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Skeletal Information

Some joints do not move, like the lambdoid and coronal sutures of the skull. 

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Babies have more bones than adults because some of their bones have not fused together, like in their skulls. 

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Bones are not solid, but hollow on the inside and filled with bone marrow. This reduces weight, and the marrow produces red blood cells. 

Background:

The skeletal system helps maintain the body's shape, allows movement, stores minerals, makes blood cells, and protects organs. It is composed of bones, cartilage, joints, and other supporting structures.

The skeletal system has many different functions that include:

  • Giving the Body Shape:

    • Bones provide a “scaffold” for the body by giving muscles something to attach to. 

  • Allowing Movement:

    • Works with skeletal muscle and acts as a pulley and lever system to allow movement.  

  • Storing Minerals:

    • The hardness of the bone provides a mineral reservoir. Most of the minerals are stored in the organic and inorganic components of the osteons (functional units of bones). 

  • Making Blood Cells:

    • The red marrow in bones is responsible for making red blood cells through a process called hemopoiesis. The red marrow in bones contains specialized stem cells called hemocytoblasts, which are the cells that are responsible for making blood.

  • Protecting Organs:

    • Bones protect internal organs by surrounding them with a hard covering. The ribs around the lung and heart, and the skull around the brain are two examples of places in which this occurs.

Skeletal Anatomy:

  • Bones:

    • Bones are characterized based on shape:   

      • Long Bones: Long bones are longer than they are wide and are mostly located in the appendages (arms or legs). The long bones of the leg are the tibia, fibula, femur, metatarsals, and phalanges (toes). The long bones of the arm are the humerus, radius, ulna, metacarpals, and phalanges (fingers). 

      • Short Bones: Short bones are usually cube-shaped and can be found in the carpals (wrists) and tarsals (ankles). The short bones in the wrist are the scaphoid, lunate, triquetral, hamate, pisiform, capitate, trapezoid, and trapezium. The short bones of the ankle are the calcaneus, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and medial cuneiform. 

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​(Image retrieved from https://www.registerednursern.com/types-of-bones-anatomy/)

  • Flat Bones: Flat bones are usually flat, long, and curved in shape. Most of the bones of the cranium (skull) are flat bones. These bones include the frontal bone, parietal bones, occipital bone, nasal bones, lacrimal bones, and vomer bone. The sternum (chest bone), ribs, scapula (shoulder blade), ilium, pubis, and ischium are other examples of flat bones. 

  • Sesamoid Bones: Sesamoid bones are small and round. They are typically embedded in tendons to either reinforce or decrease the stress being exerted on a tendon. Examples of sesamoid bones include the patella (kneecap), hallucis (toe) sesamoids, lesser metatarsal sesamoids, interphalangeal (between finger bones) joint sesamoid of the great toe, os perineum, sesamoid within the anterior (front) tibial tendon, pollicis (thumb) sesamoids, second and fifth metacarpal sesamoids, interphalangeal joint sesamoid of the thumb, and pisiform.   

  • Irregular Bones: Irregular bones are bones that vary in shape and structure, and do not fit into any of the other categories of bones. Some examples of irregular bones include the vertebrae of the spinal column, the sacrum, coccyx (tailbone), temporal bone, sphenoid, ethmoid, zygomatic, maxilla, mandible (jaw), palatine, inferior nasal concha, and hyoid bone.

  • Joints:

    • Joints are an area of the body where two bones meet so that movement can occur. There are six main types of joints found in the human body: ball-and socket, hinge, condyloid, pivot, plane, and saddle joints.

      • Ball-and-socket Joints: are freely moveable in all directions and typically consist of a bone with a rounded head that sits in the cup of another bone. Some examples include the glenohumeral (shoulder) and acetabulofemoral (hip) joints. 

      • Hinge Joints: open and close in one direction and glide only in one plane of motion. Examples include the humeroulnar and tibiofemoral joints.

      • Condyloid Joints: allow for forward/ backward and side to side movement, but not rotation. Some examples include the radiocarpal (wrist) and temporomandibular (jaw) joints.

      • Pivot Joints: allows rotational movement around a single axis. Examples include the atlantoaxial and radio-ulnar joints.

      • Plane Joints: allow for bones to slide over one another. Examples include the joints between the metacarpal bones of the hand and those between the cuneiform bones of the foot.

      • Saddle Joints: allow for back-and-forth and side-to-side movement. Some examples include the carpometacarpal joint of the thumb, sternoclavicular joint, incudomalleolar joint of the middle ear, and the calcaneocuboid joint of the heel.

Skeletal Diseases:

One well-known bone disease is called osteoporosis. Osteoporosis causes a decrease in bone density, which often happens in old age. The bones in older people begin to break down because their body stops putting calcium onto bone which makes them very fragile and prone to breakage. This is primarily due to a decline in the production of hormones that regulate osteoblast activity. The best way to take care of your bones is by controlling diet and exercise. A diet high in calcium and vitamin D is important for maintaining healthy bone mass, and exercise stimulates bone deposition to increase bone mass. Click here to learn more about Osteoporosis. 

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Another skeletal disease that can occur is Rickets. Rickets is a childhood disease that occurs when the body does not get enough Vitamin D, which is a vitamin that helps the body process the calcium that bones need to grow and harden. Severe Vitamin D deficiency, as in the case of Rickets, causes the bones to become soft and bend. This often results in the legs appearing to be “bowed.” Treatment of Rickets can involve prescription of Vitamin D or Calcium supplements. In severe cases of Rickets where the legs become bowed, leg braces or surgery can be done to correct the problem. Click here to learn more about Rickets.  

Developments

To learn more about recent developments in orthopedic medicine, check out the following links:

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