Blood

Blood• Blood can actually be considered one of your body’s tissues.

– Formed elements

• all the blood cells

– red blood cells (RBCs) (erythrocytes)

» transport O2

– white blood cells (WBCs) (leukocytes)

» immune response

• and the platelets

– membrane sacs that help seal broken blood vessels

– Plasma

• proteins used for blood clotting and osmotic pressure

• Serum

» nutrients (glc, aas, fats)

» waste (mostly urea)

» dissolved gases (O2, CO2, N2)

» electrolytes (Na+, K+, Cl-)

Blood

Blood - hemopoiesis• production of blood cells

– erythropoiesis -RBCs

• kidneys produce erthropoietinwhen O2 levels drop

• new RBCs produced inred bone marrow

• negative feedback loop• production of blood cells

– leukopoiesis -WBCs

• triggered by infections or other attacks on the body

• production of blood cells

– leukopoiesis -WBCs

• triggered by infections or other attacks on the body

Blood - hemopoiesis• production of blood cells

– erythropoiesis -RBCs

• kidneys produce erthropoietinwhen O2 levels drop

• new RBCs produced inred bone marrow

• negative feedback loop

• production of platelets

– thrombopoiesis

• megakarocytes

– bone marrow

– lungs

• pinches off pieces of cytoplasm

Blood - erythrocytes• Red blood cells transport O2

(and some CO2)

– hemoglobin

• 4 protein chains (globins)

– 2 alpha chains

– 2 beta chains

• 4 heme groups

– site where O2 molecules bind

• Polycythemia

– too many red blood cells

• increase blood volume

• increase blood viscosity

• increase blood pressure

– heart over worked

– can lead to embolism, stroke, heart failure

• Anemia

– too few blood cells carrying O2

– hemorrhagic anemia - excessive blood loss

– hemolytic anemia - destruction of RBCs or too little erythropoiesis

– sickle-cell anemia and thalassemia

• both caused by abnormal hemoglobin

Blood - erythrocyte disorders

• All cells have membrane proteins that label the cell as “friend” or “foe” to the immune system

– antigens

– allow your immune system can differentiate your body cells from foreign or infected cells

• Antigens on RBCs called agglutinogens

– react with antibodies in blood called agglutinins– mismatched transfusions cause agglutination (transfusion reaction)

• agglutinins bind toagglutinogens and linkRBCs together

• cause RBCs toform “clumps” (agglutination)

Blood Types

• ABO blood groups

– type A and type B agglutinogens (antigens)• just A type agglutinogens - type A blood

• just B type agglutinogens - type B blood

• both agglutinogens - type AB blood

• no agglutinogens - type O blood

– transfusion rxns can occur because you also have agglutinins (antibodies)

• type A blood - antiB agglutinins

• type B blood - antiA agglutinins

• type AB blood - no agglutinins

• type O blood - both agglutinins

Blood Types

• ABO blood groups

– type AB blood• no agglutinins - sometimes called universal recipient

• what about agglutinins in donor’s blood?

– type O blood - both agglutinins• no agglutinogens - universal donor?

• But has both types of agglutinins

Blood Types

• Rh group

– Rh+ have the Rh agglutinogen– Rh- do not have Rh agglutinogen

• will produce antiRh agglutinin if exposed to Rh+ blood

Blood Types

• Rh- Mom exposed to Rh+ blood of newborn at birth

• no problem during first pregnancy

Blood Types - hemolytic disease of the newborn (HDN)

• Mom produces antiRh agglutinins


• Mom’s antiRh agglutinins attack Rh+ RBCs of fetus in next pregnancy


• Can be prevented by treating with RhoGAM

Hemostasis• The stoppage of bleeding (3 ways)

– 1) Vascular Spasm• constriction of the injured blood vessel via:

– pain receptors

– smooth muscle damage

– serotonin (released from platelets)

– 2) Platelet plug formation• platelets react with collagen

• adhere to inner surface of blood vessel

• contract and draw the vessel walls together

• release chemicals (degranulation)– serotonin (vasoconstrictor)

– ADP (platelet aggregation)

– thromboxane A2 (both of the above)

2

1

Hemostasis• The stoppage of bleeding (3 ways)

– 1) Vascular Spasm

– 2) Platelet plug formation

– 3) Coagulation• the formation of fibrin

• two pathways– intrinsic mechanism

– extrinsic mechanism

3

Hemostasis - coagulation pathways• Intrinsic mechanism

– platelet degranulation releases fact. XII

– triggers a cascade of rxns

– fact. X activated

– becomes prothrombin activator

– converts prothrombin to thrombin

– converts fibrinogen to fibrin

– becomes fibrin polymer

Hemostasis - coagulation pathways• Extrinsic mechanism

– damaged tissues release thromboplastin

– fact. VII activated

– results in fact. X activation– becomes

prothrombin activator

– converts prothrombin to thrombin

– converts fibrinogen to fibrin

– becomes fibrin polymer

Hemostasis - coagulation pathways• Fibrin formation

– intrinsic mech. - 3-6 min.

– extrinsic mech. - ~15 sec.

• Clot retraction (30 minutes)

• Healing stimulated byplatelet-derived growth factor(PDGF)

3

Hemostasis - coagulation pathways• Classical hemophilia

– lack of fact. VIII

• hemophilia B– lack of fact. IX

• clotting fact. can be produced by transgenic bacteria

3

Circulatory System

• Basic structure of arteries and veins

lumen

Tunica intima -mostly endothelium

Tunica media -mostly smooth muscle

Tunica externa -mostly connective tissue

The structure of blood vessels• Blood flows from heart

– into arteries• conducting

– large– very elastic

• distributing– feed specific organs– very muscular

• resistance– arterioles– deliver blood to capillary bed

• metarterioles– control blood flow within capillary bed

The structure of blood vessels

– capillary bed• very thin walled

- just tunica intima

• site of exchange between blood and body cells

– nutrients, O2 CO2 , wastes

The structure of blood vessels

– veins• deliver blood back to heart

– metavenules

– venules

– veins

• much less smooth muscle than arteries

• more fragile than arteries– varicose veins are just veins

that have broken open and leak blood

• contain valves to prevent blood flowing backwards

Precapillary sphincters

• Blood flows from arteriole

• to metarteriole– precapillary sphincters open or close

and determine if blood flows into capillary bed,

– or is shunted straight thru thoroughfare channel (metavenule).

– constantly adjusted (homeostasis again) - depends on activity of the body

– capillary bed• very thin walled

- just tunica intima

• site of exchange between blood and body cells

– nutrients, O2 CO2 , wastes

Blood Pressure• BP is not constant

throughout circulatory system

• when heart contracts (systole)BP goes up

– systolic pressure

• when heart relaxes (diastole) BP goes down

– diastolic pressure

• as blood flows further from the heart

– BP also decreases

• By the time blood reaches the veins, hardly any pressure is provided by the heart

– So where does pressure come from that moves blood out of your legs and toward your heart??

Skeletal Muscle Pump

• Veins often run in the middle of skeletal muscle

• as muscles contract, veins get squeezed

• blood is pushed through vein

• venous valves - prevent blood from flowing backward

• blood is squeezed toward heart

• What happens if you stand motionless for 60 minutes or so?

The Circulatory system

• Your body can control blood flow to diff. areas by changing peripheral resistance.

• Regulation of peripheral resistance

– Local control

• accumulation of metabolic by products

• CO2, H+, lactic acid (+ others)

• trigger vasodilation (decrease peripheral resistance)

• increased blood flow carries by products away

• blood vessels constrict back to normal size

• homeostasis



– Local control


– Neural control

• baroreflex

• negative feedback



– Local control


– Neural control

• baroreflex

• chemoreflex

DecreasedCO2 levels

chemoreceptorsfire fewer APs



• Remember autonomic nervous system?

– sympathetic division• fight and flight

• diverts blood flow to prepare for stressful activity

– parasympathetic division• rest and digest

• diverts blood flow to GI tract

The Circulatory system• So the circulatory system transports nutrients and wastes to

and from the cells…

• How do things move between the blood in the capillaries and the cells outside?

• Three routes of capillary exchange

– diffusion

• most important

– transcytosis

• least important

– filtration and reabsorption

Documents

Blood