Blood and Circulation

• Blood is part of the cardiovascular system
• Blood is transported rapidly via the cardiovascular system
• The pumping heart powers the system

Learning Objectives

• Identify blood components
• Describe primary blood functions
• Outline functions and features of red blood cells
• Explore the hemoglobin structure and function
• Explain how red blood cells are produced and matured

Blood and Circulation

• Blood is the only fluid tissue in the human body
• Blood is classified as a connective tissue

Blood Components

• Living cells are known as formed elements
• Non-living matrix is plasma
• Fibers = Fibrin

Blood Circulation Overview

• Blood goes from the heart through arteries that divide until they form capillaries
• Oxygen (O₂) and nutrients pass through capillary walls into tissues
• Carbon dioxide (CO₂) and wastes travel from tissues into the blood
• Oxygen-deficient blood exits capillaries and moves via veins towards the heart
• This blood goes to the lungs, releases CO₂, and picks up O₂
• Oxygen-rich blood goes back to the heart

Blood Composition

• Is the body's only fluid tissue
• Composed of liquid plasma and formed elements
• Formed elements: Erythrocytes/red blood cells (RBCs), Leukocytes/white blood cells (WBCs), and Thrombocytes/platelets

Blood Sample Breakdown

• Plasma accounts for 55% of blood
• Red blood cells average (5-6 million /ml)
• White blood cells average (5000/ml)
• Platelets are also present

Blood Components Percentages

• Plasma accounts for 55% of whole blood by volume
• Leukocytes and platelets make up less than 1% of whole blood
• Erythrocytes account for 45% of whole blood by volume

Plasma Constituents

• Proteins make up around 7% of plasma
• Other solutes make up around 1% of plasma contents
• Water makes up 92% of plasma
• Plasma transports organic and inorganic molecules, formed elements, and heat

Formed Elements

• Platelets account for 0.1% in formed elements
• Red blood cells account for 99.9% in formed elements

Plasma Proteins

• Albumins (60%) contribute to osmotic pressure and transport lipids and steroid hormones
• Globulins (35%) transport ions, hormones, lipids, and have immune functions
• Fibrinogen (4%) is a clotting system component converted into insoluble fibrin
• Regulatory proteins are other enzymes, proenzymes and hormones (less than 1%)

Other Solutes

• Electrolytes are essential for cellular activity and contributing to osmotic pressure
• Include Na+, K+, Ca2+, Mg2+, СГ, НСО3, НРО42-, SO42-
• Organic nutrients used for ATP production, growth, and maintenance
• Lipids (fatty acids, cholesterol, glycerides), carbohydrates (glucose), and amino acids
• Organic wastes are carried to breakdown or excretion sites like urea, uric acid, creatinine, bilirubin, and ammonium ions

Blood Properties

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

Blood Functions

• Blood supports substance distribution
• Regulation of blood levels of particular substances
• Protection of the body

Blood Transport

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

Blood 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

Blood Protection

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

Blood Plasma Contents

• Blood plasma contains over 100 solutes
• Proteins like albumin, globulins, and clotting proteins
• Non-protein nitrogenous substances like lactic acid, urea, creatinine
• Organic nutrients, like glucose, carbohydrates, amino acids
• Electrolytes, like sodium, potassium, calcium, chloride, bicarbonate
• Respiratory gases like oxygen and carbon dioxide

Plasma Proteins Synthesis

• More than 90% of plasma proteins are synthesized in the liver
• Albumins make up 60% of plasma proteins, are responsible for viscosity and osmotic pressure, and acts as carrier and buffer
• Globulins make up ~35% of plasma proteins, include immunoglobins attacking foreign pathogens, and transport globulins
• Fibrinogen is converted to fibrin during clotting
• Removing fibrinogen leaves serum

Serum

• Blood plasma from which fibrinogen is removed

Formed Elements

• Erythrocytes, leukocytes, and platelets make up the formed elements
• Only WBCs are complete cells
• RBCs have no nuclei/organelles, and platelets are cell fragments
• Formed elements survive in the bloodstream only a few days
• Most blood cells don't divide but are renewed by cells in bone marrow

Erythrocytes

• Red Blood Cells
• Biconcave, anucleate discs with no organelles
• Filled with hemoglobin (Hb), a gas transport protein
• The plasma membrane proteins like spectrin provide flexibility
• Allow them to change if needed
• Dimensions for reference are 2.0 um at the side and 7.5 um on top

Erythrocyte Characteristics

• Erythrocytes exemplify the relationship between structure and function.
• A biconcave shape provides a huge surface area relative to volume
• Discounting water, erythrocytes are more than 97% hemoglobin
• ATP is generated anaerobically
• Erythrocytes do not pull from the oxygen they transport

Erythrocyte Function

• Erythrocytes specialize in respiratory gas transport
• Hemoglobin reversibly binds with oxygen
• The majority of blood's oxygen is bound to hemoglobin.
• The protein glo bin comprises two alpha and two beta chains
• Heme group bears an atom of iron, which binds to one oxygen molecule.
• Hemoglobin molecule transports four oxygen molecules.
• There are around 250 million hemoglobin molecules per erythrocyte.
• Oxyhemoglobin is hemoglobin bound to oxygen
• Oxygen loading occurs in the lungs
• Deoxyhemoglobin is what remains after oxygen diffuses into tissues (reduced Hb)
• Carbaminohemoglobin is hemoglobin bound to carbon dioxide
• Carbon dioxide loading occurs in the tissues

Production of Erythrocytes

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

Hematopoiesis Information

• Hemocytoblasts are hematopoietic stem cells giving rise to all formed elements
• Hormones and growth factors control cell division toward blood cell development
• New blood cells enter blood sinusoids

Erythropoiesis

• Proerythroblasts develop into early erythroblasts
• The developmental pathway splits into three phases
  • Phase 1, ribosome synthesis in early erythroblasts
  • Phase 2, hemoglobin accumulates in late erythroblasts and normoblasts
  • Phase 3, normoblasts discharge the nucleus forming reticulocytes
• Reticulocytes then become mature erythrocytes

Regulation of Erythropiesis

• Erythrocytes in circulation remain balanced between RBC production and destruction
• Little red blood cell leads to tissue hypoxia
• Too many red blood cells causes undesirable blood viscosity
• Erythropoiesis is hormonally controlled
• Depends on adequate supplies of iron, amino acids, and B vitamins

Erythropoiesis Control

• Erythropoietin (EPO) released by the kidneys is triggered by:
  • Hypoxia from reduced RBCs
  • Decreased oxygen availability
  • Increased demand for oxygen
• Enhanced erythropoiesis result in an increase of the RBC count and oxygen capability

Hypoxia Causes

• Hemorrhage due to RBC losses
• RBC numbers reducing from destruction
• Not enough hemoglobin
• Low iron
• Unavailable O₂
• High altitudes
• EPO leads to faster maturation of committed bone marrow cells
• There is an increased reticulocyte count from 1-2 days
• Testosterone also drives EPO production, resulting in more RBCs in men

Erythropoiesis Requirements

• Erythropoiesis requires:
  • Proteins, lipids, and carbohydrates -Iron, B₁₂, and folic acid
• The body stores iron in Hb (65%), the liver, spleen, and bone marrow
• Intracellular iron is stored in ferritin and hemosiderin
• Circulating iron is loosely bound to the transport protein transferrin

Erythrocyte Lifecycle

• A RBC will survive to 100-120 days
• As they age, they become rigid and fragile
• They start to degeneration when they are old
• Dying erythrocytes get engulfed by macrophages
• Reused hem and globin gets separated

Fate and Destruction

• Heme degrades to a yellow bilirubin pigment
• The liver secretes bilirubin into bile for the intestines
• The intestines metabolize it into urobilinogen
• The degraded pigment leaves the body in feces as stercobilin
• Globin metabolizes into amino acids, released in circulation
• Hb in the blood is collected by haptoglobin and phagocytized

Erythrocyte Disorders

• Anemia is a disease where the blood has low oxygen carrying capacity
• Symptoms manifest as fatigue, paleness, and shortness of breath
• Insufficient RBC or low iron result in low oxygen carrying capacity. - B12 deficiency is a potential cause

Anemia Types

• Hemorrhagic anemia comes from blood loss
• Hemolytic anemia comes from premature rupture
• Aplastic anemia is destruction / inhibition of BM

Decreased Hemoglobin Manifestation

• Iron-deficiency is secondary from the hemorrhagic anemia and issues absorbing iron
• Pernicious anemia stems from low vitamin B12 and lack of intrinsic factor

Anemia Treatments

• Anemia is treated by injections of B12

Abnormal Hemoglobin

• The thalassemias are absent or faulty globin chain and low hemoglobin
• Sickle-cell anemia is a genetic code with hemoglobin S disorder
  • 1 in ~400 African Americans are affected
  • The protein Hbs has a single altered amino acid substitution in beta chain
  • Causes RBC to be sickle-shaped

Other RBC Diseases

• Malaria attacks the RBC
• It results in a high fever
• Malaria is avoided by sickle-cell shaped carriers
• Polycythemia arises with increased RBC amount
  • Blood becomes viscous
  • Usually occurs in people with cancer
  • Can naturally occurs from people at high elevations
  • Blood doping occurs within events- - Athletes insert blood 2 days before the day - Is banned in Olympics

Questions

• A grown adult retains 5 liters of blood
• Plasma is about 90% water, it is a straw colored portion of blood
• Plasma carries RBCs, hormones, and digested materials