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THE MUSCULOSKELETAL SYSTEM

Category: Medical

Topic: Basic Anatomy and Physiology

Level: EMT

Next Unit: The Nervous System

15 minute read

The musculoskeletal system is made up of the skeleton which gives the body its shape and the muscles which attach to it. The muscles give the skeleton the ability to push and pull against other bones, creating voluntary movement, as well as provide structure, support, and shape for the body. The major sections of the skeleton that need to be considered are the:

  • head and spine
  • chest wall
  • upper extremities
  • pelvic girdles
  • lower extremities

A basic knowledge of the major bones in this area is mandatory for understanding the possible manifestations of trauma and illness.

Head and Spine

  • The skull protects the brain.
  • The orbit bones surround and protect the eyes.
  • The cranium is the "shell" of the skull that surrounds and protects the brain.
  • The mandible is the lower jaw bone.
  • The maxillae are the fused bones that form the upper jaw.
  • The zygomaticbones are the cheekbones.
  • The vertebrae are the bones that make up the spinal column.

The vertebrae are grouped by region.

  • The CERVICAL SPINE is found primarily in the neck and consists of 7 vertebrae, C1-C7.
  • The THORACIC SPINE lies behind the thorax and ribs in the upper back and consists of 12 vertebrae, T1-T12.
  • The LUMBAR SPINE consists of 5 vertebrae found in the lower back, C1-C5.
  • The SACRAL VERTEBRAE also consist of 5 vertebrae and are found fused behind the pelvis, as the SACRUM.

 

Chest Wall

STERNUM: the breastbone which lies in the center of the chest. There are 3 sections to the sternum (breastbone):

  1. the CENTRAL BODY of the stermum,
  2. the upper portion called the MANUBRIUM and
  3. the lower portion called the XIPHOID PROCESS.

CLAVICLE: connects the shoulder to the sternum. It is the bone most commonly broken.

SCAPULA (plural, scapulae): the "shoulder blade," the flat, curved, large bone that connects the humerus to the clavicle. The highest portion of the shoulder where the shoulder bone sticks out is called the acromion process. The acromioclavicular joint is the point where the acromion and the clavicle meet.

 

Extremities

UPPER EXTREMITY: In each upper extremity, you have the

  • HUMERUS: the long bone that extends from the shoulder to the elbow.

The forearm is made up of two bones:

  1. RADIUS: the long bone in the forearm on the thumb side; 
  2. ULNA: the long bone which lies on the pinky side of the forearm.
  • CARPALS are the bones of the wrist and
  • METACARPALS are the bones in the hand.
  • PHALANGES (singular, phalanx): the bones of the fingers.

PELVIC GIRDLE: The pelvis is the bowl-shaped structure that supports the spine and protects organs of the lower abdomen. There are several parts of the pelvis.

  • The wide wings of the pelvis are each called the ILIUM.
  • The lower rear portions that connect the two is called the ISCHIUM.
  • The PUBIS is the front and center part of the pelvis where the two bilateral bones meet.
  • The socket formed by the bones of the pelvis where the femur articulates is called the ACETABULUM.

LOWER EXTREMITY:

  • The FEMURS are the long bones in the thigh and are the strongest of the long bones.
  • The PATELLA is another name for the kneecap.
  • The lower leg has two bones,
  1. the larger and more central bone is the TIBIA, whereas
  2. the smaller leg bone that lies more towards the lateral/real of the lower leg is the FIBULA.
  • TARSAL BONES: bones that make up the ankle. (The tarsals of the wrist are the counterparts to the carpals of the ankle.)
  • METATARSALS: bones that make up the feet. (They are the counterpart to the hand's metacarpals.)
  • PHALANGES are used to refer to the bones of both the fingers and toes.

The muscular system is mainly made up of the system of skeletal muscles that support the body and permit movement. Muscles contract (flex) when stimulated by nerve impulses.

 

Muscles

There are three types of muscle:

  1. STRIATED (skeletal) muscle,
  2. SMOOTH muscle, and
  3. CARDIAC muscle.

 

STRIATEDMUSCLE: used to move bones and is mostly controlled voluntarily. Skeletal (striated) muscle is also referred to as "skeletal" or "voluntary" muscle. They are generally found in opposing pairs (e.g., bicep vs tricep) and when one side is relaxed and one side is flexed, the long bone moves in the direction of the flexed side. Skeletal muscles are attached to bone by tendons.

SMOOTH MUSCLE:  like that found in the stomach and intestines, controlled automatically by the nervous and endocrine systems. Smooth muscle is often referred to as involuntary or visceral muscle. Smooth muscle is responsible for the movement in all organs in the body from intestines to blood vessels.

CARDIAC MUSCLE: the only muscle in the human body capable of discharging its own electrical impulse without any signal from the nervous system.

The ability of cardiac muscle to generate its own electrical impulse is known as automaticity. Specialized areas of cardiac cells known as the "nodes" or "pacemakers" are responsible for generating the organized electrical pulses that cause strong and rhythmic contractions. If the normal part of the pacemaker fails, the next element of the cardiac electrical system takes over, and ultimately the muscle itself is able to fire in place of the pacemaker. Cardiac muscle can only work without oxygen for a short amount of time; unlike the skeletal muscle, its ability to utilize anaerobic respiration is significantly limited. This is why cardiac ischemia commonly leads to cell death and significant lasting deficits.