The cardiovascular system: blood

THE CARDIOVASCULAR SYSTEM: BLOODChapter 11: Hematology

THE FUNCTIONS OF BLOOD1. Transportation: of dissolved gases, nutrients,

hormones, and metabolic wastes.2. Regulation: of

1. pH, 2. blood clotting, 3. body temperature, and 4. renal control.

3. Protection: against harmful toxins and pathogens

ANATOMY OF BLOODBlood is a fluid connective tissue that contains:Plasma (55%)

Dissolved proteinsDenser than water

Formed elements (45%)Blood cellsPlatelets (cell fragments)

MEASURING BLOODWhen we take blood, there are 3 characteristics we look at:

1. Temperature (100.4°F)2. Viscosity (5x Water’s)3. pH (7.35-7.45), Slightly Alkaline

PLASMAWater takes up 92% of plasma volume8% Electrolytes, Proteins, Nutrients

Proteins: Albumins (60%): of plasma proteins, produced in the liver, maintain osmotic balance (via water retention)

Globulins (35%): Immunoglobulins: attack foreign proteins and pathogens; antibodiesTransport (escort) Proteins: carry compounds that are not water soluble (i.e. lipids)

Fibrinogens: function in blood clotting when converted to fibrin.*Liver synthesizes many of these proteins.

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FORMED ELEMENTSProduced via hemopoiesis (hematopoiesis)Composition: (Hematocrit)

99.9 % Red Blood Cells (Erythrocytes)<.1% White Blood Cells (Leukocytes)

~ 1 to every 1000 RBCs<.1% Platelets

RED BLOOD CELLSShape: Biconcave discsMature RBCs lack nuclei and other organs (Erythropoiesis)

Life cycle: ~120 days; 1% replaced each day (3 million new cells each second!)

Hemoglobin: made of two globular proteins; contains heme pigment which holds an iron ion that binds with oxygen

HEMOGLOBIN – IRON IN THE BLOOD

hemoglobin

heme a

heme b

close up of Fe

Cause: genetic mutation that affects the globular protein of hemoglobin

Sickled cells can easily clot and cause oxygen starvation of tissues

CLINICAL NOTE: SICKLE CELL ANEMIA

ANTIGENS – CAN TRIGGER AN IMMUNE RESPONSE Antibody generator Four Blood Types:

Type A: surface antigen A, plasma Anti-B Antibodies Type B: surface antigen B, plasma Anti-A Antibodies Type AB: surface antigen A & B, no anti-A or B antibodies Type O: no surface antigens A or B, plasma Anti-A & Anti-B Antibodies (+/-): Determined by presence or absence of Rh antigens on RBCs

Cross-reactions: mixing of blood types can cause agglutination (clumping) of RBCs and eventual hemolysis (RBC destruction)

Anti-Rh antibodies are not normally present in plasma, unless exposure sensitizes an individual.

PLATELETS – THROMBOCYTESCell fragments that function in blood clotting

Formed from megakaryocytes

“Stick” together at injury sites to stop bleeding (hemostasis)

WHITE BLOOD CELLS – LEUKOCYTESLarger than RBCs, have nuclei, lack hemoglobinFunction: defense against pathogens, toxins, wastes and abnormal/damaged cells

Two groups: granulocytes & agranulocytesAmoeboid movementMigration out of the blood streamSome capable of phagocytosis

Granulocytes Neutrophils Eosinophils Basophils

Agranulocytes Monocytes Lymphocytes

NEUTROPHILS70% of WBSsFirst to arrive at an injury site

Active phagocytes (esp. bacteria)

Produced in bone marrow10-hour lifespanDeath recruits other WBCs and forms pus

EOSINOPHILS2-4% of WBSsTwo-lobed and dyed red by eosin

Attack anti-body labeled materials by exocytosis (secretion) of toxins

Produced in bone marrow

BASOPHILS<1% of WBSsDeep purple/blue with many granules

Migrate to injury sites and stimulates inflammation (via histamine) and prevents blood clotting (heparin)

Stimulated basophils release chemicals to attract other basophils and eosinophils

Produced in bone marrow

MONOCYTES2-8% of WBSsAbout twice as big as a RBCLarge free or fixed macrophages

Aggressive phagocytesActive monocytes release chemicals to attract and stimulate other neutrophils, monocytes, phagocytes, and draw fibroblasts to the region.

Produced in bone marrow

LYMPHOCYTES20-30% of WBCsLarge nucleus with “halo” of cytoplasm

Integrates with lymphatic system

Do not rely on phagocytosis

Produced in bone marrow and lymphoid tissues

ABNORMAL AMOUNTS OF LEUKOCYTESToo few: leukopeniaToo many: leukocytosisExtreme leukocytosis: leukemia

Cancer of blood-forming tissues.

HEMOSTASISHemo “blood” + stasis “halt”: stops bleeding1. Vascular Phase: constriction of damaged blood vessels

(~30mins); blood vessel spasm2. Platelet Phase: “sticky” platelets form a platelet plug3. Coagulation Phase: conversion of fibrinogen to fibrin

ABNORMAL HEMOSTASISExcessive coagulation

Thrombus: blood clot attached to wall

Embolus: moving blood clot i.e. strokes, pulmonary embolism: immobile embolus within a blood vessel.

Inadequate coagulationHemophilia

Missing clotting factor Symptoms including excessive bleeding (external and internal)