Hiso Lecture 3

• Transport nutrients, waste, and hormones between circulation and tissues/organs
• Maintains environemtn of bodily tissues/organs through nutrient, waste, and interstital fluid exchange
• Control rate of blood flow to organs/tissues

• Tunica intima
• Tunica media
• Tunica adventitia

• Muscular sphincters that control blood flow to capillary beds
• Respond to increased blood flow, local metabolites, and sympathetic input to control flow through beds.

Capillaries

Allows for gas and nutrient exchange in the capillary bed to the surrounding tissues

• Stream-lines of flow within a vessel
• Stream-lines flow at different rates and do not mix
• Faster flow in the center of the vessel compared to flow along the edges

• Flow within vessels occurs in many directions
• Resistance to flow is greater in comparison to laminar flow
• Turbulent flow is enhanced with high velocity, large vessel diameter, and decreased blood viscosity

Athersclerosis. Increases blood pressure and puts added pressure on the heart.

• Ability of a vessel to stretch (elastic)
• Is an increase in volume due to an increase in pressure

• Ability of vessel to stretcha nd hold increased volume
• Total volume of blood "stored" in any portion of hte circulation at a given vascular pressure.
• Indicates the volume increase in a particular vessel (veins) due to increase in pressure.

MAP of 60mmHg

Varicose veins

• Venous distention that makes the valves unable to prevent fluid back-up
• Creates high hydrostatic pressure allowing fluid to leak into the interstitium = edema

• Intercellular clefts (pores) between adjacent cells that allow fluid and small molecules to "leak out"
• Vesicles within endothelial cells transport materials through cellular cytoplasm
• Fenestrations in endothelial cells

• Continuous
• Fenestrated
• Sinusoidal

• No fenestrations, substances move thru cell MB or between endothelial cells
• Skeletal m, CTs, nervous tissue, lungs, gonads

• True fenestrations, vary in size and number in tissues
• Kidney, endocrine glands, intestines

• Wide spaces between cells permits movement of large molecules
• Liver, spleen, bone marrow, lymph nodes, adrenal cortex

Fluid forces within capillaries and interstitium

• capillary hydrostatic pressure
• interstitial fluid pressure

• O2
• CO2
• Fat

• Water
• Ions
• Glucose
• Most proteins

Solute pressure of plasma proteins

• Plasma colloid osmotic pressure (oncotic pressure)
• Interstitial fluid colloid osmotic pressure

Proteins in solution create osmotic force on fluid

Albumin within the plasma (into capillary)

Interstitial fluid solutes (out of capillary)

• Remove excess fluid from the interstitium and return them to general circulation
• Absob and transport dietary fats to circulation
• Production of immune cells; monocytes and lymphocytes

• COP
• IFHP

• CHP
• IFOP

vein

• skeletal muscles
• pulsing arteries
• interstinal peristalsis
• increase in interstitial fluid filtrate

Liver & intestines

increase

• Increased CHP
• Decreased COP
• Increased IFOP
• Increased capillary permeability

Reflexive smooth muscle contraction

• Skeletal muscle contraction
• Bodily movements
• Pulsation of arteries adjacent to lymphatics
• External compression

• Incomplete or absent basal lamina
• One end of lymph capillary ends blindly
• Have wider lumens than blood capillaries
• Anchoring filaments assist in maintaining open channels of smaller capillaries

• Deliver oxygen, nutrients
• Remov CO2, hydrogen ions
• Maintain ionic concentration of tissues
• Transport hormones

blood flow

Rapid changes in local dilation and concstriction

• Arterioles, met-arterioles, and pre-capillary sphincters are controlled within seconds of changes in the metaboli needs of a tissue
• Changes create immediate increase or decreases blood flow

Adaptation over days-to-months

• Tissues adapt to chronically altered metabolic needs by increasing overall vascularity
• Vascularity increase occurs
• in number and size of capillaries and
• arterioles

Increased metabolic rate or decreased oxygen (or other nutrient) availability causes icnreased release of vasodilator molecules from "needy" tissue

• CO2
• ADP
• Histamine
• K+
• H+ ions
• Adenosine

• High altitude
• Pneumonia
• Carbon Monoxide poisoning
• Exercise

• Oxygen (and other nutrients) are required for muscle contraction and metabolic activity of other tissues
• Decreased availability of oxygen (and/or other nutrients) creates vasodilation

• Increase in blood flow to a tissue due to icnreased metabolic activity
• E.g. Skeletal muscle during intesnse exercise

• Transient increase in blood flow to tissue immediately following an ischemic period
• E.g. - Create blockage to blood flow; once blockage is remove BF increases over normal to compensate for ischemia

• Shear stress on arterial wall (increased blood flow) stimulates release of EDRF (endotehlium-derived relaxing factor or nitric oxide - NO)
• NO causes larger arteries to dilate to support increased blood flow in the smaller vessels

A chronically increased demand for blood flow (e.g. endurance training)

• Vascular endothelial growth factor
• A small peptide released from tissues under increased metabolic demand

• Blockage
• Can actually cause growth of collateral circulation to create a "bypass"
• Occurs frequently in coronary arterial system

Substances that are released by the endocrine system can affect the level of vasoconstriction/vasodilation

Vasoconstrictors released form the adrenal gland (sympathetic system)

• Vasoconstrictor produced in the liver
• Circulates in the blood in an inactive form
• Usually activated in the lung by the kidney hormone renin
• Serves as a strong vaseconstrictive agent

• Vasoconstrictor formed by the hypothalamus and released from the posterior pituitary
• Main function is to increase water resorption from the renal tubules back into the blood

• Vasoconstrictor produced by endothelium of damaged vasculature
• Powerful stimulator of vasoconstriction to reduce blood loss during hemorrhage

• Activated by kallikrein from cells and the blood, especially from tissue damage or intial stages of the inflammatory process
• Powerful stimulator of vasodilation and increased vascualr permeability

• Vasodilator released from nearly all bodily cells (especially mast cells/basophils)
• Also stimulates increased vascular permeability
• Main "cause" of allergic reactions