9: The Appendicular Muscles

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Muscles of the rotator cuff

Information

The rotator cuff is the name given to the group of four muscles that are largely responsible for the ability to rotate the arm. Three of the four rotator cuff muscles are deep to the deltoid and trapezius muscles and cannot be seen unless those muscles are first removed and one is on the anterior side of the scapula bone and cannot be seen from the surface.

On the anterior side of scapula bone is a single muscle, the subscapularis. It is triangular in shape and covers the entire bone. Its origin is along the fossa that makes up most of the “wing” of the scapula and it inserts on the lesser tubercle of the humerus bone. The subscapularis muscle is shown in Figure 9.1.

Figure 9.1. The subscapularis muscle of the rotator cuff, in red, anterior view.

On the posterior side of the scapula bone are the other three muscles of the rotator cuff. All three insert on the greater tubercle of the humerus, allowing them, in combination with the subscapularis, to control rotation of the arm. The supraspinatus muscle is above the spine of the scapula. The infraspinatus muscle is below the spine of the scapula. The relatively

thin teres minor muscle is the most inferior of the rotator cuff muscles. The three posteriorly- positioned muscles of the rotator cuff are shown in Figure 9.2.

Figure 9.2. The muscles of the rotator cuff and arm, posterior view.

The teres major muscle has its origin on the scapula, like the rotator cuff muscles, but is not involved in rotating the arm. It inserts lower on the humerus than the rotator cuff muscles and is involved in adducting the arm (bringing it closer to the midline of the body.)

LAB 9 EXERCISES 9-1

Using the full-scale arm model, locate and identify all four muscles of the rotator cuff, as well as the deltoid muscle and the teres major muscle.
The following are muscles of arm rotation and adduction. For each, give its origin(s) and insertion(s) and whether or not it is part of the rotator cuff.

Muscle	Origin(s)	Insertion(s)	Part of rotator cuff?
Subscapularis
Supraspinatus
Infraspinatus
Teres major
Teres minor
Deltoid

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CC LICENSED CONTENT, ORIGINAL

A&P Labs. Authored by: Ross Whitwam. Provided by: Mississippi University for Women. Located at: http://www.muw.edu. License: CC BY-SA: Attribution-ShareAlike
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Figure 9.1. The subscapularis muscle of the rotator cuff, in red, anterior view.. Authored by: Was a bee. Provided by: Images in Figure 9.1 were made out of, or made from, content published in a BodyParts3D/Anatomography web site. The content of their website is published under the Creative Commons Attribution 2.1 Japan license. The author and licenser of the contents is http://lifesciencedb.jp/bp3d/?lng=en.. Located
at: commons.wikimedia.org/wiki/F...le_frontal.png. License: CC BY-SA: Attribution-ShareAlike

Figure 9.2. The muscles of the rotator cuff and arm, posterior view.. Authored by: OpenStax College. Located

at: http://cnx.org/resources/e5ba9b5bb7343a347f55336ebd7a61f3b35b0cdc/1119_Muscles_that_Move_the_Humerus.jpg. Lice nse: CC BY-SA: Attribution-ShareAlike

158

Muscles of the upper arm

Information

Anatomists refer to the upper arm as just the arm or the brachium. (The lower arm is the forearm or antebrachium.) There are three muscles on the upper arm that are parallel to the long axis of the humerus, the biceps brachii, the brachialis, and the triceps brachii.

The biceps brachii is on the anterior side of the humerus and is the prime mover (agonist) responsible for flexing the forearm. It has two origins (hence the “biceps” part of its name), both of which attach to the scapula bone. It inserts on the radius bone. The biceps brachii has two synergist muscles that assist it in flexing the forearm. Both are found on the anterior side of the arm and forearm. One of these is the brachioradialis muscle which is largely on the forearm (see the next section) and the other is the brachialis, which is largely on the upper arm. The brachialis muscle is deep to the biceps brachii and both its origin and its insertion are more distal to the shoulder than its equivalents on the biceps brachii. Like the biceps brachii the origin of the brachialis is on the humerus. Parts on the brachialis can be seen peeking out from under the biceps brachii, especially lower on the arm. The locations of these three muscles are shown in Figure 9.3.

Figure 9.3. The muscles of the arm.

On the posterior side of the arm is the triceps brachii muscle. It the antagonist to the biceps brachii. When the triceps brachii contracts it extends the forearm, undoing any flexing brought about by contractions of the biceps brachii. As a result, when the triceps brachii is contracted, the biceps brachii and its synergists must be relaxed, and vice versa. The triceps brachii has three origins, called the long head, the lateral head, and the medial head. Figure 9.4 shows the three origins of the triceps brachii in different colors. It is easiest to view the triceps brachii from the posterior, but the medial head and its origin are deep to the lateral head and the long head, and so is the medial head of the triceps brachii is partially obscured from the posterior.

Figure 9.4. The three heads of the triceps brachii color-coded to distinguish them. Keep in mind, despite the

different colors all three are parts of the same one muscle.

LAB 9 EXERCISES 9-2

Using the full-scale arm model, locate and identify the biceps brachii, brachialis, and triceps brachii muscles.
The following are muscles of arm rotation and adduction. For each, give its origin(s) and insertion(s).

Muscle	Origin(s)	Insertion(s)
Biceps brachii
Brachialis
Triceps brachii

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A&P Labs. Authored by: Ross Whitwam. Provided by: Mississippi University for Women. Located at: http://www.muw.edu. License: CC BY-SA: Attribution-ShareAlike
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Figure 9.3. The muscles of the arm.. Authored by: OpenStax College. Located
at: cnx.org/resources/6669b272a691b9377071de429a1336fec0469a5c/1120_Muscles_that_Move_the_Forearm.jpg. Lice nse: CC BY-SA: Attribution-ShareAlike

Figure 9.4. The three heads of the triceps brachii color-coded to distinguish them. Keep in mind, despite the different colors all three are parts of the same one muscle.. Authored by: Was a bee. Provided by: Images in Figure 9.4 were made out of, or made from, content published in a BodyParts3D/Anatomography web site. The content of their website is published under the Creative Commons Attribution 2.1 Japan license. The author and licenser of the contents is http://lifesciencedb.jp/bp3d/?lng=en. Located

at: commons.wikimedia.org/wiki/F...nimation02.gif. License: CC BY-SA: Attribution- ShareAlike

Muscles of the lower arm and hand

Information

Anatomists refer to the lower arm as the forearm or antebrachium. The musculature of the forearm is complicated. Figure 9.5 shows the muscles of the forearm.

Figure 9.5. Muscles of the forearm.

Figure 9.6 shows the muscles of the hands.

Figure 9.6. The muscles of the hands.

LAB 9 EXERCISES 9-3

Using the full-scale arm model, locate and identify the muscles of the forearm selected by your instructor.
Write down the muscles of the forearm selected by your instructor and, for each, give the location of that muscle and what effect contracting that muscle has.

Muscle	Location & description	Action(s)

LICENSES AND ATTRIBUTIONS

CC LICENSED CONTENT, ORIGINAL

A&P Labs. Authored by: Ross Whitwam. Provided by: Mississippi University for Women. Located at: http://www.muw.edu. License: CC BY-SA: Attribution-ShareAlike
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
Figure 9.5. Muscles of the forearm.. Authored by: OpenStax College. Located
at: cnx.org/resources/6669b272a6...he_Forearm.jpg. Lic ense: CC BY-SA: Attribution-ShareAlike

Figure 9.6. The muscles of the hands.. Authored by: OpenStax College. Located

at: https://cnx.org/resources/49b609261e...f_the_Hand.jpg. Licen se: Public Domain: No Known Copyright

Muscles of the hips and thighs

Information

There are three layers of gluteal muscles on the posterior hips, just like there are three layers of muscles in the abdominal trunk. The largest of them is the most superficial muscle,

the gluteus maximus. Its origin is on the ilium of the coxal bone, and it inserts part-way down the shaft of the femur. It helps maintain erect posture, abducts the thigh, and rotates the thigh outward.

Below the gluteus maximus is the smaller gluteus medius. The gluteus medius muscle helps abducts the thigh along with the gluteus maximus, but can rotate the thigh inward where the gluteus maximus rotates the thigh outward.

The below the gluteus medius are several muscles, one of which is the gluteus minimus, the smallest of the gluteal muscles. It is a synergist for the gluteus medius.

Figure 9.7. The three layers of gluteal muscles, gluteus maximus, gluteus medius, gluteus minimus.

Like the forearm, the upper leg, or thigh, has a dense arrangement of many muscles. On the anterior side, the most prominent of the muscles are the sartorius muscle and the four muscles that make up quadriceps muscle group (the “quads”.)

The quadriceps sounds like it should be just one muscle, akin to the triceps brachii, but it is a group of four muscles, three visible on the surface, and the fourth obscured. The three surface muscles of the quadriceps are the rectus femoris in the center, the vastus medialis on the medial side, and the vastus lateralis on the lateral side. These three muscles are visible in Figure 9.9. Below the rectus femoris and largely hidden by it is the vastus intermedius. This

muscle’s position can be seen in Figure 9.9. The four muscle of the quadriceps all extend the lower leg, and the rectus femoris additionally can flex the thigh at the hip.

Figure 9.9. The superficial muscles of the thigh.

Figure 9.9. The quadriceps group of four muscles. The view on the left has the rectus femoris cut away to show

the vastus intermedius which is below it.

The sartorius muscle is a distinctively long and thin muscle that crosses the thigh diagonally. It is visible in Figure 9.9. Sartorius comes from the Latin for tailor, and this is sometimes called the tailor’s muscle, although the reasons for the nickname are obscure. It may be because the shape of the muscle is thin and long, like a tailor’s measuring tape; it may be because it is close to the inseam a tailor measures when tailoring pants, or it may be because it helps bring about the cross-legged position that tailors often adopt when working.

In the posterior thigh the bulk of the musculature is made up of three long muscles that are collectively called the hamstrings. The origin of this nickname is obscure, but it may have to do with the practice of butchers of hanging the thighs of butchered animals such as pig (the “hams”) by the tendons of these three muscles. Move from the medial edge to the lateral edge of the posterior thigh, the hamstring muscles are the semimembranous muscle,

the semitendinosus muscle, and the biceps femorismuscle. Notice the upper leg has a “biceps” muscle just like the upper arm does. This is why you have to indicate which biceps you are taking about when discussing one or other of these muscles. On the medial edge of the posterior thigh is the gracilis muscle. It is also visible on the medial edge of the thigh from the anterior.

Figure 9.10. The muscles of the posterior thigh.

Figure 9.11. The hamstring group of muscles of the posterior thigh.

LAB 9 EXERCISES 9-4

Using the full-scale leg model, locate and identify the muscles of the thigh listed in the table below.
Write down the muscles of the thigh in the table below and, for each, give the location of that muscle and what effect contracting that muscle has.

Muscle	Location & description	Action(s)
Rectus femoris
Vastus intermedius
Vastus medialis
Vastus lateralis
Sartorius
Gracilis
Semimembranosus
Semitendinosus
Biceps femoris

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CC LICENSED CONTENT, ORIGINAL

A&P Labs. Authored by: Ross Whitwam. Provided by: Mississippi University for Women. Located at: http://www.muw.edu. License: CC BY-SA: Attribution-ShareAlike
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
Figure 9.7. The three layers of gluteal muscles, gluteus maximus, gluteus medius, gluteus minimus.. Authored by: Beth ohara~commonswiki. Located at: commons.wikimedia.org/wiki/F..._Muscles_3.PNG. License: CC BY- SA: Attribution-ShareAlike
Figure 9.7. The three layers of gluteal muscles, gluteus maximus, gluteus medius, gluteus minimus.. Authored by: Beth ohara~commonswiki . Located at: commons.wikimedia.org/wiki/F..._Muscles_1.PNG. License: CC BY- SA: Attribution-ShareAlike
Figure 9.9. The superficial muscles of the thigh.. Authored by: OpenStax College. Located
at: cnx.org/resources/49a26b0c63...e_the_Femur.jp
1. License: CC BY-SA: Attribution-ShareAlike
Figure 9.9. The quadriceps group of four muscles. The view on the left has the rectus femoris cut away to show the vastus intermedius which is below it.. Authored by: CFCF. Provided by: Images in Figure 9.4 were made out of, or made from, content published in a BodyParts3D/Anatomography web site. The content of their website is published under the Creative Commons Attribution 2.1 Japan license. The author and licenser of the contents is http://lifesciencedb.jp/bp3d/?lng=en. Located
at: en.Wikipedia.org/wiki/Quadri...driceps_3D.gif. License: CC BY-SA: Attribution-ShareAlike
Figure 9.9. The quadriceps group of four muscles. The view on the left has the rectus femoris cut away to show the vastus intermedius which is below it.. Authored by: Athikhun.suw. Located
at: commons.wikimedia.org/wiki/F...ius_muscle.jpg. License: CC BY-SA: Attribution- ShareAlike
Figure 9.10. The muscles of the posterior thigh.. Authored by: OpenStax College. Located
at: cnx.org/resources/49a26b0c6351a2052a16c4fcd339bc092505e492/1122_Gluteal_Muscles_that_Move_the_Femur.jp
1. License: CC BY-SA: Attribution-ShareAlike
Figure 9.11. The hamstring group of muscles of the posterior thigh.. Authored by: BruceBlaus. Located
at: commons.wikimedia.org/wiki/F..._Hamstring.png. License: CC BY-SA: Attribution-ShareAlike

PUBLIC DOMAIN CONTENT

Figure 9.7. The three layers of gluteal muscles, gluteus maximus, gluteus medius, gluteus minimus.. Authored by: Dr. Johannes Sobotta. Provided by: Sobotta's Human Anatomy 1909. Located at: commons.wikimedia.org/wiki/F...Sobo_1909_575- 576.png. License: Public Domain: No Known Copyright

Muscles of the lower leg and foot

Information

The muscles of the lower leg, called simply the leg by anatomists, largely move the foot and toes. The major muscles of the lower leg, other than the gastrocnemius which is cut away, are shown in Figure 9.12. The gastrocnemius muscle has two large bellies, called the medial head and the lateral head, and inserts into the calcaneus bone of the foot via its calcaneal tendon (also known as the Achilles tendon.) The soleus muscle is deep to the gastrocnemius, and the two muscles serve together as the calf of the leg. The gastrocnemius muscle is shown in Figure 9.13.

Figure 9.13. The gastrocnemius muscle

Figure 9.14 shows the muscles of the feet.

LAB 9 EXERCISES 9-5

Using the full-scale leg model, locate and identify the muscles of the lower leg listed in the table below.

For each of the muscles of the leg, give the location of that muscle and what effect contracting that muscle has.

Muscle	Location & description	Action
Gastrocnemius
Soleus
Tibialis anterior
Fibularis longus

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CC LICENSED CONTENT, ORIGINAL

A&P Labs. Authored by: Ross Whitwam. Provided by: Mississippi University for Women. Located at: http://www.muw.edu. License: CC BY-SA: Attribution-ShareAlike
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
Figure 9.12. The muscles of the lower leg.. Authored by: OpenStax College. Located
at: cnx.org/resources/adeb0a7399f...Move_the_Foot_ and_Toes.jpg. License: CC BY-SA: Attribution-ShareAlike
Figure 9.13. The gastrocnemius muscle. Authored by: Nikai . Located
at: commons.wikimedia.org/wiki/F...trocnemius.png. License: CC BY-SA: Attribution-ShareAlike
Figure 9.14. The muscles of the feet.. Authored by: OpenStax College. Located

at: cnx.org/resources/747c45c729...f_the_Foot.jpg. Licens e: CC BY-SA: Attribution-ShareAlike

IDENTIFY THE MUSCLES OF THE ARM


2


3


4

LAB 9 EXERCISES 9-7

IDENTIFY THE DEEP MUSCLES OF THE ARM &

SHOULDER

LAB 9 EXERCISES 9-9

IDENTIFY MUSCLES OF THE ABDOMEN & LEG

LAB 9 EXERCISES 9-9

*connective tissue


6

7

9

IDENTIFY THE MUSCLES OF THE THIGH & LEG


4


5

LAB 9 EXERCISES 9-10

IDENTIFY THE MUSCLES OF THE THIGH


5


6

LAB 9 EXERCISES 9-11

MUSCLES OF THE LEG

MODELS: Arm and Leg

Name	Action	Origin	Insertion
Forearm movers
Biceps brachii	Flexes arm at elbow	Scapula	Radius
Brachialis	Flexes arm at elbow	Humerus	Ulna
Triceps brachii	Extends arm at elbow	Humerus & Scapula	Ulna
Pronator teres	Pronates forearm	Humerus & Ulna	Radius
Supinator	Supinates forearm	Humerus & Ulna	Radius
Brachioradialis	Flexes arm at elbow (beer raising)	Humerus	Radius
Hand & finger movers
Flexor carpi radialis	Flexes & abducts hand at wrist	Humerus	Carpal Bones
Palmaris longus	Flexes hand at wrist	Humerus	Carpal Bones
Flexor carpi ulnaris	Flexes & adducts hand at wrist	Humerus	Carpal Bones
Extensor carpi radialis	Extends & abducts hand at wrist	Humerus	Carpal Bones
Extensor digitorum	Extends fingers	Humerus	Digits
Extensor carpi ulnaris	Extends & adducts hand at wrist	Humerus	Carpal Bones
Muscles of the thigh & leg
Flexor digitorum longus	Flexes toes	Tibia	Digits
Flexor hallucis longus	Flexes hallux	Fibula	big toe
Tibialis anterior	Dorsiflex foot at ankle, inverts foot	Tibia	1st metatarsal
Extensor digitorum longus	Extends toes	Tibia & fibula	digits
Fibularis (peroneus) longus	plantarflexes	Tibia & fibula	1st metatarsal
Gastrocnemius	plantarflexes	Femur	calcaneous
Soleus	Plantarflexes	Femur & tibia	calcaneous
Name	Action	Origin	Insertion
Muscles of the leg & thigh
Psoas major	Flexes thigh at hip (also flexes vertebral column)	Thoracic and Lumbar Vertebrae	Femur
Iliacus	Flexes thigh at hip	Ilium	Femur
Adductor longus	Adducts thigh at hip	Pubis	Femur
Adductor magnus	Adducts thigh at hip	Pubis and Ischium	Femur
Gracilis	Adducts thigh at hip	Pubis	Tibia
Gluteus maximus	Extends thigh at hip, rotates thigh laterally	Ilium, Sacrum and Coccyx	Femur, ITB
Gluteus medius	Abducts thigh at hip, rotates thigh medially	Ilium	Femur
Sartorius	Flexes leg at knee (also flexes + rotates thigh at hip)	Ilium	Tibia
Tensor fascia latae	tenses the ITB, supports knee	Ilium	ITB
Iliotibial band (IT band/tract)	Not a muscle	n/a	n/a
Quadriceps femoris
Rectus femoris	Extends leg at knee (also flexes thigh at hip)	Ilium	Tibia
Vastus lateralis	Extends leg at knee	Femur	Tibia
Vastus medialis	Extends leg at knee	Femur	Tibia
Vastus intermedius	Extends leg at knee	Femur	Tibia
Hamstrings
Biceps femoris	Flexes leg at knee (also extends thigh at hip)	Ischium & Femur	Tibia & Fibula
Semitendinosus	Flexes leg at knee (also extends thigh at hip)	Ischium	Tibia
Semimembranosus	Flexes leg at knee (also extends thigh at hip)	Ischium	Tibia