Surgical Anatomy

Surgical Anatomy: General Principles - Scalpel Signposts

• Surgical Planes & Layers:
  • Skin (Epidermis, Dermis)
  • Superficial Fascia (e.g., Camper's, Scarpa's)
  • Deep Fascia (invests muscles, forms compartments)
  • Muscle layers
  • Periosteum/Peritoneum (lines bone/abdomen)
  • Dissect in natural avascular planes.
• Surgical Incisions:
  • Goal: Optimal exposure, minimal damage.
  • Respect nerves & vessels.
  • Types: Midline, Paramedian, Transverse (Pfannenstiel), Oblique (Kocher's, McBurney's).
• Tissue Handling & Haemostasis:
  • Gentle technique aids healing.
  • Meticulous haemostasis prevents haematoma.
• Wound Closure & Healing:
  • Primary Intention: Edges apposed, clean wound.
  • Secondary Intention: Open wound, granulation.

⭐ Incisions along Langer's lines (skin cleavage lines) are key for best cosmetic results (finer scars).

Surgical Anatomy: Thorax & Abdomen - Core Cavity Cuts

• Thorax: Surgical Access & Landmarks
  • Incisions: Median sternotomy (midline), thoracotomy (posterolateral/anterolateral).
  • Pleural Spaces: Visceral & parietal pleura; costodiaphragmatic recess.
  • Mediastinum: Key structures for surgical approach: heart, great vessels (aorta, SVC/IVC, pulmonary vessels), esophagus, trachea, phrenic/vagus nerves.
  • Diaphragmatic Apertures: Caval (T8), Esophageal (T10), Aortic (T12). (📌 I Eat Apples - IVC T8, Esophagus T10, Aorta T12)
• Abdomen: Incisions & Hernia Sites
  • Common Incisions: Midline, paramedian, Kocher's (subcostal), McBurney's (appendectomy), Pfannenstiel (pelvic).
  • Anterior Abdominal Wall Layers: Skin → Subcutaneous tissue (Camper's, Scarpa's) → External oblique → Internal oblique → Transversus abdominis → Transversalis fascia → Extraperitoneal fat → Peritoneum.
  • Inguinal Region:
    • Inguinal Canal: Spermatic cord (male) / Round ligament (female).
    • Hesselbach's Triangle (Direct Hernia): Boundaries: Rectus abdominis (medial), inferior epigastric vessels (superolateral), inguinal ligament (inferior).
  • Femoral Triangle: NAVEL (Nerve, Artery, Vein, Empty space, Lymphatics) from lateral to medial.

⭐ Calot's Triangle (Hepatobiliary Triangle): Critical for Cholecystectomy

• Boundaries: Common hepatic duct (medial), cystic duct (inferior), inferior edge of liver (superior).
• Contents: Cystic artery (usually), cystic lymph node (of Lund), autonomic nerve fibers. Right hepatic artery can be at risk.

Surgical Anatomy: Head, Neck & Pelvis - Precision Zones

• Head & Neck Critical Zones:
  • Carotid Triangle: Boundaries (SCM, post. digastric, sup. omohyoid). Contents: Carotid sheath (CCA bifurcation, IJV, CN X).
  • Submandibular Triangle: Contents: Submandibular gland, facial A/V, CN XII, lingual N.
  • Thyroid Gland: Recurrent Laryngeal Nerve (RLN) in tracheoesophageal groove, vulnerable at Ligament of Berry. External branch SLN at superior pole.

    ⭐ The RLN is most commonly injured during thyroidectomy, especially near Berry's ligament or inferior thyroid artery branches.

  • Parotid Gland: Facial nerve (CN VII) branches (📌 "To Zanzibar By Motor Car").
  • Pterygopalatine Fossa: Maxillary artery, V2.
• Pelvic Precision Zones:
  • Ureteric Course: "Water under the bridge" - Ureter inferior to uterine artery (female) / vas deferens (male). Vulnerable in hysterectomy, colectomy.
  • Key Spaces:
    • Space of Retzius (Retropubic): Between pubic symphysis & bladder.
    • Presacral Space: Between rectum & sacrum; risk of presacral venous plexus injury.
  • Neurovascular:
    • Internal iliac artery branches.
    • Obturator nerve: Risk in pelvic lymphadenectomy.
    • Pudendal nerve (Alcock's canal).
  • Female: Cardinal ligament (uterine artery). Uterosacral ligaments.
  • Male: Denonvilliers' fascia. Neurovascular bundles posterolateral to prostate.

High‑Yield Points - ⚡ Biggest Takeaways

• Triangle of Calot (cystohepatic): critical in cholecystectomy; contains cystic artery.
• McBurney's point: indicates base of appendix; crucial for appendicectomy.
• Hesselbach's triangle: anatomical landmark for direct inguinal hernias.
• Anterior abdominal wall layers: essential knowledge for incisions and hernia repair.
• Recurrent laryngeal nerve: high risk of injury during thyroidectomy.
• Axillary nerve: vulnerable in proximal humerus fractures and deltoid approaches.
• Spermatic cord contents: remembered by "Rule of 3s" (e.g., 3 arteries, 3 nerves).