Chapter 8 The Muscular System

Muscle tissue is made of a collection of similar muscle cells (or fibers). There are three types of muscle found in the human body: –Skeletal Muscle –Cardiac Muscle –Smooth Muscle

Some muscle tissues in the body are “voluntary” muscles –This means that you can control the actions of these muscles with your mind Ex. Skeletal muscle Other muscle tissues are “involuntary” muscles –This means that we normally do not have control over their contractions Ex. Smooth muscle

The primary function of muscle tissue is movement through contractions. –Skeletal muscle contractions allow us to move –Cardiac muscle contraction pump blood throughout our body –Smooth muscle contraction perform many vital functions, including moving food through our digestive tract.

Most skeletal muscle attach to two bones that have a moveable joint between them. –The muscle’s attachment to the bone that is most stationary is called the origin. –The muscle’s attachment to the bone that is more moveable is called the insertion. Tendons anchor muscles firmly to bones (this is a type of connective tissue)

Skeletal muscle tend to work in coordinated teams: –Prime mover – the muscle mainly responsible for producing a movement –Synergist – muscle that help produce the movement along with the prime mover –Antagonist – muscle that produce an opposite movement to the prime mover

The secondary function of muscle tissue is posture or muscle tone. –Our body is constantly held in proper position by tonic contractions The whole muscle does not contract, but enough fibers contract to maintain the muscle shape and position.

An addition function of muscle tissue is heat production. –The contraction of muscle fibers produces heat which is used to help maintain a proper body temperature (98.6º)

There are several terms that are commonly used to describe muscle movements: –Flexion –Extension –Abduction –Adduction –Rotation and Circumduction –Supination and Pronation –Dorsiflexion and Plantar Flexion

Flexion – a movement that makes the angle between two bones at their joint smaller than at the beginning of the movement Extension – a movement that makes the angle between two bones at their joint larger that at the beginning of the movement

Abduction – means to move a body part away from the midline of the body Adduction – means to move a body part towards to midline of the body

Rotation – movement around a longitudinal axis Circumduction – movement where the distal end of a part moves in a circle

Supination – a hand position where the palm is turning to face forward or up Pronation – a hand position where the palm is turning to face backward or down

Dorsiflexion – a movement where the top of the foot and toes point upward Plantar flexion – a movement where the bottom of the foot and toes are pointed downward

Muscle on your Maniken ® Temporalis –Origin: Temporal region of the skul –Insertion: Mandible Function – closes the jaw

Oribicularis Oculi –Origin: Maxilla and Frontal bone (encircles eys) –Insertion: Maxilla and Frontal bone Function – Closes the eye

Orbicularis oris –Origin: Encircles the lips –Insertion: Encircles the lips Function – draws lips together (kissing)

Intercostals –Origin: inferior border of the ribs –Insertion: superior border of the ribs Function – to raise the ribs and expand the chest cavity to aid in inhalation (breathing)

Serratus Anterior –Origin: lateral surface of the ribs (1-8) –Insertion: medial border of the scapula Function – to move the shoulder forward

Pectoralis Minor –Origin: anterior surface of the ribs (3-5) –Insertion: coracoid process of the scapula Function – to rotate the shoulder forward

Pectoralis Major –Origin: tendon of the external oblique (abdominal portion) Sternum and upper ribs (sternal portion) Clavicle (clavicular portion) –Insertion: lateral edge of the most proximal part of the humerus Function – adduction and medial rotation of the humerus

Brachialis –Origin: halfway down the humerus –Insertion: proximal ulna Function – elbow flexion

Triceps medial head –Origin: proximal half of the dorsal humerus –Insertion: distal end of elbow on the ulna Function – extension of the elbow