Trapezius – large fan shaped muscle.
Action: Elevate and depress the shoulders (shrugging, pushing shoulders
down). Stabilize the scapula ( like when raising arms above head).
Works with other muscles to retract and rotate the scapula, especially in
the shoulder complex. Mobility and stabilization roles.
Innervation: Accessory nerve (back of the skull, neck, shoulders
Serratus Anterior - protraction of the scapula.
Action: Reaching forward, pushing. When works together with
pectoralis minor, draws scapula laterally and forward around chest wall.
(under boob near arm pit area) Serratus is superior to external abdominal
obliqu
Pectoralis Minor – muscles working on the scapula, so move the
shoulder blade.Same function as serratus anterior above, works together
with it. Also an accessory muscle to breathing. Help expand thoracic
cavity. When it works with serratus anterior, help draw the scapula
laterally and forward around the chest wall.
Innervation — Medial and lateral pectoral nerv
Pectoralis Major — works on humerus (arm). Large chest muscles.
Super cial muscle. Action: Flex, adduct, medially rotate the humerus.
Innervation — Medial and lateral pectoral nerve
Latissimus Dorsi – large muscle along back.
Action: Adduct and medially rotate humerus. Some overlap between the
pectoralis major and latissismis dorsi, so often work together.
But difference is that latissimus dorsi can also do shoulder extension,
like backward swing (bowling, bring it back, pulling an oar) Attachment
point (insertion) is humerus
Deltoid – large muscle on the top part of humerus. Made up of anterior,
lateral, posterior bers. Different actions:
Anterior – ex and medially rotate the shoulder.
This study source was downloaded by 100000897367967 from CourseHero.com on 06-24-2025 06:15:23 GMT -05:00
https://www.coursehero.com/file/250325282/lab-6pdf/
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, Lateral – abduct the arm/away from body
Posterior – Extend and laterally rotate the shoulders. Pull arm back
behind the body or laterally rotate the shoulder.
Innervation — Axillary Nerve
Teres Major — shoulder extension and medial rotation. Inferior to
deltoid and superior to latissimis dorsi.
Action: Pull arm behind body, rotate the shoulder in
Innervation: Lower Subscapular nerve
Rotator Cuff – S.I.T.S. – stabilizes (hugs) the humeral head inside the
glenoid cavity of the scapula
Supraspinatus – shoulder abduction, lateral rotation. Will resist a
downward slippage of the humeral head downward when arms are
relaxed or carrying an object like when carrying a suitcase. Located right
on the scapula above the scapular spine
Infraspinatus – lateral/external rotation of shoulder. Stabilization,
prevent humeral head fro slipping upward when shoulder is at rest.
Teres Minor – lateral/external rotation of the shoulder. Prevent upward
slippage of humeral head inside the glenoid cavity during abduction.
Innervation — Axillary Nerve
Subscapularis – only rotator cuff muscle that does not function in
lateral/external rotation. Instead, medial/internal rotation of shoulder. Sits
on anterior surface of scapula is in the subscapular fossa.
Innervation: Lower Subscapular nerve.
Biceps Brachii – large muscle we see on the anterior surface of our
upper arm. Main function is supination of the forearm. Also assist in
elbow exion and shoulder exion.
Innervation — Musculocutaneous Nerve.
Has 2 parts/2 heads of attachment. Converge into 1 tendon.
Brachialis – the prime muscle that performs elbow exion
This study source was downloaded by 100000897367967 from CourseHero.com on 06-24-2025 06:15:23 GMT -05:00
https://www.coursehero.com/file/250325282/lab-6pdf/
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Action: Elevate and depress the shoulders (shrugging, pushing shoulders
down). Stabilize the scapula ( like when raising arms above head).
Works with other muscles to retract and rotate the scapula, especially in
the shoulder complex. Mobility and stabilization roles.
Innervation: Accessory nerve (back of the skull, neck, shoulders
Serratus Anterior - protraction of the scapula.
Action: Reaching forward, pushing. When works together with
pectoralis minor, draws scapula laterally and forward around chest wall.
(under boob near arm pit area) Serratus is superior to external abdominal
obliqu
Pectoralis Minor – muscles working on the scapula, so move the
shoulder blade.Same function as serratus anterior above, works together
with it. Also an accessory muscle to breathing. Help expand thoracic
cavity. When it works with serratus anterior, help draw the scapula
laterally and forward around the chest wall.
Innervation — Medial and lateral pectoral nerv
Pectoralis Major — works on humerus (arm). Large chest muscles.
Super cial muscle. Action: Flex, adduct, medially rotate the humerus.
Innervation — Medial and lateral pectoral nerve
Latissimus Dorsi – large muscle along back.
Action: Adduct and medially rotate humerus. Some overlap between the
pectoralis major and latissismis dorsi, so often work together.
But difference is that latissimus dorsi can also do shoulder extension,
like backward swing (bowling, bring it back, pulling an oar) Attachment
point (insertion) is humerus
Deltoid – large muscle on the top part of humerus. Made up of anterior,
lateral, posterior bers. Different actions:
Anterior – ex and medially rotate the shoulder.
This study source was downloaded by 100000897367967 from CourseHero.com on 06-24-2025 06:15:23 GMT -05:00
https://www.coursehero.com/file/250325282/lab-6pdf/
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, Lateral – abduct the arm/away from body
Posterior – Extend and laterally rotate the shoulders. Pull arm back
behind the body or laterally rotate the shoulder.
Innervation — Axillary Nerve
Teres Major — shoulder extension and medial rotation. Inferior to
deltoid and superior to latissimis dorsi.
Action: Pull arm behind body, rotate the shoulder in
Innervation: Lower Subscapular nerve
Rotator Cuff – S.I.T.S. – stabilizes (hugs) the humeral head inside the
glenoid cavity of the scapula
Supraspinatus – shoulder abduction, lateral rotation. Will resist a
downward slippage of the humeral head downward when arms are
relaxed or carrying an object like when carrying a suitcase. Located right
on the scapula above the scapular spine
Infraspinatus – lateral/external rotation of shoulder. Stabilization,
prevent humeral head fro slipping upward when shoulder is at rest.
Teres Minor – lateral/external rotation of the shoulder. Prevent upward
slippage of humeral head inside the glenoid cavity during abduction.
Innervation — Axillary Nerve
Subscapularis – only rotator cuff muscle that does not function in
lateral/external rotation. Instead, medial/internal rotation of shoulder. Sits
on anterior surface of scapula is in the subscapular fossa.
Innervation: Lower Subscapular nerve.
Biceps Brachii – large muscle we see on the anterior surface of our
upper arm. Main function is supination of the forearm. Also assist in
elbow exion and shoulder exion.
Innervation — Musculocutaneous Nerve.
Has 2 parts/2 heads of attachment. Converge into 1 tendon.
Brachialis – the prime muscle that performs elbow exion
This study source was downloaded by 100000897367967 from CourseHero.com on 06-24-2025 06:15:23 GMT -05:00
https://www.coursehero.com/file/250325282/lab-6pdf/
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