Human Blood Composition Quiz

Hematology

• Hematology is the study of blood and blood disorders.
• The blood is a connective tissue comprising 8% of the body's weight.
• Normal adult male blood volume is ~5L, while women average ~4L.
• Blood consists of formed elements (blood cells) and plasma (the fluid phase).
• Blood accounts for ~55% plasma, ~1% buffy coat (leukocytes and platelets), and ~45% erythrocytes (red blood cells).

Blood and Hematopoiesis

• Hematopoiesis is the process of blood cell production.
• The blood is comprised of:
  • The blood
  • Bone marrow
  • Spleen
  • Hematopoiesis
• Blood transports oxygen and nutrients to the lungs and tissues, and brings waste products to the kidneys and liver, also carries hormones, enzymes, and vitamins.
• Blood also protects against infection and forms clots to prevent blood loss.
• Blood regulates body temperature and maintains normal tissue pH.

Plasma

• Plasma is the liquid component of blood (or cells-free blood).
• It has a yellowish color and mixes water, sugar, fat, protein, and salts.
• It comprises 90% water and 10% dry matter.
• Plasma's main function is transporting blood cells, nutrients, waste products, antibodies, clotting proteins, hormones, and proteins that maintain fluid balance. (e.g., EPO, TPO).
• Key plasma proteins are:
  • Albumin (60%): Blood buffer, maintaining pH and regulating osmotic pressure
  • Globulin (α, β, & γ) (36%): a role in transport (α, β) and immunity (γ).
  • Fibrinogen (4%): forms fibrin filaments

Blood Cells (RBC, Platelets, and WBC)

• Erythrocytes (RBCs), platelets (thrombocytes) and leucocytes (WBCs) are not real cells.
• Erythrocytes lack a nucleus.
• Platelets are cell fragments. They survive only a few days in the blood and don't divide.
• Blood cells arise from hematopoiesis in bone marrow.
• All blood cells are derived from a common pluripotent stem cell.

Bone Marrow

• Bone marrow is a flexible tissue within bones.
• It accounts for approximately 4% of the total body mass in a 65kg adult.
• It produces approximately 500 billion blood cells per day.
• Bone marrow is a primary lymphoid organ.
• Red bone marrow is found in the flat bones and the epiphyses of long bones.
• Yellow bone marrow is found in the medullary cavities of long bones.
• Key cell types in bone marrow stroma include:
  • Fibroblasts
  • Macrophages
  • Adipocytes
  • Osteoblasts
  • Osteoclasts
  • Endothelial cells

Spleen

• The spleen is a secondary lymphoid organ and the largest in the lymphatic system.
• It filters blood and is the site of B and T cell proliferation and antibody formation.
• Its very vascular, so its size and weight vary.
• Located between the fundus of the stomach and the diaphragm in the left upper quadrant of the abdomen
• Types of pulp in the spleen are:
  • Red pulp: filters blood and removes aged/damaged RBCs and microorganisms.
  • White pulp: the immune component and consists of splenic nodules.
• Functions of the spleen include:
  • Storage of several cell lines: thrombocytes (30%) and leukocytes
  • Cell maturation: reticulocytes complete their maturation in the spleen
  • Filtration: pitting (removes inclusions) and culling (removes defective blood cells)
  • Immunological function (largest secondary lymphoid organ)

Hematopoiesis

• Hematopoiesis is the process of blood cell production, multiplication, and specialization, all within bone marrow.
• It begins with the most basic blood cell, the stem cell (hematopoietic stem cell, HSC) or "pluripotent hematopoietic stem cell.”
• The rate of production is approximately 10^13 cells/day, with 2 million RBC/second.
• The process is maintained by growth factors. -Pluripotent cells → progenitors → precursor cells → mature cells
• Cell growth requires:
  • Medullar microenvironment
  • Growth factors (e.g., cytokines)
  • Vitamins and oligo-elements

Red Blood Cells (RBC) characteristics & Disorders

• RBCs utilize hemoglobin for oxygen transport and carbon dioxide removal.
• They live for approximately 120 days.
• In humans, RBCs lack a nucleus and have a biconcave shape.
• Normal RBC concentration is 4.5-5.5 million/mm³ in women and 4.5-6 million/mm³ in men.
• RBCs are highly flexible to pass through microvasculature.

Erythropoiesis

• Erythrocytes are continually produced in the red bone marrow of large bones.
• Erythropoiesis is the production of RBCs from CFU-GEMM progenitors, occurring in erythroblastic islands within the bone marrow.
• The entire sequence from stem cell to erythrocyte takes about one week.
• The developing cells are called reticulocytes just before and after leaving the bone marrow
• Approximately 2.4 million new erythrocytes are produced per second in a healthy adult.

Erythropoiesis Regulation

• The principal factor regulating erythropoiesis is a hormone called erythropoietin (EPO).
• EPO is secreted primarily by the kidneys and secondarily by liver cells.
• EPO is stimulated by hypoxia
• Erythropoiesis needs vitamin B9, B12, iron, and B6.

Iron

• The total iron store in the body is approximately 4g, mostly as hemoglobin, and the daily requirement is usually about 1 mg.
• Iron is absorbed in the duodenum and 80-90% are transported to erythroblast for making hemoglobin.
• Iron metabolism includes:
  • Absorption
  • Utilization
  • Storage
  • Transport processes
  • Hepcidin

Iron Overload

• There is no mechanism for excretion of excess iron.
• Iron overload may be a result of increased intestinal absorption via various causes (e.g., hereditary hemochromatosis), or parenteral administration of iron,

Vitamin B12

• Vitamin B12 is found in animal products.
• Absorption occurs in the jejunum with the help of intrinsic factor, secreted by parietal cells in the stomach.
• Involved in methylation of DNA, myelin, amines, proteins, etc., also required for DNA synthesis.

Hemoglobin

• Hemoglobin (Hb) is a crucial protein in RBCs, composed of heme and globin.
• Hemoglobin's heme part contains iron (Fe2+ ) to bind oxygen.
• The heme pocket allows oxygen binding while protecting the iron atom from oxidation. Adults have two alpha and two beta chains in their Hemoglobin (Hb). Fetal hemoglobin (HbF) has two alpha and two gamma chains.
• Myoglobin is a related hem-containing protein found in muscle, providing oxygen reserve.

RBC Structure

• The erythrocyte plasma membrane consists of specific proteins that make up the cytoskeleton.
• These proteins keep the shape and flexibility of the RBCs essential for circulation.
• Key proteins in RBC structure include: band 3, glycophorins (A, B, C, and D), spectrin, ankyrin, protein 4.1 and actin.
• Membrane protein and lipid abnormalities can alter RBC shape and deformability, causing hemolysis (e.g., hereditary spherocytosis and elliptocytosis).

RBC Metabolism

• Glycolysis is essential for ATP production in RBCs.
• The pentose phosphate pathway produces NADPH, crucial for protecting against oxidative stress.

Hemolysis

• Hemolysis is the destruction of RBCs.
• Types: extracellular and intracellular
• In extravascular hemolysis RBCs are destroyed outside the circulatory system
• In intravascular hemolysis RBCs are destroyed inside the circulatory system

RBC Morphological Abnormalities

• Anisocytosis: Variation in RBC size
• Target cells: Increased staining in central pallor
• Microcytosis: Decreased size
• Macrocytosis: Increased size
• Schistocytes: Fragmented cells
• Sickle cells: Sickle-shaped cells
• Stomatocytosis: Central linear slit
• Acanthocytosis: Irregular spicules
• Tear drop cells: Shaped like tear drops
• Rouleaux formation: Stacked cells
• Red cell agglutination: Irregular clumps of cells

Howell-Jolly bodies:

Small round cytoplasmic inclusions that stain like the nucleus. Found in: Hemolytic anemias Post splenectomy

Complete Blood Count (CBC)

• A CBC is a test that provides information about blood cells.
• It includes counts for RBCs (and other hematological parameters such as hematocrit).
• Abnormalities in cell counts can indicate many disease forms. Measurements of: RBC count, hemoglobin (Hb) g/dL, hematocrit (Hct), MCV, MCH, MCHC, RDW

Variations in CBC

• Increased or decreased numbers of various blood cell types can point to several conditions. Example: Increased RBC counts may suggest polycythemia.
• Variations in types of WBC can indicate conditions such as infections, inflammation, etc.

Anemias

• Anemia is defined as a decrease in circulating Hb, below the normal range which is 130 g/L in men and 120 g/L in women.
• Types: Microcytic, Macrocytic, Normocytic
• Possible causes include iron deficiency, chronic inflammation, thalassemia for microcytic anemias
• Vit B12 or B9 deficiency for macrocytic anemias
• Hemopathies or extra or intravascular hemolysis for normocytic anemias
• Confirm the presence of anemia by determining normal total plasma volume

Chronic Inflammation Anemia

• Ferritin is elevated, transferrin decreased.
• Inflammatory markers increase.
• MCV is often <80fL (microcytic)

Thalassemia

• A heterogeneous group of inherited anemias characterized by abnormal globin chain production.
• Types: a-thalassemia (various deletions) and b-thalassemia (mutations).
  • a-thalassemia can cause hypochromic, microcytic hemolytic anemia.
  • b-thalassemia can lead to ineffective erythropoiesis.

Macrocytic Anemias

• MCV > 100 fl.
• Can be secondary to disease processes such as: cobalt deficiency, folic acid deficiency etc..
• Symptoms may include neurological disorders and digestive problems.

Normocytic Anemias

• Reticulocytes < 120 G/L (non-regenerative).
• Can be caused by conditions such as hemopathy, renal failure, or endocrine disorders

Hemopathies

• Causes of decreased bone marrow quality are: erythroblastopenia (decreased erythroid precursors), the presence of all lines decreasing (all blood cell lines), or bone marrow infiltration by abnormal cells (e.g., leukemia, lymphoma).
• Conditions such as viral infections or drug interactions can affect bone marrows.

Extracorpuscular Hemolytic Anemias

• Hemolytic anemias are due to causes external to the red blood cell itself.

Alloimmune Hemolytic Anemias

• Alloimmune hemolytic anemias occur due to reactions between antibodies and blood cells from different individuals, such as in blood transfusions or Rh incompatibility during pregnancy.

Drug-Induced Hemolytic Anemias

• Certain medications (e.g., penicillin, quinine) can trigger immune responses that lead to hemolytic anemia.

Polycythemia

• Polycythemia is an increase in the number of red blood cells.
• Classification includes primary (e.g., polycthemia vera) or secondary (e.g., high altitude, kidney tumors). -Primary: due to mutations -Secondary: due to increased production of erythropoietin (EPO).

Paroxysmal Nocturnal Hemoglobinuria

• A rare disease in which red blood cells are abnormally destroyed due to deficiency of a protein (CD59) which inhibits complement activation on RBC surfaces
• Causes aplastic anemia, secondary iron deficiency, organ damages, and thrombosis

Test your knowledge on the composition and functions of human blood. This quiz covers topics like hemoglobin types, blood components, and the role of various proteins in blood function. Perfect for students studying biology or health sciences.