Topography and Skeletotopy
The organ is located in the posterior region of the left hypochondrium. Its outer surface adheres to the costal part of the diaphragm. The projection of the spleen coincides with the left costodiaphragmatic recess, and skeletotopically it is situated in the space between the 9th and 11th ribs. The posterior end of the organ is 4–6 cm away from the spine, which corresponds to the level of the 10th–11th thoracic vertebrae.
Normally, the organ does not extend beyond the anterior axillary line. The shape of the spleen can be oval or oblong, with short and wide shapes being more common in adults, and long and narrow ones in children.
Ligamentous apparatus and fixation
Fixation of the organ is ensured by a complex of peritoneal ligaments extending to its hilum (hilus lienis):
- Phrenicolic ligament (lig. phrenicolienale) — the main fixing element containing the neurovascular bundle.
- Pancreaticosplenic ligament (lig. pancreaticolienale) — the lower part of the anterior layer of the phrenicolic ligament, extending from the tail of the pancreas.
- Gastrolienal ligament (lig. gastrolienale).
- Phrenicocolic ligament (lig. phrenicocolicum) serves as a support for the lower pole of the organ ("hammock") and forms a blind pouch (saccus caecus lienis).
Structure of Parenchyma and Capsule
Externally, the spleen is surrounded by a fibrous capsule (tunica fibrosa), which is closely fused with both the visceral peritoneum and internal trabeculae. The main feature of the capsule is that it cannot be separated from the parenchyma surgically. The capsule is strong and elastic, allowing the organ to adapt to volume changes. In significant splenomegaly (enlargement), the elasticity may be insufficient, creating a risk of traumatic or spontaneous parenchymal ruptures.
Blood Supply and Drainage
Arterial inflow is provided by the splenic artery (a. lienalis) — the largest branch of the celiac trunk. With age, its length and tortuosity increase significantly (becoming spiral-shaped in elderly individuals). Intraorgan arterial anastomoses are poorly developed, which is why branch thrombosis leads to segmental ischemic infarctions.
Venous drainage is carried out via the splenic vein (v. lienalis), whose diameter is 1.5 to 2 times greater than that of the artery. Posterior to the head of the pancreas, it joins the superior mesenteric vein to form the portal vein.
Briefly: answers to topical questions
What is the syntopy of the spleen?
The syntopy of the spleen is determined by its location in the left hypochondrium and its proximity to neighboring organs.
- Diaphragmatic surface (facies diaphragmatica) — faces the diaphragm, and through it the 9th–11th ribs, left lung, and pleura.
- Visceral surface (facies visceralis) — has a number of impressions:
- Gastric impression (impressio gastrica) — contacts the fundus of the stomach.
- Renal impression (impressio renalis) — adheres to the upper pole of the left kidney and the adrenal gland.
- Colic impression (impressio colica) — contacts the left colic flexure.
- Pancreatic impression (impressio pancreatica) — adheres to the tail of the pancreas.
What branches does the splenic artery give off before entering the hilum of the spleen?
Before entering the hilum of the spleen, the splenic artery gives off a number of extraorgan branches to the pancreas, stomach, and greater omentum.
- Pancreatic branches (rr. pancreatici) — supply the body and tail of the pancreas.
- Left gastroepiploic artery (a. gastroepiploica sinistra) — heads toward the greater curvature of the stomach and gives off the left omental artery into the greater omentum.
- Short gastric arteries (aa. gastricae breves) — numbering 1–6 branches, run within the gastrolienal ligament to the gastric fundus.
Where does lymph drainage from the spleen go?
Lymph drainage from the spleen occurs via efferent lymphatic vessels that emerge from the organ's hilum along with blood vessels.
- Pancreaticolienal lymph nodes — lymphatic vessels of the spleen drain into these nodes. Some nodes are located directly at the hilum of the spleen (in the splenic pedicle), while others are located along the course of the splenic artery.
- Celiac lymph nodes (nodi lymphoidei coeliaci) — serve as a collector of lymph from the spleen; lymph passes to them through corresponding regional nodes.
What are the sources of innervation of the spleen?
The spleen receives predominantly sympathetic autonomic innervation from the splenic plexus (plexus splenicus / plexus lienalis), located along the course of the splenic artery. Sources of the plexus formation:
- Celiac plexus (plexus coeliacus) — the main source (left half of the plexus). Sympathetic postganglionic fibers depart from the celiac ganglia.
- Vagus nerve (n. vagus) — provides parasympathetic fibers passing through the celiac plexus.
- Additional sources — left suprarenal and left phrenic plexuses.
Afferent (sensory) fibers from the capsule and trabeculae run within the sympathetic and vagus nerves.
The spleen — "nine-eleven" (9th–11th ribs), lies deep in the left hypochondrium, and its artery twists into a spiral with age.
Class and exam questions
What is the normal skeletotopy of the spleen?
The organ is projected between the 9th and 11th ribs along the midaxillary line, and its posterior end corresponds to the level of the 10th–11th thoracic vertebrae.
Why do infarctions occur during thrombosis of the splenic artery branches?
Intraorgan arterial anastomoses of the spleen are small in diameter and rare, which is why cessation of blood flow in a branch leads to ischemia of the corresponding segment.
What role does the phrenicocolic ligament play?
It performs a supportive function ("hammock"), supporting the lower end of the spleen, and forms a blind pouch into which the anterior pole of the organ descends.
What else to study on this topic
- Age-related changes in the length and tortuosity of the splenic artery
- Structure and layers of the phrenicolic ligament
- System of tributaries of the splenic vein
- Lymphatic drainage and regional lymph nodes
- Sources of innervation and the splenic plexus
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