a&p ii | exam 1 blood and hemostasis

blood

blood

only fluid tissue in the body

classified as a connective tissue

functions of blood

transports (nutrients, wastes, and hormones)

regulates (homeostasis)

protects (against infections)

composition of blood

plasma

formed elements

• erthrocytes (RBC)

• leukocytes (WBC)

• platelets

erythrocytes

red blood cells

transports oxygen and carbon dioxide

leukocytes

white blood cells

make up our immune system that protects us from infection and cancer

platelets

cell fragments that function in hemostasis

produced by a type of leukocyte found in red bone marrow (megakaryocytes)

• contain granules loaded with Ca 2+ and enzymes that aid in hemostasis

plasma

fluid that surrounds formed elements

consists of water, electrolytes, plasma proteins, nutrients, hormones, respiratory gases, and metabolic waste

hematocrit

percent of blood volume occupied by erythrocytes

• plasma = 55%

• leukocytes and platelets

• erythrocytes = 45% (hematocrit)

normal hematocrit

men = 47 ± 5%

women = 42 ± 5%

erythrocyte structure

biconcave disc

no nucleus or membrane-bound organelles

lots of hemoglobin (efficient oxygen and respiratory gas carrier)

erythrocyte function

transports oxygen and carbon dioxide

hemoglobin

a protein that transports O2

consists of globin and 4 heme groups that allows it to carry 4 oxygen molecules

iron-containing heme pigment plays a role in its transport

hematopoiesis

process of blood cell formation

occurs in red bone marrow

driven by hematopoietic stem cells

erythropoiesis

formation of erythrocytes

takes 2-15 days to complete development

2 million erythrocytes are made every second

nutrients essential for erythrocyte production

iron

folic acid

vitamin B12

iron

required for hemoglobin synthesis

bound to ferratin in the liver and transports in the blood via transferrin

Fe must be replaced through a diet

folic acid

vitamine obtained from leafy plants

used to make thymine

required for DNA synthesis

vitamin B12

obtained from animal products

supports the function of folic acid

erythropoietin (EPO)

glycoprotein that regulates erythrocyte production

stored in the kidney

stimulated by a

• decreased erythrocyte count

• decreased amount of hemoglobin

• decreased availability of O2

anemia

decrease O2 in the blood due to loss of erythrocytes or hemoglobin

anemia due to blood loss

acute hemorrhagic anemia

chronic hemorrhagic anemia

anemia due to deficiency in erythrocyte production

iron-deficiency anemia

pernicious anemia (destruction of stomach mucous lining)

renal anemia (lack of EPO)

aplastic anemia (destruction/inhibition of red marrow)

anemia due to excessive erythrocyte destruction

thalassemias (absense of globin chain)

sickle-cell anemia (abnormal hemoglobin)

hemostasis

processes that stop blood from escaping a damaged blood vessel

3 components

• vascular spasm (transient)

• platelet plug formation (rapid)

• blood clot formation (slow)

vascular spasm

first response to bleeding

• triggered the damage and contractions of smooth muscles (vasoconstricition)

minimizes blood flow long enough for a platelet plug to form

step 1 of a platelet plug

platelets adhere to a damaged endothelium and exposes of collagen

plasma (vWF) binds to exposed collagen

vWF bind to platelets to anchor them to the damaged site

step 2 of a platelet plug

platelets are triggered when binded to vWF and secrete chemical mediators and thromboxane A2

step 3 of a platelet plug

chemical mediators and thromboxane A2 direct changes to platelet surfaces causing them to adhere to each other

step 4 of platelet plug

positive feedback results in rapid formation of a platelet plug

blood coagulation

transforming blood into a solid gel (forming a clot)

occurs around platelet plug

involves fibrin to act as a glue to strongly reinforce the platelet plug

process is divided into 3 phases

phase 1 of blood coagulation

can occur via the intrinsic or extrinsic pathway

phase 2 and 3 of blood coagulation

prothrombin activator formed by one of the pathways turn into an active enzyme that catalyses the creation of cross-linked fibrin mesh

agents that limit the growth of a blood clot

heparin and antithrombin III

heparin

an extracellular matrix molecule found on the surface of intact endothelial cells

antithrombin III

plasma protein made by the liver

binds to heparin, causing its own activation which inactivates clotting factors

fibrinolytic system

dissolves blood clots

requires plasminogen and tissue plasminogen activator (t-PA)

t-PA

activates when it binds to firbin

activated t-PA converts plasminogen into plasmin

plasminogen

activated t-PA turns this into plasmin which cutes the fibrin mesh tissue formed from the clot into small, soluble fragments