NURS 1114: Blood Components and Functions

• NURS 1114 discusses the cardiovascular system
• Highlights the importance and functions of blood

Learning Objectives

• Identify the components of blood
• Describe the major functions of blood
• Outline the characteristics and functions of red blood cells
• Explore the structure of hemoglobin and its functions
• Explain the production and maturation of red blood cells

The Cardiovascular System

• Provides nutrients, waste products, respiratory gases, and cells for rapid transport
• Powered by the pumping action of the heart

Blood

• Is the only fluid tissue in the human body
• Classified as a connective tissue with living cells called formed elements
• Contains a non-living matrix called plasma and fibers called fibrin

Overview of Blood Circulation

• Blood leaves the heart via arteries, branching into capillaries
• Oxygen (O₂) and nutrients from the blood diffuse across capillary walls, entering tissues
• Carbon dioxide (CO₂) and wastes move from tissues into the blood
• Oxygen-deficient blood leaves the capillaries and flows in veins back to the heart
• The blood then flows to the lungs, releasing carbon dioxide and picking up oxygen
• The oxygen-rich blood returns to the heart

Composition of Blood

• Is the body's only fluid tissue
• Is composed of liquid plasma and formed elements
• Formed elements include erythrocytes/red blood cells, leukocytes/white blood cells, and thrombocytes/platelets
• Plasma makes up 55% of blood volume
• Red blood cells make up 45% of blood volume
• Leukocytes and platelets make up <1% of blood volume

The Composition of Whole Blood

• Includes Plasma proteins like Albumins (60%), globulins (35%) and fibrinogen (4%) and regulatory proteins (<1%)
• Albumins help w/ pressure to transport lipids and hormones
• Globulins transport ions, hormones and lipids while aiding in immune function
• Fibrinogen is an essential component of blood's clotting system
• Regulatory protiens are enzymes anf proenzymes and hormones
• Includes electrolytes like; Na+, K+, Ca2+, Mg2+,СГ, НСО3, НРО42-, SO42-
• Includes organic nutrients such as glucose, carbohydrates, and amino acids, used for ATP production and cell growth;
• Includes organic wastes like urea, uric acid, creatinine, bilirubin, and ammonium ions
• The formed elements are 99.9% red blood cells

Physical Characteristics and Volume

• Blood is a sticky, opaque fluid with a metallic taste
• Color varies from scarlet (oxygen-rich) to dark red (oxygen-poor)
• The pH is between 7.35-7.45
• Temperature is around 38°C, slightly higher than "normal" body temperature
• Accounts for approximately 8% of body weight
• Average volume of blood is 5–6 L for males, and 4–5 L for females

Functions of Blood

• Blood performs a number of functions dealing with substance distribution, regulation of blood levels of particular substances, and body protection

Distribution

• Transports oxygen from the lungs and nutrients from the digestive tract
• Moves metabolic wastes from cells to the lungs and kidneys for elimination
• Delivers hormones from endocrine glands to target organs

Regulation

• Maintains appropriate body temperature by absorbing and distributing heat
• Maintains normal pH in body tissues using buffer systems
• Maintains adequate fluid volume in the circulatory system

Protection

• Prevents blood loss by activating plasma proteins and platelets, and initiating clot formation when a vessel is broken
• Prevents infection by synthesizing and utilizing antibodies, activating complement proteins, and activating WBCs to defend the body against foreign invaders

Blood Plasma

• Contains over 100 solutes
• Includes proteins like albumin, globulins, and clotting proteins
• Includes non-protein nitrogenous substances like lactic acid, urea, and creatinine
• Contains organic nutrients such as glucose, carbohydrates, and amino acids
• Includes electrolytes such as sodium, potassium, calcium, chloride, and bicarbonate
• Transports respiratory gases like oxygen and carbon dioxide

Plasma Proteins

Albumins

• More than 90% of plasma proteins are synthesized in the liver
• 60% of plasma proteins, responsible for viscosity and osmotic pressure of blood
• Acts as a carrier protein and a buffer

Globulins

• Make up ~35% of plasma proteins and include immunoglobulins to attack foreign proteins/pathogens
• Transport ions, hormones, and other compounds

Fibrinogen

• Is converted to fibrin during clotting, removal of fibrinogen leaves serum

Composition of Blood

• Serum refers to Blood plasma from which the protein fibrinogen has been removed
• Serum of blood is preferred over plasma for all blood chemistry tests

Formed Elements

• Erythrocytes, leukocytes, and platelets make up the formed elements
• Only WBCs are complete cells, while RBCs have no nuclei or organelles
• Platelets are just cell fragments
• Most formed elements survive in the bloodstream for only a few days and are renewed by cells in bone marrow

Erythrocytes (RBCs)

• Biconcave discs, anucleate, with essentially no organelles
• Filled with hemoglobin (Hb), which functions in gas transport
• Contain the plasma membrane protein spectrin and other proteins
• These proteins give erythrocytes their flexibility and allow them to change shape
• Have a biconcave shape with a large surface area relative to volume
• Discounting water content, erythrocytes are more than 97% hemoglobin
• ATP is generated anaerobically, so the erythrocytes do not consume the oxygen they transport
• Dedicated to respiratory gas transport
• Hemoglobin reversibly binds with oxygen, where most oxygen in the blood is bound to it

Erythrocytes Function

• Hemoglobin is composed of the protein globin, made up of two alpha and two beta chains, each bound to a heme group
• Each heme group bears an atom of iron, which can bind to one oxygen molecule
• Each hemoglobin molecule transports four molecules of oxygen
• Each erythrocyte has 250 million hemoglobin molecules

Oxyhemoglobin

• Hemoglobin is bound to oxygen and oxygen loading takes place in the lungs

Deoxyhemoglobin

• Is Hemoglobin after oxygen has diffused into tissues (reduced Hb)

Carbaminohemoglobin

• Hemoglobin is bound to carbon dioxide and carbon dioxide loading takes place in the tissues

Production of Erythrocytes

• Hematopoiesis refers to blood cell formation
• Hematopoiesis occurs in the red bone marrow of the axial skeleton, girdles, and epiphyses of the humerus and femur
• Hemocytoblasts give rise to all formed elements

Hematopoiesis

• Hemocytoblasts (hematopoietic stem cells) gives rise to all formed elements
• Hormones and growth factors push the cell toward a specific pathway of blood cell development
• New blood cells enter blood sinusoids

Production of Erythrocytes: Erythropoiesis

• A hemocytoblast is transformed into a committed cell called the proerythroblast
• Proerythroblasts develop into early erythroblasts
• Phase 1 involves ribosome synthesis in early erythroblasts
• Phase 2 involves hemoglobin accumulation in late erythroblasts and normoblasts
• Phase 3 involves ejection of the nucleus from normoblasts and formation of reticulocytes
• Reticulocytes then become mature erythrocytes

Regulation and Requirements for Erythropoiesis

• The number of circulating erythrocytes remains constant and reflects a balance between RBC production and destruction
• Too few red blood cells can lead to tissue hypoxia, while too many red blood cells causes undesirable blood viscosity
• Erythropoiesis is hormonally controlled and depends on adequate supplies of iron, amino acids, and B vitamins

Hormonal Control of Erythropoiesis

• Erythropoietin (EPO) release by the kidneys is triggered by hypoxia due to decreased RBCs, decreased oxygen availability, and increased tissue demand for oxygen
• Enhanced erythropoiesis increases the RBC count in circulating blood and the oxygen carrying ability of the blood

Causes of Hypoxia

• Hemorrhage or increased RBC destruction reduces RBC numbers
• Insufficient hemoglobin, or iron deficiency
• Reduced availability of O₂ (e.g., high altitudes)

Effects of EPO

• More rapid maturation of committed bone marrow cells
• Increased circulating reticulocyte count in 1–2 days
• Testosterone also enhances EPO production, resulting in higher RBC counts in males

Dietary Requirements of Erythropoiesis

• Requires proteins, lipids, carbohydrates, iron, vitamin B12, and folic acid
• The body stores iron in Hb (65%), the liver, spleen, and bone marrow
• Intracellular iron is stored in protein-iron complexes such as ferritin and hemosiderin
• Circulating iron is loosely bound to the transport protein transferrin

Fate and Destruction of Erythrocytes

• The life span of an erythrocyte is 100-120 days
• Old erythrocytes become rigid and fragile, and their hemoglobin begins to degenerate
• Dying erythrocytes get engulfed by macrophages
• The heme and globin are separated and the iron is salvaged for reuse
• Heme degrades to a yellow pigment called bilirubin
• The liver secretes bilirubin into the intestines as bile
• The intestines metabolize it into urobilinogen, and it leaves the body in feces as stercobilin
• Globin is metabolized into amino acids released into circulation, while released Hb is captured by haptoglobin

Erythrocyte Disorders

• Anemia occurs when blood has low O₂ carrying capacity, like insufficient RBC or iron deficiency
• Anemia is a sign and symptom of something being wrong, not a diagnosis
• Can be because of Insufficient amount of erythrocytes, decreased hemoglobin content and abnormal hemoglobin production

Anemia: Insufficient Erythrocytes

• Hemorrhagic anemia results from acute or chronic loss of blood
• Hemolytic anemia involves prematurely ruptured erythrocytes
• Aplastic anemia results from a destruction or inhibition of red bone marrow

Anemia: Decreased Hemoglobin Content

• Iron-deficiency anemia results from hemorrhagic anemia, inadequate intake of iron, or impaired iron absorption
• Pernicious anemia results from a deficiency of vitamin B12 or lack of intrinsic factor needed for absorption of B12
• Treatment is intramuscular injection of B12

Anemia: Abnormal Hemoglobin

• Thalassemias are absent or faulty globin chains in hemoglobin
• Results in Erythrocytes that are thin, delicate, and deficient in hemoglobin
• Sickle-cell anemia results from a defective gene coding for an abnormal hemoglobin called hemoglobin S (HbS)
• HbS has a single amino acid substitution in the beta chain and causes RBCs to become sickle-shaped in low oxygen environemnts

RBC Diseases

Sickle-cell anemia

• HbS results from a change in just one of the 287 amino acids in the beta chain in the globin molecule
• Found in 1 out of 400 African Americans
• If you have sickle cell shapped RBC you can not get malaria because the malaria attacks the RBC

Polycythemia

• Polycythemia is excess RBCs that increase blood viscosity
• Usually caused by cancer; however, naturally occurs at high elevations
• Blood doping can cause polycythemia when athletes remove blood 2 days before an event and then replace it
• Blood doping is banned byOlympics.

Questions

• An average adult usually has five liters of blood
• Plasma is the straw colored, non-living part of blood consisting of 90% water
• Plasma carries RBC, Hormones, Digested materials