Download MBBS Anatomy PPT 6 Pectoral Region Notes

OBJECTIVES

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? By the end of the lecture the students should be able

to :

? Identify and describe the muscles of the pectoral region.

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? Pectoralis major.
? Pectoralis minor.
? Subclavius.
? Serratus anterior.
? Action of these muscles

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? Clavipectoral Fascia
? Blood & Nerve Supply
? Clinical Relevance

Pectoral region

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1. Bony landmark :

Sternum:

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Jugular notch (body of T2)

Sternal angle of Louise (T4-5)

Xiphosternal joint (T9)

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Ribs & costal cartilage

Scapular: acromian,

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coracoid process

Clavicle:

Humerus:

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?supraclavicular fossa

head

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?infraclavicular fossa

.2Superficial structure

- skin & derivative of skin (breast)

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Breast : nipple, areolar, mammary

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gland (F)

1. Surface Anatomy (position) :

Nipple ? 4-5" from the midline,

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intercostal space 4

Breast ? between rib 2-7

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2. Components :

- subcutaneous fat, mammary gland

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- Lactiferous duct

- Cooper's ligament (suspensory

ligament)

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- Retinaculum cutis fascia

The majority of the breast is in the superficial fascia, except the tail part

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(Tail of Spence) extends upward laterally into deep fascia at the lower border of

pectoralis major.

2/3 of the gland lies on pectoralis major

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1/3 of the gland lies on serratus anterior

Deltopectoral Triangle

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-deep fascia separating deltoid and pectoralis muscles

- Platysma = superficial muscle, thin plate, extends from the mandible to the

clavicle

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3. Muscles of pectoral

region

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a. Pectoralis Major

b. Pectoralis Minor

c. Serratus Anterior

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d. Subclavious
Pectoralis major

Origin

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Anterior sternal half of the

clavicle;

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Manubrium and Sternum upto

sixth costal cartilages

Cartilages of al the true ribs,

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Aponeurosis of the abdominal

external oblique

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Insertion

By a bilaminar tendon into the

lateral lip of the bicipital

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groove of the humerus

Innervation

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Medial and lateral pectoral

nerves

Flexion of the

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Actions

humerus,

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Adduction of the

humerus and

Medial rotation of

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the humerus.

Clavicular part : flexion,

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adduction, and medial

rotation of the

humerus.

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Sternocostal part

extension of the flexed

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arm as in climbing.

It aids in deep

inspiration.

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Origin

It

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Pectoralis minor

arises from the upper margins and outer

surfaces of the third, fourth, and fifth ribs,

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Inserted into the medial border and upper

surface of the coracoid process of the scapula.

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Innervation

Medial and lateral pectoral nerves

Actions

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Protracts the scapula with serratus anterior

Depresses the shoulder with the rhomboids

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and levator scapulae

Important

The pectoralis minor muscle is covered by

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the clavipectoral fascia.

The medial pectoral nerve pierces the

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pectoralis minor .

Axil ary artery is divided into three parts by

pectoralis minor.

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Clavipectoral fascia

Encloses subclavius and Pectoralis

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Minor.

It is pierced by :

Lateral pectoral nerve.

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Thoraco- acromial artery

Cephalic vein.

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Lymph nodes from pectoral

region to apical group of axil ary

lymph nodes

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PectoralGirdle : clavicle,

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scapular, ribs

Clavipectoral fascia /

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Costocoracoid

membrane

- deep fascia separating the

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pectoralis and the subclavious

Serratus anterior Origin

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Arises from ribs 1 to 8, to be inserted into

the medial border of the scapula.

Insertion

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? Medial border of the scapula between

the superior and inferior angles.

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? 1st and 2nd digitations to upper angle of

scapula.(C5)

? 3rd and 4th digitations to medial border on

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costal surface upto the inferior angle.

? Lower 4 digitations to inferior angle of

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scapula.

Action

Protraction of the scapula along with

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pectoralis minor.

? The fibres inserted on inferior angle

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rotate scapula laterally and upwards in

overhead abduction with trapezius.

Assists in respiration.

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Innervation

long thoracic nerve(Nerve of Bell)

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-Blood supply to the pectoral region

1. Axillary artery

2. Perforating branches of the internal thoracic a.

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1. Axillary artery :

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divided into 3 parts

First part :

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Supreme thoracic a.

Second part :

1.Thoraco-acromial trunk

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Acromial branch

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Pectoral branch

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Clavicular branch

Deltoid branch

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2. Lateral thoracic a.

Third part :

give branches to supply head of humerus and

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scapular regions

Venous drainage at the pectoral region

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.1Deep veins - axillary v. <= from the muscles

.2Superficial veins

- cephalic v. (from upper limb) at the

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deltopectoral triangle, it pierces the

clavipectoral fascia (or infraclavicular fossa)

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into the axillary v.

-from mammary gland, it drains into deep veins

=> internal thoracic v. and lateral thoracic v.

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Nerve Supply of the pectoral region

.1- medial & lateral pectoral nerve (terminal

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branches from the cords of the Brachial plexus (C5-

8 & T1)

- nerve to subclavius (a branch from upper trunk of

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the Brachial plexus)

- long thoracic nerve (nerve roots from C5-6-7 of

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the Brachial plexus)


Brachial plexus (C5-8 & T1)

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.2Spinal n. / Sensory (cutaneous) n

- Supraclavicular nerve (C3-4, medial, intermediate & lateral branches)

- Intercostal nerve T3-7 (anterior & lateral cutaneous branches)

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*Dermatome at the pectoral region: C3-4, T3-7

Applied aspect

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? Serratus anterior is called the

Boxer's muscle since it is

responsible for pushing and

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punching movements.

? Paralysis of this muscle results

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in a "winged scapula" ,results

in protrusion of the scapula on

the af ected side when the

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patient is asked to push

against the wall with both

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arms extended.

? Winged scapula occurs in

lateral thoracic nerve

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paralysis


Paralysis of Serratus anterior

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muscle.

Clinical Relevance

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.1Chest wall ? heart /lung sound

.2Clavipectoral fascia

- protection of the vessels and nerves underneath

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-limit spreading of the abscess from upper limb to the

neck

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.3Fracture of clavicle

-common site is at 1/3 from the lateral

-Poland Anomaly

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-Cardiac Catheterisation- Basilic vein

1. Which one of the fol owing muscles performs adduction of the arm ?

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a. Pectoralis minor.

b. Pectoralis major.

c. Subclavius.

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d. Serratus anterior.

2. Serratus anterior is innervated by :

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a. Thoracodorsal nerve.

b. Long thoracic nerve.

c. Axil ary nerve.

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d. Radial nerve.


3. Which one of the fol owing muscles contributes in rotation of the scapula above the head?

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a. Pectoralis major.

b. Pectoralis minor.

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c. Serratus anterior.

d. Teres major.

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4. Which one of the fol owing do not pierces clavipectoral fascia?

a. Lateral Pectoral Nerve.

b. Lymph Nodes.

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c. Cephalic Vein.

d. Lateral thoracic artery.

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5. Nerve to subclavius is a branch from which part of brachial plexus?

a. Roots.

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b. Divisions.

c. Cords.

D. Trunks.

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