Blood Components and Their Functions

• Blood consists of solid elements (cells/fragments) and a liquid portion with vital substances for bodily function.
• Centrifugation separates blood, collecting heavy solid parts at the bottom and the liquid part (plasma) at the top.
• Plasma is the liquid part and needs correct solute amounts to maintain proper osmotic composition for blood function.
• Low blood osmolality prevents water movement into tissues, while high osmolality causes water to leave into tissues, potentially causing swelling.
• Plasma makes up about 55% of total blood volume and is approximately 90% water, with the remaining portion composed of proteins, ions, glucose, amino acids, dissolved gases, and wastes.

Plasma Constituents and Functions

• Water acts as a solvent, carrying substances and absorbing heat.
• Salts (electrolytes): Ionic solutes that are carried in the blood and are important for many cellular functions.
• Sodium: Major cation outside cells, establishes resting membrane potential in neurons/muscle cells, maintains osmotic balance by regulating blood volume/urine formation.
• Potassium: Important cation inside cells, re-establishes resting membrane potential after depolarization in neurons/muscle cells.
• Chloride: Predominant extracellular anion, contributes to osmotic pressure gradient, maintains proper hydration.
• Magnesium: Needed for muscle, nerve, and enzyme function, maintains blood sugar/pressure, essential for protein, bone, and DNA synthesis.
• Calcium: Necessary for muscle contraction, enzyme activity, and blood coagulation, stabilizes cell membranes, essential for neurotransmitter/hormone release, stored in bone/teeth to strengthen them.
• Bicarbonate: The 2nd most abundant anion, maintains acid-base balance as a buffer.
• Plasma proteins: Dissolved proteins in blood.
• Albumin: Maintains osmotic balance and viscosity, buffers pH.
• Fibrinogen: Important for blood clotting.
• Globulins: Important for defense (antibodies) and lipid transport.
• Nutrients include glucose, fatty acids, amino acids, and vitamins.
• Waste products include urea, uric acid, lactic acid, and bilirubin.
• Respiratory gases include oxygen (O₂) and carbon dioxide (CO₂).
• Hormones transport to target tissues.
• The solid components of blood are known as formed elements, which account for about 45% of the total blood volume.

Formed Elements

• Erythrocytes (Red blood cells): Transport oxygen on Hemoglobin and binds a limited amount of carbon dioxide.
• Leukocytes (White blood cells).
• Thrombocytes (Platelets): Megakaryocyte fragments that promote blood clotting.
• There are approximately 4-6 million/mm³ RBCs.
• RBCs outnumber white blood cells (WBCs) by about 600 to 1.
• The RBC to platelet ratio is approximately 16 to 1.
• Blood cell morphology is the visual identification using size, shape, and nuclear characteristics
• It is determined using a blood smear.
• RBCs do not need staining due to hemoglobin (Hg).
• All other formed elements need staining to help visualize under the microscope to aide identification of their structural features.

Granulocytes

• Blood cells with dark-staining granules in cytoplasm
• Neutrophils release chemicals to recruit leukocytes, destroying bacteria via phagocytosis. (60% of the total leukocytes in the blood or 1800-7800 cells/µl)
• Eosinophils release chemicals against parasites/fungi and mediate allergic responses.(Fewer than 3% of total leukocytes in the blood or 0-450 cells/µl)
• Basophils release chemicals that mediate inflammation/inprove blood flow damaged tissue (Fewer than 1% of total leukocytes in the blood or 0-200 cells/µl)

Agranulocytes

• Monocytes turn into macrophages/dendritic cells to kill invaders via phagocytosis or alert other blood cells. (4-8% of total leukocytes in the blood or 0-800 cells/µl)
• Lymphocytes
• T lymphocytes control the immune system and directly attack infected/tumor cells.
• B lymphocytes make antibodies for long-term immunity.
• T and B lymphocytes combined make up 30-40% of total leukocytes in the blood or 1000-4800 cells/µl
• Hematology studies blood, blood-forming tissues, and blood disorders.
• Blood disorders can be inherited/acquired, affecting blood components and their function, and can be chronic/acute, curable or incurable.
• Anemia involves reduced RBC/hemoglobin levels, decreasing blood's oxygen-carrying capacity.
• Sickle-cell anemia: Inherited disorder where abnormal hemoglobin causes RBCs to sickle.
• Iron-deficiency anemia: Insufficient iron leads to unhealthy RBCs with pale/colorless areas.
• Blood cancers affect blood cell production/function.
• Chronic granulocytic leukemia: Overproduction of immature WBCs (myleoblasts) in bone marrow/blood results in nonfunctional granulocytes.
• Acute lymphoblastic leukemia: Overproduction of immature lymphocytes (lymphoblasts).
• Mononucleosis: Overproduction of lymphocytes with irregular nuclei.

Hemostasis and Blood Clotting

• Hemostasis stops blood flow via vessel spasm, platelet plug formation, & coagulation.
• Blood coagulation should only occur in response to injury.
• Abnormal clots: Thrombus (abnormal clot) and Embolus (clot that breaks away), both dangerous as they can block flow to critical organs.

Blood Vessels

• A closed system transporting blood.
• Blood is pumped away from the heart through arteries.
• Arteries branch into smaller vessels to reach capillary beds for gas, nutrient, and waste exchange.
• Blood drains from capillaries via veins, returning to the heart.

Blood Vessel Structure

• 3 tissue layers make up walls of arteries/veins.
• Tunica interna: Innermost lining of endothelium and basal lamina.
• Tunica media: Middle layer of smooth muscle tissue and elastic fibers, controlled by the sympathetic nervous system.
• Tunica externa: Outermost layer of dense irregular connective tissue with collagen fibers.
• Arteries have a thicker tunica media with more smooth muscle and elastic fibers, appearing circular in cross-sections.
• Arteries closer to the heart have more elastic fibers in the tunica media/collagen in the tunica externa due to higher pressure.
• Artery lumen diameter is controlled by the sympathetic nervous system, regulating blood flow/pressure.
• Decreased diameter results from sympathetic stimulation, reducing blood flow in capillaries/veins downstream and increasing pressure inside the artery.
• Arteries branch into arterioles and then into capillaries, which lack a tunica media.
• Capillaries are thin-walled, consisting only of a tunica interna and basal lamina, allowing only one red blood cell to pass through.
• Veins have a thinner tunica media, wider lumen, and often appear collapsed on slides.
• Atherosclerosis is caused when fatty deposits turn into Plaque buildup.
• Plaque consists of cholesterol, fatty substances, calcium, cellular waste, and fibrin (a clotting material).
• Anticoagulant drugs may be used to prevent clot formation or to dissolve existing clots.
• Basophils/mast cells secrete heparin to prevent abnormal clots. Atherosclerosis occurs when blood flow is decreased/blocked
• Atherosclerosis in coronary arteries can cause heart attacks.

Explore the roles of blood cells in immunity, oxygen transport, and hemostasis. Understand eosinophil elevation, platelet function, and granulocyte actions. Learn about monocyte roles and calcium's importance in blood-related processes.