---

Osteology of the Scapula - MS1 Level

---

Anterior (Costal) View

---

Posterior View

---

The "3-3-2-3" Framework (Easy Memory Tool)

• 3 Angles
• 3 Borders
• 2 Surfaces
• 3 Processes

---

1. Three Angles

The lateral angle is the most important - it is expanded into the neck of the scapula and ends in the glenoid cavity.

---

2. Three Borders

---

3. Two Surfaces

Costal (Anterior) Surface

• Mostly hollow = subscapular fossa
• Filled by the subscapularis muscle (a rotator cuff muscle)
• The serratus anterior attaches along the medial edge

Posterior (Dorsal) Surface

• Divided by the spine of the scapula into two fossae:
  • Supraspinous fossa (above spine) - smaller; origin of supraspinatus
  • Infraspinous fossa (below spine) - larger; origin of infraspinatus medially, teres minor superolaterally, teres major inferolaterally
• The two fossae communicate at the spinoglenoid notch (important - suprascapular nerve passes through here to reach infraspinatus)

---

4. Three Processes

A. Spine of the Scapula

• A triangular bony ridge on the posterior surface
• Divides the posterior surface into supra- and infraspinous fossae
• Trapezius inserts on its superior surface; deltoid originates from its inferior surface
• Continues laterally as the acromion

B. Acromion

• The "roof" of the shoulder joint
• Projects laterally/anteriorly over the glenohumeral joint
• Articulates with the clavicle at the acromioclavicular (AC) joint
• Middle deltoid originates here
• Clinically: os acromiale = failure of fusion of ossification centers (seen in 7-15% of people); can cause impingement syndrome

C. Coracoid Process ("Crow's Beak")

• Hook-shaped projection from the superior border of the scapular neck
• Projects anteriorly and laterally
• Origin: Short head of biceps brachii + coracobrachialis (from tip); pectoralis minor (from medial surface)
• Ligaments: coracoacromial ligament (to acromion), coracoclavicular ligaments = conoid + trapezoid (to clavicle)
• Important landmark - brachial plexus and axillary vessels lie medial and inferior to it

---

5. The Glenoid Cavity

• Shallow, comma-shaped socket at the lateral angle
• Only 1/3 to 1/4 the size of the humeral head (hence the shoulder's wide range of motion - but also instability)
• Supraglenoid tubercle - above the cavity; origin of long head of biceps brachii (intracapsular tendon)
• Infraglenoid tubercle - below the cavity; origin of long head of triceps brachii (extracapsular)

---

6. Quick Muscle Attachment Summary

---

7. Clinical Points (MS1 High-Yield)

• Suprascapular notch - suprascapular nerve entrapment here causes supraspinatus + infraspinatus weakness (external rotation + abduction weakness)
• Spinoglenoid notch - a second site of suprascapular nerve compression; only affects infraspinatus (external rotation weakness alone)
• Winged scapula - loss of serratus anterior function (long thoracic nerve injury); medial border of scapula protrudes posteriorly when pushing against a wall
• AC joint injury - acromion forced downward relative to clavicle when falling on an outstretched arm

---

---

Gross Anatomy of the Breast & Axillary Lymph Nodes - MS1 Level

---

PART 1: GROSS ANATOMY OF THE BREAST

Position & Extent

• Vertically: Rib 2 to Rib 6
• Horizontally: Sternum to mid-axillary line
• It also overlies the serratus anterior and external oblique muscles laterally

Mnemonic for borders: "2 to 6, Sternum to Side"

The Axillary Tail (of Spence)

---

Breast Cross-Section - Complete Diagram

---

Structural Layers (Surface to Deep)

---

Three Tissue Components

1. Glandular epithelium - the secretory machinery
2. Adipose tissue - dominant in postmenopausal women
3. Fibrous stroma - connective tissue scaffold

---

The Duct System (like an inverted tree)

Nipple (15-20 openings)
   ↑
Lactiferous sinuses (ampullae - dilated just below NAC)
   ↑
Lactiferous ducts (major ducts, 15-20 total)
   ↑
Segmental ducts → Subsegmental ducts
   ↑
Terminal ductules → Acini
   = TDLU (Terminal Duct Lobular Unit)

Key fact: There are 15-20 lobes, each with its own lactiferous duct opening at the nipple. The TDLU is where most breast cancers originate.

---

Cooper's Ligaments (Suspensory Ligaments)

• Fibrous bands running from the chest wall (deep fascia) to the dermis
• Give the breast its shape and support
• When infiltrated by cancer, they shorten and pucker the skin
• This causes skin dimpling and the classic "peau d'orange" (orange peel) appearance

Memory hook: Cooper's ligaments = the "tent pegs" of the breast. When cancer pulls on them, the tent surface dimples.

---

Blood Supply

The internal thoracic artery (via perforators) is the dominant supply - this is why medial breast tumors can spread to internal mammary nodes.

---

Nerve Supply

High yield: The T4 intercostal nerve provides sensation to the nipple. Injury during breast surgery can cause nipple anesthesia.

---

PART 2: AXILLARY LYMPH NODES

Lymphatic Drainage of the Breast - Overview

---

The Three Levels of Axillary Nodes

Mnemonic: "LAM" - Lateral, Along, Medial (relative to pectoralis minor)

---

Complete Axillary Node Map (with all named groups)

Named Groups - Easy Memory System

---

Drainage Pathway

Breast → Level I → Level II → Level III (Apical)
                                    ↓
                        Subclavian lymphatic trunk
                                    ↓
                Right lymphatic duct (right side)
                Thoracic duct (left side)
                                    ↓
                   Junction of subclavian + internal jugular veins

---

Rotter's Nodes (Interpectoral nodes) - Exam Favorite

• Located between pectoralis major and pectoralis minor
• Part of Level II
• Can be bypassed by cancer skipping Level I entirely ("skip metastases")
• Surgically important: must be removed in modified radical mastectomy

---

Other Lymphatic Drainage Routes (Minor Pathways)

---

Important Nerves at Risk During Axillary Surgery

Mnemonic: Nerves to protect = "Long Thoraco-Medial Intercostal" = LTMI - "Let The Muscle live, Intercostal too"

---

Clinical High-Yield Summary

---