MUSCULAR SYSTEM: APPENDICULAR MUSCLES

CHAPTER OBJECTIVES

When you have completed this chapter you should be able to:

Describe the location and actions of the main muscles of the upper limb.

Describe the location and actions of the main muscles of the lower limb.

Describe the boundaries of the femoral triangle and identify its contents.

Describe the boundaries of the popliteal fossa and identify its contents.

Before attempting this chapter - please look at the chapter on joints.

Appendicular muscles refer to the muscles of the arms and legs.

Upper Limb Muscles

Shoulder

The rotator cuff is the name given to a complex of 4 muscles. They all originate on the scapula and their tendons insert into the greater and lesser tubercles of the humerus. The rotator cuff tendons blend with each other as well as the articular capsule of the shoulder joint and help reinforce it. The rotator cuff not only allows the shoulder joint to move but is also very important in holding the head of the humerus within the glenoid cavity of the scapula.

Rotator Cuff Muscles	Description	Action
Supraspinatus	Originates from the top of the scapula; supraspinous fossa. It inserts onto the greater tubercle of the humerus.	Abducts arm.
Infraspinatus	A large triangular muscle originating from the back of the scapula; infraspinous fossa. It inserts onto the greater tubercle of the humerus.	Extends arm. Laterally rotates arm.
Teres Minor	A long rectangular muscle originating from the lateral border of the back of the scapular. It inserts onto the greater tubercle of the humerus.	Adducts arm. Laterally rotates arm.
Subscapularis	A large triangular muscle originating from the front of the scapula; subscapular fossa. It inserts onto the lesser tubercle of the humerus.	Medially rotates arm.

Other Shoulder Muscles	Description	Action
Deltoid	A thick powerful muscle which covers the shoulder joint and upper humerus. It inserts onto the deltoid tuberosity  on the lateral side of the humerus.	Abducts the shoulder.
Trapezius	A broad flat triangular muscle found on the neck and upper back. The two muscles together form a trapezium, hence the name.	Elevates, retracts and elevates the scapula. (One side) Laterally flexes neck. (Both sides) Extend neck.
Pectoralis Major	Large muscle found on the front of the chest wall. It inserts via its tendon onto the front of the humerus.	Flexes shoulder. Adducts arm. Medially rotates arm.
Teres Major	Rectangular muscle originating from the bottom tip of the back of the scapula. It inserts via a flat tendon onto the front of the humerus.	Extends shoulder. Adducts arm. Medially rotates arm.
Serratus Anterior	It originates from the medial border of the scapula and inserts onto the upper 8 ribs via finger-like projections.	Protracts scapula. Depresses scapula. Rotates Scapula.
Latissimus Dorsi	Large flat triangular muscle found on the lower back. It originates from the spines of the lower thoracic, the lumbar and sacral vertebra. It inserts onto the front of the humerus.	Extends shoulder. Adducts arm. Medially rotates arm.

Arm

The muscles of the arm act upon the shoulder and elbow joints and are the strongest muscles in the upper limb.

Arm Muscles	Description	Action
Biceps Brachii	Large muscle found on the front of the arm; it has two heads. Long Head (arises within the shoulder joint capsule; supraglenoid tubercle). Short Head (arises from the coracoid process).  Both heads merge to insert via a thick tendon onto the radius (radial tuberosity).	Flexes elbow. Flexes shoulder. Abducts arm. Supinates forearm.
Triceps Brachii	Large muscle found on the back of the arm; it has three heads. Long Head (arises from the scapula; infraglenoid tubercle). Lateral head (arises from the humerus). Medial Head (arises from the humerus). The common tendon inserts onto the ulna (olecranon).	Extends elbow. Adducts arm.
Coracobrachialis	Found on the front of the arm, it originates from the coracoid process of the scapula. It inserts onto the shaft of the humerus.	Flexes shoulder. Adducts arm.
Brachialis	Found passing in front of the elbow, it originates from the shaft of the humerus and inserts onto the ulna; coronoid process.	Flexes elbow.

SELF-TEST

Complete the following questions before you go onto the next section:

List the 4 muscles of the rotator cuff. Why are they important?

Name and identify all of the heads of the biceps and triceps muscles.

Name 4 muscles that medially rotate the arm.

Forearm

The forearm muscles are mainly concerned with moving the wrist and fingers. The muscle bellies lie in the forearm and as they approach the wrist they become tendinous before passing into the the wrist and hand.

Name	Description	Action
Brachioradialis	Found on the front of the forearm, it originates from the distal end of humerus and inserts onto the distal end of the radius.	Flexes the elbow.
Pronator Teres	Found deep across the front of the elbow, it originates from the distal end of the humerus and the coronoid process of the ulna. It inserts onto the shaft of the radius.	Flexes the elbow. Pronates the forearm.
Supinator	Found deep across the back of the elbow, it originates from the lateral epicondyle of the humerus and inserts onto the radius.	Supinates the forearm.

Flexors

The flexors of the wrist and hand are located on the front of the forearm. A number of the flexor muscles of the forearm arise from a common flexor tendon which arises from the medial epicondyle of the humerus. At the front of the wrist the flexor tendons travel underneath the flexor retinaculum. This holds the flexor tendons in place and prevents them from bowing outwards when they contract.

Name	Description	Action
Flexors	Found on the front (palmar side) of the arm.	Flex the wrist and fingers.
Flexor Carpi Radialis	Arises from the common flexor tendon, becomes a thin tendon at the wrist and inserts onto the base of the 2nd metacarpal.	Flexes the wrist. Abducts the hand.
Flexor Carpi Ulnaris	Arises from the common flexor tendon, becomes a thin tendon at the wrist and inserts onto the 5th metacarpal and the carpal bones (pisiform and hamate).	Flexes the wrist. Adducts the wrist.
Flexor Digitorum Superficialis	Arises from the common flexor tendon, divides into 4 thin tendons each of which inserts onto a finger.	Flexes fingers 2-5.
Flexor Digitorum Profundus	Arises from the ulna, divides into 4 thin tendons each of which inserts onto to a finger.	Flexes wrist. Flexes fingers 2-5.
Flexor Pollicis Longus	Arises from the ulna, becomes a thin tendon at the wrist and inserts onto to the thumb.	Flexes the thumb.

Extensors

The extensors of the wrist and hand are located on the back of the forearm. A number of the extensor muscles of the forearm arise from a common extensor tendon whicharises from the lateral epicondyle of the humerus. At the back of the wrist the extensor tendons travel underneath the extensor retinaculum. This holds the extensor tendons in place and prevents them from bowing outwards when they contract.

Name	Description	Action
Extensors	Found on the back (dorsal side) of the arm	Extend the wrist and fingers.
Extensor Carpi Ulnaris	Arises from the common extensor tendon, becomes a flat tendon at the wrist and inserts onto the base of the 5th metacarpal.	Extends the wrist. Adducts the wrist.
Extensor Carpi Radialis Longus	Arises from the supracondylar ridge of the humerus, becoming a flat tendon at the wrist and inserts onto the 2nd metacarpal.	Extends the wrist. Abducts the wrist.
Extensor Carpi Radialis Brevis	Arises from the common extensor tendon, becomes a flat tendon at the wrist and inserts onto the 3rd metacarpal.	Extends the wrist. Adducts the wrist.
Extensor Digitorum	Arises from the common extensor tendon, divides into 4 thin tendons each of which inserts onto a finger.	Extends the wrist. Extends fingers 2-5.
Extensor Digiti Minimi	Arises from the common extensor tendon, becomes a thin tendon at the wrist and inserts onto the little finger.	Extends the little finger.
Extensor Pollicis Longus	Arises from the ulna it becomes a thin tendon at the wrist and inserts onto the first finger.	Extends the thumb.
Extensor Pollicis Brevis	Arises from the radius it becomes a thin tendon at the wrist and inserts onto the base of the thumb.	Extends the thumb.
Extensor Indicis	Arises from the ulna becomes a thin tendon at the wrist and inserts onto the index finger.	Extends the index finger.

Hand (intrinsic muscles)

The intrinsic muscles of the hand are the small muscles of the hand are split into thenar, hypothenar and mid palmar groups.  These muscles assist the flexors and extensors of the forearm to move the thumb and fingers. The thenar group control movements of the thumb, the hypothenar group control the movements of the little finger and the mid palmar group control the movement of fingers 2-5.  As the name suggests the mid palmar group lie between the metatarsals.

Name	Description	Action
Thenar (thumb) group	Muscles of the thumb.	Thumb movements
Adductor Pollicis	A triangular muscle with 2 heads; it arises from the 3rd metacarpal and inserts onto the thumb.	Adducts thumb.
Abductor Pollicis Brevis	A long thin muscle; it arises from the ulna and radius and inserts onto the thumb.	Abducts thumb.
Opponens Pollicis	The fleshy part of the thumb; it arises from the flexor retinaculum and trapezium and inserts onto the thumb.	Opposes thumb.
Flexor Pollicis Brevis	A thin muscle, it arises from the flexor retinaculum and carpal bones (trapezium, trapezoid and capitate) and inserts onto the thumb.	Flexes thumb.
Hypothenar (little finger) Group	Muscles of the little finger.	Little finger movements.
Abductor Digiti Minimi	A small muscle arising from the flexor retinaculum and pisiform and inserting onto the little finger.	Abducts little finger.
Flexor Digiti Minimi Brevis	A small thin muscle arising from the flexor retinaculum and hamate and inserting onto the little finger.	Flexes little finger
Opponens Digiti Minimi	A small muscle arising from the flexor retinaculum and hamate and inserting onto the little finger.	Opposes little finger to thumb.
Mid palmar Group	Muscles of the palm.	Metacarpal and finger movements.
Palmar interosseous(1-3)	Three muscles which originate from the 2nd, 4th and 5th metacarpal bones and insert onto the 2nd, 4th and 5th fingers respectively.	Adducts fingers 2, 4 and 5. Flex metacarpophalangeal joints. Extends interphalangeal joint.
Dorsal Interosseous (1-4)	Four muscles which arise from the adjacent sides of the 1st and 2nd, 2nd and 3rd, 3rd and 4th and 4th and 5th metacarpal bones. They insert onto the 2nd-4th fingers respectively.	Abducts fingers 2-4. Flex metacarpophalangeal joints of fingers 2-4. Extends interphalangeal joint.
Lumbricals (1-4)	Four muscles which originate in the palm from the tendons of flexor digitorum profundus and insert onto the 2nd-5th fingers.	Flex metacarpophalangeal joints of fingers 2-5. Extends interphalangeal joints of fingers 2-5.

SELF-TEST

Complete the following questions before you go onto the next section:

Which side of the forearm are the flexors and extensors located?

Name 2 muscles that originate in the forearm and flex the fingers.

List the names of 5 intrinsic muscles of the hand.

Lower Limb Muscles

The muscles of the lower limb are large and strong for locomotion. They can be divided into muscles of the hip, thigh, calf (leg) and foot.

Hip

Muscles of the hip include muscles which originate in the trunk as well as those within the thigh region.

Muscles of the Hip	Description	Action
Iliopsoas	This is the name given to two muscles which combine to form a conjoined tendon before inserting onto the femur. Psoas major (a thick muscle arising from the lumbar vertebrae). Iliacus (fan shaped muscle arising from the iliac fossa). Iliopsoas passes under the inguinal ligament and crosses in front of the hip joint to insert onto the femur.	Flex hip. Abduct hip. Flex trunk.
Gluteals (3 muscles)	This is the group of muscles that form the buttocks. Gluteus Maximus Gluteus Medius Gluteus Minimus They all arise from the body of the ilium and insert onto the femur; maximus inserts onto the gluteal tuberosity and medius and minimus inserted onto the greater trochanter of the femur.	Extend hip. Abduct hip. Laterally rotates femur.
Tensor Fasciae Latae	Small muscle arising from the iliac crest of the os coxa (hip bone) and inserting into the iliotibial tract.	Abducts hip. Laterally rotates femur.
Piriformis	Arises from the front of the sacrum and inserts onto the greater trochanter of the femur.	Abducts hip. Laterally rotates femur.
Gemelli	Two thin muscles, superior and inferior which arise from the lesser sciatic notch and insert onto the greater trochanter.	Laterally rotates hip. Abducts hip.
Obturator Internus	Arises within the pelvis from the margins of the obturator foramen. Its tendon makes a 90 degree turn around the lesser sciatic notch and inserts onto the greater trochanter.	Laterally rotates femur. Abducts hip.
Obturator Externus	Arises outside the pelvis from the margins of the obturator foramen. Its tendon inserts onto the intertrochanteric fossa.	Laterally rotates femur.
Quadratus Femoris	A flat quadrilateral muscle arising from the ischial tuberosity and inserting onto the femur.	Adducts hip Laterally rotates femur.

Thigh

The thigh has a group of strong muscles on the front called the quadriceps and on the back called the hamstrings.

Muscles of the Thigh	Description	Action
Quadriceps (4 muscles)	Large bulk of 4 muscles on the front of the thigh. They arise from the femur and attach via a conjoined tendon to the patella. Vastus lateralis (outside of the thigh). Vastus Medialis (inside of the thigh). Vastus Intermedialis (underneath other vastus muscles). Rectus Femoris (front of thigh).	Extends knee.
Hamstrings (3 muscles)	Large bulk of 3 muscles on the back of the thigh. They arise from the ischial tuberosity and insert onto the tibia. Biceps Femoris (two heads; long and short). Semitendinosus (has a long thin tendon). Semimembranosus (it is membranous at its origin).	Flexes knee.
Sartorius	The longest muscle in the body, it arises from the anterior superior iliac spine, travels obliquely across the front of the thigh and attaches to the tibia. It assists the hamstrings and aids in crossing and uncrossing your legs.	Flexes hip. Flexes knee. Rotates femur.
Adductors	Three muscles that form the inside (medial side) of the thigh. Adductor Magnus Adductor Longus Adductor Brevis	Adducts hip
Gracilis	Long thin muscle on the medial side of the thigh. It assists the adductors.	Adducts hip

Femoral Triangle

The femoral triangle is an area found at the top of the front of the thigh. It is bordered laterally by sartorius, medially by adductor longus and superiorly by the inguinal ligament. Its floor is composed of the iliopsoas and pectineus muscles and its roof by superficial fascia and skin. It is an important landmark due to the structures that pass through it as well as its superficial position. Passing through it is a large neurovascular bundle consisting of the femoral artery, vein and nerve. It also contains the inguinal lymph nodes and is where the saphenous vein joins with the femoral vein.

BOUNDARIES OF THE FEMORAL TRIANGLE

Popliteal Fossa

The popliteal fossa is a diamond-shaped space at the back of the knee. It is bound above and medially by semimembranosus and semitendinosus, above and laterally by biceps femoris and below and medially and laterally by the two heads of gastrocnemius. The floor is formed by the back of the femur and the roof is formed by the fascia lata and overlying skin. Passing through the popliteal fossa are the popliteal artery and vein, and the tibial and common peroneal nerves. It is also where the small saphenous vein joins the popliteal vein.

BOUNDARIES OF THE POPLITEAL FOSSA

SELF-TEST

Complete the following questions before you go onto the next section:

List all the muscles that laterally rotate the hip joint (femur).

Name the individual components of the quadriceps and hamstring muscles.

Name 3 structures that pass through the femoral triangle and the popliteal fossa.

Leg (calf)

Just like the forearm muscles move the wrist and fingers, most of the calf muscles are concerned with moving the ankle and toes. The muscle bellies lie in the leg and as they approach the ankle they become tendinous before passing into the foot.

Flexors and Plantar Flexors (Ankle Extensors)

The flexors of the toes and the plantar flexors of the ankle are located on the back and lateral side of the leg and ankle and in the sole of the foot. When reaching the ankle the tendons of the flexors curl around the medial and lateral malleoli to enter the sole of the foot. At the sides of the ankle the flexor tendons travel underneath the flexor retinaculum medially and the peroneal retinaculum laterally. This holds the flexor tendons in place and prevents them from bowing outwards when they contract.

Name	Description	Action
Posterior compartment	Found on the back of the leg.	Flexes the knee, ankle (plantar flexes) and toes.
Gastrocnemius	Together with soleus it forms the bulk of the calf. It arises from the femur via two heads, medial and lateral which form the borders of the popliteal fossa. The two heads merge with soleus inferiorly to form the tendo calcaneus (Achilles tendon) which inserts onto the back of the calcaneus.	Flexes knee. Plantar flexes ankle.
Soleus	Together with gastrocnemius it forms the bulk of the calf. It arises from the tibial and fibula and merges with gastrocnemius to form the tendo calcaneus (Achilles tendon) which inserts onto the back of the calcaneus.	Plantar flexes ankle.
Tibialis posterior	Lies deep in the calf arising from the back of the tibia and fibula. It becomes tendinous at the back of the ankle where it travels into the sole of the foot.	Assists plantar flexion (extension) of the ankle. Inverts foot.
Flexor Digitorum Longus	Arising from the back of the tibia it lies deep in the calf. It becomes tendinous at the back of the ankle where it travels into the sole of the foot. In the foot it divides into 4 tendons which attach to the 4 lateral toes.	Plantar flexes ankle. Flexes the 4 lateral toes.
Flexor hallucis longus	Arises deep in the calf from the back of the fibula. It becomes tendinous at the back of the ankle where it enters the sole of the foot to attach to the big toe (hallux).	Flexes big toe (hallux). Assists plantar flexion of the ankle.
Lateral (peroneal) compartment of the leg	Found on the outside of the leg.	Plantar flexes the ankle and everts the foot.
Peroneal Longus	It arises from the lateral (outside) surface of the fibula, runs down the side of the leg, becoming tendinous around the ankle to attach to the base of the 5th toe.	Plantar flexes ankle. Everts foot.

Extensors

The extensors (dorsiflexors) of the ankle and toes are located on the front of the leg and ankle and on the dorsum of the foot. At the front of the ankle the extensor tendons travel underneath the extensor retinaculum. This holds the extensor tendons in place and prevents them from bowing outwards when they contract.

Muscles of the Leg	Description	Action
Anterior (extensor) compartment of the leg	Muscles found in the front of the leg.	Extends the ankle joint (dorsiflexes) and the toes.
Tibialis anterior	It arises from the tibial shaft and runs down the front of the leg becoming tendinous at the ankle to attach to the medial cuneiform.	Dorsiflexes ankle. Inverts foot.
Extensor digitorum Longus	It arises from the front of the tibia and fibula and runs down the front of the leg dividing at the ankle into 4 tendons which attach to the 4 lateral toes.	Extends the 4 lateral toes. Assists dorsiflexion of the ankle.

Foot (Intrinsic Muscles)

The intrinsic muscles of the foot assist the flexors and extensors of the leg to move the toes.

Intrinsic muscles of the foot	Description	Action
Extensor digitorum brevis	A thin muscle on the dorsum of the foot; arising from the top of the calcaneus it divides into the 2nd-4th toes.	Extends (dorsiflexes) toes 2-4.
Extensor hallucis brevis	A thin muscle on the dorsum of the foot, arising from the top of the calcaneus and inserting onto the proximal phalanx of the hallux (big toe).	Extends (dorsiflexes) hallux.
Dorsal Interosseous (1-4)	Four muscles which arise from the adjacent sides of the 1st and 2nd, 2nd and 3rd, 3rd and 4th and 4th and 5th metatarsal bones. They insert onto the 2nd-4th toes respectively.	Abducts toes 2-4.
Plantar interosseous (1-3)	There are 3 muscles which originate from the 2nd, 4th and 5th metatarsal bones and insert onto the 2nd, 4th and 5th toes respectively.	Adducts toes 2, 4 and 5.
Lumbricals (1-4)	Four slender muscles which originate in the sole of the foot from the tendons of flexor digitorum longus and insert onto the 2nd-5th toes.	Flex metatarsophalangeal joints of toes 2-5. Extends interphalangeal joints of toes 2-5.
Flexor digitorum accessorius	Arises on the sole of the foot from the calcaneus and inserts onto the lateral border of the tendon of flexor digitorum longus.	Assists flexion of the 4 lateral toes.
Flexor digiti minimi brevis	A small muscle on the sole of the foot. It arises from the base of the 5th metatarsal and inserts onto the proximal phalanx of the 5th toe.	Flexes the 5th toe.
Abductor digiti minimi	Found in the lateral part of the sole; it arises from the calcaneus and inserts onto the 5th toe.	Abducts the 5th toe.
Flexor hallucis brevis	Arises on the sole of the foot from two heads attached to the cuboid and all 3 cuneiforms. It inserts via two tendons to the base of the proximal phalanx of the hallux. Each tendon contains a sesamoid bone.	Flexion of the hallux.
Adductor hallucis	Consists of two heads; transverse and oblique, which unite to insert into the hallux (big toe).	Adducts the hallux. Assists flexion of the hallux.
Abductor hallucis	A large muscle found on the medial part of the sole; it arises from the calcaneus and inserts onto the hallux (big toe).	Abducts the hallux.

SELF-TEST

Complete the following questions before you go onto the next section:

Name 4 muscles found in the posterior compartment of the leg.

Describe the function of the retinaculum around the ankle.

Name 4 intrinsic muscles that flex the toes.

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