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/2757strengthen-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
Quiz
Label #1-11
Practice Quiz
Practice Quiz
Answer Guide
1. 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.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
Gluteus Maximus
Gluteus Medius
Adductor Magnus
Psoas Major
Iliacus
Tensor Fasciae Latae
Adductor Magnus
Adductor Brevis
Adductor Longus
Gracilis
Piriformis
Pectineus