Results for "platelets"
Human Blood
** Human blood is a specialized connective tissue that circulates throughout the body, delivering oxygen, nutrients, and hormones while removing waste products and defending against pathogens. **CONTENT:** ## Overview Human blood is a **fluid connective tissue** that makes up roughly 7–8 % of total body weight, averaging about 5 liters in an adult. It consists of a liquid **plasma** matrix (≈55 % of volume) in which a diverse array of **cellular components**—red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes)—are suspended. The primary function of blood is to **transport** essential substances: oxygen bound to hemoglobin in erythrocytes, nutrients absorbed from the gastrointestinal tract, hormones secreted by endocrine glands, and immune factors that protect against infection. Simultaneously, blood carries metabolic waste such as carbon dioxide and urea to excretory organs for elimination. The circulatory system propels blood through a closed network of **arteries, veins, and capillaries** driven by the rhythmic contraction of the heart. This continuous flow maintains **homeostasis** by regulating temperature, pH, and fluid balance. Blood also plays a critical role in **hemostasis**, the process that stops bleeding through platelet aggregation and clot formation, and in **immunological surveillance**, where leukocytes patrol for pathogens and abnormal cells. Because of its multifaceted roles, any disruption—whether from anemia, infection, clotting disorders, or trauma—can have systemic consequences, underscoring the importance of prompt medical evaluation when symptoms arise. ## History/Background The scientific study of blood dates back millennia. Ancient Egyptian papyri (c. 1500 BCE) describe bloodletting as a therapeutic practice, while Hippocrates (460–370 BCE) recognized blood as a vital fluid. In the 17th century, **William Harvey** (1578–1657) revolutionized understanding by demonstrating the **circulatory loop** in his seminal work *De Motu Cordis* (1628), establishing that blood moves in a closed system propelled by the heart. The 19th century saw the discovery of **red blood cells** by Karl Ernst von Baer (1792–1876) and the identification of **hemoglobin** by Felix Hoppe-Seyler (1825–1895). The development of the **microscope** and later **staining techniques** allowed detailed visualization of leukocytes and platelets. In the 20th century, breakthroughs such as the **ABO blood group system** (Karl Landsteiner, 1901) and the **Rh factor** (Landsteiner & Wiener, 1940) enabled safe blood transfusion practices, dramatically reducing mortality from hemorrhage and surgery. ## Key Information - **Plasma (≈55 % of blood volume):** Mostly water (90 %), containing electrolytes, proteins (albumin, globulins, fibrinogen), nutrients, hormones, and waste products. - **Erythrocytes:** Biconcave, anucleate cells (~5 × 10⁶ cells/µL) that transport up to 1 g of oxygen per deciliter of blood via **hemoglobin**. Their lifespan is ~120 days; removal occurs in the spleen and liver. - **Leukocytes:** Five major types (neutrophils, lymphocytes, monocytes, eosinophils, basophils) constitute <1 % of blood cells but are essential for **innate and adaptive immunity**. - **Platelets:** Cell‑derived fragments (~150 000–450 000/µL) that aggregate at vascular injury sites, releasing clotting factors to form a fibrin mesh. - **Blood groups:** Determined by surface antigens on erythrocytes; mismatched transfusions can trigger **hemolytic reactions**. - **Blood pressure:** Average arterial pressure is ~120/80 mmHg; deviations can indicate cardiovascular disease. - **Diagnostic value:** Complete blood count (CBC), blood chemistry panels, and coagulation tests provide critical information for disease detection and management. **When to seek professional care:** Persistent fatigue, unexplained bruising, shortness of breath, or abnormal bleeding should prompt evaluation by a healthcare provider, as these may signal underlying blood disorders. ## Significance Blood is indispensable to life; its efficient transport system sustains cellular metabolism, supports organ function, and enables rapid response to injury and infection. Understanding blood physiology has driven **medical innovations** such as transfusion medicine, organ transplantation, and targeted therapies for hematologic malignancies (e.g., leukemia, lymphoma). Public health initiatives—blood donation programs, screening for infectious agents (HIV, hepatitis), and the development of synthetic blood substitutes—rely on comprehensive knowledge of blood composition and compatibility. Moreover, blood biomarkers (troponin, D‑dimer, C‑reactive protein) are cornerstone tools in diagnosing heart attacks, clotting disorders, and inflammatory conditions, illustrating blood’s role as a “liquid biopsy.” As research advances in genomics and personalized medicine, blood continues to serve as a window into systemic health, guiding preventive strategies and therapeutic decisions. **INFOBOX:** - Name: Human Blood - Type: Fluid Connective Tissue / Circulatory Fluid - Date: Circulatory system fully described (1628, William Harvey) - Location: Human body (systemic distribution) - Known For: Transport of gases, nutrients, waste; immune defense; hemostasis **TAGS:** blood, circulatory system, hematology, plasma, erythrocytes, leukocytes, platelets, transfusion medicine
Health & MedicineSpleen
The **spleen** is a vital organ found in almost all vertebrates, acting primarily as a blood filter and playing a crucial role in the immune system. ## Overview The **spleen** is a vital organ found in almost all vertebrates, including humans, and is located in the upper left region of the abdomen, beneath the diaphragm. It is a soft, spongy, and highly vascular organ, weighing approximately 150 grams in adults. The **spleen** is similar in structure to a large lymph node and is composed of two main types of tissue: red and white pulp. The red pulp is responsible for filtering the blood, removing old or damaged red blood cells, and recycling the iron from these cells. The white pulp, on the other hand, is composed of lymphoid cells and plays a key role in the immune system, helping to defend the body against infections. The **spleen** performs several important functions, including filtering the blood, storing red blood cells, and acting as a reservoir for immune cells. It also plays a role in the production of antibodies and the activation of immune cells, such as T-cells and B-cells. In addition, the **spleen** helps to remove pathogens, such as bacteria and viruses, from the blood and prevents them from entering the bloodstream. The **spleen** is also involved in the production of blood cells, including red blood cells, white blood cells, and platelets. ## History/Background The **spleen** has been known to humans for thousands of years, with ancient civilizations recognizing its importance in the body. The Greek physician Hippocrates (460-370 BCE) is credited with being the first to describe the **spleen** in detail, noting its role in filtering the blood and storing red blood cells. The Roman physician Galen (129-216 CE) also wrote extensively on the **spleen**, describing its structure and function in detail. In the Middle Ages, the **spleen** was believed to be responsible for a range of diseases, including melancholy and epilepsy. It wasn't until the 17th century that the **spleen** was recognized as a vital organ, playing a crucial role in the immune system. ## Key Information * **Location**: The **spleen** is located in the upper left region of the abdomen, beneath the diaphragm. * **Function**: The **spleen** acts primarily as a blood filter, removing old or damaged red blood cells and recycling the iron from these cells. * **Structure**: The **spleen** is composed of two main types of tissue: red and white pulp. * **Size**: The **spleen** weighs approximately 150 grams in adults. * **Blood supply**: The **spleen** receives its blood supply from the splenic artery and returns blood to the body through the splenic vein. * **Lymphatic system**: The **spleen** is connected to the lymphatic system, helping to defend the body against infections. ## Significance The **spleen** plays a crucial role in the immune system, helping to defend the body against infections and diseases. It also plays a key role in the production of blood cells, including red blood cells, white blood cells, and platelets. The **spleen** is also involved in the removal of pathogens, such as bacteria and viruses, from the blood. In addition, the **spleen** helps to regulate the amount of red blood cells in the body, removing old or damaged cells and recycling the iron from these cells. INFOBOX: - Name: Spleen - Type: Organ - Date: Ancient civilizations recognized the importance of the spleen - Location: Upper left region of the abdomen - Known For: Filtering the blood and storing red blood cells TAGS: spleen, blood filter, immune system, lymphatic system, red blood cells, white blood cells, platelets, blood cells, organ.
Health & MedicineAnatomy Encyclopedia Entry 1778665744
** The **Spleen** is a vital organ in the human body responsible for filtering the blood, storing red blood cells, and playing a key role in the immune system. **CONTENT:** ### Overview The **Spleen** is a soft, oval-shaped organ located in the upper left region of the abdomen, just below the diaphragm. It is a vital part of the lymphatic system, which helps to protect the body against infection and disease. The **Spleen** is approximately 5 inches (13 cm) long and weighs around 6 ounces (170 grams) in adults. Its primary function is to filter the blood, removing old, damaged red blood cells and recycling the iron from them. The **Spleen** also stores red blood cells, platelets, and white blood cells, and helps to activate the immune system by filtering out pathogens and other foreign substances. The **Spleen** has a rich blood supply, with two main arteries that bring oxygenated blood to the organ and two main veins that remove deoxygenated blood. The **Spleen** is also connected to the stomach and small intestine through the splenic artery and vein, which allows it to receive nutrients and waste products from the digestive system. In addition to its filtering and storage functions, the **Spleen** also plays a role in the production of antibodies, which are proteins that help to fight off infections. ### History/Background The **Spleen** has been known to humans for thousands of years, with ancient civilizations such as the Egyptians and Greeks recognizing its importance in the body. The Greek physician Hippocrates (460-370 BCE) wrote extensively about the **Spleen**, describing its role in filtering the blood and storing red blood cells. In the Middle Ages, the **Spleen** was believed to be a seat of emotions, with the concept of "spleen" being used to describe a range of mental and physical symptoms. It wasn't until the 17th century that the **Spleen** was recognized as a separate organ, distinct from the liver and other abdominal organs. ### Key Information The **Spleen** is a vital organ that plays a key role in the immune system. Some of its key functions include: - **Filtering the blood**: The **Spleen** removes old, damaged red blood cells from the blood and recycles the iron from them. - **Storing red blood cells**: The **Spleen** stores red blood cells, platelets, and white blood cells, which are released into the bloodstream as needed. - **Activating the immune system**: The **Spleen** filters out pathogens and other foreign substances from the blood, helping to activate the immune system. - **Producing antibodies**: The **Spleen** produces antibodies, which are proteins that help to fight off infections. ### Significance The **Spleen** is an essential organ that plays a critical role in maintaining the body's overall health. Without a functioning **Spleen**, the body would be unable to filter the blood, store red blood cells, and activate the immune system. The **Spleen** is also important for maintaining a healthy balance of red blood cells and platelets in the body. **INFOBOX:** - **Name:** Spleen - **Type:** Organ - **Date:** Ancient civilizations (Egypt, Greece) - **Location:** Upper left region of the abdomen - **Known For:** Filtering the blood, storing red blood cells, activating the immune system **TAGS:** spleen, anatomy, lymphatic system, immune system, blood filtration, red blood cells, platelets, white blood cells, antibodies.