MICROCIRCULATION. VENOUS BLOOD FLOW.

Microcirculatory bedArterioli & pre-capillariesCapillariesArterio-venous anastomosesPost-capillaries

Functional state of capillaries

bloodplasma

Medium capillaries parametersRadius 3-6 mLength 750 mCross section square 30 m2Square of exchange 14 000 m2 Linea velocity of blood flow 0,3 mm/seTime of erythrocyte staying in the capillary 2-3 se

TYPES OF CAPILLARIESCONTINUUS pores of 4-5 nm

FENESTRAED fenestra in the endothelium of 0,1 m

SINUSOIDAL

Capillary endothelium in relaxed muscle

B. Capillary endothelium in contracted muscle

TRANSCAPILLARY EXCHANGE

CVh/bl=30h/t=-6/t=4/pl=27f13h/pl=10/pl=28h/t=-6/t=48

Filtration-absorption mechanismNet hydrostatic pressure

h/n=h/pl h/t=30-(-6)=36

Net oncotic pressure/n=/pl-/t=27-4=23

Filtration-absorption mechanismFiltration pressuref=h/n-/n=36-23=13

Absorption pressureh/n=10-(-6)=16/n=28-4=24ab=/n-h/n=24-16=8

LYMPHATIC SYSTEMDRENAGE SYSTEM excretes from extracellular fluid proteins & high molecular substances, which cant be reabsorbed into blood capillaries.

2L of lymph are produced per day

Lymphatic vessel

Muscle elements-Lymphatic capillaryvalvesLympho-angion

VENAE ARE BLOOD DEPOTSHEARTBIG ARTERIESSMALL VEINSCAPILLARIESLUNGSBIG VIENSSMALL ARTERIES

Factors enabling blood flow in veins1. Pressure difference (12mm Hg 0 mm Hg )2. Recoil force of heart & thorasic cavity3. Valves in veins4. Skeletal muscles contraction

VASCULAR TONE REGULATION

VASCULAR TONEBASILAR MIOGENIC TONE TONE, PROVIDED BY SMOOTH MUSCLES AUTOMATICITY.

AORTHAVEINARTERIOLA

Factors, influencing vascular toneMyogenicVasoactive tissue methabolitesHumoral factors, circulating in bloodTonic nervous impulses

Local regulatory mechanismsMechanical stretching of vessel wall with bloodOxygen deficitMethabolitesBiologically active substances which act paracrineRegulating factors of endothelial cells of the vessels

Influence of blood pressure on the myogenic vascular tone

Tone increaseTone decrease

Vasodilating methabolitesDecreased pressure of 2 Lactic acidPyruvic acidAdenosinIncreased pressure of 2

decrease, + concentrationincrease

Biologically active substancesVasodilatorsKinins (bradikinins)Prostaglandines (1,2,1,1, 2, F2)Hystamine Vasoconstrictor - serotonin

Endothelium regulating factorsArachidonic acid methabolites (prostacyclin PGI2)Factor of vessel relaxation (NO)Factor of vessel contraction (ECF-endothelin)Free radicals

Humoral factors, circulating in blood

Hormones, causing vasoconstrictionEpinephrin, norepinephrinVasopressinRenin-angiotensin-aldosteron system

Epinephrin & norepinephrinEpinephrin in high concentration constricts the vessels via -adrenoreceptors-adrenoreceptors are sensitive to norepinephrine in physiological concentrations

Vasopressin Is released from posterior pituitary ADH causes vessels constrictionReceptors V1 & V2Employs intracellular messengers

Renin-angiotensinogen-aldosterone systemkidneyJGAReninangiotensinogenangiotensinIlungsangiotensin IIAdrenal cortexaldosteronevesselsSensitivity to epinephrine constriction+

Hormones, causing vasodilationEpinephrine in physiological concentrations via -adrenoreceptors.- adrenoreceptors are located in coronary vessels, brain & kidney vessels

Nervous influences

Sympathetic nervous systemAdrenergic fibersCholinergic fibers Epinephrine &norepinephrine-drenoreceptorsconstriction-drenoreceptorsdilationachetylcholineM-cholinoreceptors

Sympathetic nervous systemM-cholinoreceptors are in the vessels of skeletal muscles.

Parasympathetic nervous systemSalivatory glands vessels Pelvic organs vesselsPia mater vessels

Acetylcholine

m-cholinoreceptorsdilation

vasoconstrictorsNervous:Sympathetic nervous system via -adrenoreceptors (all vessels)

Hymoral:Epinephrine, norepinephrineVasopressinRenin-angiotensin-aldosterone system

VasoconstrictorsLocal:SerotoninEndothelial factor of vessel constriction (endothelin)

vasodilatorsNervous:Sympathetic NS via -drenoreceptors;Sympathetic NS via cholinergic fibersParasympathetic fibers xon-reflex

Axon-reflex

CNSMechanical, thermal or chemical skin irritationLocal vessel dilation

vasodilatorsHumoral:Epinephrine via -adrenoreceptors;Hystamine

Local:MethabolitesBiologically active substances (prostaglandines, kinins)Endothelial factorsMechanical stretching of vascular wall

Tonic influence of sympathetic NSClaude Bernard experiment