Week 1: Wednesday Flashcards
what is the role of endothelium
anticoagulant
favors anticoagulant mechanisms
* has smooth surface
* negative charge
what does the endothelium produce
- vasodilators
- inhibitors of coagulation
what is the role of endothelium in procoagulant properties
- vasocontriction
- disruption of endothelial integrity (exposes collagen - activates primary hemostasis; tissue factor - activates secondary hemostasis)
- synthesizes pro-thrombotic factors (Von Willebrand factor)
what is primary hemostasis
- formation of the primary platelet plug
- interaction with endothelium (exposure of collagen)
- provide surface for coagulation factors (secondary hemostasis)
what are platelets
- produced in bone marrow
- lifespan - 6 days
- pre-formed substances in platelet granules (enhance platelet function and attract more platelets to site)
how do plateletes work
- damage to vessel wall (exposure of collagen)
- adhesion
- activation
- aggregation
what is platelet adhesion
- dependent on local blood flow
- static or low speed flow - platelets adhere to collagen of sub-endothelium
- high speed flow - von Willebrand factor mediated platelet adhesion
what is von willebrand factor (VWF)
- synthesized by megakaryocytes and endothelial cells
what is the function of VWF
- mediator of platelet adhesion in rapid blood flow conditions
- decrease of factor VIII clearance
what is platelet activation
- happens secondary to adhesion (collagen) or agonist mediated activation
- thrombin (CF II) is biggest activator
- shape change - pesudopodia
- release of platelet granules (attract, activate more platelets)
what is platelet aggregation
- platelets interact to provide the surface for coagulation factors
- hemostatic plug
- linked to each other by fibrinogen
what are the signs of primary hemostasis
- petechiation, ecchymoses (small bruises)
- spontaneous muscosal bleeding (GI, urogenital, oral/nasal)
- surgical bleeding
what is diagnosis of primary hemostasis
- platelet count
- platelet function tests
- VWF level (most common)
what is secondary hemostasis
- formation of fibrin that crosslinks the primary platelet plug
- fibrinogen (factor I) converted to fibrin by thrombin (factor II)
- stable clot
- coagulation factors
- sequentially active/change other factors in a highly organized process
what are coagulation factors
- proteins (produced in liver; factors III and VIII - endothelium)
- enzymatic and non-enzymatic
- some circulate in inactive form, need to be activated (by other factors; factors II, VII, IX, X - activated by VK)
what is the cell based model of hemostasis
- overlapping phases takes place on different cell surfaces
- initiation
- amplification
- propagation
- starts with exposure of tissue factor
what is tissue factor (TF)
- factor II
- most important factor in initiation of secondary hemostasis
- inactive in intravascular space, active in cytoplasm and extracellular domains
- secondary hemostasus gets activated when TF gets exposed from endothelial damage
what phase in TF
initiation phase
what phases are on the activated platelet surface
- amplification
- propagation
what is the phospholipid bilayer of platelets
- phophatidylserine (PS) and phosphatidylethanolamine (PE) localized to the inner membrane surface
- PS and PE flip to outer surface with platelet activation
what enzymes flip PS and PE to the outer surface and scramble them
- floppase
- flippase
- scramblase
what is the initiation phase of hemostasis
cell based model
- exposure of tissue factor
- trace thrombin
what is the amplification phase of hemostasis
cell based model
- thrombibn travels to platelet
- activates more factors
- activates and attracts more platelets
what is the propagation phase of hemostasis
cell based model
- thrombin converts fibrinogen to fibrin
what is secondary hemostasis cascade model
- two arms of cascade (extrinsic, intrinsic, common pathway)
- operate independently
- redundant
what arm of the cascade model is prothrombin time (PT)
extrinsic
what arm of the cascade model is activated partial thromboplastin time (aPTT)
intrinsic
what does the cascade model test for
time (sec) for blood to go from fluid to clot
what are clinical signs of bleeding in secondary hemostasis
- body cavities (thoracic and abdominal)
- joints
- brain
- muscle
- subcutaneous tissue
what are tests of secondary hemostasis
- PT
- aPTT
- activated clotting time (ACT)
- individual factor levels
what is the termination phase
- endogenous antithrombotic elements
- regulation of hemostasis
- contains hemostasis to a localize area
what is used to deactivate a clot
- tissue factor pathway inhibitor
- antithrombin
- thrombomodulin
- protein C
what is fibrnolysis
uses plasmin to turn fibrin to fibrin degradation products
what does the circulatory system do
- mediates movements of all body fluids
- regulates body temp and distribution of hormones and leukocytes
what do arteries do
transport oxygen and nutrients to tissues
what do veins do
transport of CO2 and metabolic waste from tissues
what are the two functional components of the circulatory system
- blood vascular system
- lymph vascular system
what is the blood vascular system organized into
- heart
- arteries
- arterioles
- capillaries
- venules
- veins
this circuit of ___ ___ sustains the blood flow maintained by the heart
blood vessels
what does the arterial system provide
a distribution network for capillaries
interchange of gases and metabolites between tissues and blood
what does the venus system do
returns blood from the capillaries to the heart
what is endothelium
flat epithelium in blood vessels
what is the tunica intima
inner lining made of single layer of endothelium supported by basement membrane and collagenous tissue
what is the tunica media
intermediate muscular layer
what is the tunica externa/adventitia
outer supporting tissue layer
what are companion vessels
artery traveling with vein because they supply the same body region and lie next to each other
what structural component is not in the vein
internal elastic layer in tunica intima
what do arteries look like
thick and have contractile muscular walls
____ permit change in vessel size in response to ____ ____ change and allow artery to absorb the pressure
elastic; blood pressure
what gives an artery the ability to change in size actively
contractility
what induces vasoconstriction
arterial smooth muscle contract and contrists artery
what is vasodilation
when smooth muscle relax to increase artery diameter
what does the venous system look like
- larger in diamter than arteries
- thinner walls than arteries because blood pressure is lower
what is less prominent in the venous system
elastic and muscular components
what is reveral in blood flow prevented by
valves in medium sized veins
where is a major part of the total blood volume contained
within the venous system
what is microcirculation
regulates exchange of gases, fluids, nutrients and metabolic waste
where does exhange occur
in capillaries that have extremely thin wall which lack a tunica media and form interconnected networks
blood flow is slow so there is sufficient time for ____ or ____ ____
diffusion or active transport
what are the 3 types of capillary endothelium
- continuous - uninterrupted lining
- fenstrated - contains pores/fenstrations
- discontinous-
what are endothelial cells
flat polygonal cells interconnected by junctional complexes
what do endothelial cells act as
permeability barrier
what do endothelial cells synthesize
- extracellular matrix components for basement membrane maintenance
- products regulating blood coagulation, thrombosis and the balance between vascoconstriction/vasodilation
what do endothelial cells regulate
acute and chronic inflammatory responses through the expression of cell adhesion molecules and immune mediators
endothelial cell function is _______-dependent
compartment
what is the function of the nervous tissue
to recieve external and internal stimuli which are then analyzed and integrated to produce appropriate and coordinated responses
what is the nervous tissue composed of
network of neurons which constitute most sensory receptors, the conducting pathways, and sites of integration and analysis
what is the function of the neuron supported by
glial cells
the functions of the nervous system depend on the ____ of neurons
excitability
what does excitability involve
a change in membrane permeability in reponse to appropriate stimuli and the plasma membrane becomes depolarized inducing action potential which then spread along the plasma membrane
where are action potentials conducted
along the axon to influence other neurons/target organs
what are axons commonly reffered to as
nerve fibers
axons in the CNS are surrounded by ____ while in the PNS they are enclosed by _____ ___
oligodendrocytes; Schwann cells
small diameter axons are enveloped by the cytoplasm of
Schwann cells (non-myelinated nerves)
large diameter fibers are wrapped by cocentric layers of
schwann cell plasma membrane forming a myelin sheath (myelinated nerves)
what are myelinated nerves comprised of
fascicles
what are fasicles
bundles of funiculus that are group of axons
what are bundles of fascicles bounded by
epineurium
what is the CT called that surrounds each myelinated nerve fiber
endoneurium
what are fascicles bound by
perineurium
what is the neurovascular bundle
- consists of the binding of blood vessels and nerves with CT
- risk during surgery
