Muscles of the arm and leg

• A&P
• Higher Education (non-degree)

ANATOMY AND PHYSIOLOGY FOR SPORTS MASSAGE 

THE STRUCTURE AND FUNCTION OF THE SKELETAL SYSTEM

ANATOMY AND PHYSIOLOGY FOR BEAUTY THERAPY 

THE STRUCTURE AND FUNCTION OF THE MUSCULAR SYSTEM

What are you going to learn?

In this lesson you're going to learn to . . .

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Describe characteristics of types of muscle tissue

Locate and describe action of the major anterior and posterior skeletal muscles

Identify and locate muscle attachment and insertion points. 

Describe the role of muscles during movement

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Explain different types of muscle contraction

Explain the principle of muscle contraction

KEY WORDS

pronator, supinator, extensor, flexor, adductor, abductor, origin, insertion

Muscles are named according to their size, shape, the direction of the fibres, their location, number of origins or heads, their origin and insertion, and their action. 

If you understand these, it will help you to locate and position the muscle more easily.

1. Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short).

2. Shape: deltoid (triangular);  teres (round); trapezius (like a trapezoid, a four-sided figure with two sides parallel).

3. Direction of fibres: rectus (straight); transverse (across); oblique (diagonally); orbicularis (circular).

4. Location: pectoralis (chest);  brachii (arm); supra- (above); infra- (below); sub- (under or beneath); lateralis (lateral).

5. Number of origins: biceps (two heads); triceps (three heads); quadriceps (four heads).

6. Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle, insertion on the mastoid process); brachioradialis (origin on the brachium or arm, insertion on the radius).

7. Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to flex a structure); extensor (to extend a structure); levator (to lift or elevate a structure); masseter (a chewer).

SKELETAL MUSCLE ATTACHMENTS 

Learning the muscular system often involves memorising details about each muscle, like where a muscle attaches to bones and how a muscle helps move a joint. 

A skeletal muscle attaches to bone (or sometimes other muscles or tissues) at two or more places. 

Origin

If the place is a bone that remains immobile for an action, the attachment is called an origin. 

Insertion

If the place is on the bone that moves during the action, the attachment is called an insertion. 

MUSCLE ACTION 

The muscles surrounding synovial joints are responsible for moving the body in space. These muscle actions are often paired, like flexion and extension or abduction and adduction. Below the common terms are listed and defined. 

Flexion and Extension

Flexion: decreasing the angle between two bones (bending).

Extension: increasing the angle between two bones (straightening a bend).

Example: At the elbow joint

The triceps brachii muscle extend the elbow. The biceps brachii, brachialis, and brachioradialis flex the elbow.

Abduction and Adduction

Abduction: moving away from the body’s midline.

Adduction: moving toward the body’s midline.

Example: At the hip joint

The gluteus medius, gluteus minimus, tensor fasciae latae, and sartorius are muscles that abduct the hip. The pectineus, adductor longus, adductor brevis, adductor magnus, and gracilis adduct the hip.

Dorsiflexion and Plantarflexion

Dorsiflexion: bringing your foot upward toward your shin.

Plantar flexion: depressing your foot down. 

Example: at the ankle joint

The tibialis anterior dorsiflexes the ankle joint. Whereas the gastrocnemius plantarflexes the ankle joint. 

Elevation and Depression

Elevation: moving a body part up.

Depression: moving a body part down.

Example: at the shoulder girdle

The upper traperzius, rhomboids and levator scapula are muscles that elevate the shoulder girdle. Whereas the lower traperzius and pectorial minor depress the shoulder girdle.

Eversion and Inversion

Inversion: turning the sole of the foot inward.

Eversion: turning the sole of the foot outward.

Example: at the ankle joint

The tibialis anterior and tibialis posterior are muscles that invert the ankle joint. Whereas the peroneus longus, peroneus brevis and peroneus tertius evert the ankle joint.

Protraction and Retraction

Pronation: rotating the forearm so the palm is facing backward or down.

Supination: rotating the forearm so the palm is facing forward or up.

Example: at the shoulder girdle

The mid / lower traperzius and rhomboids are muscles that retract the shoulder girdle. Whereas the pectorialis minor and serratus anterior protract the shoulder girdle.

Pronation and Supination

Pronation: rotating the forearm so the palm is facing backward or down.

Supination: rotating the forearm so the palm is facing forward or up.

Example: at the elbow joint

The pronator teres and pronator quadratus pronate the forearm. Whereas the biceps brachii and brachioradialis supinate the forearm. 

Which action involves the straightening and increasing the angle between body parts?

1. Flexion
2. Extension
3. Abduction
4. Adduction

What term refers to the bending movement that decreases the angle between body parts?

1. Flexion
2. Extension
3. Adduction
4. Abduction

Which term describes the movement of a body part away from the midline of the body?

1. Abduction
2. Flexion
3. Extension
4. Adduction

UPPER LIMB SKELETAL MUSCLES   

Wrist Extensors

Origin- Lateral humerus

Insertion- Back of hand

Primary action/s- Extension of wrist.

Flexor carpi radialis

Origin- Mid humerus 

Insertion- Bases of metacarpal bones 2-3

Primary action/s- Flexion of the wrist

Extensor digitorum

Origin- Lateral surface of the humerus

Insertion- Superficially down the forearm extending into tendons which attach to the four phalanges. 

Primary action/s-  Extension of the fingers and wrist

Wrist Flexors

Origin- Medial humerus

Insertion- Palm of hand

Primary action/s- Flexion of wrist.

Thenar muscles

Origin- Trapezium

Insertion- proximal phalanx of the thumb.

Primary action/s- Abduction and flexion of the thumb

Bicep Brachii

Origin- Long head: superior scapula, Short head: anterior scapula

Insertion- Radius 

Primary action/s- Flexion of shoulder and elbow joint, supination of forearm. 

Upper Limb Skeletal Muscles

Deltoid

Caps the top of the Humerus & shoulder attaches to the Clavicle & Scapula, and to the other side of the Humerus bones

ROLE OF MUSCLES DURING MOVEMENT  

While many muscles may be involved in any given action, muscle function terminology allows you to quickly understand the various roles different muscles play in each movement.

Prime movers and antagonists are often paired up on opposite sides of a joint, with their prime mover/antagonist roles reversing as the movement changes direction.

Prime movers / agonist

The prime mover, sometimes called the agonist, is the muscle that provides the primary force driving the action. 

Antagonist

An antagonist muscle is in opposition to a prime mover in that it provides some resistance and/or reverses a given movement. 

Fixator / Stabilisers

Stabilisers act to keep bones immobile when needed. Your back muscles, for example, are stabilizers when they are keeping your posture sturdy.

Synergists.

One or more synergists are often involved in an action. Synergists are muscles that assist the prime mover in its role.

What is the function of smooth muscle tissue?

1. Support and protection of body organs
2. Voluntary movements of limbs
3. Contraction of the heart
4. Involuntary movements of internal organs

What type of muscle tissue is found in the heart?

1. Smooth muscle
2. Nervous tissue
3. Cardiac muscle
4. Skeletal muscle

Which muscle is responsible for flexing the wrist?

1. Abductor pollicis longus
2. Flexor carpi ulnaris
3. Extensor digitorum
4. Adductor pollicis

Which muscle type is responsible for movement in the body?

1. Cardiac muscle
2. Smooth muscle
3. Skeletal muscle
4. Connective tissue

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