Anatomy of the Pectoral and Scapular Regions Question And Answers

Pectoral Region Introduction

• Pectoral region lies on the front of the chest.
• It consists of structures that connect the upper limb to the anterolateral chest wall.

Pectoral Region Question And Answers

Question 1. Briefly mention the superficial fascia of the pectoral region.
Answer:

Superficial Fascia

• It lies under the skin of the pectoral region and is continuous with surrounding superficial fascia. Its contents are:
  • Moderate amount of fat
  • Cutaneous nerves derived from the cervical plexus and intercostal nerves
  • Cutaneous arterial branches from internal thoracic and posterior intercostal arteries
  • Platysma muscle
  • Breast/mammary gland.

 

 

Question 2. Write a short note on platysma muscle.
Answer:

Platysma muscle:

• It is a thin broad sheet of subcutaneous muscle
• Origin: From the deep pectoral fascia
• Insertion: Into the base of mandible and skin
• It runs upwards and medially covering the neck
• Nerve supply: Fascial nerve
• It protects the underlying external jugular vein from external pressure.

Question 3. Explain in detail about the breast under the headings—situation and structure, blood supply, nerve supply, and lymphatic drainage.
Answer:

• The breast is a modified sweat gland.
• It is present in both sexes but rudimentary in males whereas well-developed in females after puberty.
• It is an important accessory organ of the female reproductive system and provides nutrition to the newborn in the form of milk.

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Situation, Relations, and Extent

• It is situated in the superficial fascia of the pectoral region except the tail which pierces the deep fascia of the axilla through the ‘foramen of Langer’ and is called the ‘tail of Spence’
• Breast extends:
  • Vertically: From 2nd to 6th rib
  • Horizontally: Lateral border of sternum to midaxillary line.
  • Superficial relations: Skin and superficial fascia
  • Deep relations:
    • Retromammary space: Loose areolar tissue separating breast from deep pectoral fascia, hence breast is freely movable over the pectoralis major
    • Pectoral fascia
    • 3 muscles over which base of the gland rests
      • Pectoralis major
      • Serratus anterior
      • External oblique (a part)
    • Structures deeper to them
      • Clavipectoral fascia
      • Pectoralis major

Structure of Breast

1. The structure of consists of:
   • Skin
   • Areola
   • Parenchyma
   • Stroma
2. Structure of Breast Skin
   • It covers the gland and presents the nipple and areola.
   • Nipple is the conical projection situated usually at the
     center of breast corresponding to the 4th intercostal space.
   • It is pierced by 15–20 lactiferous ducts.
   • It is rich in sensory nerve endings and very sensitive to touch.
3. Structure of Breast Areola
   • It is the circular area of pigmented skin surrounding the base of the nipple.
   • It is rich in sebaceous glands, especially in the outer margin, which produces oily secretion preventing nipple and areola from drying and crusting.
   • In pregnancy, the areola becomes darker and enlarged.
   • Montgomery’s tubercles are the enlarged sebaceous glands around the nipple in pregnancy.
4. Structure of Breast Parenchyma
   • It is the glandular part of the mammary gland which secretes milk.
   • It consists of 15–20 lobes arranged in a radial fashion around the nipple and opens into it through lactiferous ducts.
   • Each lobe consists of lobules which are filled with clusters of acini-secreting milk.
   • Lactiferous sinuses are dilated part of lactiferous duct that helps to secrete milk.
5. Structure of Breast Stroma
   • It is the supporting framework of the mammary gland.
   • It is made up of fibrofatty tissue.
   • The fibrofatty tissue is modified to form suspensory ligaments of cooper and suspends breast tissue to the skin and pectoral fascia.

Blood Supply

• Breast is highly vascular. It is supplied by:

1. Branches of lateral thoracic artery;
2. Branches of internal thoracic artery;
3. Branches of acromiothoracic and superior thoracic arteries
4. Branches of 2nd, 3rd and 4th posterior intercostal arteries

• Arterial Supply
  • Internal thoracic artery through its perforating branches
  • Axillary artery through:
    • Lateral thoracic
    • Superior thoracic
    • Acromiothoracic arteries
  • Posterior intercostal arteries through lateral branches.
• Venous Drainage
  • Axillary vein
  • Internal thoracic vein
  • Posterior intercostal vein.

Nerve Supply

• Cutaneous supply by 4th, 5th, and 6th intercostal nerves.

Lymphatic Drainage

• Lymphatic drainage of the breast is of great importance as they are the common channels through which metastasis of the breast cancer cells occurs to the opposite breast and other organs.
• The lymph nodes draining the breast are:

1. Axillary lymph node:

• They drains about 75% of the lymph from the breast.
• Among them, lymphatics end mainly in the anterior/pectoral group.
• Lymph from the anterior and posterior groups passes to central and lateral groups and through them to the apical group.
• Eventually, lymph reaches in the supraclavicular lymph nodes.

2. Internal mammary nodes are arranged along the internal thoracic vessels.

• They drains about 20% of the lymph from the breast.
• They drains from both inner and outer half of the breast.

3. Supraclavicular nodes.

45. Cephalic/deltopectoral lymph nodes.

5. Posterior intercostals nodes.

6. Subdiaphragmatic lymph nodes.

7. Subperitoneal lymph plexus.

• Lymphatic vessels draining the breast are:
  • Superficial lymphatics drain the skin over the breast except for the nipple and areola to the surrounding lymph nodes (axillary, internal mammary, posterior intercostal nodes) radially.
  • It is important to note that superficial lymphatics of the breast of one side communicate with those of the opposite side. So unilateral breast malignancies become bilateral through metastasis.
  • Deep lymphatics drain the parenchyma of the breast along with the nipple and areola.
  • The subareolar plexus of sappy is a plexus of lymphatics present deep to the areola. They drain into anterior axillary lymph nodes.
  • Lymphatics from the deeper part of the breast drain directly into the apical group of axillary lymph nodes or to the internal mammary lymph nodes.
  • Few lymph vessels from the inner part of the breast communicate with the subdiaphragmatic and subperitoneal lymphatic plexus.

Clinical Anatomy

• Knowledge of lymphatic drainage of the breast is very importance as lymphadenopathy is an early and important sign for staging, treatment, and prognosis of breast cancer.
• Though lymphatics cancer cell can communicate with the opposite breast and other organs in the body.
• Self-examination of the breast stands as the simplest, yet important, way to find out malignancy in early stage itself. On examination note:
  • Symmetry of breast and nipple
  • Change in the color of skin
  • Retraction of nipple
  • Discharge from nipple
  • Any palpable lump
• Cancer cells from the breast can shed of to the peritoneal cavity and moves to the ovary causing ovarian tumor known as Krukenberg’s tumor.
• Tubercle of Montgomery stands as an important medico-legal evidence of pregnancy.
• Suspensory ligament of Cooper degenerates on aging and breast becomes pendulous as age advances.
• Gynecomastia is the development of breasts in males due to hormonal imbalance and other reasons.

Question 4. Write briefly about clavipectoral fascia. What are the structures passing through it?
Answer:

It is a fibrous sheet situated deep to the clavicular part of the pectoralis major muscle.

Clavipectoral fascia Extend

• Vertically: From the clavicle above to the axillary fascia below.
• Medially: Attached to the first rib and costoclavicular ligament and blend with the external intercostal membrane of the upper two intercostal spaces.
• Laterally: Attached to the coracoids process and blends with coracoclavicular ligament.
• The clavipectoral fascia is split into two laminae in the upper part to enclose the subclavius muscle.
• The anterior lamina is attached to the clavicle while the posterior lamina is continuous with the investing layer of deep cervical fascia.
• It is split into two laminae in the lower part to enclose the pectoralis minor muscle.
• After enclosing the muscle, it extends downwards as the suspensory ligament of axilla which helps to pull up the dome of axillary fascia.

Structures Piercing the Clavipectoral Fascia

• Lateral pectoral nerve
• Cephalic vein
• Thracoacromial vessels
• Lymphatics from the breast and pectoral region to the apical group of axillary lymph nodes.

Question 5. Enumerate pectoral muscles.
Answer:

Enumerate pectoral muscles They are:

• Pectoralis major
• Pectoralis minor
• Known as key muscle of axilla as it divides the axillary artery into:
  • Subclavius
  • Serratus anterior (not strictly a muscle of pectoral region).

Question 6. Write a short note on the pectoralis major muscle.
Answer:

Pectoralis Major

Pectoralis Major Origin

• Small clavicular head: Medial half of anterior aspect of clavicle
• Large sternocostal head:
  • Lateral half of the anterior surface of sternum up to 6th rib
  • The medial end of 2nd to 6th costal cartilages
  • The aponeurosis of the external oblique muscle of the abdomen

Pectoralis Major Insertion

• Inserted into lateral lip of intertubercular sulcus by a U shaped bilaminar tendon
• Anterior lamina of tendon is formed by clavicular fiers
• Posterior lamina formed by sternocostal fiers
• Two laminas are continuous inferiorly
• Lower sternocostal and abdominal fibers are twisted in a way such that the lowest fibers are inserted highest

Pectoralis Major Nerve Supply

• Lateral pectoral nerve
• Medial pectoral nerve

Pectoralis Major Actions

• Clavicular head: Flexes arm
• Sternocostal head: Adducts and medially rotates the arm.

Question 7. Write about the origin, insertion, nerve supply, and actions of the remaining pectoral muscles.
Answer:

Question 8. Write a note on serratus anterior muscle.
Answer:

Serratus Anterior Origin

• 8 digitations from upper 8 ribs
• Fascia covering intervening intercostal muscles

Serratus Anterior Insertion: Costal surface of the scapula along its medial border

Serratus Anterior Nerve Supply: Nerve to serratus anterior (from the root of C5, C6, and C7)

Serratus Anterior Actions

• Pulls scapula forwards around the chest wall (along with pectoralis major)
• Keep medial border of scapula in fim contact with the chest wall
• Rotates scapula laterally and upwards during overhead abduction of arm

Mnemonic

• Serratus anterior: Innervation
• SALT: Serratus Anterior = Long Thoracic

Mnemonic Clinical Anatomy

• Injury to long thoracic nerve (nerve of bell) can occur in:
  • Stab wounds
  • During removal of breast tumor
  • Sudden pressure on shoulder from above
  • Carrying heavy load on shoulder
• It results in paralysis of serratus anterior and results in winging of scapula

Pectoral Region Multiple Choice Questions

Question 1. On climbing a tree, which of these two muscles at together?

1. Teres major and teres minor
2. Latissimus dorsi and teres major
3. Pectoralis major and latissimus dorsi
4. Teres major and pectoralis major

Answer: 3. Pectoralis major and latissimus dorsi

Question 2. Ligaments of cooper are modifiations of:

1. Axillary fascia
2. Pectoral fascia
3. Fatty tissue of breast
4. Fibrous stroma of breast

Answer: 4. Fibrous stroma of breast

Question 3. Which among these does not pierce clavipectoral fascia?

1. Lateral pectoral nerve
2. Cephalic vein
3. Thracoacromial vessels
4. Subclavian artery

Answer: 4. Subclavian artery

Question 4. Which among these are not an early warning sign of breast cancer?

1. Change in the color of skin
2. Gliding mass under the skin of breast
3. Retraction of nipple
4. Discharge from nipple

Answer: 2. Gliding mass under the skin of breast

Question 5. Which among these is not a pure pectoral muscle?

1. Pectoralis major
2. Pectoralis minor
3. Serratus anterior
4. Subclavius

Answer: 3. Serratus anterior