Slides provided by Dr Kavya on 20 March 2026
https://share.google/4ljlhGGLuIGDPazZt
Video provided by Dr Kavya on 20 March 2026:
https://youtu.be/RezL2xWFCe8?si=eFCWL784uZHpt4gG
Notes from Grok/
Here are comprehensive notes summarizing the two resources on spleen anatomy. The YouTube video by Armando Hasudungan (2017) offers a concise, illustrated overview emphasizing gross anatomy, histology, blood supply, and physiology (immune and filtration functions), with clinical correlations. The Slideshare presentation “Anatomy of Spleen” by Dr. Supriti Verma Bhatnagar (35 slides) provides a detailed gross anatomy focus, including development, external features, relations, ligaments, and clinical notes.
The notes integrate overlapping content while highlighting unique emphases from each source for completeness. They are organized into clear sections for easy reference.
Introduction and General Overview
• The spleen is the largest lymphoid organ and a key component of the reticulo-endothelial (mononuclear phagocyte) system. It functions as a haemo-lymph organ, involved in blood filtration, immune surveillance/response, and hematopoiesis (primarily fetal, with potential in adults under stress like severe anemia).
• It is an intraperitoneal organ (covered by visceral peritoneum except at the hilum), located in the left hypochondrium/epigastrium (left upper quadrant of the abdomen), between the fundus of the stomach and the diaphragm.
• Position: Lies posterior to the left 9th–11th ribs, separated from them by the diaphragm, left lung/pleura, and costodiaphragmatic recess. Its long axis runs downward, forward, and laterally along the 10th rib.
• Not normally palpable in healthy adults (undercover of the thoracic cage); becomes palpable in splenomegaly, often first at the anterobasal angle in the 9th intercostal space behind the mid-axillary line.
• “Organ of odd numbers” (Hari’s dictum): Approximately 1 inch (3 cm) thick, 3 inches (7–8 cm) broad, 5 inches (12–13 cm) long, weighs 7 oz (150–200 g, range 80–300 g).
Nuances/Edge Cases: Size and weight vary with age, body habitus, and pathological states (e.g., atrophy in aging or certain diseases; enlargement in infections, hematologic disorders, or portal hypertension). Accessory spleens (splenunculi) may occur due to incomplete fusion during development.
Gross Anatomy and External Features
• Shape: Variable, often ovoid or wedge-shaped, molded by adjacent structures (described as shoe-like or curved).
• Ends/Poles:
• Anterior (lateral) end: Expanded, directed downward and forward, reaches the mid-axillary line.
• Posterior (medial) end: Rounded, directed upward, backward, and medially; rests near the upper pole of the left kidney.
• Borders:
• Superior border: Sharp, with 1–2 notches near the anterior end (remnant of fetal lobulation).
• Inferior border: Rounded and blunt.
• Surfaces:
• Diaphragmatic surface: Convex, smooth; relates to the diaphragm, left lung/pleura, costodiaphragmatic recess, and 9th–11th left ribs.
• Visceral surface: Concave and irregular; features impressions—gastric (fundus of stomach), renal (anterior surface of left kidney), colic (splenic flexure of colon), and pancreatic (tail of pancreas).
• Angles: Anterobasal (junction of superior border and lateral end; clinically important for palpation in splenomegaly) and posterobasal.
• Hilum: On the medial/visceral surface; entry/exit point for splenic vessels, nerves, and lymphatics. Not covered by peritoneum.
Relations (key neighbors):
• Superiorly: Diaphragm.
• Anteriorly: Stomach (fundus).
• Inferiorly: Splenic flexure of colon (supported by phrenico-colic ligament).
• Medially/Posteriorly: Left kidney, tail of pancreas.
• Laterally: Ribs/diaphragm.
Peritoneal Attachments and Ligaments
• The spleen is suspended by peritoneal folds (derived from dorsal mesogastrium).
• Gastro-splenic ligament: Connects fundus of stomach to anterior lip of hilum; contains short gastric and left gastroepiploic vessels.
• Lienorenal (splenorenal) ligament: Connects anterior surface of left kidney to posterior lip of hilum; contains tail of pancreas, splenic vessels, and nerves.
• Lienophrenic (phrenicosplenic/suspensory) ligament: Attaches spleen to diaphragm.
• Phrenico-colic ligament (sustentaculum lienis): Peritoneal fold from left colic flexure to diaphragm; supports the spleen inferiorly.
Clinical Note: These ligaments are relevant in surgical mobilization during splenectomy and in understanding spread of pathology (e.g., pancreatic tail involvement).
Development and Accessory Spleens
• Develops in the 5th week of gestation from mesenchymal cells in the dorsal mesogastrium.
• Forms nodules that fuse into a lobulated spleen; notches on the superior border reflect this multi-origin development.
• Accessory spleens (splenunculi): Unfused nodules; common locations include derivatives of dorsal mesogastrium, broad ligament of uterus, or spermatic cord. They may hypertrophy after splenectomy and retain splenic function.
Microstructure (Histology)
• Encapsulated organ with fibrous capsule sending trabeculae inward (trabecular framework).
• Divided into white pulp (2–5% of volume; lymphoid tissue) and red pulp (75%; vascular/filtration tissue), separated by a marginal zone/sinus.
• White Pulp: Immune compartment.
• Periarteriolar lymphoid sheath (PALS): T-cells and macrophages around central arteries.
• Lymphoid follicles: B-cells (may form germinal centers).
• Marginal zone: Macrophages for antigen presentation.
• Function: Adaptive immune response—antigen presentation to T-cells, B-cell activation, antibody production (IgM, IgG). No afferent lymphatics; antigens arrive via blood.
• Red Pulp: Filtration compartment.
• Cords of Billroth (splenic cords): Reticular fibers rich in macrophages.
• Venous sinuses: Lined with endothelial cells having intercellular slits.
• Blood flow: Open circulation—blood from penicillar arteries enters cords, then filters through slits into sinuses (healthy RBCs pass; damaged ones trapped and phagocytosed).
Blood Flow Pathway: Splenic artery branches → central arteries (in white pulp) → penicillar/end arteries → red pulp cords/sinuses → splenic vein.
Blood Supply and Drainage
• Arterial Supply: Splenic artery (largest branch of celiac trunk; tortuous course along superior border of pancreas body/tail). Divides into superior/inferior branches, then segmental arteries. Also gives short gastric and left gastroepiploic arteries (via gastro-splenic ligament) supplying part of stomach.
• Venous Drainage: Splenic vein (formed from venous sinuses); drains spleen, pancreas, and part of stomach. Joins inferior mesenteric vein, then with superior mesenteric vein forms the portal vein (to liver).
• Segmental Anatomy: End arteries imply limited collateral circulation, increasing risk of infarction.
Nuance: The tortuous splenic artery accommodates splenic mobility and pancreatic relations.
Nerve Supply
• Primarily sympathetic fibers from the celiac plexus.
• Supply vascular smooth muscle and trabecular smooth muscle (vasomotor and contractile functions); minimal parasympathetic input noted.
Functions (Physiology)
1. Blood Filtration (Red Pulp): Removes old/damaged/abnormal RBCs (e.g., those with Howell-Jolly bodies, Heinz bodies), recycles iron from hemoglobin, sequesters ~1/3 of platelets (reservoir for coagulation), and clears pathogens/opsonized particles.
2. Immune Surveillance and Response (White Pulp): Monitors blood-borne antigens; activates T- and B-lymphocytes; produces antibodies. Plays a role in monocyte reservoir and innate/adaptive immunity.
3. Hematopoiesis: Significant in fetus; minor/reserve role in adults (e.g., extramedullary hematopoiesis in certain anemias or myeloproliferative disorders).
4. Other: Blood reservoir (can release RBCs in hemorrhage); iron metabolism.
Implications: Asplenia/hyposplenia (congenital, post-splenectomy, or functional) leads to:
• Increased risk of overwhelming post-splenectomy infection (OPSI), especially from encapsulated bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis) due to reduced opsonization and antibody production.
• Peripheral blood changes: Howell-Jolly bodies, target cells, thrombocytosis (initially).
• Vaccination and antibiotic prophylaxis recommended post-splenectomy.
Clinical Relevance and Applied Anatomy
• Splenomegaly: Causes include infections, portal hypertension, hematologic malignancies (e.g., leukemia, lymphoma), hemolytic anemias. Palpable below costal margin.
• Rupture: Common in trauma (falls, accidents) due to protected yet vascular nature; difficult to control bleeding → often requires splenectomy (partial or total).
• Splenectomy Indications: Trauma, hypersplenism, certain blood disorders, or iatrogenic.
• Asplenia/Hyposplenia: Increased infection risk and altered blood picture.
• Accessory Spleens: May cause recurrent symptoms if missed during surgery for conditions like idiopathic thrombocytopenic purpura (ITP).
• Imaging/Surgical Notes: Relations to pancreas, stomach, and colon important for procedures; vascular anatomy guides embolization or ligation.
Edge Cases: Wandering spleen (due to lax ligaments), splenic infarcts (from emboli or segmental artery occlusion), involvement in systemic diseases (e.g., sickle cell disease causing autosplenectomy).
CONCISE SUMMARY FROM GROK:
Here is a concise summary (approximately 480 words) of the spleen anatomy from the YouTube video by Armando Hasudungan and the Slideshare presentation “Anatomy of Spleen.”
Introduction
The spleen is the largest lymphoid organ and a haemo-lymph organ in the reticulo-endothelial system. It lies in the left hypochondrium (upper quadrant), under the diaphragm and ribs 9–11, between the fundus of the stomach and diaphragm. It is intraperitoneal, not normally palpable, and measures roughly 1 × 3 × 5 inches (3 × 7–8 × 12–13 cm), weighing 150–200 g (Hari’s dictum of odd numbers). Its long axis runs downward, forward, and laterally along the 10th rib.
Gross Anatomy
• Shape: Wedge- or shoe-shaped, often lobulated in fetal life.
• Poles: Anterior (lateral) end expanded and directed downward/forward; posterior (medial) end rounded, near the left kidney.
• Borders: Superior (sharp, with 1–2 notches from fetal lobulation); inferior (rounded).
• Surfaces:
• Diaphragmatic (convex, relates to diaphragm, left pleura, and ribs 9–11).
• Visceral (concave, with gastric, renal, colic, and pancreatic impressions).
• Hilum: On the visceral surface; entry/exit for vessels and nerves (uncovered by peritoneum).
Relations: Stomach (fundus), left kidney, tail of pancreas, splenic flexure of colon, and diaphragm.
Peritoneal Ligaments
• Gastro-splenic: Connects stomach to anterior hilum; contains short gastric and left gastroepiploic vessels.
• Lienorenal (splenorenal): Connects kidney to posterior hilum; contains pancreatic tail and splenic vessels.
• Lienophrenic: Suspensory to diaphragm.
• Phrenico-colic: Supports inferiorly from colonic flexure.
Development
Arises in week 5 from mesenchymal cells in the dorsal mesogastrium. Multiple nodules fuse; superior notches reflect this. Unfused nodules form accessory spleens (splenunculi) in mesogastrium derivatives.
Blood Supply and Nerve Supply
• Artery: Tortuous splenic artery (largest celiac trunk branch) runs along pancreas, dividing into segmental branches. Short gastric and gastroepiploic branches via gastro-splenic ligament.
• Vein: Splenic vein drains to portal vein (via superior mesenteric vein).
• Nerves: Sympathetic from celiac plexus (vasomotor and trabecular smooth muscle).
Histology
Capsule with trabeculae divides the spleen into:
• White pulp (2–5%): Immune zone — periarteriolar lymphoid sheath (T-cells), follicles (B-cells), marginal zone (macrophages). No afferent lymphatics; antigens arrive via blood. Supports adaptive immunity and antibody production (IgM, IgG).
• Red pulp (75%): Filtration zone — cords of Billroth (macrophage-rich) and venous sinuses with slits. Blood flows from penicillar arteries through cords; healthy RBCs pass slits into sinuses; damaged cells are phagocytosed. Open circulation pathway.
Functions
• Red pulp: Filters old/damaged RBCs (removes Howell-Jolly bodies), recycles iron, sequesters ~1/3 platelets, clears pathogens.
• White pulp: Immune surveillance — antigen presentation, T/B-cell activation, antibody production.
• Fetal hematopoiesis; minor adult role in stress. Acts as blood reservoir.
Clinical Relevance
Not palpable normally; palpable first at anterobasal angle in splenomegaly (e.g., infections, leukemia, portal hypertension). Prone to traumatic rupture (difficult hemostasis → splenectomy). Post-splenectomy risks: overwhelming infections (encapsulated bacteria), Howell-Jolly bodies in blood, thrombocytosis. Accessory spleens may cause recurrence in conditions like ITP. Hyposplenia/asplenia increases infection susceptibility; vaccinations and prophylaxis recommended.
The video emphasizes dynamic histology, blood flow, and immune/filtration physiology with clear illustrations. The Slideshare provides detailed gross features, ligaments, relations, and development. Together they offer complementary gross-to-microscopic and clinical insights.
(Word count: 480)
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