What is the spleen, and what is its primary function?

The spleen is an organ found in almost all vertebrates, structurally similar to a large lymph node, and its primary role is to filter blood. It plays crucial roles in the immune system and in managing red blood cells.

What are the key roles of the spleen concerning red blood cells and the immune system?

The spleen removes old red blood cells, holds a reserve of blood that can be useful during hemorrhagic shock, and recycles iron. It also houses antibody-producing lymphocytes in its white pulp and monocytes that help clear antibody-coated bacteria and blood cells, contributing to the immune response.

How does the spleen metabolize hemoglobin from old red blood cells?

As part of the mononuclear phagocyte system, the spleen metabolizes hemoglobin from senescent red blood cells. The globin component is broken down into amino acids, while the heme component is converted into bilirubin, which is then processed by the liver.

What is the spleen's relationship with monocytes and tissue healing?

Monocytes within the spleen, upon moving to injured tissue, transform into dendritic cells and macrophages. This transformation aids in promoting tissue healing.

What happens to the body's susceptibility to infections when the spleen is absent?

The spleen is analogous to a large lymph node, and its absence leads to a predisposition to certain infections, as it is a central organ in the mononuclear phagocyte system.

Where is the human spleen located, and what is its typical color?

In humans, the spleen is located in the left upper quadrant of the abdomen and is typically purple in color.

What is the surgical procedure for removing the spleen called?

The surgical removal of the spleen is known as a splenectomy.

Describe the anatomical position of the human spleen relative to the diaphragm and ribs.

The human spleen is situated beneath the left part of the diaphragm and is located under the ninth, tenth, and eleventh ribs.

What are the two main surfaces of the spleen, and what organs do they contact?

The spleen has a gastric surface that faces the stomach and pancreas, and a renal surface that contacts the left kidney and occasionally the left adrenal gland.

What ligaments are attached to the spleen?

The spleen is attached by four ligaments: the gastrosplenic ligament, the splenorenal ligament, the colicosplenic ligament, and the phrenocolic ligament.

What are the typical dimensions and weight range of an adult human spleen?

In healthy adult humans, the spleen is approximately 7 to 14 centimeters (3 to 5.5 inches) in length and weighs between 1 ounce (28 grams) and 8 ounces (230 grams).

What factors influence the weight of a human spleen, and which factors do not?

The weight of a spleen primarily correlates with height, body weight, and the degree of acute congestion, but it does not significantly correlate with sex or age.

What is the significance of the hilum of the spleen?

The hilum is a fissure on the spleen where the gastrosplenic ligament attaches, and it serves as the point of insertion for the splenic artery and splenic vein, as well as openings for lymphatic vessels and nerves.

What type of lymphatic vessels does the spleen possess, and what system is it part of?

The spleen possesses only efferent lymphatic vessels and is a component of the lymphatic system.

What are penicilliary radicles, and what do they supply within the spleen?

Penicilliary radicles are arterioles that supply the germinal centers within the spleen.

What nerve plexus innervates the spleen, and what is it connected to?

The spleen is innervated by the splenic plexus, which connects a branch of the celiac ganglia to the vagus nerve.

How does the spleen develop, and what is unique about its origin compared to other gut organs?

The spleen develops from mesenchymal tissue within and from the dorsal mesentery. This is unique because most other gut organs are derived from endodermally.

What are the two main types of tissue found within the spleen, and what are their primary functions?

The spleen contains red pulp, which functions in mechanical filtration of red blood cells, and white pulp, which is responsible for active immune responses through humoral and cell-mediated pathways.

Describe the composition and function of the spleen's red pulp.

The red pulp consists of blood-filled sinuses (or sinusoids), splenic cords made of reticular fibers, and a marginal zone bordering the white pulp. Its function is the mechanical filtration of red blood cells, and in mice, it serves as a reserve of monocytes.

Describe the composition and function of the spleen's white pulp.

The white pulp is composed of nodules called Malpighian corpuscles, which contain lymphoid follicles rich in B-lymphocytes and periarteriolar lymphoid sheaths rich in T-lymphocytes. Its function is to mount an active immune response.

What are some of the spleen's less prominent functions, particularly in adults?

Less prominent functions include producing all types of blood cells during fetal life, producing opsonins, properdin, and tuftsin, releasing neutrophils after myocardial infarction, and storing lymphocytes and platelets.

How does the spleen contribute to hematopoiesis, especially during fetal development?

While the bone marrow is the primary site of hematopoiesis in adults, the spleen is crucial for hematopoietic functions during fetal life, up to the fifth month of gestation. After birth, it retains the ability to produce lymphocytes.

What is splenomegaly, and what are some of its potential causes?

Splenomegaly is the enlargement of the spleen. It can be caused by various conditions including sickle cell anemia, malaria, leukemia, Gaucher's disease, Hodgkin's disease, viral infections like mononucleosis, and tumors.

When is a spleen considered normally palpable in children, and when might it be considered abnormal?

A spleen is normally palpable in preterm infants, about 30% of full-term neonates, and 5-10% of infants and toddlers. However, a spleen easily palpable below the costal margin in a child over three to four years old is generally considered abnormal until proven otherwise.

What is splenic injury, and what can cause it?

Splenic injury refers to damage to the spleen, often caused by trauma such as from a road traffic collision, which can lead to rupture of the spleen and requires immediate medical attention.

What is asplenia, and what are its potential causes?

Asplenia refers to a non-functioning spleen, which can be congenital, result from traumatic injury, surgical removal (splenectomy), or be caused by diseases like sickle cell anemia.

What are the health implications of asplenia or hyposplenia?

Conditions like asplenia (non-functioning spleen) or hyposplenia (partially functioning spleen) can lead to a modest increase in circulating white blood cells and platelets, a reduced response to certain vaccines, and an increased susceptibility to infections, particularly sepsis from encapsulated bacteria.

How does the spleen contribute to immunity against encapsulated bacteria?

The spleen's marginal zone produces IgM memory B cells, which generate natural antibodies. These antibodies are crucial for facilitating phagocytosis, either directly or via complement deposition on the bacterial capsule, which is important for defense against encapsulated bacteria.

What is splenosis, and how does it occur?

Splenosis is a condition where displaced fragments of splenic tissue autotransplant within the abdominal cavity, often occurring after physical trauma or splenectomy, forming accessory spleens.

What is polysplenia, and what other developmental abnormalities can it be associated with?

Polysplenia is a congenital disease characterized by multiple small accessory spleens instead of a single, normal-sized spleen. It is often accompanied by other developmental issues such as intestinal malrotation, biliary atresia, or cardiac abnormalities like dextrocardia.

What is splenic infarction, and what causes it?

Splenic infarction is a condition where blood flow to the spleen is compromised, leading to tissue death due to oxygen deprivation. It typically occurs when the splenic artery or one of its branches becomes occluded, for example, by a blood clot.

What are the typical symptoms of splenic infarction?

While splenic infarction can be asymptomatic, the typical symptom is severe pain in the left upper quadrant of the abdomen, which may radiate to the left shoulder. Fever and chills can also develop in some cases.

What historical misconceptions existed regarding the spleen's physiological role?

Historically, the spleen was often misunderstood as a reservoir for juices related to digestion, and in ancient Greek medicine, it was believed to store black bile, one of the four humors, linking it to melancholia.

How has the spleen been viewed in Traditional Chinese Medicine and the Talmud?

In Traditional Chinese Medicine, the spleen is considered a key organ representing the Yin aspect of the Earth element. In contrast, the Talmud refers to the spleen as the organ of laughter.

What is the etymological origin of the word 'spleen,' and what did it represent idiomatically?

The word 'spleen' originates from the Ancient Greek word splēn, and idiomatically, it was the equivalent of the heart in modern English, often associated with emotions.

How did William Shakespeare use the term 'spleen' in his works?

William Shakespeare frequently used the word 'spleen' to signify melancholy, but also caprice and merriment, as seen in his depiction of Cassius's irritable nature in Julius Caesar.

How was 'spleen' perceived as a disease in 18th-century England?

In the early 18th century, physicians like Richard Blackmore considered 'spleen' to be one of the most prevalent diseases in England, akin to consumption, and it was also seen as a fashionable affliction among the upper classes.

What does the French term 'splénétique' refer to, and how did it gain popularity?

In French, 'splénétique' refers to a state of pensive sadness or melancholy. This usage was popularized by the poems of Charles Baudelaire, particularly in his collection Le Spleen de Paris.

In what culinary traditions is spleen used as an ingredient?

Spleen is used in culinary traditions such as Sicilian cuisine, where cow spleen sandwiches are eaten, and in Jerusalem mixed grill, which features chicken spleen as a main ingredient.

How does the spleen's structure and function differ in various animal groups, such as fish, amphibians, and mammals?

In cartilaginous and ray-finned fish, the spleen is primarily red pulp and elongated. Amphibians often have a more rounded spleen with more white pulp. Reptiles, birds, and mammals generally have plentiful white pulp, with spleen shape varying. Mammals, unlike most vertebrates, lose the ability to produce red blood cells in their spleen in middle age.

Which vertebrates are known to lack a spleen, and what tissue serves a similar function in them?

Lampreys and hagfishes, which are early-branching jawless fishes, are the only vertebrates lacking a spleen. However, they possess a diffuse layer of haematopoietic tissue within their gut wall that is homologous to the spleen's red pulp.

What is the significance of the image captioned 'Thalassemia-enlarged spleen taken after splenectomy'?

This image shows a spleen that has been surgically removed from a child with thalassemia, illustrating its enlarged size due to the condition, and highlighting the result of a splenectomy.

What is the significance of the image captioned 'Spleen seen on abdominal ultrasonography'?

This caption refers to an image that shows the spleen as it appears when visualized using abdominal ultrasonography, a common medical imaging technique.

What is the significance of the image captioned 'Maximum length of spleen on abdominal ultrasonography'?

This caption indicates an image that illustrates how the maximum length of the spleen is measured or visualized using abdominal ultrasonography.

What information is conveyed by the image caption 'Back of lumbar region, showing surface markings for kidneys, ureters, and spleen'?

This caption describes an anatomical illustration that highlights the surface markings of the kidneys, ureters, and spleen in the back of the lumbar region of the body.

What does the image caption 'Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green)' illustrate?

This caption describes an anatomical diagram that displays the surface markings for bones, the lungs (colored purple), the pleura (colored blue), and the spleen (colored green) on the side of the thorax.

What is the role of the spleen in the lymphatic system?

The spleen is considered a secondary lymphoid organ, playing a role in the lymphatic system by housing lymphocytes and filtering blood.

What is the difference between the spleen's function in fetal life versus adulthood?

During fetal life, the spleen produces all types of blood cells. In adults, while it retains the ability to produce lymphocytes, its primary roles shift to filtering blood and immune functions, rather than widespread hematopoiesis.

What are the primary components of the spleen's white pulp?

The primary components of the spleen's white pulp are lymphoid follicles, which are rich in B-lymphocytes, and periarteriolar lymphoid sheaths, which are rich in T-lymphocytes.

What are the primary components of the spleen's red pulp?

The primary components of the spleen's red pulp include blood-filled sinuses (or sinusoids), splenic cords composed of reticular fibers, and a marginal zone that borders the white pulp.

What are the potential causes of splenic infarction?

Splenic infarction can be caused by the occlusion of the splenic artery or one of its branches, often due to a blood clot.

Spleen Wiki: The Spleen: A Vital Nexus of Filtration and Immunity

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Introduction

A Blood Filter

The spleen is a vital organ found in nearly all vertebrates, functioning analogously to a large lymph node. Its primary role is to act as a sophisticated filter for the blood, playing critical roles in both the circulatory and immune systems.

Immune & Hematologic Roles

It is indispensable for the removal of senescent red blood cells and the recycling of iron. Furthermore, the spleen houses antibody-producing lymphocytes and monocytes, crucial for mounting immune responses against pathogens and clearing antibody-coated cellular debris.

Vertebrate Ubiquity

While present in most vertebrates, the spleen is notably absent only in jawless fish like lampreys and hagfish. Its structure and function are remarkably conserved, highlighting its fundamental importance across diverse biological lineages.

Anatomical Structure

Location and Dimensions

In adult humans, the spleen is typically located in the left upper quadrant of the abdomen, beneath the diaphragm and protected by the 9th, 10th, and 11th ribs. It is a smooth, convex organ, with its surfaces shaped by adjacent organs like the stomach and left kidney.

Standard measurements for a healthy adult spleen range from 7 to 14 centimeters in length, with weight varying between 28 to 230 grams. These dimensions correlate primarily with height and body weight.

Ligaments and Hilum

The spleen is anchored by several ligaments, including the gastrosplenic and splenorenal ligaments, which also provide pathways for its vascular and neural supply. The hilum, a prominent fissure on its medial surface, serves as the entry and exit point for the splenic artery, splenic vein, lymphatic vessels, and nerves.

Spleen Size Reference

Spleen length can be accurately assessed via ultrasonography. The following table provides typical reference ranges (5th to 95th percentile) for spleen length based on height and sex in adults.

Spleen Length by Height and Sex (cm)
Height (cm)	Spleen Length (cm)
Height (cm)	Women	Men
155–159	6.4–12.0	—
160–164	7.4–12.2	8.9–11.3
165–169	7.5–11.9	8.5–12.5
170–174	8.3–13.0	8.6–13.1
175–179	8.1–12.3	8.6–13.4
180–184	—	9.3–13.4
185–189	—	9.3–13.6
190–194	—	9.7–14.3
195–199	—	10.2–14.4

Vascular and Neural Supply

Arterial and Venous Pathways

The spleen receives its primary arterial blood supply from the splenic artery, a major branch of the celiac trunk. This artery bifurcates at the hilum, supplying the organ's parenchyma. Collateral circulation is often provided by short gastric arteries.

Venous drainage occurs via the splenic vein, which also exits at the hilum. The splenic vein is a critical component of the portal venous system, collecting blood from the spleen and eventually merging with the superior mesenteric vein to form the portal vein.

Innervation

The spleen is innervated by the splenic plexus, which originates from the celiac ganglia and receives contributions from the vagus nerve. This neural network influences splenic blood flow and potentially modulates immune cell activity within the organ.

Functional Tissues: Pulp

Red Pulp: Filtration and Storage

The red pulp constitutes the majority of the spleen's volume and is primarily responsible for filtering aged or damaged red blood cells. It comprises splenic sinuses (blood-filled channels) and splenic cords, rich in reticular fibers and macrophages. In certain conditions, it can also serve as a reserve for monocytes and red blood cells.

White Pulp: Immune Response

The white pulp is organized around central arterioles and consists of lymphoid tissues, including periarteriolar lymphoid sheaths (PALS) rich in T-lymphocytes and lymphoid follicles containing B-lymphocytes. This is the site where immune responses are initiated, with lymphocytes proliferating and producing antibodies.

Other Key Functions

Beyond filtration and immune surveillance, the spleen has other significant roles:

Fetal Hematopoiesis: It is a primary site of blood cell production during fetal development.
Immune Factor Production: Synthesizes opsonins, properdin, and tuftsin, which aid in immune defense.
Monocyte Reserve: Stores monocytes that can be rapidly deployed to sites of injury or inflammation.
Platelet Storage: Holds a reserve of platelets, releasing them during emergencies.

Embryonic Development

Mesenchymal Origin

Uniquely among the digestive tract's associated organs, the spleen develops from mesenchymal tissue rather than endoderm. It forms within the dorsal mesentery, yet it shares its blood supply with the foregut organs via the celiac trunk.

Postnatal Maturation

In humans, the spleen is functional at birth. While its primary hematopoietic role ceases after birth, it retains its capacity to produce lymphocytes, continuing its crucial immune functions throughout life. In some mammals, spleen-like structures called haemal nodes supplement its functions.

Clinical Significance

Splenomegaly (Enlarged Spleen)

Splenomegaly, or an enlarged spleen, can result from numerous conditions, including infections (e.g., malaria, mononucleosis), hematologic disorders (e.g., sickle cell anemia, leukemia), storage diseases (e.g., Gaucher's disease), and neoplastic processes. It often indicates an underlying pathology requiring investigation.

Splenic Injury and Rupture

Trauma, particularly blunt abdominal trauma from incidents like road traffic collisions, can lead to splenic rupture. This is a critical medical emergency due to the spleen's rich blood supply, potentially causing severe internal hemorrhage.

Asplenia and Hyposplenia

Asplenia (absence or non-functionality of the spleen) or hyposplenia (partial function) significantly compromises the immune system. Individuals with these conditions are predisposed to severe infections, particularly from encapsulated bacteria, due to impaired clearance mechanisms and reduced antibody production.

Splenic Infarction and Hyaloserositis

Splenic infarction occurs when blood flow to the spleen is obstructed, leading to tissue death. This can cause acute abdominal pain. Hyaloserositis involves the spleen being coated with fibrous hyaline material, potentially affecting its function.

Historical and Cultural Context

Ancient Perceptions

Historically, the spleen's function was poorly understood, often linked to the humoral theory of medicine. It was associated with "black bile" and believed to influence melancholy, a concept popularized by ancient Greek physicians and later explored in literature, notably by Shakespeare, who used "spleen" to denote moods ranging from irritability to melancholy.

Etymology and Modern Usage

The term "spleen" derives from the Greek word 'splēn'. In modern French, "splénétique" describes a state of pensive sadness, a usage influenced by Romantic literature. In English, the word retained its association with melancholy and capricious moods.

Spleen in Other Animals

Aquatic and Avian Spleens

In fish, the spleen is typically elongated and lies within the serosal lining of the intestine. Amphibians often have a more rounded spleen with a greater proportion of white pulp. Birds and many mammals possess a spleen that adapts its shape to surrounding organs, and in many species, it retains the capacity for red blood cell production throughout life.

Mammalian Variations

Mammalian spleens vary; aquatic mammals often have bluish spleens, with deep-diving pinnipeds possessing particularly large ones for red blood cell storage. Marsupials exhibit a unique Y-shaped spleen that develops postnatally. Some mammals also possess haemal nodes, small spleen-like structures throughout the body.

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References

"Finally, the Spleen Gets Some Respect" By Natalie Angier, The New York Times, August 3, 2009

"Hyaloserositis". Online Medical Dictionary. Accessed on: June 21, 2008.

Blackmore, Richard: Treatise of the spleen and vapors. London, 1725

A full list of references for this article are available at the Spleen Wikipedia page

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Important Notice

This content has been generated by an AI and is intended for educational and informational purposes only. It is based on publicly available data and may not be exhaustive or entirely up-to-date. The information provided is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition or treatment. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

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The Spleen: A Vital Nexus of Filtration and Immunity

💡 Dive in with Flashcard Learning! 💡

Introduction ℹ️

💧 A Blood Filter

🛡️ Immune & Hematologic Roles

🌍 Vertebrate Ubiquity

Anatomical Structure 📐

📍 Location and Dimensions

🔗 Ligaments and Hilum

📏 Spleen Size Reference

Vascular and Neural Supply ⚡

🩸 Arterial and Venous Pathways

🧠 Innervation

Functional Tissues: Pulp 🔬

🔴 Red Pulp: Filtration and Storage

⚪ White Pulp: Immune Response

🔄 Other Key Functions

Embryonic Development 🌱

🌳 Mesenchymal Origin

👶 Postnatal Maturation

Clinical Significance ⚠️

📈 Splenomegaly (Enlarged Spleen)

💔 Splenic Injury and Rupture

🚫 Asplenia and Hyposplenia

🩸 Splenic Infarction and Hyaloserositis

Historical and Cultural Context 📜

🤔 Ancient Perceptions

🌐 Etymology and Modern Usage

Spleen in Other Animals 🐾

🐠 Aquatic and Avian Spleens

🐎 Mammalian Variations

Study Aids 📚

💡 Interactive Learning

Teacher's Corner 🧑‍🏫

Edit and Print this course in the Wiki2Web Teacher Studio

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❓ Test Your Knowledge! ❓

Gamer's Corner 🎮

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References

📜 References

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Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

Introduction

A Blood Filter

Immune & Hematologic Roles

Vertebrate Ubiquity

Anatomical Structure

Location and Dimensions

Ligaments and Hilum

Spleen Size Reference

Vascular and Neural Supply

Arterial and Venous Pathways

Innervation

Functional Tissues: Pulp

Red Pulp: Filtration and Storage

White Pulp: Immune Response

Other Key Functions

Embryonic Development

Mesenchymal Origin

Postnatal Maturation

Clinical Significance

Splenomegaly (Enlarged Spleen)

Splenic Injury and Rupture

Asplenia and Hyposplenia

Splenic Infarction and Hyaloserositis

Historical and Cultural Context

Ancient Perceptions

Etymology and Modern Usage

Spleen in Other Animals

Aquatic and Avian Spleens

Mammalian Variations

Study Aids

Interactive Learning

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice