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Properties of BloodChapter 15
Large artery
Muscle
connective tissue
smaller artery
artery vs vein
arteriole
Capillaries
Blood can be divided into 2 componentsBlood can be divided into 2 components I. Plasma – fluid portion II. Formed elements – red and white blood cells and platelets (cell fragments)
Plasma – 55%Formed elements – 45% (mostly red blood cells)
I. Plasma 90% water 10% solutes proteins nutrients waste products gases electrolytes
Concentrations of small solutes are similar in plasma and interstitial fluid O2 and CO2 diffuse through membranes Water soluble materials diffuse through pores Concentrations of proteins are higher in plasma – capillaries are less permeable
* remember this?
Plasma Proteins – three main categories 1. albumins – generally used to transport materials like hormones most abundant of the plasma proteins synthesized by the liver 2. globulins – clotting proteins antibodies (gamma globulin) proteins that transport fat soluble hormones (steroid hormones) 3. fibrinogen – a filamentous protein from the liver, critical in clot formation
Other proteins in blood plasma include enzymes and hormones examples: angiotensinogen (liver), and renin (kidney)
Other solutes in blood plasma nutrients – absorbed from intestines sugars (glucose), amino acids, fatty acids, cholesterol, etc
waste products from cellular metabolism – urea, uric acid, etc
electrolytes – sodium, potassium, calcium, chloride, etc
gases – O2, CO2, N2
II. Formed elements in blood plasma red blood cells (erythrocytes Pronunciation: i-'rith-ro-sIts) white blood cells (leukocytes) platelets - pieces of bone marrow cells (megakaryocytes)
Blood cells produced in bone marrow children – marrow in all bones produces blood cells adults – only skull, chest, pelvis, long bones
Red blood cells 7 µm across 5,000,000 per cubic mm, Thus : 5,000,000,000 per cc (ml), 5,000,000,000,000 per liter, 25,000,000,000,000 per 5 liters lack a nucleus and mitochondria (what is their energy source?) have a large number of hemoglobin molecules (over 250,000,000 hemoglobin molecules per cell)
glycolysis
Hemoglobin Four subunits two α subunits, two β subunits Each subunit contains a heme group (the site where O2 binds to hemoglobin ) with one atom of iron one molecule of O2 binds to one iron atom CO2 binds to other sites on the hemoglobin molecule
ribbon model of hemoglobin
Production of red blood cells is regulated by erythropoietin hormone secreted by kidneys stimulates cell birth and maturation of erythrocyte precursor cells in bone marrow Breakdown of red blood cells happens in the liver and spleen breakdown products include bilirubin – gives yellow color to plasma and urine, and iron Lifetime is about 120 days (how many cells are born every day?)
~208,000,000,000 25 trillion cells / 120 days = 208 billion
Iron is supplied via dietary sources hemoglobin requires about 15mg of iron per 100ml blood (750mg / 5 liters) much of the iron is recycled from the liver
Iron-deficiency anemia When iron levels drop below what is required by hemoglobin, the blood’s capacity to carry O2 decreases
Pernicious anemia Low levels of vitamin B12vitamin B12 reduce levels of red blood cell birth B12 is essential for making DNA in dividing cells (and in maintaining myelin in nerve cells) remember that a huge number of red blood cells must be born every day B12 comes from meat, eggs, dairy products, or supplements
Blood loss is another cause of anemia
Symptoms: chronic fatigue, shortness of breath
Hematocrit (hct)
the percentage of blood volume that is red blood cells usually about 45%
determined by spinning the blood – the red blood cells are denser so they collect at the bottom
Scanning Electron Micrograph (SEM) of white blood cells attacking a cancer cell.
White blood cells
White blood cells Far fewer than red blood cells (1/1000 the number) Lifetime – a few days to a few weeks Found in blood and outside of blood • can squeeze through capillary pores • can move on their own 5 types of white blood cells Involved in immune response (more later)
5 types of white blood cells
Platelets pieces of bone marrow cells (megakaryocytes) critical role in blood clotting
• Around 100,000,000,000 platelets are produced each day• Lifespan: 7-10 days
Hemostasis: mechanisms that stop bleeding three steps 1) vascular spasm 2) platelet plug formation 3) blood clot formation
Vascular spasm • remember that injury triggers sympathetic inputs that trigger vasoconstriction? • there are also local chemicals that trigger vasoconstriction (vascular spasm) brief constriction of arterioles to reduce bleeding • antagonizes vasodilation from other local chemicals (inflamation)
(inappropriate vascular spasms are bad – reduced blood flow eg migraine)
Platelet plug formation platelet adhesion – platelets stick to tissues under the endothelial cells that line vessels von Willebrand factor is a plasma protein that binds platelets to the injured area von Willebrand factor is secreted by bone marrow cells, platelets, and endothelial cells 1) binds to collagen fibers (the basement membrane of the endothelial cells 2) then binds to platelets 3) triggers platelets to become sticky and to secrete other chemicals
von Willebrand factor triggers platelets to secrete chemicals • epinephrine and serotonin local vasoconstriction, temporarily opposes vasodilation • ADP causes platelet membranes to stick to each other initiates positive feedback: more platelets, more ADP, etc
ADP also triggers platelet membrane to release TXA2 (thromboxane A2)
TXA2 promotes • vasoconstriction • platelet stickiness • release of ADP (poss. feedback)
Platelets contain actin and myosin – sticking together triggers tightening
Platelet plug formation is actively inhibited by uninjured endothelial cells
Nitric oxide and prostacyclin inhibit plug formation • continuously released by endothelial cells (remember we said nitric oxide was continuously released ?)
Blood clot formation 1) involves a cascade of enzymatic events 2) results in formation of a sticky meshwork of fibrin proteins
Fibrin is the activated form of the plasma protein fibrinogen (which we mentioned earlier)
Fibrinogen is activated to fibrinby another protein, thrombin
Fibrin first forms a loose meshwork that is stabilized by factor XIIIa
End part of the coagulation cascade
Note that thrombin activates both fibrinogen and factor XIII (the “a” indicates activated form)
Thrombin is activated by yet another protein, factor Xa, and thrombinitself promotes activationof factor Xa (positive feedback)
There are two pathways to thrombin activation An intrinsic pathway (beginning in the vessel) An extrinsic pathway (beginning in nearby tissue)
Usually activated together since tissue damage outside of vessels usually occurs when vessels are damaged
Intrinsic pathwayIntrinsic pathway Begins when blood contacts collagen Activates factor XII XIIa Etc.
Note that Platelet Factor 3 (PF3) is necessary PF3 is secreted from activated platelets in the platelet plug (why important?)
PF3PF3
PF3PF3
• coagulation factors circulate in the plasma (most from liver)• numbers DO NOT correspond to their location in the sequence
Extrinsic pathwayExtrinsic pathway Begins when blood contacts factors from nearby damaged cells
from damaged tissue
in blood
Why use a cascade?Why use a cascade?Is there some advantage? Is there some advantage?
ping pong balls and mouse traps see youtube demo of chain reaction
http://www.stago.fr/Commun/img/NotreEnt/Thrombose_normal.mpg
Thrombus - A blood clot that forms in a vein and remains there. Embolus - A thrombus that travels from the vein where it formed to another location. Deep vein thrombosis - A blood clot occurring in a leg or pelvic vein. Pulmonary embolism - a blood clot that has traveled to the lungs.
blood-filled infarcted (dead) lung tissue
late stem cell stem cell in bone marrow
proerthroblast (fate determined)
basophilic erythroblast(size decreases)
Erythropoiesis
polychromatophilic erythroblastnow producing hemoglobin
ready to extrude its nucleus
mature erythrocyte
mature erythrocyte
extruding its nucleus mature erythrocytesready to enter the blood
cell nucleus