Information I will assume you to know heading into this week’s lectures: Basic definition of veins vs. arteries. Elastic, smooth muscle properties of arteries, veins, capillaries. Definition of interstitial fluid, plasma, ECF Gradients for glucose, O 2, CO 2 at capillaries Action of one-way valves and skeletal contractions in helping venous return Basic aspects of RBC’s – no nuclei, no organelles, no ribosomes.Hold hemoglobin

Blood vessels are more than little tubes bringing blood to your body They are dynamic, changing flow, growing branches according to conditions

Reconditioning of blood Intestines, kidneys, and skin receive blood flow in excess to their needs

Flow rate of blood Resistance is the opposition to blood flow through a vessel. It depends on: –blood viscosity –vessel length –vessel radius P R F= pressure gradient resistance or

Effect of radius on surface area Friction increases as surface area of contact increases more vessel wall contact with blood less contact

Effect of radius on resistance

Arteries are a pressure reservoir Large radius of arteries, little resistance Elastic recoil from arteries drives flow of blood during diastole Arteries temporarily expand and hold pumped blood

Mean arterial pressure is the driving force for blood flow. mean arterial pressure = diastole pressure plus 1/3 the pulse pressure /3 (40) = 93 Blood pressure drops sharply once in arterioles

Arterioles give most resistance Arteriole radius changes to alter the distribution of blood and regulate blood pressure Vascular tone is a baseline of vascular resistance - changes in radius are possible

Local control of arteriolar resistance Mean blood pressure is identical to all organs Differences in arteriolar resistance determines the distribution of blood to different organs Mechanisms: endothelium cells release chemicals when O 2 and CO 2, acidity

Figure Page 354 Increased flow to skeletal muscles due to exercise

Extrinsic (outside) controls on arterioles: Sympathetic signals cause general arteriole constriction, increasing mean pressure Local controls dilate arterioles where blood is needed.

Increased SNS constrict

Increased SNS constrict dilate Local controls using signals from tissues

Capillaries O 2, CO 2 nutrients and wastes passively diffuse Thin vessels increase surface area of vessel wall contact

Diffusion at capillaries Distance: Walls are one cell thick Area: small radius, high surface area of contact Speed: small radius causes slow flow

Capillary walls have pores Pores allow the passage of small, water- soluble molecules (ions, glucose) Lipid-soluble substances dissolve through cell membrane

Bulk flow Some substances cross the capillary wall by bulk flow of fluids –Ultrafiltration –Reabsorption

blood to venue inward reabsorption tissue cells outward ultrafiltration blood Bulk flow at capillaries Bulk flow occurs by the differences in hydrostatic and osmotic pressures between plasma and interstitial fluids

Bulk flow at capillaries When fluids leave capillaries, most plasma proteins remain Plasmaproteins blood to venue inward reabsorption tissue cells outward ultrafiltration blood

Bulk flow at capillaries Plasma has a higher concentration of proteins, producing osmotic pressure from interstitial fluid to plasma “Plasma-colloid osmotic pressure” osmotic pressure blood to venue inward reabsorption tissue cells outward ultrafiltration blood Plasmaproteins

Arteriole Venule blood pressure (hydrostatic) blood pressure (hydrostatic) Plasma colloid pressure 25 Plasma colloid pressure Ultrafiltration 9 Reabsorption Interstitial pressure 1 Forces of bulk flow

Bulk flow Fluid is exchanged b/w plasma and interstitial fluid Site of short-term maintenance of fluid balance

Venule Arteriole Tissue cells lymphatic vessel Lymphatic system also absorbs interstitial fluid

Lymphatic System Lymph formed from interstitial fluid Functions: –Drainage channels –Absorption of fats from intestine –Deliver pathogens to “nodes” where there are many lymphocytes

Fluid pressure fluid cannot push out from inside Lymphatic vessels

Problems with vessels Aneurysm Hemorrhage Why do aneurysms form?

Blood pressure problems Hypertension – Blood pressure over 140/90 – Associated w/ smoking, stress, obesity – Caused by high blood volume, clogging of vessels, repeated constriction of vessels from stress (Sympathetic NS)

Blood pressure problems Hypertension – Blood pressure over 140/90 – Baroreceptors can adjust to higher BP – High BP puts stresses on vessels, elasticity (atherosclerosis, strokes) and stresses on heart (heart attacks), kidneys

Blood pressure problems Treatments for hypertension: – Low salt diet, reduce stress, exercise – ACE inhibitors (reduce blood volume) – Alpha, beta blockers (reduce sympathetic effects) – Calcium blockers (reduce cardiac contractions)

Circulatory shock – blood pressure drops too low to serve tissues. – From weak heart, blood loss, dilation from allergic response – Body compensates w/sympathetic signals, fluid shifts Blood pressure problems

Components of blood Plasma Blood cells: erythrocytes leukocytes (WBC), and platelets. –Hematocrit is the % of blood occupied by RBC. (RBC)

What is plasma? Ions: mostly Na+ and Cl-. Gasses, waste, nutrients, hormones Plasma proteins: –Albumins establish an osmotic gradient, carry some hormones –Globulins (alpha, beta, gamma) transport molecules, serve as antibodies –Fibrinogen - blood clotting

Hemoglobin Heme - contains iron and binds with one molecule of O 2 Globin - 4 protein chains Turns bright red when combined with oxygen CO 2, CO, H + can also bind

RBCs live for about 4 months Spleen removes old RBCs RBCs are produced in bone marrow from pluripotent stem cells

Kidney controls RBC production Kidney is sensitive to anemia and releases erythropoietin

Blood doping Erythropoietin (EPO) can be synthesized and injected to illegally enhance endurance An athlete’s own blood can be stored and reinjected to boost RBC’s Hematocrit can detect

Causes of anemia? Anemia – O 2 to tissues is low – Due to RBC, erythropoiesis, or hemoglobin – “Pernicious anemia” – lack of B 12 results in low RBC production – Aplastic anemia – bone marrow production

How the body repairs itself Initial response: –vascular spasm - reduces blood flow through the vessel –platelet plug - Aggregation of platelets. Platelets attach to areas with exposed collagen –These processes are stimulated by ADP

Platelets Platelets are cell fragments that are functional for 10 days Reduce blood loss (maintain hemostasis) Platelets and a RBC

Prostacyclin and nitric acid Normal endothelium Inhibits platelet aggregation Normal endothelium Prostacyclin and nitric acid Positive feedback at injury site Initial stimulus is exposed collagen Repair is contained to site of injury Platelets Vessel wall ADP Collagen platelet plug forming Exposed collagen at injury

How the body repairs itself Stopping blood loss: –Fibrinogen (plasma protein) is converted into fibrin (thread-like protein). This conversion is catalyzed by thrombin –Fibrin threads trap RBCs, forming a clot –Thrombin is formed from inactive prothrombin in plasma

These final 6 slides will not be shown but relate the information you should already understand from Bio 101,101 or 115

smooth muscle endothelium elastic tissue smooth muscle endothelium smooth muscle, elastic fibers endothelium valve Artery Arteriole Capillary Vein Arteries contain connective tissue with elastin and collagen Veins include valves Not shown

Interstitial fluid is an intermediary from blood to cells 80% of ECF is interstitial fluid Not shown

Main nutrients Not shown

Veins returning blood Veins have large radii and low resistance. Walls are thin, not elastic Most blood volume is in veins Not shown

Veins Valves prevent engorgement and backflow Sympathetic NS constricts veins to increase venous return Skeletal muscles also help return Not shown

RBCs RBCs have no nuclei, ribosomes, or organelles Packed with hemoglobin “Doughnut-like” shape Not shown