the anatomy of pectoral region
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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.
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