Chapter 17

Blood

life-sustaining transport vehicle of the cardiovascular system

Functions of blood

• transport

• regulate

• protection

Transport functions

• deliver oxygen and nutrients to body cells

• transport metabolic wastes to lungs and kidneys for elimination

• transporting hormones from endocrine organs to target organs

Regulation functions

• maintaining body temp

• maintaining normal PH

• Maintaining fluid volume

Protection functions

• prevent blood loss

• prevent infection

Fibers in the blood

• albumins

• globulins

• fibrinogen

Formed elements

• all come from red bone marrow

• three types include erythrocytes, leukocytes and platelets

Fixed microphages

stuck in 1 tissue type

wandering microphages

destroys anything bad

Total blood volume

5 liters

hypoxia

oxygen drops

Eyrythropoetin

controls myeloid cells to carry out eyrythropoeisis

Granulocytes

• neutrophils

• eosinophils

• basophils

TPO

controls myeloid cells to carry out thrombopoesis to make platelets

Erythrocytes

• small diameter cells that contribute to gas transport

• disc shape, anucleate, no organelles

• filled with hemoglobin

• 90-100 day life expectancy

Features for efficient gas transport

• biconcave shape offers big surface area for gas exchange

• hemoglobin takes up 97% of cell volume

• no mitochondria in RBCs

Function of Erythrocytes

• RBCs are dedicated to respiratory gas transport

• globin binds with oxygen

Globin

• carries oxygen

• composed of 4 polypeptide chains

Oxyhemoglobin

• produced by oxygen loading in lungs

• ruby red color

Deoxyhemoglobin

• produced by oxygen unloading in tissues

• dark red color

carbaminohemoglobin

produced by CO2 loading in tissues

Hematopoeisis

• formation of all blood cells

• occurs in red bone marrow

Hematopoetic Stem Cells (hemocytoblasts)

• gives rise to all formed elements

• hormones and growth factors push cell towards specific pathway of blood cell development

Balance between RBC production and destruction is depended on

• hormonal controls

• dietary requirements

Erythropoietin (EPO)

• hormone that stimulates formation of RBC

• always small amount in blood to maintain basal metabolic rate

• released in kidneys in response to hypoxia

Free iron ions are toxic so iron is bound with proteins:

• stored in cells as ferritin and hemosiderin

• transported in blood bound to protein transferrin

What do microphages in the spleen do?

engulf and breakdown dying RBC

Erythrocyte disorders

• anemia

• polycythemia

Anemia

• blood has abnormally low oxygen carrying capacity

• fatigue, pallor, dyspnea, chills

• caused by blood loss or not enough RBC

Polycythemia

abnormal excess of RBCs; increases blood viscosity, causing sluggish blood flow

Polycythemia vera

Bone marrow cancer leading to excess RBC

Secondary polycythemia

caused by low oxygen levels or increased EPO production

Blood doping

Athletes remove, store, and reinfuse RBCs before an event to increase oxygen levels for stamina

Leukocytes (WBC)

formed element that is complete cell with nucleus and organelles

Granulocytes

• contain visible cytoplasmic granules

• neutrophils, eosinophils, and basophils

• larger, shorter lived than RBC

Agranulocytes

• do not contain visible cytoplasmic granules

• lymphocyte, monocyte

Diapedesis

Process of blood cells leaving capillaries

Leukopoiesis

Stimulated by interleukins and colony- stimulating factors

Platelets

• fragments of megakaryocytes

• contain serotonin, calcium, enzymes, ADP, and platelet- derived growth factor for clotting process

Thrombopoietin

Regulates platelet formation

Hemostasis

• fast series of reactions for stoppage of bleeding

• requires clotting factors

Hemostasis clotting steps

• vascular spasm (slow down blood flow)

• platelet plug formation

• coagulation

Collagen fibers

targeted by platelets

Fibrinolysis

removal of clot

Myeloid Stem Cell

Transforms into proerythroblast

Proerythroblast

divides many times, transforming into basophilic erythroblasts

Basophilic erythroblasts

synthesize many ribosomes, which stain blue

Polychromatic erythroblasts

synthesize large amounts of red-hued hemoglobin; cell now shows pink and blue areas

orthochromatic erythroblasts

contains mostly hemoglobin, so appear just pink; eject most organelles; nucleus degrades, causing concave shape

Reticulocytes

Still contain small amount of ribosomes

Two types of leukocytes

granulocytes and agranulocytes

Formation of platelets

• hematopoietic stem cell

• megakaryoblast

• megakaryocyte (I/II)

• megakaryocyte (IV)

• platelets

Intrinsic pathway

Clotting factors are present within the blood

Extrinsic pathway

Clotting factors are located outside the blood

Platelet derived growth factor

stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall