Introduction and Blood flow lecture 1&2 Flashcards
What are the functions of blood and the key components of the vascular system
Functions of blood:
Transport - Gases (O2 and CO2), Nutrients (carbohydrates, amino acids, fats proteins from gut to tissues), Hormones, Waste products (from tissues to liver/kidney for processing and excretion), Heat, Signals, Structure adapted to function.
Regulation - Fluid, pH, temp
Protection - immune system
Key comonents of vascular system are:
Cells (RBC, WBC, Platelets), Liquid (plasma), Pump and the piping (heart pumps blood, blood vessels carry blood to all parts of the body), Lymphatics (drainge of tissue back into blood
Describe types of white blood cells, the vascular and lymphatic system
Neutrophils (Granulocytes) - most abunadnt, respond by chemotaxis to bacterial damage, phago cytose pathogens and release lysosomes to kill pathogen.
Eosinophils (Granulocytes) - combat histamine in allergic responses, phagocytize antigen-antibody compleses and destroy some parasitic worms
Basophils (Granulocytes) - least common, exit capillaries and enter tissue fluid where they release heparin, histamne and seritonin dueing allergic reactions to stimulare inflammation.
Agranulocytes (Lymphocytes) - involved in specific immune responses
Agranulocytes (Monocytes) - largest WBC, slow to response to infection and can enlarge and diffrentiate into wandering macrophages that clean up cellular debris and micrboes following infection
Vascular system has lots of blood vessles. Things can go wrong in piping and with cells.
Lymphatic system allows fluid in tissues to be reabsorbed bacj into blood.
Describe the constituents of blood
55% plasma
45% cells
40-45% RBC- haematocrit
99% of cells are RBC
Plus platelets and WBC
Blood is a structural solution, and behaves as a liquid (macroscopic) and is a suspension of solid particles (Microscopic).
Describe red blood cells in circulation
Biconcave disc
No organelles, anucleate and plasma membrane supported by spectrin.
Aggregate in still blood but are easily separated as flow increases
Only low pressure is needed to get RBCs into small capillaries ie. 3um diameter
They have an elastic shape- easily deformed and stretch to align with flow
Characteristics and circulation of the blood
Large vessels = blood is a liquid
Small vessels = blood flows differently due to being same size as vessel
Within a large vessel = blood viscocity matters
Within a small vessel = cells have to sqeeze and cellular properties and blood viscotiy influcece this .
Driving force for flow is a pressure gradient.
Flow rate=….?
Pressure difference/resistance to flow
Affected by vascular component- radius and length And blood component- viscosity
Describe blood flow
Newtonian fluid - viscocity doesnt change
Blood is a non newtonian fluid as viscocity changes depending on shear rate
TUbes are not rigid and striaght, they are tapered and curved and the walla deform.
Blood is not consistant, it is pulsitile.
At high flow rates, there is red cell deformations, cells align with flow, decreased viscosity with high shear rate
At low flow rates, red cells aggregate, mediated by plasma proteins (mainly fibrinogen), increases visocity at low shear
Poiseulle’s law- Flow rate= dP/P
CO=ABP/TPR
What are the factors controlling blood viscosity and consequecnes of Anaemia?
Intrinsic- (structure of the blood) - haematocrit, plasma viscosity
Also, red cell aggregation and deformation (blood is non-Newtonian, increased flow decreases viscosity)
Extrinsic-(flow conditions)-Viscocity depends on shear rate.
Shear rate is the velocity gradient across the vessel- low in the centre and high at the sides because of the parabolic shape
Consequences or anaemia: Reduced oxygen carrying capacity (O2 saturation likely to be normal), Reduced viscocity and resistance to flow (cardiac output may be high to try compensate dont have this spare capacity in exercise as Cardiac output is already high)
Describe the factors affecting the plasma viscosity
Plasma proteins:
-Albumin -Immunoglobulin -Fibrinogen- (involved in RBC aggregation and clotting). Fibroinogen involved in visocity and can affect it a lot. Increased fibroinogen causes increased plasma viscocity, increased red cell aggregation and increased ESR (erythrocyte sedimentation rate).
Hyperglobulinaemia- elevated immunoglobulins eg in myeloma, macroglobulinaemia➡️ hyperviscosity syndrome
What is ESR?
Erythrocytes sedimentation rate- the amount of RBC aggregation in stationary blood More sedimentation the worse off the patient
Describe some blood rheology and circulatory pathology
Hyperviscosity syndrome- immunoglobulins, haematocrit, hyperleukotic leukaemia (elavated WBC = increased viscosity), abnormal RBCs, increase in viscocity.
Acute phase response- atherosclerotic vascular disease, diabetes, smoking
Increased fibrinogen leads to increased plasma viscosity, increased red cell aggregation and therefore increased ESR
Describe blood viscosity in intermediate sized vessels and velocity profile
Diameter-
haematocrit is lower in smaller vessels around 30% in vessels less than 100microns
Apparent viscosity decreases with decreasing diameter between 100-10microm
Haematocrit in many arteroiles, is lower than systemic haematocrit. Flow resistance is slower than expected from systemic viscocity. Resistance still depends on haematocrit.
Velocity profile:
Profile is blunted at haematocrits over 30%, occurs both at high and low flow rates. White cells/platelets moves towards edge of the flow. Fibrinogen involved in aggregation and clottingbut these are not linked. White cells and platelts have neglible effects on blood viscocity.
Atherosclerotic lesions develop at focal points of disturbed flow - have increased permeabiliy to macromolecules, increased turnover (proliferation and apoptosis), Increased adhesiveness to monocytes and altered levels of eNOS.
What important physiological indicators are there in the blood?
Haematocrit- oxygen carrying capacity and viscosity and also ESR
Plasma: - viscosity, Fibrinogen concentration
Blood content- red cell count and haemoglobin concentration
Cellular characteristics- mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration
