chapter 12: Blood Functions and Composition

Introduction to Blood

• Blood is a type of connective tissue that includes a fluid matrix known as plasma
• The circulatory system consists of blood, the heart, and blood vessels
• Blood transports substances, maintains homeostasis, and distributes heat throughout the body
• Blood provides nutrients and oxygen to cells while removing metabolic wastes and CO₂
• Red blood cells (gas transport), white blood cells (infection fighting), and platelets (bleeding stoppage), and plasma (liquid matrix) are components of blood
• Red blood cells, white blood cells, and platelets constitute the formed elements of blood.
• Formed elements are produced in red bone marrow

Volume and Composition of Blood

• Plasma consists of water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular wastes
• Normal blood pH ranges from 7.35 to 7.45
• Formed elements typically make up 45% of blood volume, primarily red blood cells and the percentage is called hematocrit (HCT)
• Plasma makes up 55% of the total blood volume
• White blood cells and platelets account for less than 1% of blood volume
• The average adult has about 5.3 quarts (5 liters) of blood

Formed Elements: Red Blood Cells (Erythrocytes, RBCs)

• Biconcave discs give RBCs flexibility for vessel travel, brings oxygen close to hemoglobin, and increases surface area for gas exchange
• RBCs lose nuclei and organelles during development, preventing reproduction or protein production
• RBCs are ⅓ hemoglobin
• Hemoglobin transports oxygen and some carbon dioxide through the blood
• Oxyhemoglobin forms when oxygen combines with hemoglobin and gives blood its bright red color
• Deoxyhemoglobin, which is darker, occurs when oxygen is released
• ATP is produced by glycolysis.
• RBCs lack mitochondria, so they don't use the oxygen they transport

Red Blood Cell Counts

• Adult males typically have 4,700,000 to 6,100,000 cells per mm³ (or µL)
• The number for adult females is 4,200,000 to 5,400,000 cells per mm³
• RBC number determines the blood's oxygen-carrying capacity, affecting overall health
• RBC counts are a tool when diagnosing and assessing diseases

Control and Production of Red Blood Cells

• Red blood cell (RBC) production is called erythropoiesis
• In embryos and fetuses, RBC production happen in the yolk sac, liver, and spleen
• After birth, RBC production occurs in the red bone marrow (hematopoiesis)
• Hematopoietic stem cells (hemocytoblasts) produce RBCs, undergoing development stages
• Red blood cells have an average life span of 120 days.
• Erythropoietin keeps the number of RBCs constant and is released by the kidneys and liver when low oxygen levels are present
• Polycythemia is an excessive increase in red blood cells which causes viscous and slow-moving blood & oxygen deficiency

Dietary Factors of RBC Production

• Vitamins B₁₂ and folic acid are necessary for DNA synthesis, especially in hematopoietic tissue
• Iron is needed for hemoglobin synthesis with most iron coming from old red blood cells recycling
• Anemia occurs from a deficiency in red blood cells or hemoglobin, reducing oxygen-carrying capacity

Anemia Types

• Hemorrhagic anemia can occur from Hemorrhage
• Hemolytic anemia can be caused from incompatibility during bacterial infections or blood transfusions destroying RBCs
• Pernicious anemia can be caused from a deficiency of intrinsic factor from the stomach causing inadequate vitamin B12 absorption
• Aplastic anemia can be caused from viruses, radiation, cancer and certain drugs destroying bone marrow
• Iron-deficiency anemia is caused by menstruation, persistent bleeding ulcers, and/or dietary malnourishment
• Sickle cell anemia is caused by variations in a gene resulting in abnormal hemoglobin structure

Red Blood Cell Breakdown

• Red blood cells become more fragile and damaged when passing through narrow capillaries
• Macrophages in the liver and spleen ingest damaged red blood cells (RBCs)
• Hemoglobin from the decomposed red blood cells is turned into heme and globin
• Heme is made into iron and biliverdin which gets turned into bilirubin and both pigments excrete in bile
• Globin is made into amino acids and reused
• Iron is stored in the liver and recycled back into bone marrow

White Blood Cells (WBCs, leukocytes)

• Help defend against disease
• They form from hemocytoblasts (hematopoietic stem cells) in red bone marrow
• WBCs can exit the bloodstream to fight infection through diapedesis
• Outside circulation, WBCs move by amoeboid motion and are attracted chemicals from tissues called positive chemotaxis
• Hormones promote the production of WBCs in 2 categories: interleukins and colony-stimulating factors (CSFs)
• Circulating blood contains 5 types of WBCs distinguished by granular structure and cytoplasm stain

Types of White Blood Cells - Granulocytes

• Granulocytes are WBCs with granular cytoplasm and a short life span(about 12 hours)
• Neutrophils have fine, purple-staining cytoplasmic granules and a nucleus with 2-5 lobes and comprise 50 to 70% of leukocytes and are strong phagocytes
• Eosinophils have coarse granules stain deep red, are bilobed, make up 1 to 3% of leukocytes, can kill certain parasites and moderate inflammation
• Basophils have fewer granules than eosinophils that stain blue, account for less than 1% of leukocytes, promote by inflammation by secreting heparin & histamine

Types of White Blood Cells - Agranulocytes

• Agranulocytes do not have have granular cytoplasm, but are long lived
• Monocytes are the largest cells, have variably-shaped and make up 3 to 9% of leukocytes, which have a life-span of weeks - months and migrate to differentiate into macrophages
• Long-lived lymphocytes are the smallest of the WBCs and have a large, round nucleus and account for 25 to 33% of the cells; attack specific foreign pathogens and include B cells, T cells, and NK cells

White Blood Cell Counts

• Normally the white blood cell count (WBCC or WBC) is 3,500 to 10,500 mm³ (or µL) of blood
• WBCS numbers may change under abnormal conditions
• Leukocytosis (>10,500 WBCs/μL) occurs during an infection, smoking, or leukemia
• Leukopenia (<3,500 WBCs/µL) occurs as a result of viral infections including immunodeficiency, chickenpox, typhoid fever, measles, mumps, poliomyelitis, or influenza
• A differential white blood cell count (DIFF) counts the type of leukocytes in a blood sample.
• Percentages alter characteristically in certain illnesses, which can help diagnose

Blood Platelets

• Platelets are not complete cells but are cytoplasmic fragments of megakaryocytes in the bone marrow
• A platelet smaller than a red blood cell and moves by ameboid movement
• Hematopoietic stem cells develop into megakaryocytes and platelets in response to thrombopoietin
• Platelets help repair damaged blood vessels by adhering to their broken edges resulting in hemostasis
• Normal platelet counts vary from 150,000 to 400,000 per mm³ (µL) of blood
• Platelets tend to live about 10 days

Platelet Counts

• Normal platelet counts range from 150,000 to 400,000 per mm³ (µL) of blood
• Thrombocytosis is a high platelet count.
• Thrombocytosis can be the result of infections or genetic defects
• Thrombocytopenia is a low platelet count.
• Thrombocytopenia's causes include chemical and radiation exposure, genetic conditions and autoimmune diseases
• Thrombocytopenia can increase the risk of internal bleeding

Plasma

• Plasma is the clear, straw-colored part of blood
• Plasma suspends both cells and platelets
• Water comprises 92% of plasma, which also contains substances
• Plasma transports nutrients/gases, helps maintain electrolyte balance, and maintains optimal pH

Plasma Proteins

• Plasma proteins make up the most abundant of its dissolved substances
• Plasma proteins are not a source of energy
• Plasma proteins found in blood and interstitial fluids
• Plasma contains 3 groups of plasma proteins: albumins, globulins, fibrinogen

Plasma Protein Types

• Albumins make up 60% of plasma proteins, originate in the liver, and maintain colloid osmotic pressure
• Globulins make up 36% of plasma proteins
• Alpha globulins originate in the liver and transport lipids/fat-soluble vitamins
• Beta globulins originate in liver and transport lipids/fat-soluble vitamins
• Gamma globulins originate in lymphatic tissues, and make up the antibodies of immunity
• Fibrogen makes up 4% of plasma proteins, originates in the liver, and helps in blood coagulation

Plasma Gases and Nutrients

• The most important blood gases are oxygen and carbon dioxide
• Nutrients in plasma are amino acids, simple sugars, nucleotides, and lipids that are absorbed from the digestive tract
• Glucose can be used for energy or transported to the liver for conversion to glycogen or fat
• Amino acids are transported to the liver to produce new proteins, or be for energy
• Lipids attach to proteins for transport through the bloodstream since they are not soluble in the water

Plasma Nonprotein Nitrogenous Substances

• Nonprotein nitrogenous substances (NPNs) contain nitrogen but aren't proteins
• NPNs consist of amino acids, urea, uric acid, creatine and creatinine
• Protein catabolism by-products are urea and uric acid; and nucleic acid, respectively
• Amino acids come from breakdown of proteins
• Creatinine comes from phosphate creatine breakdown in muscles

Gases and Nutrients

• Important blood gases includes oxygen and carbon dioxide
• Plasma nutrients are amino acids, sugars, nucleotides, lipids, vitamins, and minerals, that are absorbed from the digestive tract
• Glucose can be used for energy or be transported to the liver to convert to glycogen or fat
• The liver uses transported amino acids to make new proteins or for energy
• Lipids travel to the liver and attach to proteins for transport because they are not soluble in the water

Plasma Electrolytes

• Plasma electrolytes come by absorption from the intestine or by-products from cellular metabolism
• Plasma Electrolytes consist of sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate ions
• Sodium and potassium are abundant electrolytes
• Some of these ions are important in plasma osmotic/pH maintenance

Hemostasis

• Hemostasis controls bleeding.
• After vessel injury, 3 processes prevent blood loss : vascular spasm, platelet plug formation, and blood coagulation

Vascular Spasm

• Vascular spasm is caused through the constriction of a small constricted blood vessels
• The effect lasts around 30 minutes
• This constriction then releases sereotonin
• Vascular spasm constriction decreases blood loss

Platelet Plug Formation

• Platelets are repelled by smooth endothelial linings
• Platelets stick to rough surfaces and the collagen in connective tissue
• Platelets adhere to exposed edges of damaged blood vessels, forming a network to membranes
• The accumulation of platelets form a plug which is effective on smaller vessel injuries

Blood Coagulation

• Blood coagulation controls bleeding and uses clotting factors and calcium
• Blood coagulation (1st step): tissue releases thromboplastin which activates clotting leading to the production prothrombin activator
• Prothrombin activator converts prothrombin (plasma) into thrombin
• Thrombin then catalyzes a rx that converts fibrinogen to fibrin and results in blood clot
• Fibrin threads then create a network that trap blood cells and platelets forming a blood clot
• The body promotes more clotting through a system of positive feedback but is temporary and restores hemeostatic environment

Clot Dissolution and Abnormal Clot Formation

• Dissolution takes place when blood flows which helps to transport away any excess levels of thrombin
• As a clot from blood release heals, clot dissolution occurs through transformation that converts active plasmin which digests the fibrin
• A thrombus is an abnormal presence of clot in a blood vessel.
• A thrombus becomes an embolus when it dislodges
• Coronary thrombosis=clot in vessel that supports the heart
• Pulmonary embolism=traveling clot that blocks portion of lung
• Infarction=clot that blocks blood flow and kills supplied tissue
• Atherosclerosis creates buildup of fatty deposits in walls of arteries that is sometimes attributed to abnormal clot formations

Blood Groups and Transfusions

• Blood exists in different types, and certain combinations are compatible
• Compatibility tests prior to donors and recipients which test for: ABO blood type, Rh status and cross-matching
• These blood types which include Rh types must be the same prior to transfusion
• Crossmatching involves mixing recipient serum with donor red blood cells to check for agglutination

Blood Antigens and Blood Antibodies

• An antigen is a molecule that evokes an immune response.
• Antibodies are a protein produced by the immune system to attack specific antigens to protect its own cells
• Aggluitination occurs following a transfuction and is the the clumping of red blood cells (RBCs).
• Antibodies present during transfusion that react with RBCs are agglutinins
• During a transfuction, agglutinins agglutinogens and serious effects will take place
• There are only a few types of of antigens that produce transfuction: (O, Rh)
• Reaction symptoms include: feeling anxious, breathing problems and flushing, severe pain and RBC lysis

ABO Types (Incompatible Transfusions)

• Blood groups are based on the presence or absence of antigens
• Antigens are carbohydrates attached to glycolipids on RBCs
• Blood types are genetic
• Types
• Type A: has antigen A, but anti-B antibodies
• Type B: has antigen B, but anti-A antibodies
• Type AB: has both A and B antigens, but neither antibody(universal recipient).
• Type O: has neither antigen, but both types of antibodies(universal donor)
• Antibodies react with antigens from the same type and creates agglutination from transfusions
• Donor RBCs agglutination may result in its antibodies due to possible presence
• An ABO blood type that consists of type A may not donate a RBC transfuction that contains B agents

ABO Types

• Blood type A: Acceptable Donation Types: A & O
• Blood type B: Acceptable Donation Types: B & O
• Blood type O: Acceptable Donation Types: O Only
• Blood type AB: Acceptable Donation Types: A,B,AB,O

Blood Rh Groups

• The name of Rh comes from the study of rhesus monkeys
• Humans include Rh types: Antigens or Factors
• Antigen D: is most commonRh type
• Rh positive: Antigen D is present
• Rh negative: Antigen D is absent.

Transfusions

• If a Rh- person has contact with Rh+ through transfuction or pregnancy they may develop antibodies
• Erythroblastosis Fetalis is a disease in a fetus where it gains anitbodies because it is Rh+ and the mother is Rh-
• Erythroblastosis Fetalis: Is preventable with RhoGAM, and should be performed on 28 weeks when there Rh and antibody reactions

Test your knowledge of blood’s primary functions, components, and conditions indicated by blood pH levels. Questions cover the roles of formed elements, plasma composition, and the significance of hematocrit readings in understanding blood health.