The Anatomy of Pectoral Region

Pectoralis major

OriginAnterior sternal half of the

clavicle; Manubrium and Sternum upto

sixth costal cartilagesCartilages of all the true ribs, Aponeurosis of the abdominal

external oblique Insertion By a bilaminar tendon into the

lateral lip of the bicipital groove of the humerus

Innervation Medial and lateral pectoral

nerves

Actions Flexion of the

humerus, Adduction of the

humerus and Medial rotation of

the humerus. Clavicular part : flexion,

adduction, and medial rotation of the humerus.

Sternocostal part extension of the flexed arm as in climbing.

It aids in deep inspiration.

Origin It arises from the upper margins and outer surfaces of the third, fourth, and fifth ribs, Inserted into the medial border and upper surface of the coracoid process of the scapula.

InnervationMedial and lateral pectoral nerves ActionsProtracts the scapula with serratus anteriorDepresses the shoulder with the rhomboids and levator scapulae

ImportantThe pectoralis minor muscle is covered by the clavipectoral fascia. The medial pectoral nerve pierces the pectoralis minor .Axillary artery is divided into three parts by pectoralis minor.

Pectoralis minor

Clavipectoral fasciaEncloses subclavius and Pectoralis Minor.It is pierced by :Lateral pectoral nerve.Thoraco- acromial arteryCephalic vein. Lymph nodes from pectoral region to apical group of axillary lymph nodes

Serratus anterior Origin Arises from ribs 1 to 8, to be inserted into

the medial border of the scapula. Insertion• Medial border of the scapula between

the superior and inferior angles.• 1st and 2nd digitations to upper angle of

scapula.(C5)• 3rd and 4th digitations to medial border on

costal surface upto the inferior angle.• Lower 4 digitations to inferior angle of

scapula.Action Protraction of the scapula along with

pectoralis minor.• The fibres inserted on inferior angle

rotate scapula laterally and upwards in overhead abduction with trapezius.

Assists in respiration. Innervation long thoracic nerve(Nerve of Bell)

Applied aspect

• Serratus anterior is called the Boxer’s muscle since it is responsible for pushing and punching movements.

• Paralysis of this muscle results in a "winged scapula" ,results in protrusion of the scapula on the affected side when the patient is asked to push against the wall with both arms extended.

• Winged scapula occurs in lateral thoracic nerve paralysis

The mammary gland or The breast

Modified Sweat Gland (Apocrine Type)

Lies in Superficial fascia of pectoral region.

BUT

A small extension known as Axillary tail of Spence

pierces the axillary fascia through a small foramen

called the Foramen Of Langer and lies in the axilla.

EXTENT

VERTICALLYFrom second to sixth rib

in midclavicular line.

HORIZONTALLYFrom lateral border of sternum to midaxillary line along the fourth

rib.

Deep relationsThe Base of the Mammary gland called Mammary Bed rests upon the following structures (from Superficial to deep)(a)Retromammary Space(b)Deep Fascia (Pectoral Fascia)(c)Muscles- Pectoralis Major, Serratus Anterior, External Oblique.

RETROMAMMARY SPACEA Space deep to the base of the gland, lies

superficial to deep fascia, contains loose areolar tissue, makes the gland freely movable.

PRESENTING PARTS

(A)Nipple Lies in fourth intercostal space, has high nervous

innervation and openings of 15-20 lactiferous ducts.

(B) AreolaPigmented area at the base of nipple, contains

modified sebaceous glands which become enlarged during pregnancy and lactation forming Tubercles of Montgomery

STRUCTURE

3 COMPONENTS

(A) FIBROUS TISSUE(B) GLANDULAR TISSUE

(C) AREOLAR TISSUE

FIBROUS TISSUE

• Forms Suspensory Ligaments of Cooper which anchor gland to overlying skin and underlying deep fascia.

• Divide the gland into 15-20 lobes. • They may become contracted from fibrosis around a

carcinoma and produce a characteristic pitting of the skin of the breast (peau d orange)

(B) GLANDULAR TISSUE

• Consists of 15-20 lobes.• Arranged in a radiating

manner around the areola. • In lobes are alveoli which

secrete milk.• Alveoli lined by

myoepithelial cells under oxytocin control.

• Each lobe has one lactiferous duct.

• The lactiferous duct dilates near its opening in the nipple to form lactiferous sinus which acts as reservoir of milk.

Axillary Lymph Nodes

Anterior or Pectoral group receive lymph from upper half of anterior wall trunk and from major part of breast.

Posterior or Scapular group receive lymph from posterior wall of upper half of trunk and from axillary tail of breast.

Lateral group receives lymph from upper limb.

Central group receives lymph from preceding groups and drains into apical group. (intercostobrachial N)

Apical or infraclavicular (subclavian) group lie deep to clavipectoral fascia. They receive lymph from the central group, from upper part of breast and from the thumb.

Lymphatic drainage of Breast

Superficial portion of the

breast drains into the subareolar plexus Of Sappey.

Deep portion of the breast drains to the submammary plexus.

All the lymphatic of the breast converge into the Sappey plexus.

Lymphatic drainage of breast The lateral quadrants drain into

the anterior axillary or pectoral group of lymph nodes. (75%)

The medial quadrants drain by internal thoracic group of nodes. (20%)

A few lymph vessels follow posterior intercostals arteries and drain into posterior intercostals nodes. (5%)

Some vessels communicate with lymph vessels of opposite breast and with lymph vessels of anterior abdominal wall(Subdiaphragmatic and subperitoneal lymph plexuses)

ARTERIAL SUPPLY

Perforating branches of the Internal thoracic artery

Lateral mammary branches from the Lateral thoracic artery

Twigs from the Intercostal arteries

Pectoral branch of the Thoracoacromial artery

Venous Supply

• Venous drainage of the breast is mainly accomplished by the axillary vein.

• The subclavian, intercostal, and internal thoracic veins also aid in returning blood to the heart.

Nerve Supply• 4th through 6th intercostal nerves

Applied AspectMammography is a radiographic examination of the breast. This technique is

used for screening the breasts for benign and malignant tumours of the breast.

Breast cancer occurs in upper lateral quadrant (about 60% cases) and forms a palpable mass in later stages.

It enlarges, attaches to Cooper’s ligaments and produces shortening of ligaments, causing depression or dimpling of overlying skin.

It may attach to and shorten lactiferous ducts and cause retraction of nipple.

Obstruction of superficial lymph vessels by cancer cells may produce edema of skin giving rise to an orange skin appearance called Peau d’orange appearance.

The cancer can spread through veins to the vertebrae and brain because the veins draining the breast communicate with the vertebral venous plexus.

Localized cancer is treated by simple mastectomy . Localized cancer of breast with early metastasis of axillary

lymph nodes, radical mastectomy is done to remove the primary tumor and the lymph vessels and nodes that drain the area. These are removed

a large area of skin overlying the tumor and including the nipple, all the breast tissue the pectoralis major and associated fascia, the pectoralis minor and associated fascia ,all the fat, fascia and lymph nodes in axilla fascia covering upper part of rectus sheath,the serratus anterior, the subscapularis and the latissimus dorsi

muscles In modified radical mastectomy, the pectoral muscles are left

intact.

In a breast abscess an acute infection of the mammary gland occurs in which pathogenic bacteria gain entrance to the breast tissue through a crack in the nipple.

The abscess is localized to a lobe which id drained through a radial incision to avoid damage to the radially arranged ducts.