Musculoskeletal System

Musculoskeletal System

Functions of the Musculoskeletal System

The musculoskeletal (muss skyoo loh SKELL uh tul) system (MS) consists of three interrelated parts: bones, joints (articulations), and muscles. Bones are connected to one another by fibrous bands of tissue called ligaments (LIH gah ments). Muscles are attached to the bone by bands of tissue called tendons (TEN duns). The tough fibrous covering of the muscles (and some nerves and blood vessels) is called the fascia (FASH ee ah). Cartilage (KAR tih lij) is a flexible form of connective tissue that covers the ends of many bones, gives form to the external ear, and tip of the nose, and provides support and protection to many other sites in the body.

Imagine a body without bones and muscles! Where would the organ systems be placed? What would protect the vital organs? And how would a person move? The musculoskeletal system meets these needs by:

Along with these functions, some bones are responsible for storage of minerals (calcium [Ca] and phosphorus [P]) and the continual formation of blood, a process called hematopoiesis (hee mah toh poh EE sis), in the bone marrow.


Orthopedics is the healthcare specialty that deals with the majority of musculoskeletal disorders. Historically, the word orthopedics comes from orth/o (straight) and ped/o (child) because corrective procedures for disorders like knock knees and bowlegs were most successful with the softer bones of children. The specialist is called an orthopedist.

Rheumatology is a specialty that deals with disorders of connective tissue, including bone and cartilage. The origin of the term is derived from the Greeks who believed that many joint disorders were caused by an effusion (outpouring) of fluid into the joint space. The specialist is called a rheumatologist.

Physiatry, also called physical medicine, concerns diagnosis and treatment of disease or injury with the use of physical agents such as exercise, heat, massage, and light. The specialist is called a physiatrist.

image Exercise 1: Combining Forms for the Musculoskeletal System

Match the musculoskeletal combining forms with their meanings. More than one answer may be correct.

Decode the following terms using your knowledge of musculoskeletal word parts and suffixes learned in Chapter 1.

Anatomy and Physiology


Types of Bones

Most adult bodies contain 206 bones. These bones are categorized as belonging either to the axial (ACK see ul) skeleton, which consists of the skull, rib cage, and spine, or the appendicular (ap pen DICK yoo lur) skeleton, which consists of the shoulder bones, collar bones, pelvic bones, arms, and legs (Fig. 3-1). Human bones appear in a variety of shapes that suit their function in the body. See Fig. 3-1 and the following table for the locations and descriptions of these bones.

Bone Structure

All bones are composed of mature bone cells, called osteocytes (OS tee oh sytes), and the material between the cells, called the matrix (MAY tricks). The matrix stores calcium and phosphorus for the body to use as needed in the form of mineral salts. Other types of bone cells include osteoblasts, cells that build bone, and osteoclasts, cells that break down bone cells to transform them as needed. The osteocytes and matrix together make up the hard, outer layer of bone known as compact bone. Within the compact bony tissue is a second layer of bone tissue called spongy or cancellous (KAN seh lus) bone. This spongy bone is composed of the same osteocytes and matrix, but, as its name implies, it is less dense. Within the spongy layer lie the medullary cavity and the red bone marrow, which produces all of the blood cells needed by the body.

Each long bone (Fig. 3-2) is composed mainly of a long shaft called the diaphysis (dye AFF ih sis). Each end of the bone is called an epiphysis (eh PIFF ih sis) (pl. epiphyses). Underneath the epiphyses are the epiphyseal (eh pee FIZZ ee ul) plates, the areas where bone growth normally occurs. Around the ages from 16 to 25, the plates close, and bone growth stops. The epiphysis and epiphyseal plates together form the metaphysis (meh TAFF ih sis).

Fig. 3-2 Long bone.

The outer covering of the bone is called the periosteum (pair ee OS tee um), and the inner aspect of the bone is known as the endosteum (en DOS tee um). These two coverings hold the cells responsible for bone remodeling: osteoblasts and osteoclasts. The shape of a bone enables practitioners to speak very specifically about a particular area on that bone. For instance, any groove, opening, or hollow space is called a depression. Depressions provide an entrance and exit for vessels and protection for the organs they hold. Raised or projected areas are called processes. These are often areas of attachment for ligaments or tendons. The tables that follow give examples of bone depressions and processes.

image Exercise 2: Bone Basics

Match the bone word parts with their meanings.

Fill in the blank.

Axial Skeleton

The axial skeleton includes the skull, spine, and rib cage (see Fig. 3-1).


The skull is made up of two parts: the cranium (KRAY nee um) that encloses and protects the brain and the facial bones (Fig. 3-3).


Frontal bone: Forms the anterior part of the skull and the forehead.

Parietal (puh RYE uh tul) bones: Form the sides of the cranium.

Occipital (ock SIP ih tul) bone: Forms the back of the skull. Notable is a large hole at the ventral surface in this bone, the foramen magnum (meaning large), which allows brain communication with the spinal cord.

Temporal (TEM poor ul) bones: Form the lower two sides of the cranium. The mastoid process is the posterior part of the bone behind the ear.

Ethmoid (EHTH moyd) bone: Forms the roof and walls of the nasal cavity.

Sphenoid (SFEE noyd) bone: Anterior to the temporal bones and the basilar part of the occipital bone.

Paranasal sinuses: Air-filled cavities that are named for the bones in which they are located. Each is lined with a mucous membrane (Fig 3-3, B).

The last three bones of the skull, the ossicles, are tiny bones within the ear. These will be discussed in Chapter 14.

Facial Bones

Use Fig. 3-3 to locate the names and locations of the majority of the following facial bones:

Rib Cage

The ribs consist of 12 pairs of thin, flat bones attached to the thoracic vertebrae in the back and to costochondral (kost toh KON drul) tissue in the front (see Fig. 3-1). The ribs can be categorized as follows:

In addition to ribs, the rib cage includes the sternum (STUR num), also known as the breastbone. The sharp point at the most inferior aspect of the sternum is called the xiphoid (ZIH foyd) process. The combining form xiph/o derives from the Greek word for sword, which the xiphoid resembles.


The spinal, or vertebral, column is divided into five regions from the neck to the tailbone. It is composed of 26 bones called the vertebrae (VUR teh bray). Fig. 3-4, A. The following table lists and illustrates the bones in the spine. Fig. 3-4, B illustrates a vertebra with the laminae (sing. lamina), spinous transverse processes, and facets. Laminae are thin, platelike arches in the vertebrae. Facets are processes that articulate between vertebrae.

image Exercise 4: Axial Skeletal Combining Forms

Match each axial skeletal term with its correct combining form.

Decode the following terms below using your knowledge of word parts.

Appendicular Skeleton

The appendicular skeleton is composed of the upper appendicular and lower appendicular skeletons.

Upper Appendicular

The upper appendicular skeleton (Fig. 3-5) includes the shoulder girdle, which is composed of the scapula, clavicle, and upper extremities. Refer to Fig. 3-1 for a correlation of each bone’s description with its location.

The upper extremities (see Fig. 3-5) consist of the following:

Humerus (HYOO mur us): Upper arm bone.

Radius (RAY dee us): Lower lateral arm bone parallel to the ulna. The distal end articulates with the thumb side of the hand.

Ulna (UL nuh): Lower medial arm bone. The distal end articulates with the little finger side of the hand. The olecranon (oh LECK ruh non) is a proximal projection of the ulna that forms the tip of the elbow. Commonly known as the funny bone, this structure is actually a process.

Carpus (KAR pus): One of eight wrist bones.

Metacarpus (meh tuh KAR pus): One of the five bones that form the middle part of the hand.

Phalanx (FAY lanks): One of the 14 bones that constitute the fingers of the hand, two in the thumb and three in each of the other four fingers (pl. phalanges). The three bones in each of the four fingers are differentiated as proximal, medial, and distal. The joints between these are referred to as proximal and distal interphalangeal (PIP, DIP) joints. When one is referring to a whole finger (or toe), the term digitus is used.

Lower Appendicular

The lower half of the appendicular skeleton can be divided into the pelvis and the lower extremities (Fig. 3-6). The acetabulum (pl. acetabula) is the socket into which the femoral head fits. The pelvic bones (also called the pelvic girdle) consist of the following three bones:

The lower extremities include the following:

image Exercise 9: The Appendicular Skeleton

Match the upper appendicular combining forms with their meanings.

Match the lower appendicular combining forms with their meanings.

Decode the terms.


Joints, or articulations as they are sometimes called, are the parts of the body where two or more bones of the skeleton join. Examples of joints include the knee, which joins the tibia and the femur, and the elbow, which joins the humerus with the radius and ulna. Joints provide range of motion (ROM), the range through which a joint can be extended and flexed. Different joints have different ROM, ranging from no movement at all to full range of movement. Categorized by ROM, they are as follows:

Diarthroses, or synovial (sih NOH vee ul) joints, as they are frequently called, are the most complex of the joints. Because these joints help a person move around for a lifetime, they are designed to efficiently cushion the jarring of the bones and to minimize friction between the surfaces of the bones. Many of the synovial joints have bursae (BURR see) (sing. bursa), which are sacs of fluid that are located between the bones of the joint and the tendons that hold the muscles in place. Bursae help cushion the joints when they move. Synovial joints also have joint capsules that enclose the ends of the bones, a synovial membrane that lines the joint capsules and secretes fluid to lubricate the joint, and articular cartilage that covers and protects the bone. The menisci (sing. meniscus) consist of crescent-shaped cartilage in the knee joint that additionally cushions the joint. Ligaments are strong bands of white fibrous connective tissue that connect one bone to another at the joints.

Oct 6, 2017 | Posted by in GENERAL SURGERY | Comments Off on Musculoskeletal System
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