T1. ¿Qué es la Sangre y cómo se forma?

What is Blood and How is it Formed?

Overview of Blood

• Blood is a vital liquid tissue that circulates through the cardiovascular system in humans and other animals, primarily transporting oxygen and nutrients to cells while removing waste products.

• It plays a crucial role in immune defense and body temperature regulation.

Methods of Blood Collection

• Blood can be obtained through venipuncture, where blood is drawn from a vein in the arm using a needle.

• Capillary puncture is another method, involving drawing small amounts of blood from areas like the fingertip or heel, often used for newborn screening.

• For blood donation, collected blood separates into components: red blood cells settle at the bottom, followed by white blood cells and platelets, with plasma remaining on top.

Components of Blood

Cellular Elements

• The main components include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.

• Red blood cells transport oxygen;

• White blood cells defend against infections;

• Platelets prevent excessive bleeding.

Types of White Blood Cells

• Leukocytes are categorized into neutrophils, lymphocytes, eosinophils, basophils, and monocytes. Each type has specific functions in immune response.

Understanding Hematology Tests

Hemogram Analysis

• A hemogram evaluates overall health by analyzing three major series: red cell series (hemoglobin levels), platelet series (volume), and morphological assessment via peripheral smear.

Erythrocyte Characteristics

• Erythrocytes have a biconcave shape allowing flexibility; they contain hemoglobin which gives them their characteristic red color.

Life Cycle of Red Blood Cells

Functionality and Lifespan

• Red blood cells are specialized to carry oxygen for about 120 days before being removed from circulation by macrophages.

Types of Leukocytes

Neutrophils

• Neutrophils have segmented nuclei and granules; they play a key role in fighting infections through processes like adhesion to pathogens.

Eosinophils & Basophils

Overview of Blood Components and Functions

Monocytes and Lymphocytes

• Monocytes are large blood cells, comparable in size to red blood cells, with a cerebriform nucleus. They play a crucial role in the immune system and have phagocytic capabilities.

• Lymphocytes are smaller than monocytes but have a relatively large nucleus compared to their cytoplasm. They are also integral to the immune response.

Platelets

• Platelets are among the smallest structures found in blood, with counts reaching up to 450,000 per milliliter. They follow red blood cells in abundance.

• Platelets lack a true nucleus; they are fragments of megakaryocyte cytoplasm. Their primary function is in hemostasis, where they adhere and aggregate to form clots at injury sites.

Plasma Composition

• Plasma has a characteristic yellow color due to proteins and remains stable at room temperature with constant agitation. It contains inorganic substances like water, minerals, and organic compounds such as proteins.

• The pH of plasma ranges from 7.3 to 7.4, indicating slight alkalinity. Key components include albumin and metabolic byproducts like amino acids and glucose.

Functions of Blood

• Blood serves four main functions: transportation (of nutrients and gases), regulation (of body temperature), protection (against pathogens), and hemostasis (clotting).

Blood Collection Techniques

• Blood is typically collected from venous access points using various techniques such as butterfly needles or syringes for stability during procedures or donations.

Hemocomponents and Derivatives

• From whole blood, hemocomponents can be derived including packed red blood cells (PRBC), platelet-rich plasma (PRP), cryoprecipitate, along with classic derivatives like clotting factors.

Hematopoiesis Process

• Hematopoiesis refers to the formation of blood cells which evolves throughout an individual's life—from extramedullary stages early on to primarily occurring in bone marrow during adulthood.

Bone Marrow Location

Hematopoiesis: Understanding Blood Cell Formation

The Role of Organs in Hematopoiesis

• The spleen and liver play a crucial role in hematopoiesis, particularly as precursor organs before birth. They can also regenerate blood under certain pathological conditions.

Structure of Bone Marrow

• A diagram illustrates the arrangement of elements within the bone marrow, including capillaries and sinusoids, which are structured based on mobility and their relationship with the microenvironment for final maturation into the bloodstream.

Hierarchical Distribution of Blood Cells

• Hematopoiesis is traditionally described as a hierarchical distribution where mature cells form a pyramid structure; more abundant mature cells like erythrocytes and leukocytes are at the base, while less abundant progenitor cells are at the top.

Characteristics of Hematopoietic Stem Cells

• Hematopoietic stem cells (HSCs) possess self-renewal capabilities and can differentiate into various mature blood cell types. In contrast, mature cells lack this ability to self-renew.

Functionality of Hematopoietic Stem Cells

• HSCs can toggle between differentiation into specific lineages (e.g., erythroid lineage for red blood cells) or maintaining their status as progenitors through genetic mechanisms that regulate their function.

Collection of Progenitor Cells

• Progenitor cells can be harvested from peripheral blood using apheresis techniques. However, they require stimulation with drugs to mobilize them from the bone marrow to circulation for collection.

Classification of Hematopoiesis: Myelopoiesis vs. Lymphopoiesis

• Hematopoiesis is divided into myelopoiesis (formation of myeloid lineage including erythrocytes and platelets) and lymphopoiesis (formation involving lymphocytes). Each has distinct precursor stages identifiable under microscopy.

Distinction Between Myelopoyesis and Lymphopoyesis

• Lymphocyte formation involves not only bone marrow but also thymus involvement as a primary lymphoid organ. This distinction highlights different developmental pathways for B-cells and T-cells within immune responses.

Types of Lymphocytes