Cardiovascular & Hematological Systems

Chapter 6 Pathology

Circulatory System

    circulatory system - the heart, blood vessels and blood cardiovascular system - the heart and blood vessels hematology – the study of blood functions of circulatory system ◦

transport

◦  O 2 , CO 2 , nutrients, wastes, hormones

protection

◦  limit spread of infection, destroy microorganisms and cancer cells, and initiates clotting

regulation

 fluid balance, stabilizes pH of ECF, and temperature control

Transportation

Blood   Carries oxygen to tissues Carries carbon dioxide from tissues    Transports nutrients and other substances to cells Transports waste products from cells Carries hormones to organs

Regulation

Blood  Buffers keep pH of body fluids between 7.35 and 7.45

 Substances maintain osmotic pressure to regulate fluid in tissues (fluid balance)  Transports heat generated in muscles to aid in regulation of body temperature

Protection

Blood  Carries cells and antibodies of immune system  Carries factors to protect against blood loss

Components and General Properties of Blood

  adults have 4-6 L of blood a liquid connective tissue consisting of cells and extracellular matrix ◦ plasma – matrix of blood  a clear, light yellow fluid ◦  formed elements - blood cells and cell fragments red blood cells, white blood cells, and platelets

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Components and General Properties of Blood

seven kinds of formed elements ◦ erythrocytes - red blood cells (RBCs) ◦ Platelets - thrombocytes  cell fragments from special cell in bone marrow ◦  leukocytes - white blood cells (WBCs) five leukocyte types divided into two categories:   granulocytes (with granules)  neutrophils   eosinophils basophils agranulocytes (without granules)  lymphocytes  monocytes

Formed Elements of Blood

Monocyte Platelets Small lymphocyte Neutrophil Large lymphocyte Basophil Small lymphocyte Neutrophil Eosinophil Erythrocyte Young (band) neutrophil Monocyte Neutrophil

Separating Plasma From Formed Elements of Blood

Withdraw blood

 hematocrit (packed cell vol.) centrifuge blood to separate components ◦ erythrocytes are heaviest and settle first

Centrifuge Plasma (55% of whole blood)

 37% to 52% total volume (hematocrit) ◦

Buffy coat: leukocytes and platelets (<1% of whole blood) Erythrocytes (45% of whole blood) Formed elements

◦  leukocytes and platelets 1% total volume; buffy coat   plasma the remainder of volume 47% - 63%

Plasma and Plasma Proteins

  plasma – liquid portion of blood 3 major categories of plasma proteins ◦ albumins – smallest and most abundant ◦ globulins (antibodies)   provide immune system functions alpha, beta and gamma globulins ◦  fibrinogen precursor of fibrin threads that help form blood clots

Composition of Whole Blood

Percentages show the relative proportions of the different components of plasma and formed elements.

Blood Plasma

Plasma is 55% of blood  91% water  8% protein ◦ Albumin ◦ Clotting factors ◦ Antibodies ◦ Complement • 1% other materials – Glucose – Amino acids – Lipids – Electrolytes – Vitamins – Hormones – Wastes – Drugs – Dissolved gases

Hemopoiesis

 adult production of 400 billion platelets, 200 billion RBCs and 10 billion WBCs every day  hemopoiesis – the production of blood, especially its formed elements  hemopoietic tissues produce blood cells ◦ yolk sac produces stem cells for first blood cells  colonize fetal bone marrow, liver, spleen and thymus ◦ liver stops producing blood cells at birth ◦ ◦ spleen remains involved with lymphocyte production red bone marrow produces all seven formed elements

The Formed Elements

 Produced in red bone marrow  Hematopoietic (blood-forming) stem cells can develop into any blood cell  Short-lived tissue cells

Erythrocytes

   Red blood cells (RBCs) most numerous Mature cells anuclear Contain hemoglobin ◦ Binds to oxygen for transport ◦ Carries hydrogen ions for buffering ◦ Carries carbon dioxide for elimination

Erythrocytes (RBCs)

Erythrocytes (RBCs)

  Erythrocytes are an example of the complementarity of structure and function Structural characteristics contribute to its gas transport function ◦ Biconcave shape has a huge surface area relative to volume ◦ Erythrocytes are more than 97% hemoglobin ◦ ATP is generated anaerobically, so the erythrocytes do not consume the oxygen they transport

Erythrocyte Function

 RBCs are dedicated to respiratory gas transport  Hb reversibly binds with oxygen and most oxygen in the blood is bound to Hb  Hb 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 Hb molecule can transport four molecules of oxygen

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Erythrocytes and Hemoglobin

RBC count and hemoglobin concentration indicate amount of O 2 can carry blood ◦ hematocrit (packed cell volume) – percentage of whole blood volume composed of red blood cells  men 42- 52% cells; women 37- 48% cells ◦ hemoglobin concentration of whole blood higher in men ◦ RBC count higher in men  Why values are lower in women ◦ androgens stimulate RBC production ◦ women have periodic menstrual losses ◦ hematocrit is inversely proportional to percentage of body fat

Hemoglobin (Hb)

 Oxyhemoglobin – Hb bound to oxygen ◦ Oxygen loading takes place in the lungs  Deoxyhemoglobin – Hb after oxygen diffuses into tissues (reduced Hb)  Carbaminohemoglobin – Hb bound to carbon dioxide ◦ Carbon dioxide loading takes place in the tissues

Production of Erythrocytes

 Hematopoiesis – blood cell formation  Hematopoiesis occurs in the red bone marrow of the: ◦ Axial skeleton and girdles ◦ Epiphyses of the humerus and femur  Hemocytoblasts give rise to all formed elements

Hormonal Control of Erythropoiesis

 Erythropoietin (EPO) release by the kidneys is triggered by: ◦ Hypoxia due to decreased RBCs ◦ Decreased oxygen availability ◦ Increased tissue demand for oxygen  Enhanced erythropoiesis increases the: ◦ RBC count in circulating blood ◦ Oxygen carrying ability of the blood

Erythropoietin Mechanism

Enhanced erythropoiesis increases RBC count Increases O 2 -carrying ability of blood Homeostasis: Normal blood oxygen levels Start Stimulus: Hypoxia due to decreased RBC count, decreased amount of hemoglobin, or decreased availability of O 2 Reduces O 2 in blood levels Kidney (and liver to a smaller extent) releases erythropoietin Erythropoietin stimulates red bone marrow

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Erythrocyte Homeostasis

negative feedback control ◦ drop in RBC count causes kidney hypoxia ◦ kidney production of EPO stimulates bone marrow ◦ RBC count increases in 3 - 4 days

Hypoxemia (inadequate O 2 transport) Increased O 2 transport Sensed by liver and kidneys leaves

 stimuli for increasing erythropoiesis ◦ ◦ low levels O high altitude 2 (hypoxemia) ◦ increase in exercise ◦ loss of lung tissue in emphysema

Secretion of erythropoietin Increased RBC count Accelerated erythropoiesis Stimulation of red bone marrow

Erythrocyte Disorders

  polycythemia - an excess of RBCs ◦ primary polycythemia (polycythemia vera) ◦  cancer of erythropoietic cell line in red bone marrow  RBC count as high as 11 million/  L; hematocrit 80% secondary polycythemia  from dehydration, emphysema, high altitude, or physical conditioning  RBC count up to 8 million/  L dangers of polycythemia ◦ increased blood volume, pressure, viscosity  can lead to embolism, stroke or heart failure

Anemia

 ◦ ◦ causes of anemia fall into three categories: ◦ inadequate erythropoiesis or hemoglobin synthesis   kidney failure and insufficient erythropoietin iron-deficiency anemia    inadequate vitamin B 12 from poor nutrition or lack of intrinsic factor (pernicious anemia) hypoplastic anemia – slowing of erythropoiesis aplastic anemia - complete cessation of erythropoiesis hemorrhagic anemias from bleeding hemolytic anemias from RBC destruction

Anemia

 anemia has three potential consequences: ◦ tissue hypoxia and necrosis ◦ ◦      patient is lethargic shortness of breath upon exertion life threatening necrosis of brain, heart, or kidney blood osmolarity is reduced producing tissue edema blood viscosity is low heart races and pressure drops cardiac failure may ensue

Blood Types

 blood types and transfusion compatibility are a matter of interactions between plasma proteins and erythrocytes  blood types are based on interactions between antigens and antibodies

Blood Antigens and Antibodies

 antigens ◦ complex molecules on surface of cell membrane that are unique to the individual  used to distinguish self from foreign   foreign antigens generate an immune response agglutinogens – antigens on the surface of the RBC that is the basis for blood typing

Blood Antigens and Antibodies

 antibodies ◦ proteins (gamma globulins) secreted by plasma cells  part of immune response to foreign matter   bind to antigens and mark them for destruction forms antigen-antibody complexes  agglutinins – antibodies in the plasma that bring about transfusion mismatch

ABO Group

 your ABO blood type is determined by presence or absence of antigens (agglutinogens) on RBCs ◦ blood type A person has A antigens ◦ blood type B person has B antigens ◦ blood type AB has both A and B antigens ◦ blood type O person has neither antigen  most common - type O  rarest - type AB

Universal Donors and Recipients

   Safest transfusion is same blood type universal donor ◦ Type O – most common blood type ◦ lacks RBC antigens ◦ donor’s plasma may have both antibodies against recipient’s RBCs (anti-A and anti-B)  may give packed cells (minimal plasma) universal recipient ◦ Type AB – rarest blood type ◦ lacks plasma antibodies; no anti- A or B

Type A Type B

Blood Typing

Labels on the bottles denote the kind of antiserum (antibodies) added to the blood samples. Anti-A serum agglutinates (causes to clump) red cells in type A blood, but anti-B serum does not. Anti-B serum agglutinates red cells in type B blood, but anti-A serum does not. Both sera agglutinate type AB blood cells, and neither serum agglutinates type O blood

Type AB Type O

Leukocytes

   White blood cells (WBCs) colorless, round ◦ Granulocytes    Neutrophils (polymorphs) Eosinophils Basophils ◦ Agranulocytes   Lymphocytes Monocytes Prominent nuclei Clear body of foreign material, cellular debris, pathogens

Hemostasis

Prevents blood loss when blood vessel ruptures  Contraction of smooth muscles in blood vessel wall (vasoconstriction)  Formation of platelet plug  Formation of blood clot

Uses of Blood and Blood Components

 Blood stored in blood banks up to 35 days ◦ Anti-clotting solution added ◦ Expiration date added  Blood donated before elective surgery (autologous blood)

Whole Blood Transfusions

Used for loss of large volume of blood  Massive hemorrhage from serious injuries  During internal bleeding  During or after an operation  Blood replacement in treatment of HDN

Use of Plasma

 Replace blood volume  Treat circulatory failure (shock)  Treat plasma protein deficiency  Replace clotting factors  Provide needed antibodies

Blood Disorders

Blood abnormalities  Anemia (low level of hemoglobin or red cells)   Leukemia (increase in white cells) Clotting disorders (abnormal tendency to bleed)

Anemia

Anemia causes  Excessive loss or destruction of red cells ◦ Hemorrhagic anemia ◦ Hemolytic anemia ◦ Sickle cell anemia  Impaired production of red cells or hemoglobin ◦ Deficiency anemia ◦ Thalassemia ◦ Bone marrow suppression

Leukemia

Leukemia is characterized by enormous increase in white cells  Myelogenous leukemia from bone marrow  Lymphocytic leukemia from lymphoid tissue  Bone marrow transplants sometimes successful in restoring blood-producing stem cells lost after leukemia treatment

Clotting Disorders

Abnormal bleeding through disruption of coagulation process  Hemophilia    Von Willebrand disease Thrombocytopenia Disseminated intravascular coagulation (DIC)

The Blood Slide (Smear)

Complete blood count (CBC) performed on drop stained blood slide  Red cells examined  Platelets examined  Parasites may be found  Differential white count performed