Skeletal system: pictures of bones, functions

pictures of bones, functions and Diseases affecting the skeletal system


Introduction to skeletal system

The skeletal system is composed of bones and cartilage connected by ligaments to form a framework for the rest of the body tissues.The internal skeleton that serves as a framework for the body. This framework consists of many individual bones and cartilages. There also are bands of fibrous connective tissue—the ligaments and the tendons—in intimate relationship with the parts of the skeleton. This article on Skeletal system is concerned primarily with the gross structure and the function of the skeleton of the normal human adult.
In adult there about 206 bones in human skeleton and some Authors believes that there about 207-300 bones in children skeleton, due to metamorphosis going on in children, but by their adult hood the bone will articulate and become fully formed(ossified) to turn to normal bone number in Adult which is 206 bones
The human skeleton, like that of other vertebrates, consists of two principal subdivisions, each with origins distinct from the others and each presenting certain individual features.
There are two parts to the skeleton:
  • Axial skeleton – bones along the axis of the body, including the skull, vertebral column and ribcage;
  • Appendicular skeleton – appendages, such as the upper and lower limbs, pelvic girdle and shoulder girdle.
These are (1) the axial, comprising the vertebral column—the spine—and much of the skull, and (2) the appendicular, to which the pelvic (hip) and pectoral (shoulder) girdles and the bones and cartilages of the limbs belong.

 Discussed in this article as part of the axial skeleton is a third subdivision, the visceral, comprising the lower jaw, some elements of the upper jaw, and the branchial arches, including the hyoid bone.

When one considers the relation of these subdivisions of the skeleton to the soft parts of the human body—such as the nervous system, the digestive system, the respiratory system, the cardiovascular system, and the voluntary muscles of the muscle system—it is clear that the functions of the skeletal system are of three different types: support, protection, and motion e.t.c

Of these functions, support is the most primitive and the oldest; likewise, the axial part of the skeleton was the first to evolve. The vertebral column, corresponding to the notochord in lower organisms, is the main support of the trunk.

Functions of Skeletal system

As well as contributing to the body’s overall shape, the skeletal system has several key functions, including:
  1. Support and movement;
  2. Protection;
  3. Mineral homeostasis;
  4. Blood-cell formation;
  5. Triglyceride storage.

Support and movement

Skeleton are a site of attachment for ligaments and tendons, providing a skeletal framework that can produce movement through the coordinated use of levers, muscles, tendons and ligaments. The bones(skeleton) act as levers, while the muscles generate the forces responsible for moving the bones.


Skeleton provide protective boundaries for soft organs: the cranium around the brain, the vertebral column surrounding the spinal cord, the ribcage containing the heart and lungs, and the pelvis protecting the urogenital organs.

Mineral homoeostasis

As the main reservoirs for minerals in the body, Skeleton or bones contain approximately 99% of the body’s calcium, 85% of its phosphate and 50% of its magnesium (Bartl and Bartl, 2017). They are essential in maintaining homoeostasis of minerals in the blood with minerals stored in the bone are released in response to the body’s demands, with levels maintained and regulated by hormones, such as parathyroid hormone.

Blood-cell formation (haemopoiesis)

Blood cells are formed from hemopoietic stem cells present in red bone marrow. Babies are born with only red bone marrow; over time this is replaced by yellow marrow due to a decrease in erythropoietin, the hormone responsible for stimulating the production of erythrocytes (red blood cells) in the bone marrow. By adulthood, the amount of red marrow has halved, and this reduces further to around 30% in older age (Robson and Syndercombe Court, 2018).

Triglyceride storage

Yellow bone marrow acts as a potential energy reserve for the body; it consists largely of adipose cells, which store triglycerides (a type of lipid that occurs naturally in the blood) (Tortora and Derrickson, 2009).


Bone composition

Bone matrix has three main components:

  1. 25% organic matrix (osteoid);
  2. 50% inorganic mineral content (mineral salts);
  3. 25% water (Robson and Syndercombe Court, 2018).

Organic matrix (osteoid) is made up of approximately 90% type-I collagen fibres and 10% other proteins, such as glycoprotein, osteocalcin, and proteoglycans (Bartl and Bartl, 2017). It forms the framework for bones, which are hardened through the deposit of the calcium and other minerals around the fibers (Robson and Syndercombe Court, 2018).

Mineral salts are first deposited between the gaps in the collagen layers with once these spaces are filled, minerals accumulate around the collagen fibers, crystallising and causing the tissue to harden; this process is called ossification (Tortora and Derrickson, 2009). The hardness of the bone depends on the type and quantity of the minerals available for the body to use; hydroxyapatite is one of the main minerals present in bones.

the structure of bone

Structure that made up the skeletal system

Bone architecture is made up of two types of bone tissue:

  • Cortical bone;
  • Cancellous bone.

Cortical bone
Also known as compact bone, this dense outer layer provides support and protection for the inner cancellous structure. Cortical bone comprises three elements:

  • Periosteum;
  • Intracortical area;
  • Endosteum (Bartl and Bartl, 2017)


It is generally called the skull ie the bones of the skulls. it is protects the brains and also serves as a socket to the other  part of the organs like eye(ball socket), it consists of jaws which is upper jaw=maxilla and lower part is called the Mandibular. They are about 22 bones.
skull, source: encyclopedia britannica
The cranium—the part of the skull that encloses the brain—is sometimes called the braincase, but its intimate relation to the sense organs for sight, sound, smell, and taste and to other structures makes such a designation somewhat misleading.

when it comes to the bones of the upper lims, it consist of bone shoulder joints, arm.forearm and bones of the palms(fingers) which is called phalenges.

Phanlenges, source: encyclopedia britannica


The humerus is a long bone of the upper limb, which extends from the shoulder to the elbow.
The proximal aspect of the humerus articulates with the glenoid fossa of the scapula, forming the glenohumeral joint. Distally, at the elbow joint, the humerus articulates with the head of the radius and trochlear notch of the ulna.

so, the shoulder girdle and upper limbs is about 64 bones.
Bones of the Upper limbs
There about 33 bones and they are as follows:
  • Cervical vertebrae(C1-C7)
  • Thoracic vertebrae (T1-T12)
  • Lumbar vertebrae(L1-L5)
  • Scarum vertebrae(S1-S5)
  • coccyx(C1-C4)
It is also known as the vertebral column is not actually a column but rather a sort of spiral spring in the form of the letter S. The newborn child has a relatively straight back-bone. The development of the curvatures occurs as the supporting functions of the vertebral column in humans—i.e., holding up the trunk, keeping the head erect, serving as an anchor for the extremities—are developed.
The back bones consists of the spinal cord and also the CSF in between the L2-L3. The S-curvature enables the vertebral column to absorb the shocks of walking on hard surfaces; a straight column would conduct the jarring shocks directly from the pelvic girdle to the head. The curvature meets the problem of the weight of the viscera.
Back bones, source: encyclopedia britannica
The rib cage.
The rib cage, or thoracic basket, The chest bone consists of the 12 thoracics (chest) vertebrae, the 24 ribs, and the breast bone, or sternum. The ribs are curved, compressed bars of bone, with each succeeding rib, from the first, or uppermost, becoming more open in curvature. The place of greatest change in curvature of a rib, called its angle, is found several inches from the head of the rib, the end that forms a joint with the vertebrae bone.
The first seven ribs are attached to the breast bone by cartilages called costal cartilages; these ribs are called true ribs. Of the remaining five ribs, which are called false, the first three have their costal cartilages connected to the cartilage above them. The last two, the floating ribs, have their cartilages ending in the muscle in the abdominal wall.
Bones of the chest, source: encyclopedia britannica
Through the action of a number of muscles, the rib cage, which is semirigid but expansile, increases its size. The pressure of the air in the lungs thus is reduced below that of the outside air, which moves into the lungs quickly to restore equilibrium.
These events constitute inspiration (breathing in). Expiration (breathing out) is a result of relaxation of the respiratory muscles and of the elastic recoil of the lungs and of the fibrous ligaments and tendons attached to the skeleton of the thorax.
A major respiratory muscle is a diaphragm, which separates the chest and abdomen and has an extensive origin from the rib cage and the vertebral column. The configuration of the lower five ribs gives freedom for the expansion of the lower part of the rib cage and for the movements of the diaphragm.
Pelvis, also called bony pelvis or pelvic girdle consists of sacrum,pelvis bones and lower limbs,
The bones pelvic gridle and lower limbs are about 62 bones.
In human anatomy, basin-shaped complex of bones that connects the trunk and the legs, supports and balances the trunk, and contains and supports the intestines, the urinary bladder, and the internal sex organs.
The pelvis consists of paired hip bones, 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.
Bones of the lower Limb
All three unite in early adulthood at a triangular suture in the acetabulum, the cup-shaped socket that forms the hip joint with the head of the femur (thigh bone). The ring made by the pelvis functions as the birth canal in females.
The pelvis provides attachment for muscles that balance and support the trunk and move the legs, the hips, and the trunk. In the human infant the pelvis is narrow and non supportive. As the child begins walking, the pelvis broadens and tilts, the sacrum descends deeper into its articulation with the ilia, and the lumbar curve of the lower back develops.
The forearm and the lower leg bones that have two long bones each. In the forearm are the radius—on the thumb side of the forearm—and the ulna; in the lower leg are the tibia (the shin-bone) and the fibula. The radius corresponds to the tibia and the ulna to the fibula. The knee joint not only is the largest joint in the body but also is perhaps the most complicated one.
Anterior view of the right femur (thighbone)
Bones of lower limb

Healthy bone requirement

(approximately 200–250 mg/day). Magnesium is found in many foods.
Bone Health Function
Food Sources
If you do not get enough calcium through your food or supplements, your body will take the calcium it needs from your bones.
Dairy (milk, cheese, yogurt); fortified foods (juices, cereals, almond, and soy milk); sardines or canned salmon with bones; tofu; dark green vegetables (collards, kale, broccoli, bok choy, okra); seeds (poppy, sesame, chia); almonds
Vitamin D
Necessary for calcium to be absorbed in the intestine.
Fatty fish (swordfish, salmon, sardines mackerel); fortified foods (dairy, cereal); egg yolks
Allows for proper calcium and vitamin D regulation.
Green vegetables (collards, kale, bok choy, okra); seeds (poppy, sesame, chia); nuts; legumes; whole grains; avocado
Nutrients needed for bone health based on good evidence
In healthy adults, these nutrients can be readily found in a balanced diet; rarely would a supplement be required—unless directed by your health care provider.
Bone Health Function
Food Sources
Part of bone mineral and important for neutralizing acidic foods that could otherwise be harmful to bone.
Protein foods (soybeans, fish, meat, milk, eggs); legumes; whole grains
Certain potassium salts neutralize acids that come from the body’s metabolic processes.
Fruits; vegetables; scallops; beans; whole grains; squash
Vitamin A
Influences osteoblasts (bone-building cells) and osteoclasts (bone breaking down cells).
Sweet potato; beef liver; spinach; carrots; cantaloupe; mangoes; fortified foods; eggs
Nutrients with a possible relationship to bone health
These nutrients may have a role in bone health, but the evidence is not conclusive. In healthy adults, they can be readily found in a balanced diet.
Bone Health Function
Food Sources
Mineralizes bone and stabilizes receptor proteins for vitamin D, protein synthesis.
Shellfish; beef; pork; seeds; beans; whole grains; yogurt
Vitamin B12
Appears to influence bone-building cells.
Clams; liver; fish; fortified cereal; meat; dairy products; eggs; poultry
Vitamin C
Essential to collagen formation and Increases absorption of plant-based iron.
Peppers; citrus; kiwi; broccoli; cauliflower; strawberries; Brussel sprouts; papaya
Vitamin K*
Low blood levels of vitamin K are associated with lower bone density and possibly increased fracture risk.
Collards; turnip greens; spinach; kale; broccoli; natto; soybeans; carrot juice; canned pumpkin; okra; blueberries; grapes; carrots

Diseases of the skeletal system

Even among bone diseases, symptoms you experience, specialists you see and treatment you receive are quite varied – for example, depending on whether you have osteoporosis or bone cancer. Common bone diseases in adults and children include the following:

  • Osteoporosis. One of the most prevalent bone conditions, osteoporosis involves bone loss, leading to weakened bones that are more likely to break. Osteoporosis is an invisible condition, often doing its damage without people realizing they have it. More than 53 million people in the U.S. either have osteoporosis or are at high risk for developing it, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
  •  Metabolic bone diseases. Osteoporosis is one of several metabolic bone diseases. These are disorders of bone strength caused by mineral or vitamin deficiencies (such as vitamin D, calcium or phosphorus) that result inabnormal bone mass or structure. Osteomalacia (softening of the bones), hyperparathyroidism (overactive gland leading to bone calcium loss), Paget disease of bone (abnormally large, weakened bones) and developmental bone disorders affecting children are all different types of metabolic bone diseases.
  • Fracture. Acute fractures are usually due to trauma, although they can be related to bone cancer. “Fractures are very dependent on patient demographics,” says Dr. Gerardo Miranda-Comas, director of the sports medicine fellowship in the Department of Rehabilitation and Human Performance at Icahn School of Medicine at Mount Sinai, in New York City. For instance, children’s bones are more flexible and resilient, and fractures heal more quickly. Kids are more likely to have wrist fractures while breaking a fall during sports or at play. Older adults are more vulnerable to falls and hip injuries because of balance issues, and as their bones may be more fragile, are likelier to break their hips.
  • Stress fracture. Also called overuse fractures, stress fractures are more common in active people like runners.
  • Bone cancer. Cancer that originates in the bone, called primary bone cancer, is rare, accounting for less than 1% of all new cancers diagnosed, according to the National Cancer Institute. Cancer that spreads to the bones from other parts of the body is more common, such as metastatic tumors from prostate or breast cancer. Multiple myeloma, a type of blood cancer, interferes with bone marrow function and new bone production in the hips, pelvis, ribs, shoulders and spine, increasing the risk of fracture.
  • Scoliosis. Abnormal, side-to-side curvature of the spine, resulting in an S- or C-shaped appearance when seen from behind, is called scoliosis. It’s commonly diagnosed in infants or children, but can persist into adulthood.

Age, occupation, activity level, environmental factors and genetics all play a role in bone disease risk, says Miranda-Comas, whose specializes as a physiatrist, or physical medicine and rehabilitation physician. People who work on their feet all the time or whose jobs involve heavy labor are at higher risk of bone conditions. Low sun exposure and low vitamin D also contribute. Too little physical activity puts people at risk for osteoporosis, so highly inactive people may be more vulnerable to fractures.

Osteoarthritis is on the rise, particularly when it involves weight-bearing joints such as the hips and knees, as the obesity epidemic continues, Fox notes. Gout is also partially tied to excess weight.

For rheumatoid arthritis, juvenile arthritis and spondyloarthritis, rates are fairly stable, Fox says. Family history, being middle aged, smoking and being a woman increase the risk of developing rheumatoid arthritis. Environmental factors like being exposed to asbestos may also contribute.

Symptoms of Skeletal system (bone diseases)

How and when bone pain occurs, or subtle changes in how joints look and feel, can help indicate which type of condition you might have:

  1. Joint stiffness (arthritis).
  2. Decreased range of motion (arthritis).
  3. Decreased joint function (arthritis).
  4. Bumps on small finger joints (osteoarthritis).
  5. Soft, warm, painful swelling of both wrists and hands, in large knuckles (rheumatoid arthritis).
  6. Persistent morning joint stiffness (rheumatoid arthritis).
  7. Fatigue and whole-body symptoms (rheumatoid arthritis).
  8. Bone pain at rest (systemic conditions like cancer).
  9. Bone or joint pain with activity (overuse injury).
  10. Gradual loss of height or stooped posture (osteoporosis).
  11. Unexplained back pain (osteoporosis).
  12. A shoulder or hip that’s higher than the other (scoliosis).
  13. Leg-length discrepancy (various conditions).

Diagnosis of some (bones disease) of skeletal system

Diagnosis starts with a medical history and physical examination. “It’s a complete musculoskeletal exam, not just evaluating the joint or the area that’s injured,” Miranda-Comas says. “We look for modifiable risk factors like alignment. We look for muscle imbalance or muscle weakness. We look for asymmetry. Limb length plays a big role. Within those subtle signs, we expand our evaluation and questioning in terms of trying to look for environmental factors or just activity that exposes you to injury.”
Imaging tests such as X-rays, MIR and ultrasound help determine a condition’s severity. Your doctor may order blood tests that indicate inflammatory processes, as with rheumatoid arthritis. A bone density scan called a DEXA scan is used to evaluate osteoporosis.
Depending on your medical exam findings and test results, your primary care provider may refer you to a specialist to confirm the diagnosis and recommend treatment. Orthopedists, pediatric orthopedists, orthopedic surgeons, rheumatologists, physiatrists, orthopedic oncologists and physical or occupational therapists are among the health care providers you might see.

Treatment of Bone diseases

Treatment takes different directions for rheumatoid and osteoarthritis. “We can treat rheumatoid arthritis and most patients will eventually respond to the medicines we use,” Fox says. “But we can’t cure it, meaning if we take away those medications, the arthritis can come back or will come back.”

For rheumatoid arthritis, medications to slow the disease process include older drugs like methotrexate (Trexall and others) and sulfasalazine (Azulfidine). Biologic drugs such as adalimumab (Humira) and etanercept (Enbrel) reduce inflammation by targeting the immune system. Low-dose steroids are sometime used for short-term treatment. Patients must be monitored for a variety of medication side effects.

For osteoarthritis, drug treatment is not as effective, Fox says. Surgical replacement of large joints, such as hip replacement or knee replacement, is needed in some cases.

“With most conditions, you would start considering surgery when pain is intractable, when function is compromised, when there’s failure of nonsurgical treatment in at least three to six months, in general, and with injury that might (involve) neurovascular compromise,” Miranda-Comas says.

For osteoporosis, medications called bisphosphonates,

such as alendronate (Fosamax) and risedronate (Actonel), are the mainstay of drug treatment.


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