Blood functions and composition

Blood Functions

• Transports dissolved substances, including gases, nutrients, hormones, and metabolic waste
• Regulates pH and ion composition of interstitial fluid
• Restricts fluid loss at injury sites
• Defends against toxins and pathogens
• Stabilizes body temperature

General Characteristics of Blood

• Normal temperature: 38°C (slightly above body temp)
• High viscosity (thickness)
• Slightly alkaline pH: 7.35-7.45 (even slight changes are important)

Whole Blood Composition

• Plasma (liquid matrix): 55%
• Formed elements (specialized cells): 45%

Plasma

• Approximately 55% of whole blood volume
• 90-92% water
• Composition also includes plasma proteins and other solutes
• Similar to interstitial fluid, allowing constant exchange of water, ions, and small solutes across capillary walls
• Plasma proteins make up 7% of the plasma, have large globular shapes that prevent them from leaving the bloodstream

Plasma Proteins

• Albumins: contribute to osmotic pressure, enabling capillary exchange
• Globulins: act as antibodies and transport proteins
• Fibrinogen: aids in blood clotting
• Enzymes and hormones: protein-based

Plasma Solutes

• Electrolytes: Na+, K+, Ca2+, Mg2+
• Organic nutrients
• Organic wastes

Formed Elements

• Make up 45% of blood
• 99.9% are red blood cells (RBCs)

Hematocrit

• Packed cell volume (PCV), percentage of formed elements in centrifuged whole blood
• Normal male range: 40-54%
• Normal female range: 37-47%

Blood Cell Percentages

• RBCs: 99.9% (oxygen transport)
• Platelets: <0.1% (cell fragments for clotting)
• WBCs: <0.1% (neutrophils, eosinophils, basophils, lymphocytes, monocytes, and body defense)

Hemopoiesis/Hematopoiesis

• Development of formed elements
• Occurs in red bone marrow
• Hemocytoblasts (hematopoietic stem cells - HSCs) produce two types of stem cells

Stem Cell Types

• Lymphoid stem cells: become lymphocytes
• Myeloid stem cells: give rise to all other formed elements

Myeloid Stem Cell Pathway

• Myeloid stem cell → proerythroblast → erythroblasts → reticulocyte → mature RBC
• Release colony-stimulating factors: hormones released by activated lymphocytes

Erythropoietin (EPO)

• Stimulates hormone, also called erythropoiesis
• Released into plasma in response to low tissue O2 levels (hypoxia)

Stimulus for EPO Release

• Anemia
• Reduced blood flow to kidneys
• Low O2 content in lungs (due to disease, altitude change, or lung damage)

Hematology

• Study of blood and blood-forming tissues
• CBC stands for complete blood count

Normal Values to Know

• Hematocrit: 37-54% (percentage of formed elements in whole blood)
• Hemoglobin: 12-18 g/dL (measures hemoglobin concentration in blood)
• RBC count: 4.2-4.3 million (measures RBCs per μL of whole blood)

Red Blood Cells

• 99.9% of blood’s formed elements
• Biconcave discs (thinner centers, thicker edges) to increase surface area

RBC Shape

• Large surface area to volume ratio allows more oxygen exchange
• Discs form stacks (rouleaux)
• Flexible, allowing bending and flexing in small capillaries

RBC Lifespan

• Less than 120 days
• About 1% of circulating RBCs wear out daily and 3% new RBC´s are produced per second
• Lose most organelles during development (nuclei, mitochondria, ribosomes)
• No repair, rely on anaerobic metabolism

Primary Function of RBCs

• Transports respiratory gases

Hemoglobin Structure

• Complex quaternary structure
• Four globular protein subunits, each with one molecule of heme
• Each heme contains one iron ion (Fe2+)

Hemoglobin

• Oxyhemoglobin: Fe2+ associates easily with O2 to form oxyhemoglobin (HbO2) in bright red
• Deoxyhemoglobin: Hemoglobin not bound to O2 in dark red
• Function caries oxygen, releases oxygen, binds to CO2, and carries it to lungs

RBC Formation and Turnover

• Erythropoiesis (red blood cell formation) occurs only in red bone marrow
• End of RBC life can result in hemolysis or engulfed by macrophages

Hemolysis

• Plasma membrane ruptures
• Hemoglobin not phagocytized breaks down into protein chains and is excreted in urine
  • Hemoglobinuria: Breakdown of an alarmingly large number of rbc´s causes red or brown urine
  • Hematuria: Whole RBCs in urine

Macrophages Engulf

• Engulfed in spleen, liver, or bone marrow BEFORE rupture
• Macrophages break hemoglobin into components
  • Globular protein chain to amino acid
  • Heme to biliverdin to bilirubin ends up in live
  • Iron recycling: Iron is removed from heme, transferred to liver by a transport protein to be used again

Biliverdin Breakdown

• Biliverdin (green) converts to bilirubin, which the liver excretes for bile, yellow skin and eyes from jaundice

Blood Typing

• Surface antigens are on the surface of identifying cells to the immune system
• Antibodies will attack foreign surface antigens in plasma

Four Basic Blood Types

• Type A has A surface antigens and B antibodies
• Type B has B surface antigens and A antibodies
• Type AB has A and B surface antigens and no antibodies
• Type O has no surface antigens and has A and B antibodies
• Surface antigens are called agglutinogens while antibodies in plasma are called agglutinins

Agglutinins

• Attack foreign RBCs, causing agglutination (clumping)
• Rh factor (D antigen): can be positive or negative
• Rh positive: has Rh surface antigens and no antibodies against them

Rh Negative

• Does not have Rh antigen
• Blood typing tests mix blood drops with antigen solutions
• Clumping means that antigen is present, and is crucial to avoid tranfusion reactions (mismatched blood)

Hemolytic Disease of the Newborn

• Rh- mother carries Rh+ fetus with no issue during first pregnancy
• At birth, the mother's blood produces anti-Rh antibodies, which means sensitization
• During the second pregnancy, the mother's anti-Rh antibodies can harm the fetus, causing high fatality
• Can treat with anti-Rh antibodies to kill fetal RBCs that cross placenta

White Blood Cells

• Defend against pathogens
• Remove toxins and wastes
• Attack abnormal cells
• Most WBCs in connective tissue proper and lymphatic system organs, only small numbers circulate in blood

Shared Properties of WBCs

• Spend short time in circulation
• Able to migrate out of bloodstream

Five Types of WBCs

• Never Let Monkeys Eat Bananas

WBC Types

• Neutrophils: 50-70% of circulating WBCs, very active, and first to attack, engulf, digest pathogens, release cytotoxic enzymes and chemicals, pus
• Eosinophils: 2-4% of circulating WBCs, attack parasites, sensitive to allergens and control inflammation with enzymes
• Basophils: Less than 1% of circulating WBCs, release histamines, dilates blood vessels, and heparin
• Monocytes: 2-8% of WBCs, secrete substances that attract immune system cells and fibroblast to injuries
• Lymphocytes: 20-40% OF WBCs, migrate in and our of blood, part of the body´s specific defense system
• TCells: responsible for cell-mediated immunity + coordin of Immune response
• B cells: humoral immunity, Differeniate cells synth antibodies
• Natural killer cells(NK)-cells detect+and destroy abnormal tissue cells(cancer)

Hemostasis

• Clotting response(platelets)
• The Vascular Phase
• Vascular spasm- smooth muscle contractions
• releases chemicals/local hormones that ultimately cause the plasm membrane of the blood vessels to become sticky

Coagulation Phase

• The Platelet Phase begins w/ attachment of platelets to-sticky epithelial surfaces, basement membrane, exposed collagen fibers and other platelets
• Begins in 30 seconds +after injury
• Coagulation: Involves complex steps that unltimetly lead to converison of circ fibrinogen to insoluable fibrin
  • blood cells + plateles caughts-blood clot

Nutritional Blood Disorders

• Procoagulants- Cat ll proteins (1-xl)
  • Activated enzymes lead to a chain reaction / or caascade
  • @ pathways lead to a common pathway ( @ total pathways)
  • conversit corculating fibrinogen into insoluable fibrin
  • the pathways
    • Extrinisic: begind in the vesel cell outside bloodstream
    • Intrinisic begins W activation proenzymes, exposeed to collagen fibers

Clot retraction

• Positive feedback loop rbcs+platelets stick to fibrin threads platelets contract tighter clot and pulling edges

Fibrinolysis

• Process of clot dissolving
• Nutritional blood disorders
  • activation of plasm, plaminogen

Blood disorders

• Venipuncture; obtaining blood for diasgnoiss

Nutritional Blood disorders

• i.Irondeficieny anemia result in small rbcss

Pernicoius anemia

• Vitamin bl2defciency, prevent cell divison, fewer rbc
• ca2 Vitamin k deficianies: ca2 requried for al lotting
  • Vitamins required by liver

Congential blood disorders

• siekle celd-disease

Blood Infunctions

• bacteriaemia baceria cire in blood no multoply there

Vineremia

• vinus crerculating in blood
• sepsis of the blood

blood cell caners

• Loukemias, caners of blood forming tisues
• eancers cell spread from origins in read bonemmarow
• first symps appear in imature wbcs.
• Megalied LYmolid leukemias +biths up wcbs