Chapter 3 Muscle Anatomy and Functions

Deep Muscles of the Vertebral Column

The Erector Spinae Group

1. Spinalis – most medially; along the spine

2. Longissimus – between spine and iliocostalis

3. Iliocostalis – most lateral; along the ribs

*Memory tool: “I Long for Spinach

Deep Muscles of the Vertebral Column (cont’d)

Function: • Keep the body in an erect/upright position.• Extend spine• Lateral flex spine

Muscles of the Thoracic Cage

• Affect the rib cage and the process of breathing:

1. Diaphragm – separates the thoracic and abdominal cavities

2. Intercostals – “the breathing muscles”, located between each rib

3. Transverse Thoracic – triangular muscle, acts on the abdominal wall, pulling it inwards.

Anterior Abdominal Wall

The “Abs”• Named based on the direction of the fibers

T - Transverse Abdominis I - Internal Obliques R - Rectus Abdominis E - External Obliques

transverse = across oblique = diagonal rectus = vertical

Anterior Abdominal Wall

Functions:

• Transverse Abdominis• Internal Obliques • External Obliques

Trunk Flexion & Rotation

“ “ “

• Rectus Abdominus Trunk flexion

Effective Ab Exercises

Muscles of the Shoulder

• Pectoralis Major• Deltoid Muscle

– (see previous notes)

Muscles of the Shoulder (cont’d)

• Rotator Cuff Muscles

• A group of muscles that stabilize the shoulder and hold it in place.

• Eg. When throwing a baseball, the rotator cuff muscles would help to decelerate arm movements

• All “SITS” Muscles extend from the scapula and insert on either the greater or lesser tubercle of the humerus

• “SITS” Muscles

Muscles of the Shoulder (cont’d)

• Rotator Cuff Muscles• Clockwise from top:

• S – Supraspinatus - abduction• I - Infraspinatus - lateral rotation• T – Teres Minor - lateral rotation• S – Subscapularis - medial rotation

*The subscapularis is the only rotator cuff muscle located on the anterior portion of the scapula.

Muscles of the Shoulder (cont’d)

• Memory Tool for Rotator Cuff Muscles:

• A pro baseball player has injured his rotator cuff muscle. As a result, he “sits” out of the game and gets sent to the “minor leagues”

6 Scapula Movers

(see previous notes)

3 Humerus Movers

(see previous notes)

Elbow Flexors

• 3 “B’s” bend the elbow:– Biceps Brachii– Brachialis– Brachioradialis

Elbow Extension

• Muscles which straighten the arm:

• Triceps brachii – elbow extension

• Anconeus – a small triangular muscle which assists the triceps in elbow extension

Muscles of the Forearm

• Anterior group – wrist flexion

• Posterior group – wrist extension

(You don’t have to know these in detail)

Hip Flexors

Hip Flexors

• A group of 7 muscles which function to flex the thigh, an action which brings the leg closer to the torso/chest.

• All muscles in this group originate on the pelvis and insert somewhere on the femur.

The 7 Hip Flexor Muscles:

• Anterior Group– Pectineus – Iliopsoas – Rectus Femoris– Sartorius – Adductor Brevis– Adductor Longus

• Lateral Group– Tensor Fasciae Latae

Iliopsoas

• The strongest hip flexor• Hip Flexion• External Rotation

• (3 deep muscles that function as one)– Psoas Major– Psoas Minor– iliacus

Iliopsoas

• Iliopsoas (Iliacus and psoas muscles)– Iliopsoas = Hip flexion– Psoas major = Hip flexion + trunk flexion– Psoas minor = weak trunk flexion

• The Psoas Minor muscle is present in only 40% of the population!!

Pectineus

• Sometimes considered an extension of the iliopsoas

• Upper most muscle of the medial thigh group

• Hip Flexion (primary action)• Adduction and

External Rotation

Rectus Femoris

As mentioned previously, part of the quadriceps group

The only muscle of the quadriceps group that crosses both the hip and the knee joint.

•Hip Flexion•Knee Extension

(Eg. Taking forward stride in walking)

Sartorius

• Longest muscle in the body• Most superficial thigh muscle• Not very powerful (assists)• Helps to cross the leg

• Hip Flexion• Outward rotation at hip• Knee Flexion

• http://www.livestrong.com/video/2757-strengthen-hip-flexor/

Hip Extensors

Hip Extensors

• Gluteus Maximus– Strongest, most superficial

• Hamstrings– Bicep Femoris– Semitendinosus– Semimembranosus

Gluteus Maximus

• Gluteus = Greek for “rump”

• Used mostly during power movements

– Hip Extension – External Rotation

Gluteus Maximus

• Used more in running than walking because the hip must be extended more than 15 degrees to activate the gluteus.

• Doing sprints is an effective way to tone up the gluteus maximus!!

• Other power activities which build strength:– Squats, Lunges,

Hamstrings

• Inability to touch the toes while keeping the knees extended is due to shortened, inflexible hamstring muscles

Biceps Femoris

•Largest Muscle in Hamstring group

•Located on lateral side

•Hip Extension

•Knee Flexion

•Outward Rotation

•Outward Rotation when knee is in flexed position

Semimembranosus and Semitendinosus

• Both Located on the medial side of the hamstring group but the semitendinosus lies on top

– Hip Extension– Knee Flexion– Internal Rotation of the hip– Internal Rotation of the knee

•

Hip Adductors

5 Hip Adductor Muscles

• Also known as your “groin” area

• The 5 adductor muscles can be categorized in 2 groups: Short Adductors and Long Adductors

• The “short adductors” go from the pelvis to the femur bone, while the “long adductors” go from the pelvis to the knee.

5 Adductor Muscles

• Short Adductors:– Pectineus– Adductor Brevis– Adductor Longus

• Long Adductors:– Adductor Magnus– Gracilis

The Adductor Longus Muscle is the most commonly injured.

Sprinters, hurdles, football players, soccer players and other athletes involved in sports, which require quick changes in direction, are particularly susceptible to groin strains.

The adductor Magnus is the strongest (and largest) of the adductor muscles

5 Primary Hip Adductors

• Pectineus – Adduction and hip

flexion

• Adductor Brevis – Shortest, deepest– Adduction..– Hip Flexion

• Adductor Longus – Adduction..– Hip Flexion

5 Primary Hip Adductors

• Adductor Magnus – The strongest of the

adductors– Longest, deepest muscle– Adduction..

• Gracilis – The most superficial adductor– Hip Adduction, internal

rotation– Knee flexion

Hip Abductors

Hip Abductors

• Gluteus Medius– (Lateral Butt muscle)– Abduction, internal

rotation

• Gluteus Minimus– (Deepest Butt Muscle)– Abduction, internal

rotation

• Tensor Fasciae Latae– (Lateral Muscle)

Tensor Fasciae Latae

•Hip Abduction

•Hip flexion

•Internal Rotation

Prevents external rotation of the femur when it is in the flexed position. It helps keep the foot placed straight ahead during walking and running.

Quadriceps Group

• Vastus = Large

• Vastus Lateralis• Vastus Medialis• Vastus Intermedius• Rectus Femoris

(see notes)

Conclusion

• Generalized Muscle landmarks in the lower body:

• Anterior –• Posterior – • Medial – • Lateral – 

Practice QuizLabel #1-11

Practice Quiz

Practice Quiz

Answer Guide1. Iliopsoas

2. Tensor Fasciae Latae

3. Sartorius

4. Vastus Lateralis

5. Psoas Major

6. Pectineus

7. Adductor Longus

8. Gracilis

9. Rectus Femoris

10.Vastus Medialis

11.Rectus Femoris Tendon

Answer Guide

12. Gluteus Maximus13. Gluteus Medius14. Adductor Magnus15. Psoas Major16. Iliacus17. Tensor Fasciae Latae18. Adductor Magnus19. Adductor Brevis20. Adductor Longus21. Gracilis22. Piriformis23. Pectineus