Muscle Lab 3

Muscles of the Upper Extremity

In this lab you will learn about the muscles of the shoulder, arm and forearm.

Begin by orienting the body by clicking on the following:

Anterior Torso

Locate the following muscles in your textbook and dissector:

    Deltoid--Notice that there are 3 parts to this muscle (clavicular, acromial and spinal). These are sometimes called the anterior, middle and posterior portions of the deltoid.

    Biceps Brachii--Located on the anterior portion of the arm. This is a 2-headed muscle with attachments on the glenoid fossa and coracoid process of the scapula. It functions to flex the elbow.

    Triceps Brachii--Located on the posterior portion of the arm. The triceps is the only muscle on the back of the arm. It has 3 heads. It has an opposite action to the biceps and produces elbow extension.

    Tendon of the Triceps Brachii--This tendon is used to examine the deep tendon reflexes of the upper extremity. (Locate this structure in your textbook)

Using the thumbwheel, rotate the body to 180 degrees. You should now see the posterior view of the body.

Locate the following muscles:

    Middle part of the trapezius left

    Spinal part of the deltiod left

    Muscle of the infraspinatus left

    Muscle of the teres major left

Dissect away (by clicking on):

    Middle part of the trapezius left

    Superior part of trapezius left

    Spinal part of deltoid left

    Muscle of the infraspinatus left

Locate the supraspinatus muscle left. Notice how this muscle is located on top of the spine of the scapula. You will also see a small portion just lateral to the scapula. This muscle is an important muscle of a group of muscles called the rotator cuff. The rotator cuff consists of the following:

    Supraspinatus

    Infraspinatus

    Teres minor

    Subscapularis

Of these 4 muscles it is the supraspinatus that is most often injured. Sometimes it is pinched in a small area of the scapula and can develop tendonitis. This is called impingement syndrome. If the tendon wears out enough it can tear (rotator cuff tear).

Of the 4 rotator cuff muscles the subscapularis is the most difficult to see since it attaches to the anterior part of the scapula.

Dissect away the osseous part of the scapula left.

Here you will see the subscapularis muscle.

Dissect away the latissumus dorsi left and the muscle of the subscapularis left. Here you will see another muscle that attaches to the anterior portion of the scapula--the serratus anterior.

Reorient the body by clicking on the following:

Anterior View of Upper extremity

Locate the following forearm muscles:

     Brachioradialis--This muscle is located on the lateral portion of the brachium and antebrachium. The tendon of this muscle is also used to examine deep tendon reflexes.

This view allows you to see the muscles of the posterior portion of the antebrachium (forearm). You will see a number of muscles with the name extensor in them. Examples are:

    Extensor carpi radialis

    Extensor digitorum

    Extensor digiti minimi

You will be responsible for learning these muscles as a group known as wrist extensors. These muscles all have a common insertion point on the lateral epicondyle. They are commonly involved in a tendonitis known as lateral epicondylitis or tennis elbow.

Now rotate this view 180 degrees. You are now looking from behind to see the muscles on the anterior portion of the forearm.

Locate the following:

    Muscle of the flexor carpi radialis left

    Muscle of the flexor digitorum superficialis left

    Muscle of the flexor carpi ulnaris left

We will group these muscles together and call them the wrist flexor group. They all originate on the medial epicondyle and are involved in wrist flexor tendonitis otherwise known as medial epicondylitis or golfer's elbow.

Now you will build an arm by inserting the muscles on the skeleton.

First click on the following to orient the body:

Anterior upper extremity skeleton

You will be working on the right arm. Notice the blue transverse plane. This plane represents the structures in a transverse plane on the screen below the lesson screen. You can insert muscles by clicking on the structure in the screen below.

Move your cursor over the humerus bone.

You will see the structure light up on the screen below.

Go to the screen below and click on the following structures:

    Muscle of the supraspinatus right

    Clavicular part of deltoid right

    Spinal part of the deltoid right

    Acromial part of deltoid right

Move your cursor over the blue plane in the screen on the right. Click and drag the plane downward until it is at the inferior level of the deltoid.

Go back to the screen below and click on the following:

    Muscle of the biceps brachi right

    Muscle of the coracobrachialis right

    Muscle of the triceps brachi right

    Muscle of the brachialis right

Now click and drag the plane down to the level of the elbow.

You are now ready to build the forearm. Click on the following muscles in the screen below:

    Muscle of the brachioradialis right

    Muscle of the extensor carpi radialis longus right

    Muscle of the extensor carpi radialis brevis right

    Muscle of the extensor digitorum right

    Anaconeus right

    Muscle of the flexor digitorum superficialis right

You have now constructed most of the arm and forearm. What is left are some deep muscles that go to the fingers and help with rotation of the forearm.

This concludes this lab.