and diagnose conditions such as osteoporosis.
• CT Scan (Computed Tomography): CT scans provide detailed 3D images of bone structures and surrounding tissues. They can be used to detect fractures, tumors, infections and other abnormalities.
• MRI (Magnetic Resonance Imaging): MRI scans are excellent for visualizing soft tissues such as cartilage and tendons around bones. They aid in the diagnosis of conditions such as osteoarthritis, bone infections and tumors.

Some bone scans use radioactive tracers to detect areas of increased bone activity. They can be used for identifying tumors, fractures and infections.

Laboratory tests:

Bone Metabolism Markers:

• Calcium: Total calcium and ionized calcium levels are measured to assess bone health and calcium homeostasis.
• Phosphate: Phosphate levels are evaluated alongside calcium levels to assess mineral balance.
• Alkaline Phosphatase (ALP): Elevated ALP levels may indicate increased bone turnover or liver dysfunction.
• Parathyroid Hormone (PTH): PTH levels are assessed to evaluate calcium regulation and bone metabolism.
• Vitamin D: Measurement of 25-hydroxyvitamin D levels helps assess vitamin D status, which is essential for bone health.

Inflammatory Markers:

• C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR): Elevated levels may indicate inflammation associated with bone-related disorders such as osteomyelitis or rheumatoid arthritis.
• Complete Blood Count (CBC): Anemia may be associated with certain bone marrow disorders or chronic inflammatory conditions affecting bone health.

Bone Biopsies:

In some cases, a sample of bone tissue may be obtained through a biopsy procedure for further analysis to diagnose bone cancer, infections or other conditions. There are two possible types of bone biopsy. They are:

- Needle biopsy - A needle is directly inserted into the targeted bone to acquire a sample

- Open biopsy - It is an elaborate surgical procedure in which an incision is made in the skin to enable the sample to be acquired from the bone.

Body Fluid Investigations:

Synovial Fluid Analysis: Synovial fluid from joints may be analyzed for:

• Cell Count and Differential: Detecting or Pinpointing inflammatory or infectious joint conditions.
• Crystals: Identification of monosodium urate crystals in gout or calcium pyrophosphate crystals in pseudogout.
• Culture and Sensitivity: Detection of infectious agents such as bacteria or fungi in septic arthritis.

Bone Marrow Aspiration and Biopsy:

• Bone Marrow Aspiration: In this procedure bone marrow cells are collected for cytological examination, including assessment of cellularity and presence of abnormal cells.
• Bone Marrow Biopsy: This biopsy provides tissue samples for histological examination, aiding in the diagnosis of bone marrow disorders such as leukemia, lymphoma, or metastatic cancer.

Joint Fluid Analysis:

Similar to synovial fluid analysis, joint fluid from specific joints may be evaluated for inflammatory markers, crystals, and infectious agents.

Depending on the suspected bone disease, additional specialized tests may be performed. For example, genetic testing may be used to diagnose genetic disorders like osteogenesis imperfecta, while bone scans or PET scans may be used to detect bone metastases in cancer.

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Frequently Asked Questions

1. Why are bones important for overall health?

Ans - Bones provide structure and support for the body, protect vital organs, facilitate movement, store minerals like calcium and phosphorus, and produce blood cells. Bone marrow inside certain bones creates red blood cells, white blood cells, and platelets.

2. What things are important for bone health?

Ans- Here are a few actionable tips to keep your bones healthy:

• Adequate intake of calcium, vitamin D, and other nutrients
• Exercise regularly and include strength and resistance training in your regimen
• Avoid smoking and excessive alcohol consumption
• Maintain a healthy body weight
• Get at least 8 hours of quality sleep

3. How do you know if your bones are unhealthy?

Ans - Symptoms of weak or unhealthy bones may include frequent fractures, bone pain (especially in the back or hips), loss of height, stooped posture, muscle weakness, fatigue and decreased mobility. Diagnostic tests like bone density scans can also identify bone health issues.

4. What is the composition of the bones in the human body?

Ans - Bones are made of:

1. Collagen: A protein providing flexibility and structure.

2. Minerals: Mostly calcium and phosphorus which give bones their hardness and strength.

3. Bone cells: Living cells responsible for bone growth, repair and breakdown.

Other major components of our bones include water, fat, and bone marrow, which produces blood cells.