Gallbladder Anatomy & Physiology

Summary

The gallbladder is a pear-shaped, hollow organ located on the inferior surface of the liver that serves as a reservoir for bile storage and concentration. Anatomically positioned at the intersection of the right 9th costal cartilage and lateral border of the rectus abdominis muscle, it has a normal capacity of approximately 50 mL but can accommodate up to 300 mL when the cystic duct is obstructed. The organ consists of a fundus, body, neck, and sometimes a Hartmann's pouch—a common site for gallstone impaction.

The gallbladder receives its blood supply primarily from the cystic artery, a branch of the right hepatic artery that courses through Calot's triangle. Its unique histological structure lacks a muscularis mucosa and submucosa, distinguishing it from other gastrointestinal organs. The primary functions include bile storage, concentration (5-10 fold), mucus secretion, and slight acidification of bile. Understanding gallbladder anatomy is crucial for recognizing clinical conditions such as cholecystitis, cholelithiasis, and potential surgical complications.

Anatomy & Location

• Position: Intraperitoneal organ located on the visceral surface of the liver
  • Lies in the gallbladder fossa between right and left hepatic lobes (segments IVb and V)
  • Attached to liver by peritoneum except at the gallbladder bed
• Surface landmark: Found at the intersection of:
  • Right 9th costal cartilage
  • Lateral border of rectus abdominis muscle
  • This point becomes tender in acute cholecystitis (Murphy's sign) علامة مورفي
• Relations:
  • Superior: Liver (segments IVb and V)
  • Inferior: Transverse colon, duodenum (first and second parts)
  • Posterior: Gastroduodenal artery

Gross Anatomy

• Shape & Size:
  • Pear-shaped sac شكل الكمثرى
  • Length: 7-10 cm
  • Width: 3 cm at widest point
• Capacity:
  • Normal: ~30-50 mL
  • Can distend up to 300 mL if cystic duct obstructed
• Parts of gallbladder:
  • Fundus:
    • Rounded, blind end
    • Projects beyond inferior liver margin
    • Related to anterior abdominal wall at 9th costal cartilage
  • Body:
    • Main storage area
    • In contact with visceral surface of liver
  • Infundibulum:
    • Funnel-shaped area between body and neck
  • Neck:
    • S-shaped, narrows to become cystic duct
    • Contains spiral valves of Heister
  • Hartmann's pouch جيب هارتمان:
    • Small outpouching at junction of neck and infundibulum
    • Most common site for gallstone impaction الموقع الأكثر شيوعاً لانحشار الحصوات

Microscopic Anatomy (Histology)

• Wall layers (from lumen outward):
  • Mucosa:
    • Simple columnar epithelium with microvilli
    • Numerous folds (rugae) when gallbladder is empty
    • Contains mucus-secreting goblet cells
  • Lamina propria:
    • Loose connective tissue
    • No muscularis mucosa (unlike GI tract)
  • Muscularis propria:
    • Smooth muscle fibers in irregular arrangement
    • Responsible for gallbladder contraction
  • Perimuscular layer:
    • Connective tissue with vessels, nerves, lymphatics
  • Serosa/Adventitia:
    • Serosa: covers free surface (peritoneum)
    • Adventitia: where attached to liver bed
• Special features:
  • Spiral valves of Heister:
    • Located in cystic duct and neck
    • Maintain patency and regulate bile flow
  • Rokitansky-Aschoff sinuses:
    • Deep invaginations of mucosa into muscle layer
    • Can be sites of inflammation in chronic cholecystitis

Blood Supply & Lymphatics

• Arterial supply:
  • Cystic artery:
    • Usually arises from right hepatic artery
    • Divides into superficial and deep branches
    • Courses through Calot's triangle مثلث كالو
  • Calot's triangle boundaries:
    • Medial: Common hepatic duct
    • Inferior: Cystic artery
    • Superior: Inferior surface of liver
    • Critical anatomical landmark during cholecystectomy
• Venous drainage:
  • Small veins drain directly into liver bed (portal system)
  • Cystic vein (when present) → portal vein
• Lymphatic drainage:
  • Cystic lymph node (Lund's node or node of Mascagni):
    • Located at neck of gallbladder
    • First node in lymphatic drainage
    • May be enlarged in cholecystitis
  • Drains to → hepatic nodes → celiac nodes

Innervation

• Sympathetic:
  • From celiac plexus (T5-T9)
  • Decreases gallbladder contraction
  • Increases sphincter tone
• Parasympathetic:
  • Vagus nerve (hepatic branch)
  • Stimulates gallbladder contraction
  • Relaxes sphincter of Oddi
• Sensory innervation:
  • Via sympathetic fibers
  • Referred pain: Right scapular region (via phrenic nerve C3-C5)

Physiology & Functions

• Bile storage:
  • Stores 30-50 mL of bile between meals
  • Receives ~500-1000 mL bile daily from liver
• Bile concentration:
  • Absorbs water and electrolytes (Na+, Cl-, HCO3-)
  • Concentrates bile 5-10 fold
  • Active transport mechanisms in epithelium
• Mucus secretion:
  • ~20 mL/day from tubuloalveolar glands
  • Protects epithelium from concentrated bile
• Bile acidification:
  • H+ secretion lowers pH slightly
  • Helps prevent calcium precipitation
• Regulation of gallbladder function:
  • Cholecystokinin (CCK):
    • Released from duodenal I-cells in response to fats/proteins
    • Causes gallbladder contraction
    • Relaxes sphincter of Oddi
  • Neural control:
    • Vagal stimulation during cephalic phase
    • Local reflexes via enteric nervous system

Clinical Correlations

• Murphy's sign:
  • Inspiratory arrest during palpation of RUQ
  • Indicates acute cholecystitis
• Courvoisier's law:
  • Palpable, non-tender gallbladder + jaundice = likely malignant obstruction
  • Gallstones rarely cause palpable gallbladder
• Ducts of Luschka:
  • Accessory bile ducts draining directly from liver to gallbladder
  • Present in 10-30% of individuals
  • Risk of bile leak if not identified during cholecystectomy
• Critical view of safety in cholecystectomy:
  • Two arteries entering gallbladder
  • No other structures crossing hepatocystic triangle
  • Clear view of liver bed

Table Summary