Cardiovascular system - Cardiovascular system - Blood Blood

Anatomy - Chapter20Anatomy - Chapter20

Cardiovascular system - Cardiovascular system - Blood Blood

Anatomy - Chapter20Anatomy - Chapter20

The Cardiovascular system is comprised of the heart, blood vessels, & blood

The heart acts as a “pump”, creating pressure which causes blood to move through the blood vessels of the body, allowing O2 & nutrients to be distributed to, & wastes removed from, body tissues

Physical characteristics of blood

Fluid connective tissue

matrix – “plasma” with dissolved proteins

cells & cell fragments – “formed elements”

temperature – 38o C

5x more viscous than H2O

pH – 7.35-7.45

Functions of Blood Transportation

O2/CO2

nutrients/wastes

enzymes

hormones

Regulation body temperature

pH & ion composition of interstitial fluid

intracellular fluid volume

Protection defense against pathogens

restriction of fluid loss at injury sites

Composition of Blood

55% Plasma – liquid component of blood

45% Formed elements – cells/cellular fragments

Erythrocytes – red blood cells (RBCs)

Leukocytes – white blood cells (WBCs)

Platelets – (thrombocytes)

Plasma

Formed Elements

granular

agranular

(B & T)

Hemopoiesis

Megakaryoblast

(pluripotent stem cell)

Erythrocytes (RBCs) Biconcave shape, flexible cells

around 5 million RBCs per mm3

blood

average “life span” of 120 days

Cells contains cytosol, no nucleus/organelles; filled with Hemoglobin (Hb)

Hemoglobin

Hemoglobin allows for transport of O2 & CO2

As RBCs get damaged/worn out, they must be removed from circulation & replaced

About 1% of the circulating RBCs are replaced each day, at at rate of about 3 million RBCs per second

Worn out RBCs are removed by phagocytic cells in the liver, spleen & bone marrow

Most of the RBC’s hemoglobin is recycled, the pigmented part (heme) gets converted to bile pigments

Erythropoiesis

New RBCs are made in red bone marrow (myeloid tissue) by process of erythropoiesis

stimulus for erythropoiesis is hypoxia detected by cells of kidney

Leukocytes (WBCs)

More like “typical” cells with single nucleus, organelles

5 types of WBCs characterized as granular or agranular

all function in defense

average 6000-9000 WBCs/mm3 of blood

variable “life” span depending on type of WBC- days (neutrophils) to decades (lymphocytes); in sick person, some WBCs live minutes to hours

Differential Count & Functions of WBCs

“WBC differential count” – normal range (in percentage) of WBCs in the peripheral circulation

differential count will vary during specific types of disorders, depending on which type of WBC responds

WBC response based on functions of specific type

Differential Count & Functions of WBCs Neutrophils - 50-70%

Lymphocytes – 20-30%

Monocytes – 4-8%

Eosinophils – 2-4%

Basophils - <1%

function in acute bacterial infections; phagocytic

function in chronic bacterial infections; migrate into tissues to become “wandering macrophages”

active against parasites & elevated in allergic reactions; destroy antibody-coated antigens by phagocytosis

release chemicals (histamine, heparin) during tissue inflammation

Differential Count & Functions of WBCs Lymphocytes – 20-30%

Function in “immunity” – specific resistance to disease

T cells- involved in “cell-mediated (aka cellular) immunity”; defense against abnormal cells & intracellular pathogens

B cells- involved in “antibody-mediated (aka humoral) immunity”; defense against pathogens (Ag’s) in body fluids (blood/lymph)

Platelets (Thrombocytes)

Cellular fragments (cell membrane “packet” filled with cytoplasm) from large Megakaryocytes found within bone marrow

around 350,000 platelets/mm3

platelets circulate for 9-12 days before being removed from circulation

platelets function in hemostasis– the processes that stop bleeding from damaged blood vessels – including “platelet plug formation” and “coagulation”