Pectoral region

Lecture 2

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Muscle Action

Each muscle has:

Origin Beginning.

Insertion End.

Body (belly).

Law:

When a muscle

performs its action,

its insertion, moves

towards its origin.

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3

Pectoral Region

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Pectoral RegionBreast region.

Contents:1. Skin.

2. Superficial fascia.

3. Breast.

4. Deep fascia.

5. 3 Muscles:a. Pectoralis major.

b. Pectoralis minor.

c. Subclavius.

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Pectoralis

major

Origin: Clavicle (M ½) , Sternum and upper 6 ribs. Insertion: humerus, lateral lip of intertubercular groove. Nerve Supply: Medial & lateral pectoral nerves. Action: Adducts and medially rotate the arm.

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Pectoralis

Minor

O: 3rd, 4th, 5th ribs.

Ins: Coracoid process.

NS: Medial pectoral N.

Action: Depress scapula downward and forward.

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Subclavius

Origin: 1st rib. Ins: Clavicle inferior surface. NS: N. to Subclavius. Action: Protects the underlying structures.

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Clavipectoral fascia

A sheet of CT that connects clavicle to the floor of the axilla.

It enclose subclavius and pectoralis minor and seals the gap between them.

Pierced by:

• Thoracoacromial A.

• Cephalic vein.

• Lateral pectoral N.

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Muscles connecting UL to vertebral col.

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DeltoidO: Clavicle, acromion and

spine of scapula.

Ins: Deltoid tuberosity.

Action: Its fibers runs in 3

directions

• Ant. flex shoulder.

• Post. extend should.

• Middle Abduct arm 15-900.

NS: Axillary N.

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TrapeziusO: Skull, spines of C1-T12 v.

Ins: Its fibers runs in 3

directions

• Down Clavicle.

• Horizontal Acromion.

• Up Spine of scapula.

Action:

Upper F. Elevate arm.

Middle F. adduct medial

Lower F. pull downward

Assist the serratus anterior muscle in abducting the arm 1800 above the head.

NS: Spinal accessory (IX) N.

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Latissmus dorsiO: T7-T12, L1- L5,

Sacrum & Iliac crest.

Ins: Floor of biceptal

groove

Action: extends, adducts

and medially rotate

humerus like in

canoeing.

NS: Thoracodorsal N.Dr. Maher Hadidi

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Scapular

musclesLecture 3

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Muscles connecting UL to scapula

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SupraspinatusO: Supraspinous fossa.

Ins: Greater tubercle of

humerus.

Action: Abducts arm

0-150.

NS: Suprascapular N.

InfraspinatusO: Infraspinous fossa.

Ins: Greater tubercle.

Action: Lateral rotation

of arm.

NS: Suprascapular N.

S

i

T

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Teres Minor(L. Rounded)

O: Lat. border of Scapula.

Ins: Greater tubercle.

Action: Lateral rotation of

arm.

NS: Axillary n.

Teres MajorO: Lat. border of Scapula.

Ins: Medial lip of i.t groove

Action: Adduction & Medial

rotation and of arm.

NS: Lower subscapular n.

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Subscapularis

Origin: Subscapular

fossa.

Ins: Lesser tubercle.

Action: Medial rotation

of the arm.

NS: Upper and lower

subscapular Ns.

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Serratus anterior Origin: upper 8 ribs.

Ins: Medial border of

scapula.

Act: Protraction of

scapula (pulls scapula forward over thoracic wall).

It assists trapezius to elevate arm 1800

above shoulder.

NS: Long thoracic N.

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Rotator cuff muscles of shoulder

Form of 4 muscles:

Supraspinatus

Infraspinatus

Teres minor

Subscapularis Their tendons flatten at

their insertion and blend with the capsule of the shoulder joint. They act as a handcuff that strengthen shoulder joint (superior,

posterior & anterior).

But NOT inferior?

Si

T

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Spaces between scapular muscles

Quadrangular space Borders:

• Sup. T. minor • Inf. T. major• Med. Triceps, long h.• Lat. humerus

Contents:• Axillary N.• Post. circ. hum. A,V.

Triangular space

Borders:• Sup, T. minor• Inf, T. major• Lat. Triceps, long head

Contents:• Circumflex scapular A & V.

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