circulation 1,2 and 3 Flashcards
understand the virchow`s triad and its application
layers of the arteriole
innermost - the endothelium (tunica intima )
middle layer - the thick and elastic muscular layer .(tunica media)
outermost collagen (tunica externa)
how are the endothelial cells connected to the tunica media
connected through the basal lamina where they sit on
arrangement of molecules and cells in a normal artery
red blood cells next to the lumen
neutrophils and other immune cells towards the middle
contents of the lumen
red blood cells and platelets
constituents of a thrombus
platelets
fibrin
white blood cells
appearance of the platelets , fibrin and white blood cells in the microscope
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where are platelets contained
contained in the lumen and do not get in contact with the interstitial collagen unless there is an injury
is plasma contained in the lumen
yes together with plasma proteins that are present
are clotting factors contained in plasma
yes , only red blood cells,plasma proteins ,platelets and white blood cells are not contained in plasma
Haemostasis
process by which blood is stopped from leaking and oozing
phases of haemostasis
1.vasoconstriction -Any defect of the blood vessel that causes vasodilation for example in acute inflammation will result in vasoconstriction which reduces the flow of blood and limits blood loss.
2.primary haemostasis -there is platelet plug formation platelet plug is formed under the signal Von Willibrand Factor .
3.secondary haemostasis - the coagulation cascade takes place and there is formation of a fibrin meshwork to cover for the damage.
what are platelets
platelets are cells that are produced by the bone marrow .
they are cells that are formed form a progenitor un commited cell known as a megakaryocyte.
A megakaryocyte is a large cell with many nuclei.
The megakaryocyte undergoes nuclear division but not cell division hence a big cell with many nuclei
Formation of a platelet
The formation of a megakaryocytes takes place in the bone marrow.
Platelets are formed from megakaryocytes
the megakaryocytes undergo nuclear division but not cell division .
The platelets will bud off as fragments from the cytoplasmic extension to form the present platelets that are smaller compared to megakaryocytes.
Functional rationale of platelets
Trauma that is inflicted on the blood vessel cause the exposure of the platelets with the collagen in the tunica externa.
When the platelets are exposed they release adhesion factors that make them sticky , clump together and they adhere on the blood vessels in an attempt to close the gap between the damaged vessel.
what are clotting factors
these are proteins in the blood that aid in blood clotting and are named with a roman numeral
functionale rationale of clotting factors
they are an amplification system that will result in thrombin formation
What is the function of thrombin
thrombin converts soluble fibrinogen to insoluble fibrin which forms a mesh of strands that prevent the loss of blood.
what is the clotting cascade
clotting cascade is an amplification system that results in thrombin being activated being activated .
what is initial damage
damage that leads to the exposure of interstitial collagen ( that is collagen in the connective tissue ) there is also exposure of the tissue factor that is a protein that is used up as a clotting factor.
consequences of a defect in a vessel example in trauma
blood vessel has a defect ,plasma with protein clotting factors and the red blood cells form the inner lumen leak out and are exposed to the collagen factors,tissue factor that is present in the muscles of the vessels are exposed and released, tissue factor binds with another clotting protein to initiate blood clotting cascade,
how are the clotting factor activated ?
clotting cascade is initiated when the tissue factor binds on the clotting factors , many clotting factors are serine proteases ( protein enzymes ) they have a serine amino-acid in them and they cleave clotting factors together in order to form the active molecule, the activated clotting factor will have a site for binding for the next clotting factor to cleave onto it .
end product of the clotting cascade
thrombin
function of thrombin
activation of fibrinogen to fibrin
what is the endpoint of the protein cascade
Endpoint of clotting cascade is production of insoluble fibrin strands that form a meshwork
what is coagulation
this is the solidification of blood
what are the two types of solidification of blood
thrombus formation
clot formation
what happens in a thrombus formation
thrombus formation occurs in blood that is flowing which is either arterial blood or in the venous system.
what are the physiological aims of thrombus formation ?
Prevent Blood Loss (Haemostasis):
The thrombus acts as a plug to seal the site of a vessel injury and prevent excessive bleeding.
Protect Vessel Integrity:
It stabilizes the damaged area by covering exposed tissues such as collagen, reducing further damage or inflammation.
Provide a Framework for Healing:
The thrombus serves as a temporary scaffold for the recruitment of cells (e.g., fibroblasts and endothelial cells) that repair the vessel wall.
structure of a thrombus
a pure thrombus is a pale cream colored
A thrombus consists of platelets and a mesh like a network of fibrin strands .
what is thrombosis
this is the process of formation of a thrombus
Characteristics of a thrombus
adheres on the wall of the blood vessel
occurs in flowing blood - note this
why does a thrombus of platelets and fibrin occur in flowing blood
because Platelets have molecules on their surfaces which allow adherence to interstitial collagen, even when blood is flowing past them – the clotting cascade deposits Factor VIII which enhances this further
what happens when there is clot formation in a damaged blood vessel
– blood leaks out off a vessel and becomes stationary (or stagnant), because of teh formation of the plug that prevents movement of blood.
Clot formation
in an injured , damaged vessel, there is movement of the platelets and plasma with clotting factors into the interstitial space.The platelets are exposed to the collagen and the clotting cascade is activated ,
What does a clot consists of ?
fibrin fibres and red blood cells ( hence the color because there are alot of red blood cells)
what is an example of haemostasis?
injury to a skin blood vessel ; blood flows through the blood vessel in the skin , trauma causes damage of the vessel and there is exposure of platelets and plasma proteins , clotting system is activated by collagen , there is formation of a blood clot to prevent the loss of blood, there is also vasoconstriction to prevent the loss of blood ,Fibrin ultimately formed, however this may still continue to bleed and a platelets and fibrin thrombus forms to the bridge the gap between the damaged blood vessels.
summary of the process of healing to any trauma caused on the blood vessel
Vasoconstriction helps reduce bleeding
Clot formation occurs in space around vessel and may fill void of wounded tissue
Thrombus forms in flowing blood and stops bleeding from gaps in vessels.
There is formation of a granulation tissue which will lead to angiogenesis and the blood vessel is eventually repaired.
The thrombus is removed from the site afterwards.
process of the removal of a thrombus
Thrombus is removed by a blood protein called plasminogen is converted to plasmin , the plasmin cuts down the fibrin asa way of removing the clots and thrombus , this process is known as thrombolysis.
what happens in the case of excess thrombus or clot formation ?
there is activation of the fibrinolytic system which removes the fibrin and stops the fibrin form propagating .
what is the other name of the tissue factor ?
thromboplastin
what are the factors that the fibrinolytic system depends on
plasma protein called plasminogen being converted to plasmin of which the the plasmin cuts up the fibrin and degrades the fibrin into particles.
normal physiological presence of thrombosis and clotting
wound healing
stopping bleeding during menstruation
pathological presentation of thrombosis
changes in the flow of blood either turbulent and stagnant.
changes in the constituents of the blood such as increased clotting factors .
changes in the surface of the vessel.
virchows triad summary
Changes in the intimal surface of a vessel (we have discussed one example – that is when trauma occurs)
Changes in the pattern of blood flow (either turbulent or stagnant)
Changes in the blood constituents (such as clotting factors)
pathological thrombosis
occurs in the absence of a cut or a traumatic injury
causes of thrombosis
changes in the intimal surface of a blood vessel , this is caused by destruction of the blood vessel.
changes in the pattern of flow of the blood.
changes in the constituents of the blood.
what is coronary artery thrombosis
this is the formation of a thrombus in the main arteries of the heart that supply heart muscle.
how does smoking cause thrombosis
cigarettes contain chemicals that increases the sticky nature of the platelets , they aggregate easily even in the absence of triggers.
other lifestyle factors that can cause atheroma that is the formation of a thrombus in a blood vessel
cigarettes and high lipid content in food.
how does high lipid level cause to thrombosis
alteration of the diameter of the blood vessel and that leads to abnormal flow of blood , this also predisposes platelets clumping.
what is atheroma
this is a disease that is a result of a build up of lipid under the intimal surface of a blood vessel ( remember photo )
what is a result of atheroma
there is reduced blood flow due to the constricted vessel, this increases the predisposition of the platelets to clotting factors.
example of changes in the intimal
surface of the blood vessel under virchow`s triad
atheroma - deposits of lipid material under the intimal surface
results of atheroma
sometimes the atheroma may be having deposits of collagen , rupture of the atheroma will lead to the exposure of the collagen which may initiate the clotting cascade.Because of this , there is exposure of platelets and fibrin which leads to the formation of a thrombus and the thrombus blocks the coronary artery , a clot forms in the stagnant blood.
what are lines of Zahn
they are layers of thrombus and clot
what are the consequences of a thrombus blocking an artery
- if there is complete obstruction, there is no flow beyond the point of the blockage and this leads to an infarction.
2.There could be partial blockage which means there is supply of blood ;the tissues however receive less blood flow.
ischaemia
this is tissue that has poor blood supply because of partial blockage of the blood vessel.
hypoxia
this is the reduced oxygen levels in the tissues
This is caused by prolonged ischaemia.
clinical presentation of heart tissue that is ischaemic
there is pain ; that is : chest pain and angina
infarct
this is a localised area of dead tissue that is caused by severe hypoxia
difference between infarction and ischaemia
infarction there is complete necrosis of the tissue ( localised ) irreversible while in ischaemia there is hypoxia of the tissues however there is no necrosis of the tissue.
tissues where infarction occurs
Coronary artery thrombosis – infarct in heart
Cerebral artery thrombosis – infarct in brain
Mesenteric artery thrombosis – infarct in gut( small bowel ischaemia )
what is an embolism
a mass that is travelling in the blood vessels towards the flow of blood , maybe lodged in a vessel when it reaches a vessel that is smaller than its diameter.
how are embolisms formed
they are formed when a part of a thrombus breaks off and travels off
what is thromboembolism
this is the process by which thrombi /clots embolise ( embolism formation)
how does pulmonary embolism occur
a part of thrombus breaks off, the thrombus is located in the leg where there is slow /sluggish movement of blood due to prolonged inactivity , part of the thrombus that breaks off travels up the vein into the heart then the lung where the pulmonary artery where it is lodged.
other forms of embolism
Fracture a leg marrow enters ruptured vein marrow embolises to lung vessels = Marrow embolism
Knife wound to neck. Air enters vein air embolises to heart = Air embolism (never inject a person with air in a syringe!)
WHAT IS CIRCULATORY SHOCK
CAUSED WHEN THERE IS LOW BLOOD PRESSURE AND THERE IS POOR PERFUSION OF THE BLOOD TO VITAL ORGANS
what are types of shock
circulatory shock
emotional shock
electrical shock
what causes circulatory shock ?
profound circulatory failure causing poor perfusion of vital organs; there is reduced blood pressure and there is physiological consequences.
characteristics of a vessel when it is contracting
the elastic tissue is folded up when the blood vessel is contracting
what happens when there is no blood flow in the blood vessel?
there is the collapse of the blood vessel and the blood vessel is open when there is flow of blood
blood pressure
the resistance of blood as it passes through a blood vessel
normal blood pressure
120/80
reason why venous blood pressure is very low
vein does not have an elastic tissue , there is no elastic recoil
what are the factors that normal blood pressure relies on
volume of the blood ( enough blood in the system )
smooth muscle in vessels having a certain elasticity ( elastic recoil)
heart pumping blood .( force of the heart contraction)
normal blood levels in a healthy human adult
5 litres of blood
how does enough blood in system influence the blood pressure
increase in the blood volume increases the blood pressure
decrease in the blood volume results in the collapse of the blood vessel which results in low blood pressure.
how does smooth muscles vessel tone influence the blood pressure
the tone of the smooth muscle of the artery may be decreased through dilation of the vessel ; if enough ( alot ) of the vessels are activated ( lose tone ) there is an increase in blood pooling and a consequent loss of blood pressure
how does heart pumping influence blood pressure
if the heart is not pumping and contracting enough then there is low blood pressure
the body`s method of detecting blood pressure and oxygen
carotid bodies and carotid sinuses on either side of the neck
what is a carotid body
a chemoreceptor that detects the changes in the oxygen levels
carotid sinus
blood pressure methods messurements.
they are located at the base of the internal carotid artery near its bifurcation from the normal carotid artery.
where are the carotid artery and the carotid body located
located at the right side, base of the right carotid artery bifurcation
number of the carotid sinuses and carotid base
2 on each side of the neck
what does carotid bodies consist of
the 2 carotid bodies consist of groups of cells which sense the partial pressure of oxygen and CO2
how does the carotid sinus relay the information
when the blood pressure is low the carotid sinus senses this and sends nerve signals to the brain stem which signals the heart to pump harder and faster via the nerve signals.
what other things does the brainstem do to keep the person alive
stimulation of the sympathetic nervous system which increases the tone in limbs and abdomen which pushes blood up the chest and head ( diverting the blood to major organs of the body)
what is the effect of the stimulation of the sympathetic nervous system
Adrenal glands secrete adrenaline heart pumps even harder and faster.
increased vascular tone in the vessels in limbs and abdomen.
what are effects of circulatory shock
low blood pressure and a fast pulse
causes of circulatory shock
1.hypovalaemic which is caused by a haemorrhage
2.septic shock
3.cardiogenic
4.other anaphylactic shock
case of hypovolaemic shock
rib that has fractured and penetrated the spleen causing haemorrhage.
arterial blood pressure is normal for a while before it goes lower , this is because as blood flows out of the damages spleen there is less blood in other vessels and they collapse because of this as they have no blood in them , there is eventually less blood in the inferior vena cava which also collapses.
what does the carotid nervous system upregulate
sympathetic nervous system
what does high pulse reflect in physiological response
low blood pressure
characteristics of a patient with hypovolaemic shock
Patient usually feels very ‘ill’
Rapid breathing.
Fast heartbeat – pulse fast and may be weak and thready
Pale, sweaty skin
what are the signs that can be seen in a hospital for hypovolaemic shock
Tender abdomen( sign of pain )
Blood pressure 60/40, pulse 120 = Shock
Diagnosis of abdominal trauma with hypovolaemic (or haemorrhagic) shock.
Transfused blood to restore blood volume. Operation to remove spleen.
cardiogenic shock
there is loss of function of the heart muscle, less blood is pumped into other regions of the body , so the venous pressure is normal
drugs are given to increase the function of the heart
septic shock
presence of a bacterium that produces nitric oxide , which causes vasodilation , vasodilation reduces the flow of blood , not enough blood goes to the heart and other major organs such as the brain therefore there is septic shock.
what happens in severe septic shock
Muscle of heart, just like muscle in vessels, also looses it’s tone – may then get slow heart = bradycardia
what are the complications of shock
1.decreased perfusion to the brain could be reversible ( ischaemia) could be irreversible after a long time ( infarcts), confusion , reduced consciousness , coma
2,decreased perfusion of the kidneys which is presented as reduced urine output , reduced excretion of toxic substances
