Lecture 30 - blood vessels Flashcards
types of blood vessels
o Arterial system
Elastic artery
Muscular artery
Arterioles
Capillaries
o Venous system
Venule
Veins
What is systole
o Arterial blood flows through the capillaries throughout system
o High pressure during ventricular system ejects the total stroke volume into the artery
what is diastole
o Arterial blood continues to flows through the capillaries throughout system
o Recoil of artery during ventricular diastole pushes the blood through the systemic circulation
continuous capillary
o Most common
o Edges of endothelial cells joined by tight junction (although leaky) –> intracellular cleft
o Transcytosis
fenestrated capillary
o Gaps in the endothelial cell membrane (Window)
o Diaphragm covers fenestration
o Permeable to fluids and small solutes
o Found wherever filtration and reabsorption occur (E.g. kidney, S.I.)
sinusoid capillary
o Leaky capillaries with large fenestrations
o Found in (liver, bone marrow, spleen, adrenal medulla)
o Large intracellular clefts (large molecules and cells can cross)
haemodynamic properties of blood
o As cross-sectional area increases the velocity of blood flow decreases
o Slower velocity allows increased diffusion time
Effects of gravity on venous pressure and skeletal muscle pumps
o Increased skeletal muscle activity increases venous return to the heart
o One way valves and skeletal muscle pumps move blood through venous system
Exercise on lower limb venous pressure
o Standing still = column of pressure highest due to gravity
o Movement = causes the muscle pumps to push the blood through the venous vessels
factors affecting vascular resistance
o Flow rate
o Pressure
o Radius
o Fluid viscosity
o Length of tubing
laminar and turbulent flow
o It takes less effort to push when everything is moving in same direction
o Flow velocity is highest with laminar flow therefore pressure is lowest
o Turbulent flow decreases flow velocity therefore increases pressure
Important gases and nutrients that need to be exchanged over capillary membranes
o O2
o CO2
o Glucose
o Amino acids
o Metabolites such as NH3
transcytosis
o Pinocytosis, transport vesicles across the cell, exocytosis
o Important for fatty acids, albumin and some hormones (insulin)
filtration of fluid from capillaries
Fluid exuded from the blood vessel into the interstitial space
reabsorption of fluid from capillaries
Fluid returned to the blood vessels from the interstitial space
what is hydrostatic pressure
The force applied to blood to push it through blood vessels
–> It is equal to the pressure on blood to push it through a capillary
what is bulk flow
Anything dissolved in the fluid, that can fit through the pores, will be pushed out with it
forces applied to filtration
Capillary pressure
–> Capillary hydrostatic pressure
–> Plasma oncotic pressure
Interstitial pressure
–> Interstitial hydrostatic pressure
–> Interstitial oncotic pressure
what is oedema?
An increase in interstitial fluid volume in the tissues
what is the oedema safety factor?
Lymph flow can increase
Due to
- Leak of protein into interstitial space
- decrease plasma protein
baroreflex
o Whole body – homeostatic – regulation of blood pressure
o Ensures sufficient hydrostatic pressure across the entire body to ensure adequate blood flow to brain
autoregulation
regulates blood flow to local tissue to meet metabolic demand
