lec 9

what is composition of blood

plasma, RBCs, WBC, platelets

blood - transport

• O2 and nutrients to body cells

• metabolic wastes to lungs and kidneys

blood - regulation

maintains

• body temp by absorbents and distributing heat

• normal pH

• adequate fluid volume in circulatory system

blood - protection

prevents

• blood loss (platelets)

• infection (antibodies and WBC)

what are the two types of blood cells

erythrocytes (RBC) and leukocytes (WBC)

erythrocytes contain and are found in?

hemoglobin

found in blood vessels

erythropoiesis

formation of RBC - takes abt 15 days

rate of erythropoiesis

measured by the number of immature RBCS (reticulocytes)

erythropoiesis and reticulocytes correlation

low reticulocytes count (<0.5%) → low erythropoiesis

high reticulocytes count (>2%) → high erythropoiesis

pressure

force exerted by blood

mmHg

blood flows from?

high pressure to low pressure

flow

volume of blood moved per unit time

mL/min

resistance

how difficult it is for blood to flow between 2 points at any given pressure

measure of friction that impedes flow

factors that determine resistance and which is most important?

1) blood viscosity

2) total blood vessel length

3) blood vessel radius - most important

dilated vessel inc or dec resistance

dec

constricted vessel inc or dec resistance

inc

hematopoiesis

formation of all blood cells

occurs in red bone marrow

hematopoietic stem cells (hemocytoblasts)

stem cells that gives rise to all formed element

committed cells cannot change

what occurs when there too little vs too many RBCs

too little - tissue hypoxia

too much - increase blood viscosity

dietary requirements for erythropoiesis

iron, vitamin b12, and folic acid

iron is stored in cells as

ferritin and hemosiderin

iron is transported in blood how

bound to transferrin

vitamin b12 and folic acid are necessary for?

DNA synthesis for developing RBCs

erythropoietin (EPO)

hormone that stimulates formation of RBCs

• released by kidneys in small amounts (in response to hypoxia)

• causes erythrocytes to mature faster

causes of hypoxia

• decreased RBC numbers

• insufficient hemoglobin per RBC

• reduced availability of O2

EPO regulation

• too little erythrocytes or low O2 levels stimulate EPO production

• too much erythrocytes or high O2 levels inhibit EPO production

why its dangerous for athletes to abuse artificial EPO

increases hematocrit which can lead to clotting, stroke or heart failure

life span of erythrocytes

120 days

old RBCs become fragile and Hb begins to degenerate

RBC breakdown: heme

heme is degraded to yellow pigment bilirubin

• bilirubin → liver and turns into bile

RBC breakdown: globin

globin is metabolized into amino acid and release into circulation

erythrocyte disorders are classified as?

anemia or polycythemia

anemia

low O2 carrying capacity that is too low to support normal metabolism

symptoms: fatigue, pale, dyspnea, and chills

polycythemia

abnormal excess of RBCs - increases blood viscosity

polycythemia vera

bone marrow cancer leading to excess RBCs

secondary polycythemia

low O2 levels or increased EPO production

leukocytes

WBCs - function in defense against disease

leukocytosis

WBC count over 11,000/ul → normal response to infection

two major categories of leukocytes

granulocytes: contain cytoplasmic granules (…phils)

agranulocytes: no cytoplasmic granules (…cytes)

neutrophils

granulocytes

60-70% of all leukocytes

destroy bacteria

increase in neutrophils indicates bacterial infection

eosinophils

granulocytes

2-4% of all leukocytes

phagocytize antigens and destroy some parasitic worms

increase in eosinophils indicates allergic reaction

basophils

granulocytes

0.5-1% of all leukocytes

release histamine and plays a role in allergic reactions

lymphocytes

agranulocytes

20-25% of all leukocytes

B and T cells

increase in lymphocytes indicates viral infection

monocytes

agranulocytes

3-8% of all leukocytes

macrophages - leave the bloodstream and enter the tissues

histamine

inflammatory chemical that acts as vasodilator and attracts WBCs to inflamed site

T lymphocytes

virus infected cells and tumor cells

B lymphocytes

give rise to plasma cells which produce antibodies

leukemias

overproduction of abnormal WBCs

immature, nonfunctional WBCs flood bloodstream

cancerous cells fill red bone marrow → leads to anemia and bleeding

leukopenia

abnormally low WBC count

thrombus

stationary clot

may block circulation leading to tissue death

embolus

traveling clot

thrombocytopenia

bleeding disorder - deficit number of circulating platelets

platelet count: <50,000 ul

causes petechiae

treatment: transfusion of concentrated platelets

impaired liver function

bleeding disorder - inability to synthesize clotting factos

causes: vitamin K deficiency, hepatitis or cirrhosis

what is blood viscosity and its effect blood and blood flow?

how thick blood is - friction btwn molecules of a flowing fluid

affected by plasma and the number of erythrocytes

effect: if blood has high viscosity, it increases resistance which slows down blood flow

if there is low viscosity, it reduces resistance and speeds up blood flow

iron deficiency anemia

impaired absorption of iron

pernicious anemia

autoimmune disease that destroys the stomach mucosa

produces intrinsic factor (vit B12 absorption) or low dietary B12

aplastic anemia

bone marrow failure due to toxic drugs or cancer

hemorrhage

bleeding ulcer, rapid blood loss

renal anemia

inadequate secretion of EPO in kidney disease

hemolytic anemia

excessive destruction of erythrocytes

ex. sickle cell